PB87-145777
Proceedings: Workshop on Effects of
Sewage Sludge Quality and Soil
Properties on Plant Uptake of
Sludge-Applied Trace Constituents
600987002
(U.S.) Envirormental P ro'cect ion Agency
Cincinnati , OH
Jan 87
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EPA/600/9-87/002
January 1987
PROCEEDINGS: WORKSHOP ON EFFECTS OF SEWAGE SLUDGE
QUALITY AND SOIL PROPERTIES ON PLANT UPTAKE
OF SLUDGE-APPLIED TRACE CONSTITUENTS
Sponsored by:
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
University of California, Riverside
Riverside, California 92521
and
The Ohio State University
Columbus, Ohio 43210
Location: Las Vegas, Nevada
Date: November 13-16, 1985
Cooperative Agreement No. CR-812673
Project Officer:
J. A. Ryan
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
WATER ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
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TECHNICAL REPORT DATA
/I'lftlSf rcuu ln\lnn t:(ln\ nn tin- n I rnv hi fttn ^ <»»ir"/i
1 REPORT NO
EPA/600/9-87/002
4 TITLE ANOSUBTITLE
PROCEEDINGS: WORKSHOP ON EFFECTS OF SEWAGE SLUDGE
QUALITY AND SOIL PROPERTIES ON PLANT UPTAKE OF SLUDGE-
APPLIED TRACE CONSTITUENTS
•S REPORT DATE
Jar.ua ry 1987
6 PERFORMING ORGANIZATION CODE
7 AUTHORISI
8 PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
USEPA, Cincinnati, Ohio 45268
Univ. of California-Riverside, Riverside, CA
Ohio State University, Columbus, OH 43210
12. SPONSORING AGENCY NAME AND ADDRESS
Water Engineering Research Laboratory- Cincinnati, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati . OH 45268
J RE CIP't NT'S ACCESSION NO
PW7 1457777AS
10. PROGRAM ELEMENT NO.
11. CONTRACT'GRANT NO
CR-812673
13 TYPE OF REPORT AND PERIOD COVERED
14TIP O NSORHMG A GINcVCODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer, J.A. Ryan (com 569-7653/FTS 684-7653)
Proceedings held in Las Vegas, NV, November 13-16, 1985
16. ABSTRACT
The workshop report summarizes the current research and understanding about
transfer of contaminants from sewage sludge to the human food chain via land
application. As such it addresses the important parameters in the system which can
alter the rate and degree of movement of contaminants through the environment.
The workshop group met in Las Vegas, Nevada, November 13-16, 1985. The
participants were divided into five separate but related workgroups. The topics ef
each workgroup are as follows: effects of soil properties on accumulation of trace
elements by crops, effects of sludge properties on accumulation of trace elements by
crops, effects of long-term sludge applications on accumulation of trace elements by
crops, transfer of sludge-applied trace elements to the food chain, and effects of
trace organics in sewage sludges on soil-plant systems and assessing their risk to
humans.
The report evaluates available data on effects of sludge, soil, and plant factors
on plant uotake of municipal sewage sludge-applied trace contaminants and their
transfer into the food chain. The summarized data and interpretation will be of value
to EPA in regulation and management of land application of municipal sewage sludge.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIP- ^
b.lDENTIHERS/OPEN ENDED TERMS c. COSATI Held/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Kfporll
UNCLASSIFIED
21. NO. OF PAGES
20(
20 SECURITY CLASS iTIiis pagcl
UNCLASSIFIED
22. 'RICE
EPA Form 2220-1 (R»». 4-77) PREVIOUS EDITION is OBSOLETE
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DISCLAIMER
The Information in this document has been funded wholly or in part by
the United States Environmental Protection Agency under assistance agree-
ment number CR-812673 to the University of California-Riverside and Ohio
State University. It has been subject to the Agency's peer and administra-
tive review, and it has been approved for puDlication as an IPA document.
Mention of trade names or commercial products does not constitute endorse-
ment or recommendation for use.
ii
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with
protecting the Nation's land, air, and water systems. Under a mandate of
national environmental laws, the agency strives to formulate and implement
actions leading to a compatible balance between human activities and the
ability of natural systems to- support and nurture life. The Clean Water
Act, the Safe Drinking Water Act, and the Toxics Substances Control Act
are three of the major congressional laws that provide the framework for
restoring and maintaining the integrity of our Nation's water, for preser-
1ng and enhancing the water we drink, and for protecting the environment
from toxic substances. These laws direct the EPA to perform research to
define our environmental problems, measure the impacts, and search for
solutions.
The Water Engineering Research Laboratory 1s that component of EPA's
Research and Development program concerned with preventing, treating, and
managing municipal and industrial wastewater discharges; establishing
practices to control and remove contaminants from drinking water and to
prevent its deterioration during storage and distribution; and assessing
the nature and controllability of releases of toxic substances to the air,
water, and land from manufacturing processes and subsequent product uses.
This publication is one of the products of that research and provides a
vital communication link between the researcher and the user community.
This report evaluates available data on effects of sludge, soil, and
plant factors on plant uptake of municipal sewage sludge applied trace
contaminants and their transfer into the food chain. The summarized data
and interpretation will be of value to EPA in regulation and management of
land application of municipal sewage sludge.
Francis T. Mayo, Director
Water Engineering Research Laboratory
111
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EXECUTIVE SUMMARY
Tne workshop group met in Las Vegas, Nevada, November 13-16, 1985,
to assess the state of our knowledge or, potential problems of trace ele-
ments and trace organics associated with the land application of municipal
sewage sludges. The participants were divided into five separate but
related workgroups. The topics of each workgroup, participants, and their
affiliations are as follows:
I. EFFECTS OF SOIL PROPERTIES JDN ACCUMULATION OF TRACE ELEMENTS
BY CROPS
Lee E. Sommers, Chair; Colorado State University, Fort Collins, CO
V. Van Volk, Oregon State University, Corvallis, OR
Paul M. Giordano, Tennessee Valley Authority, Muscle Shoals, AL
William E. Sopper, Pennsylvania State Univ., University Park, PA
Robert Bastian, OMPC, U. S. EPA, Washington, D.C.
11. EFFECTS OF SLUDGE PROPERTIES ON ACCUMULATION OF TRACE ELEMENTS
6V CROP'S
Richard B. Corey, Chair; University of Wisconsin, Madison, WI
Larry D. King, North Carolina State University, Raleigh, NC
Cecil Lue-Hing, Metropolitan Sanitary District cf Greater Chicago,
Chicago, IL
Delvin S. Fanning, University of Maryland, College Park, MD
Jimmy J. Street, University of Florida, Gainesville, FL
John M. Walker, OMPC, U.S. EPA, Washington, D.C.
III. EFFECTS OF LONG-TERM SLUDGE APPLICATIONS ON ACCUMULATION OF
TRACTTLEMENTS BY CROPS
Andrew C. Chang, Chair; University of California, Riverside, CA
Thomas D. Hinesly, University of Illinois, llrbana, IL
Thomas E. Bates, University of Guelph, Guelph, Ontario, Canada
Harvey E. Ooner, University of California, Berkeley, CA
Robert H. Dowdy, USDA-ARS, University of Minnesota, St. Paul, MN
Ja.Ties A. Ryan, WERL, U.S. EPA, Cincinnati, OH
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IV. TRANSFER OF SLUDGE-APPLIED TRACE ELEMENTS TO THE FOOD CHAIN
Rufus L. Chaney, Chair; USDA-ARS, Beltsville, MD
James E. Smith, Jr., CERI, U.S. EPA, Cincinnati, OH
Dale E. Baker, Pennsylvania State University, University Park, PA
Randall Bruins, ECAO, U.S. EPA, Cincinnati, OH
Dale W. Cole, College of Forestry, Washington State University,
Seattle, WA
v- EFFECTS OF TRACE ORGANICS IN SFWAGE SLUDGES ON SOIL-PLANT SYSTEMS
AND ASSE'STING THETTTRTSlTTTrHUMANS
Lee W. Jacobs, Chair; Michigan State University, East Lansing, MI
George A. O'Connor, New Mexico State University, Las Cruces, NM
Michael A. Overcash, North Carolina State University, Raleigh, NC
Matthew J. Zabik, Michigan State University, East Lansirg, MI
Paul Rygwiecz, U.S. EPA, Corvallis, OR
Peter Machno, METRO, Seattle, WA
Ahmed A. Elseewi, Southern California Edison Company, Rosemead, CA
Sydney Munger, METRO, Seattle, WA
Each workgroup started out by reviewing the existing data base and
prepared a working draft in their assigned subject matter areas. The sali-
ent features of each group's findings were presented at plenary sessions
attended by the entire workshop. At this time each oarticipant was
afforded an opportunity to provide his/her input into workgroups other
than the one he/she was assigned.
Following the workshop, chairs solicited participants for additional
data or comments they wished to incorporate into the report. A revised
draft was then prepared. These revised workgroup drafts were, in turn,
reviawed by the workshop coordinators and the chairs, and recorders of
other workgroups. Following this revision, the workshop coordinators,
workgroup chairs and recorders met, and finalized the report. Findings
of the workshop are summarized as follows:
I. Effects of Soil Properties on Accumulation of Trace Elements by Crops
Althougn greenhouse pot studies may be useful to examine mechanisms
and to »stablish relative response curves, the concentrations of
trace elements in a particular crop are greater when the crop is
grown in pots with sludge treated soils than when it is grown under
comparable conditions in the field.
• Experiments which employ either trace element salts or sludges
spiked with trace element salts do not simulate trace element up-
take by crops grown on sludge-amended soils. Therefore, results of
such studies do not provide a reliable basis for establishment of
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criteria, guidelines and regulations to control trace element
concentrations of crops grown on sludge amended soils.
Concentrations of trace elements in crops grown on sludge-amended
soils vary with soil conditions such as the content of iron and alu-
minum oxides and soil pH. Iron ana aluminum oxides ir> soils,
sludges, and sludge-amended soils may reduce solubilities of trace
elements and, in turn, their plant availabilities. In general,
trace element uptake by crops (except Mo and Se) decreases with
Increasing soil pH.
• The pH measurement of a soil depends upon the method used to prepare
the soil suspension. Suspensions of 1:1 soil:water or soil :0.01 J1
CaCl2 have been used for measuring the pH of soils and/or sludge-"
amended soils. However, the 0.01 ^ CaCl2 method is preferred
because it compensates for soluble salt contents in the soil-sludge
mixture. Soil pH's in 0.01 _M CaCl2 are generally lower than those
measui?d in water and regulations based on soil pH should specify
the method to be used.
Sewage sludge additions have been effective in correcting trace ele-
ment deficiencies (e.g., iron, copper and zinc) of crops, par-
ticularly those grown on calcareous soils. v
• Trace metal uptake by crops grown on sludge-amended soil is not
directly related to the soil's cation exchange capacity or texture.
Available research data do not support the continued use of cation
exchange capacity or soil texture alone to determine maximum
available trace metal loadings.
II. Effects oj_ Sludge Properties on^ Accumulation of_ Trace Elements J>y_ Crops
• Trace elements in raw sewage are associated primarily with suspended
solids, and they remain as suspended solids in the sludge following
wastewater treatment.
Over the past decade, concentrations of trace elements in many
publicly-operated treatment works (POTW) sludges have decreased
markedly as a result of implementing industrial waste pretreatment,
and this trend is expected to continue.
• During sewage treatment, addition of materials containing Fe, Al or
lime reduces solubilities of metals in sludges.
• A variety of factors determine equilibrium trace element solubility
in sludges, particularly the presence of trace-element precipitates
(relatively pure compounds or coprecipitated with Fe, Al, or Ca
precipitates), the strength of bonding to organic and mineral
adsorption sites, the proportion of potential adsorbing sites
vi
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filled, and the presence of dissolved ligands capable of complexing
the trace elements.
If, within the pH range normally found in soiis of a given region, a
sludge maintains the availability of a trace element below the level
that causes phytotoxicity or potentially harmful accumulation of
that element in plants, there is no need to linrr. land application
of that sludge because of that element.
If, within the pH range normally found in soils of a given region, a
sludge maintains the availability of a trace element above the level
that causes phytotoxicity or potentially harmful accumulation of
that element in plants, loading limits should be established based
on characteristics of the sludge and of the soil to which it is
applied that interact to control the availability of that elem-nt.
• Development of methods for measuring trace-element desorption
characteristics of sludges and adsorption characteristics of soils
(particularly for Cd, Zn, Ni and Cu) should be given high priority.
Immediately following land application all sludges will undergo
changes which will affect trace element solubility and plant uptake.
Tllis effect is a function of sludge treatment prior to land applica-
tion. Most research Indicates that plant availability of sludge-
derived metals stays the same or decreases with time following their
land application.
III. Effects of Long-Term Sludge Applications or± Accumulation of Trace
Elements by Crops'
• Application of Cd and Zn to soils from municipal sewage sludge will
cause the Cd and Zn concentrations of crops grown on these soils to
exceed those of untreated controls. When the sludge is applied at
rates to satisfy the N requirement of the crop grown, the Cd and Zn
contents of plant tissue remain low and at nearly constant levels
with successive sludge applications.
In sludge-treated soils maintained at pH >6.0, Cu and Ni contents of
vegetative tissue may become slightly elevated. Phytotoxicity from
sludge-applied Cu and Ni, however, has rarely been reported.
• Available data suggest that four or more years following sludge
application the trace element concentration of the affected vegeta-
tive tissue would be determined by the total amounts of trace ele-
ments in the soil and would not be affected by the frequency of
sludge application (e.g., single addition vs. multiple applications).
• Plant availability of sludge-borne metals is highest during the
first year sludge is applied. Using the first year response curve
generated by a large single sludge addition will overestimate metal
vii
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accumulation in vegetative tissue from plants grown in well stabi-
lized sludge/soil systems.
Field data indicate that trace element concentration in vegetative
tissue will not rise after the termination of sludge applications
if chemical conditions of the soil remain constant. Cadmium and Zn
levels of plants grown in soils which were no longer receiving
sludges either remained at the pretermination level or decreased
with time.
IV. Transfer of Sludge-Applied Trace Elements to the Food Chain
• Contents of some trace elements in edible crop tissues can be
increased when sewage sludges rich in these elements are applied to
soils, especially to soils that are highly acidic (Cd, Zn, Ni) or
alkaline (Mo). Under conditions which allow the concentration of a
trace element in crops to increase substantially (responsive
conditions), the relative increases in element concentration among
crop species are sufficiently consistent to be used to generate
input data for modeling the dietary exposure of the element. The
relative increase of trace element concentration among crops may
vary when the results are extrapolated from soils with average to
soils with high organic matter contents, or from acidic to
calcareous soils. High organic matter and high soil pH (except for
Mo and Se) both reduce element uptake and would not increase risk
above that determined from the risk assessment based on conditions
of maximum intake.
• Relatively high and low Cd-accumulating crop types (lettuce vs.
cabbage; carrot vs. beet) within a food group should be accounted
for when using the FDA food groups to model the dietary intake of Cd.
• Representative food intake from birth to age 50 should be used to
calculate daily Cd ingestion and not the maximum daily intake.
Increased Cd ingestion from consumption of crops grown on sludge-
amended soils can be expressed in terms of their Cd uptake relative
to a reference crop (e.g., lettuce).
• Models developed to predict Cd retention by humans should consider
not only Cd content of the diet but also other constituents in the
diet (e.g., Fe, Zn) that affect Cd retention.
• The highest exposure to sludge-applied Cd would result from
ingestion of a substantial fraction of the daily diet of foods grown
in a strongly acidic vegetable garden for many years.
• Crop culttvars differ in their Cd uptake. However, in determining
dietary Cd intake, these differences are less important than dif-
ferences caused by crop species and soil and sludge characteristics.
viii
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Surface application of sludge without soil-incorporation presents a
greater potential risk to humans, livestock and wildlife due to pos-
sible direct ingestion of sludge-borne trace elements. The bioavail-
ability of a trace element in ingested sludge is strongly influenced
by the concentration of the element, the presence of other inter-
acting elements, and the slucige redox potential. Livestock showed
no harmful effects when grazing on pastures treated with sewage
sludge containing median trace element concentrations.
Effects of Trace Organics iji Sewage Sludges on Soil-Plant Systems
and Assessing Thei r R t s k to Humans
• Sewage sludges could contain thousands of trace organics.
Organics discharged by major contributors to wastewater treatment
plants should be identified to help select compounds for analysis
in sewage sludge.
Although some industrially derived organic compounds can be pre-
sent in sewage sludge at relatively high concentrations (i.e., a
few percent dry weight) most detected compounds are present at
concentrations less than 10 mg/kg, dry weight.
Results of bioassays of sludges for their mutagenic activity are
difficult to interpret. Information obtained from these tests is
not presently adequate to predict adverse environmental impacts
associated with land application of sludge.
• Organic chemicals applied to soil may undergo adsorption, volatili-
zation, degradation, leaching, and plant uptake. Many organics are
strongly adsorbed to organic matter and/or undergo degradation, thus
reducing the potential for plant uptake or leaching.
• Because experimental data are not always available for organics
lound in sludges, use of mathematical models based on physical/
chemical properties of representative organic compounds is a logical
approach to predict the fate of similar sludge-derived organics in
soils. Field research with selected slucige organics, which are
representative of organic chemical groups, is needed to calibrate
and validate these models.
• No adverse effects on the growth of crops have been observed when
sludges containing these organics are applied to soil at fertilizer
rates for nitrogen or lower.
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CONTENTS
Disclaimer ii
Foreword iii
Executive Summary ,. iv
Figures xi ii
Tables xiv
1. Introduction 1
2. Effects of Soil Properties on Accumulation
of Trace Elements by Crops 5
Introduction 5
Background Levels of Trace Elements 6
Regional Study of Sludge Use 8
Soil Properties Influencing the Accumulation
of Trace Elements by Plants 9
. Physical Properties 9
Soil pH 9
Iron 11
Molybdenum 11
Selenium 12
Cation Exchange Capacity 12
Method of Analysis 12
Correlation of CEC and Plant Uptake of Metals 13
Conclusions 13
3. Effects of Sludge Properties on Accumulation
of Trace Elements by Crops 28
Introduction 28
Forms and Amounts of Trace Elements
in Municipal Sewage Sludges 29
Trends in Sludge Trace-metal Concentrations 30
Forms of Metals in Raw Sewage 30
Forms of Metals in Sludges 31
Metal Speciation in Soils 33
Plant-Availability of Sludge-Borne Trace Elements 33
Factors Controlling Trace Element Uptake-
Theoretical Considerations 34
Experimental Results 36
Conclusions 40
4. Effects of Long-Term Sludge Application on
Accumulation of Trace Elements by Crops 57
Introduction 57
Nature of the Experimental Data 57
xi
Preceding page blank
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Cumulative Effects from Annual Sludge Applications 58
Single vs. Multiple Application 60
Metal Accumulations Following Termination
of Sludge Applications 61
Conclusions 6?
5. Transfer of Sludge-Applied Trace Elements
to the Food Chain 76
Introduction 76
Modeling the Effect of Crop Variation in
Increased Trace Element Accumulation in
Response to Sludge Application 79
Crop Cultivar Difference in Metal Uptake
from Sludge-Amended Soil 81
Estimating Maximum Allowable Soil Cd Loading
Based on Predicted Increase in Dietary Cd 84
Transfer of Sludge-Applied Trace Elements to
Animals by Direct Ingestion of Sludge or
Sludge-Amended Soil 87
Conclusions 90
6. Effects of Trace Organics in Sewage Sludges on Soil-
Plant Systems and Assessing Their Risk to Humans 107
Introduction 107
Prevalence of Trace Organics 1n Sludges 108
Trace Organics in Soils Ill
Extraction/Leaching Procedures 112
Mutagenicity Testing of Sludges 113
Fate of Trace Organics Added to Soil-PIant Systems 114
Assimilative Pathways Within the Soil-Plant System 116
Plant Uptake/Contamination 117
Degradation 119
Volatilization 120
Leaching 121
Effects of Sludge Properties 122
Utilizing Physical/Chemical Properties and Models 123
Comparison of Municipal Sludge Exposure/Risk Assessments ... 124
Conclusions 127
7. References 158
xii
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FIGURES
Number Page
1 Basis for differentiating sludges that do not require
loading limits to prevent harmful trace element
accumulations in plants from one that does 42
2 Uptake of Cd by romaine lettuce from soils treated
with municipal sewage sludge at various rates 43
3 Effect of sludge application rate on Cd in lettuce
leaves 44
4 Effect of a one-time application of municipal sewage
sludge on the Zn and Cd contents of corn leaf tissue 45
5 Decrease in Cd uptake by corn silage with time
after application of sewage sludge at three
rates in 1979 46
6 Cadmium and Zn concentrations of composted sludge
treated Ramona sandy loam 63
7 Cadmium and Zn content of Swiss chard harvested from
soils receiving biannual (spring and fall) sludge
application from 1976-1983 64
8 Relative Zn increments of barley leaf receiving
annual sludge addition of 20 mt/ha for five years 65
9 Relative Zn increments of barley leaf receiving 100
mt/ha one-time sludge application 66
xi ii
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TABLES
Number Page
1 Metal and organic carbon contents, CEC, and pH for soils
from selected sites in the continential United States 15
2 Trace element concentrations for soils from
selected sites in the continential United States 17
3 Trace element concentrations (dry weight) in the
edible part of crops grown on untreated soils 18
4 General characteristics of soils used in W-124 study 19
5 Concentrations of Cd in DTPA soil extracts and in
leaf and grain of barley grown in 15 locations 20
6 Concentrations of Zn in DTPA soil extracts and in
leaf and grain of barley grown in 15 locations 22
7 Concentrations of Cu in DTPA soil extracts and in
leaf and grain of barley grown in 15 locations 24
8 Concentrations of Ni in DTPA extracts and in leaf
and grain of barley grown in 15 locations 26
9 Metal loadings and cumulative percent reductions to
Chicago area treatment facilities, 1971 through 1977 47
10 Meial loadings and cumulative percent reductions to
Chicago area treatment facilities, 1971 through 1984 47
11 Response of metals concentrations in digested sludge
filter cake at the Back River POTW, Baltimore, Maryland
in response to pretreatment efforts 48
12 Response of metals concentrations in sludges at two
Philadelphia POTWs in response to pretreatment program 49
13 Cadmium uptake of mixed liquor sewage sludge (MLSS)
at varying solids to Cd ratios 50
xiv
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Number Page
14 Effect of sludge properties on plateau concentrations
of Cd in tobacco leaves grown in the field long after
sludge application ........................... . .............. 51
15 Effect of sludge rate and year after sludge application
on concentrations of Cd, Zn, Cu, and Ni in oat straw and
leaves of winter wheat, soybean and corn .................... 52
16 Cadmium, Zn, Cu, and Ni concentrations in edible parts
of vegetables grown at west-southwest sewage treatment
works, Metropolitan Sanitary District of
Greater Chicago ............................................. 54
17 Effect of sludje rate applied in 1979 on concentra-
tions of Cd, Zn, and Cu in wheat, rye and four
grasses in 1981 ............................................. 5^
18 Cadmium and Zn contents of plant tissues when sludges
were applied annually at high rates ......................... 67
19 Cadmium and Zn contents of plant tissue when sludges
were applied at agronomic rates . ............................ 68
20 Copper and Ni contents of plant tissues from
sludge-treated soils ....................................... 69
21 Cadmium concentrations (mg/kg) of Swiss chard
grown on sludge-treated soils ............................... 70
22 Zinc concentrations (mg/kg) of Swiss chard grown
on sludge-treated soils ..................................... 71
23 Cadmium concentrations (mg/kg) of radish leaf grown
on sludge-treated soils ..................................... 72
24 Cadmium concentrations (mg/kg) of radish tuber grown
on sludge-treated soils ..................................... 73
25 Zinc concentrations (mg/kg) of radish leaf grown on
sludge-treated soils ........................................ 74
26 Zinc concentrations (mg/kg) of radish tuber
grown on sludge-treated soils .............................. 75
27 Trace element concentration in edible plant tissues, and
relative Cd concentrations in edible tissues of crops ....... 92
xv
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Number
28 Relative increased Cd concentration in edible tissues
of crops grown on long-term sludge-amended soils 93
29 Relative uptake of trace elements to tissues of forage
crops 94
30 Relative Cd concentration in croos grown on naturally
Cd rich Salinas Valley soils 95
31 Cadmium exposure model from the 1979 Environmental
Protection Agency sludge application regulation and
background document (EPA, 1979a, 1979b), and the 1981
draft background document. Table shows intakes of FDA
food classes by the hypothetical teenaged male diet
model (1979) or average adult diet model (1981), and
relative Cd uptake by food groups 96
32 Effect of soil pH on relative increase above control
of Cd in edible crop tissues 97
33 Comparison of relative increased Cd uptake by food
groups based on different data sources 98
34 Average adult daily intakes of foods aggregated into
food groups on wet weight and dry weight basis 99
35 Food group aggregation of food intake results from
Pennington (1983) 101
36 Comparison of food intakes, relative increased Cd
uptake, and estimated increased dietary Cd in the
EPA (1979b), 1981 EPA draft, and present document 102
37 Effect of sludge source, and time after sludge
application on sludge adherence to tall fescue and
orr.hardgrass 103
38 Effect of forage crop species, clipping crop before
sludge application, and time after application on ad-
herence of spray-applied fluid sludges to five forage
crop species 104
39 Adherence of spray-applied liquid sewage sludge to tall
fescue or 'Pensacola1 bahaigrass and sludge content of
feces of cattle which rotationally graze these pastures 106
40 Summary of organic chemical concentrations
found in sewage sludges 129
xvi
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Number page
41 Summary comparing the number of organic chemicals
tested to the number of organics not detected in
sewage sludges or found in 10, 50 or 90% of the sludges 14?
42 Summary showing the distribution of median dry
matter concentrations for data reported in Table 40 144
43 Guidelines used by one food processing company for
interpreting the significance of residues in soils
being considered for growing root crops 145
44 Illustrative range of decomposition half-life for
organic compounds 146
45 Relative persistence and initial degradative reactions
of nine major organic chemical classes 147
46 Assumptions/values used for Metro analysis 148
47 Metro assessment of lifetime cancer risk for PCB 149
48 Metro assessment of lifetime cancer risk for B(a)P 150
49 Definitions for "relative toxicity" categories as
used by Naylor and Loehr (1982a) 151
50 Examples of chemicals commonly consumed or used and
their toxicity ratings 152
51 Toxicities and application rates for several
pesticides 153
52 Toxicities, sludge concentrations, and projected
application loadings for selected priority
pollutant organics 154
53 Times and amounts of sludge which must be ingested by
the rat or cow to reach 1050 doses of three sludge
organics 155
54 Evaluation of potential intake of three sludge
organics due to sludge or soil with sludge ingested
by a "pica" child or a cow 156
55 Safety factors for ingesting soil containing
pesticide and sludge organics 157
xvii
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SECTION 1
INTRODUCTION
In the last two decades, this nation has experienced a dramatic
increase in the construction of publicly-owned treatment works with a
corresponding increase in residual solids from treating the waste water.
Because the common methods of sludge disposal, such as landfill, incin-
eration and ocean dumping may not be adequate or suitable to accommodate
the ever-increasing quantities of POTW sludge, interest in applying sludges
to agricultural, forest and disturbed land has increased.
In addition to valuable plant nutrients, sewage sludge contains
variable concentrations of trace elements and synthetic organic compounds.
Concern for trace element contamination of the food chain from land appli-
cation of sewage sludge stems from extensive prior experience with phyto-
toxicity of elements such as Cu, Ni and Zn*from smelters and other sources
(Page, 1974) and from human and livestock toxicities associated with
environmental contamination by Pb, Hg, Cd, Cu, F, Mo, As and other trace
elements (Logan and Chaney, 1983).
The Ooint Conference on Recycling Municipal Sludges and Effluents
on Land (1973) raised the issue of trace element contamination from sewage
sludge but the available data base on actual land application research was
for the most part limited to pot studies with metal salts or sludge and a
few field experiments of no more than a few years duration (Logan and
Chaney, 1983). Subsequent conferences in 1980 (CAST, 1980) and 1983 (Page
et al., 1983) reexamined these issues in light of the increasing body of
research. By 1983 Logan and Chaney had concluded that the environmental
threat from sludges applied to land at agronomic rates was minimal when
existing federal regulations and guidelines (EPA, 1979a) were followed.
Phytotoxicity from sludge-applied metals was no longer believed to be of
concern except for high-metal content sludges applied at high loading rates
on acid soils.
Inputs of sludge-borne trace elements to agricutural land in the
U.S. has been governed since 1979 by EPA regulations and guidelines (EPA,
1979a). Under various provisions of existing federal statutes, cadmium
was the only trace element addressed and the regulatory approach was to
limit annual and cumulative applications of Cd to land, based on soil pH
and soil cation exchange capacity (CEC). In addition to federal regula-
tions, many states imposed limitations on cumulative applications of ele-
ments such as Cu, Ni, Zn (to protect against phototoxicity) and Pb (to
protect the human food chain) (Logan and Chaney, 1983).
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Implicit in this regulatory approach was the belief that bioavail-
ability of sludge-applied trace elements was controlled by soil processes
such as adsorption, chelation, and precipitation and that these processes
were reflected by soil properties such as pH and CEC. By 1980, however,
data from the increasing number of long-term field studies were beginning
to indicate that sludge properties could also influence trace element
bioavailability. The sludge's effect on bioavailabi1ity of trace elements
was postulated by Corey et al. (1981) and later reiterated by Logan and
Chaney (1983) as being due to binding of trace elements by the sludge
itself. A corollary to this hypothesis is the prediction that, at high
enough sludge application rates, the solubility of trace elements in soil
would b'. controlled by the sludge and not by the soil. The implication of
this theory, if true, is that the present regulation of Cd application to
land with sludge on the basis of Cd loading and soil properties alone
ignores what may be the equally or more important sludge properties, and
may overestimate crop Cd uptake particularly from low-Cd sludges.
Parallel to, but more recent than, the evolution of our knowledge
of trace element chemistry and bioavailability is the growing concern over
contamination of the environment by synthetic organic compounds. This con-
cern has led to recent but limited studies of synthetic organic compounds
in sewage sludges (Naylor and Loehr, 1982; Overcash, 1983; Overcash et al.,
1986) and proposals for their regulation. Under the 1979 regulations, only
polychlorinated biphenyls (PCBs) were specifically controlled (EPA, 1979a).
The research data base on the fate of sludge-borne organics is extremely -
limited, as is the information on the content of various synthetic organic
compounds in sludges. As a result, uncertainties as to the health effects
and threshold exposures of any of these compounds has made the evaluation
of risk from sludge organics difficult.
In 1984, EPA began a process to reevaluate the existing regulations
and criteria by which lane* application of municipal sewage sludge is
controlled in the U.S. The Office of Water Regulations and Standards
working with several technical advisory committees and with the Environ-
mental Criteria and Assessment Office (ECAO) screened those pollutants
found in sludge that had th» potential to adversely affect the food chain,
thus possibly requiring regulation. Based on this evaluation, ?nd using
a risk assessment approach developed by ECAO, hazard indices were developed
for a number of trace elements and synthetic organic compounds, and subse-
quently were used to evaluate the potential risk from land application of
sludge (EPA, 1985). Presently, a comprehensive risk assessment methodology
which will be used to evaluate potential risk from land application of
municipal sludge is under development by ECAO Cincinnati. The result of
this and related efforts will be development of revised or, if necessary,
new regulations governing land application and other means of sludge use
and disposal.
The development of hazard indices and their use in risk assessment
is limited by the availability of valid data for the pollutants of concern.
A critical review of the data bases u^ed to develop the hazard indices
revealed that they often included studies involving metal salts addition
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rather than sludge only sources and did not include many of the long-term
field studies with sludges which were conducted in the late 1970's and
early 1980's and which are now beginning to enter the literature.
The purpose of this workshop was to brin^ together researchers in-
volved in land application of sewage sludge to evaluate their most recent
data and, in light of this information, to assess the validity of assump-
tions made in the risk assessment process on fate of sludge contaminants.
In this report, pertinent unpublished data from experiments in progress
and from papers submitted for publication were supplied by the partici-
pants and incorporation in the report where appropriate. Specifically,
the workshop wat organized into five groups and the topics and questions
addressed by group are given below:
WORKGROUP I. Effects of_ Spi1 Properties 0£ Accumulation of Trace
Elements by_ Crops
1. What information is most relevant for defining background levels
of trace elements in soils and crops? Are background levels in
soils related to soil properties?
2. What soil properties have a direct role in regulating plant uptake
of trace elements and can these be quantified?
WORKGROUP II. Effects p_f Sludge Properties on Accumulation of Trace
Elements by_ Crops
1. Is there evidence that concentration and chemical form have a sig-
nificant effect on plant uptake of sludge-applied trace elements?
2. Are there synergistic or antagonistic effects of certain trace
elements? If so, are they sufficiently well quantified to be con-
sidered in setting criteria?
WORKGROUP III: Effects of Long-Term Sludge Applications on Accumulation
of Trace Elements ])y_ Crops
1. Do the long-term field plot data show any significant differences
in plant uptake of annual vs. cumulative sludge-applied trace ele-
ments?
2. What is the evidence for increases vs. decreases of plant uptake
of sludge-applied trace elements with time after sludge applica-
tion?
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WORKGROUP IV: Transfer of Sludge-Applied Trace Elements to the Food
Chain
1. How can plant uptake rates be used to provide a basis for "good
practice" and "worst case" risk scenarios?
2. Are there sludges so low in trace constituents that no limits
should be applied?
3. What effect may routes of exposure from land application other
than crop uptake have upon "good practice" or "worst case" risk
scenarios (e.g., direct ingestion of soil from sludge-treated
land)?
WORKGROUP V: Effects of Trace Organics jn Sewage Sludges on Soil-PIant
Systems and Assessing Thei r Risk to Humans
1. How do soil and sludge properties influence rates at which sludge
organic matter is decomposed?
2. What synthetic organic compounds are absorbed by plants and what
is known concerning the machanism of absorption?
Although the complete list of trace elements for which hazard
indices were developed was addressed in the workshop, the focus of
Workgroups I-IV was limited to Cd, Zn, Mo, Fe, Pb and Se, as the other
trace elements usually present in sludges were considered to present
little potential risk to the human or animal food chain.
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SECTION 2
EFFECTS OF SOIL PROPERTIES ON
ACCUMULATION OF TRACE ELEMENTS BY CROPS
INTRODUCTION
The fate and effects of sewage sludge constituents in a soil-plant
system are influenced by factors such as climate (rainfall and tempera-
ture), management (irrigation, drainage, liming, fertilization, addition
of amendments), and composition of the sewage sludge. In addition, soil
properties affect the chemical reactions and processes which occur after
application of sewage sludge to a soil. Soil properties that affect the
reactions and resultant plant uptake of sewage sludge constituents
include pH, organic matter, cation exchange capacity, iron and aluminum
oxides, texture, aeration, specific sorption sites and water availabi-
lity. Mean values for selected soil properties are shown in Table 1.
Many of these factors are interrelated and thus create a rather complex
medium involving chemical and microbial reactions. The factors which
tend to be stable are texture, CEC, organic matter, and iron and aluminum
oxides. Factors such as pH, water content, and aeration (relates to
water content) vary frequently or are easier to adjust. For example,
soil pH can be increased by lime additions while ammoniacal fertilizers
acidify soils.
Soil cation exchange capacity (CEC) is dependent on soil proper-
ties such as organic matter, pH, and type and percentage of clay. Thus
it serves as an easily measured, integrating parameter to characterize a
soil. Soil pH, like CEC, is an easily measured soil property which pro-
vides background information relevant to assessing elemental availability
to plants. The soil pH measured in the laboratory is a representation of
that which occurs under field conditions. The pH at any individual site
in the soil may be significantly different from the pH of other sites.
For example, the pH at the root-soil interface may be lower because of
exuded organic acids. Due to differential uptake of cations and anions,
the pH in the root cylinder of active root hairs may be lower than in
older parts of the root system (RCmheld and Marschner, 1986). Also, pH
reductions with time in sludge-treated soils are due to protons generated
during oxidation of reduced forms of N and S mineralized from sludge
organic matter. Similar pH reductions occur after addition of fertili-
zers, particularly those containing ammonium.
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Plant uptake of elements from the soil solution initially requires
positional availability to the plant root. Either the element must be
moved to the root through diffusion or mass flow processes, or the root
must grow to the element. The element must then occur in a form which can
move into the plant via the uptake mechanism. This transfer requires that
the element move through a solution phase; thus, water solubility and a
variety of complexation, chelation, and other chemical reactions become
important.
Considerable research on microelement uptake by plants has been done
with metal salts. However, metals applied to a soil as a salt, co.nmonly a
sulfate, chloride, or nitrate salt, accumulate in plants more readily than
the same quantity of metal added in sewage sludge (Logan and Chaney, 1983;
Dijkshoorn et al., 1981). Metal salt additions to soils can cause for-
mation of metal chloride complexes and ion pairs which may increase metal
diffusion and plant uptake (Bingham, 1980). Metals in sludges are often
associated with the insoluble inorganic components (such as phosphates,
sulfides, and carbonates) and are not readily plant available (Soon, 1981;
Page, 1974). Elemental uptake by plants grown in soils treated with metal
salts or sewage sludge amended with metal salts will be higher than actu-
ally exists for equal amounts of metal contained in sewage sludges. If
results from sludge-treated soils are available, human or animal exposure
models should be based on these observations and not on extrapolation of
data from additions of soluble metal salts to soils.
To predict the impact of sludge use on elemental content in the
human diet, plant uptake of trace elements from sewage sludge should be
measured in field experiments. Greenhouse or pot study experiments gen-
erally create a root environment which increases the magnitude of trace
element uptake (deVries and Tiller, 1978; Davis, 1981). The enhanced
uptake of trace elements generally results from four factors: 1) the
use of acid forming fertilizers; 2) increased soluble salt content from
fertilizers in a smaller soil volume than in the field; 3) root confine-
ment; and 4) unnatural watering patterns. However, greenhouse pot experi-
ments can have value if plants are harvested in an early growth stage or
if pots are sufficiently large to allow unrestricted root growth and
natural water drainage. In addition, pot experiments are valuable for
evaluating factors affecting plant uptake of trace elements, realizing
that plant concentrations may differ from those found in a field study.
BACKGROUND LEVELS OF TRACE ELEMENTS
The trace element content of crops is a function of the plant
available level in the soil and the modifying influences of soil chemical
and physical properties. Trace element levels of soil vary with the
parent material. Except for a few special cases (Lund et al., 1981),
plant tissue concentrations are not positively correlated with the total
trace element content in untreated soils.
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Background levels of metals have been summarized for soils from
Ohio (Logan and Miller, 1983), Minnesota (Pierce et al., 1982), and
from 3,305 sites across the U.S. (Table 1; Holmgren et al., 1986).
Although quite extensive, the data contained in Table 1 were selected
on the basis of being agricultural soils removod from mobile and point
sources of contamination and means representative of all agricultural
soils in the U.S. may differ from those presented in Table 1. For most
elements, the minimum and maximum values differ by 2 to 3 orders of magni-
tude. The unusually high mean values for Pb in soils from Virginia and
West Virginia are due to metalliferous deposits near a few sites. One
statistical approach to evaluating whether a soil has been impacted by
industrial sources of metals is to compare trace element concentrations
with the concentrations at the 95th percentile. As shown, the 95th
percentile for soil metals (Table 2) is appreciably smaller than the
maximum value. Current U.S. EPA Cd limits imposed on sludge applications
(U.S. EPA, 1979a) are 5 to 10 fold greater tnan a liberal estimate of
natural background levels. Further, a soil's total trace element con-
tent enables a preliminary evaluation of metal contamination from prior
w^ste disposal activities. The total soil metal data also allows iden-
tification of sites where parent material contains unusually high levels
of a given element.
The total metal concentration reported for soils may be influenced
by the analytical methods employed, especially if a dissolution procedure
is used. The total metal content in a soil requires either a non-
destructive analytical method such as neutron activation analysis or a
total dissolution of the soil matrix with strong acids plus HF, or
partial dissolution with boiling 4^ HN03, or refluxing HN03-HC10,,
(Lund et al., 1981). Once the soil matrix is dissolved, standard atomic
absorption or equivalent methods can be used to analyze metals in the
digest.
A need still exists for a standard extractant to assess the level
of plant available metals in soils. Logan and Chaney (1983) summarize
recent research on common soil metal extractants. The DTPA-TEA reagent
used to detect trace metal deficiencies in calcareous soils (Lindsay and
Norvell, 1978) has been used to monitor soils. Other extractants which
h?.ve been used include double acid (HC1 + H2SOit), dilute HC1, Ca(N03)2,
and water saturation extracts. One approach is the "agnostic soil test
used on a routine basis for soils treated with sludges in Pennsylvania
(Baker and Amacher, 1981). This method involves equilibrating soils with
a test solution containing cations (Ca, Mg, K, and H) at the activities
and ratios determined to be near the minimum for optimum growth of plants.
The solution also contains 4x10"** _M DTPA (diethylene triamine pentaacetic
acid) to render a small exchange of trace metals. The extracted metal
provides a measure of the labile pool and the metal-DTPA formation
constants are used to calculate activities of trace metals (Ba*er and
Amacher, 1981). However, no method used has been proven acceptable to
predict plant uptake of metals from a wide range of soils (Logan and
Chaney, 1983). Ideally, extraction of a soil, sewage sludge, or a sludge
amended soil could be used to predict the eventual plant uptake of trace
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elements. With this approach, bioavailable elements of both the soil and
sewage sludge could be assessed. A procedure is also needed for quan-
titative measurement of specific sorption sites in soils.
Information on the background levels of metals in crops is also
needed to evaluate the impact of metals entering animal or human diets.
A recent survey has been conducted by the USDA-EPA-FDA for a variety of
crops grown in major regions of the U.S. (Wolnick et dl., 1983a, 1983b,
1985). As previously discussed for soils from the same survey, the data
presented in Table 3 were for crops grown on soils removed from mobile
and point sources of contamination. The data, therefore, may not be
representative of the crops for U.S. agricultural soils in general. The
Cd, Zn and Pb content of 12 common crops varies by 1 to 3 orders of mag-
nitude (Table 3). Median concentrations of Cd in leafy vegetables were
highest (spinach, 800 yg/kg); median concentrations of Cd in root crops
ranged from 68 ug/kg (peanuts) to 160 gg/kg (carrots); and for grains the
median Cd concentrations varied from 4 pg/kg (field corn) to 45 ug/kg
(soybeans). Somewhat similar median concentrations of Pb in crops were
observed (Table 3). Median concentrations of Zn across the 12 crops
tested, however, were more uniform. They varied from a low of 15 ug/kg
(rice) to a high of 46 ug/kg (lettuce).
REGIONAL STUDY OF SLUDGE USE
The regional project W-124 (Optimum utilization of Sewage Sludge
on Cropland) has collected data on the uptake of metals by barley grown
at 15 locations in the U.S. (Table 4). At each location, the same
sewage sludge sample from Chicago was applied either at 100 mt/ha in the
initial year or at 20 mt/ha each year for 5 consecutive years. A 100 mt/ha
application of this sludge resulted in addition of 20 kg Cd/ha, the upper
limit allowed by current federal regulations (U.S. EPA, 1979a). Barley was
also grown on soils fertilized according to soil test recommendations.
Barley leaf and grain and soil samples were collected and analyzed for Cd,
Zn, Cu and Ni each year (Tables 5 to 8).
The major conclusions from this experiment are summarized as:
(1) The metal content of barley grain and tissue were similar for
untreated and NPK fertilized soils.
(2) Yearly variations in plant metal composition were observed for
sludge-treated and untreated plots at most locations.
(3) Metal levels in a plant grown on untreated soil could exceed
those found at another location where sewage sludge was added to
the soil.
(4) Cadmium concentrations in barley leaf tissue were greater than
those in grain.
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(5) Sewage sludge application increased metal concentrations for soil
and plant tissues with a single 100 mt/ha or annual applications of
20 mt/ha.
(6) The initial application of 20 mt/ha caused a greater increase in
plant metal levels than the subsequent 4 annual sludge treatments.
(7) The increase in Zn and Cd in plants grown on sewage sludge treated
soils was greater than for Pb, Cu, and Ni.
(8) After the fifth year, the concentrations of Cd and Zn in the barley
tissue depended only on the total amount of sludge applied and not
upon the frequency of application (i.e., 100 mt/ha in year 1 vs.
20 mt/ha in years 1 through 5).
SOIL PROPERTIES INFLUENCING THE ACCUMULATION
OF TRACE ELEMENTS BY PLANTS
The accumulation of trace elements by plants is a reflection of the
influence of soil physical properties on plant growth, soil hydraulic pro-
perties and chemical properties such as pH, CEC, and clay mineral sorption
reactions.
Physical Properties
Soil particle size distribution (i.e., texture), structure, and
depth are important in determining soil hydraulic properties such as poro-
sity, permeability and drainage rates; these properties in turn influence
soil moisture content and aeration/respiration which impact the type and
rates of both soil microbial activity and chemical reactions, as well as
plant root development and growth rates.
Although soil texture, hard pans, and other physical features can
be observed in the field or identified from soil maps and likely influence
soil chemical reactions, clear identification of these effects in relation
to plant uptake of metals has been difficult. Soil texture, however, has
been recommended as a quantifiable soil property to limit metal loadings to
soils in the Northeast (Baker et al., 1985), although experimental data are
not available to support this concept. Presumably as the texture of the
soil becomes finer (i.e., greater clay content), the limiting application
rates may also increase.
Soil pH
The impact of pH on metal accumulation by plants has been exten-
sively reviewed (Logan and Chaney, 1983) and little additional pertinent
data has been reported which would refute their conclusions. Basically,
metal availability (except for Mo and Se) tends to decrease with liming.
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Solubility of solid phase minerals including metal carbonates, phosphates,
tes, and sulfides is enhanced at low soil pH (Lindsay, 1979); however, the
importance of this phenomenon in sewage sludge-treated soils has not been
adequately defined by solid phase equilibria studies.
Soil pH is one of the easier characteristics to measure but care
must be exercised in interpreting results. The pH measured in a soil-
neutral salt suspension will be lower than the pH measured in a soil-water
system, although some exceptions exist. When pH was measured at 19 sites
over a growing season, a maximum variation of 1.6 pH units was reported for
measurements in a 1:2 soil:water suspension or in 0.01 ^ CaCl2 (Collins et
al., 1970). Bates et al. (1982) found similar variations in Ontario, Cana-
da, soils, whether pH was measured in 0.01 _N CaCl2 or in a soil-water satu-
rated paste. These authors found greater variation in the pH for soils
cropped to corn which received large applications of N fertilizer than for
soils cropped to alfalfa.
The water content of the soil and its electrolyte content affects
soil pH readings significantly (Thomas and Hargrove, 1984). Bates et al.
(1982) measured the pH in 245 soils and obtained the following pH values:
pH 5.77 _+ 0.91 for a soil:water saturated paste; pH 5.26 _+ 0.91 for a 1:2
soil:solution of 0.01_NCaCl2; and pH 5.00 ± 0.95 for a 1:2 soil:solution
of 1 _N KC1. The differences between methods varied with pH, such that:
PHH20 = °-82 ± °-94 PHCaC12> R2 = 0.904. This variability emphasizes
the need for use of a standardized method to measure soil pH.
Soil organic matter and the resultant impact on pH buffering can
influence the effect of liming on trace element uptake. Liming acid
soils to pH 6.5 as measured in water paste (1:1 soil-water ratio), often
is costly and can require considerable amounts of lime. Some trace
element deficiencies (e.g., Fe, and Mn) may occur as pH approaches neu-
trality. In addition, the increase in soil pH may not reduce markedly
the uptake of trace elements from sludge treated soils, especially for
crops not accumulating metals. Pepper et al. (1983) attributed the inef-
fectiveness of liming on reducing Cd uptake oy corn to a drop in soil pH
during the growing season. Others (Hemphill et al., 1982; Giordano and
Mays, 1981) have observed similar effects on metal content of corn grain.
In general, lime applications reduce uptake of Zn and Ni more than Cd
(Singh and Narwal, 1984).
Metal uptake by plant species may vary in response to liming.
Giordano (CAST, 1980) observed that liming reduced Zn concentrations in
soybean seed to a greater extent than in corn grain or cotton seed.
Whereas the Ni content of soybean and cotton seed was depressed by lime,
the content of Cu in all crops and plant parts was relatively unaffected.
Soil pH influences uptake of most metals at least to some extent,
but the current recommendativ/n of pH 6.5 should be reconsidero-i for
food-chain agricultural soils since some reports indicate adequate
control of metal uptake at pH 6. For example, Hajjar (1985) conducted
a greenhouse study using soils treated with sludge at rates from 0 to
10
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27 mt/ha. Replicate soils were adjusted to pH <5.6, pH 5.7-6.0, and pH
>6.4 with either \\2SQ^ or Ca(OH)2. For both tobacco and peanut, plant
tissue concentrations of NT, Zn, and Cd decreased with increasing soil
pH; however, in general, metal uptake by peanuts was similar at pH >6.4
and pH 5.7-6.0, suggesting that attainment of pH 6.5 is not essential
for minimizing plant availability of Ni, Zn and Cd. A soil pH =6.0 may
be equally acceptable to regulate metal uptake. This conclusion is sup-
ported by field data with barley (Vlamis et al., 1985). More specific
pH values where accumulator crops such as tobacco are grown on highly
buffered acid soils may be required.
It has not been demonstrated that pH control to prevent transfer of
metals into the food chain is necessary on forested sites. If a forest
site is shifted to agricultural use or residential development, the soil
pH should be adjusted by limestone addition at that time to meet existing
standards.
Iron
Iron deficiency chlorosis on calcareous soils is a unique soil fer-
tility problem worldwide. Application of sewage sludges can correct Fe
chlorosis problems (McCaslin and O'Connor, 1982; McCaslin et al., 1985).
In New Mexico, where Fe chlorosis affects large acreages of farmland,
sludges applied at 34 to 90 mt/ha increased the levels of plant available
Fe, Zn, and P in a severely Fe-deficient calcareous soil. Sorghum grain
yields from sludge-treated soils were significantly higher than those
receiving dairy manure or chemical fertilizers. Uptake of Zn and Cd by
barley was minimal after sludge application to calcareous soils in the
regional W-124 study (Tables 5 to 8).
Molybdenum
Soon and Bates (1985) present data which show that the application
of a lime-treated sewage sludge supplying 0.21 kg Mo per hectare per year
raised the Mo concentration in both bromegrass and corn stover above the
control by significant margins (0.29 vs. 1.16 mg/kg for bromegrass, and
0.20 vs. 0.47 mg/kg for corn stover). A non-significant increase
occurred in the Mo content of corn grain even though the lime-treated
sludge increased soil pH from 7.4 to 8.1. In the same experiment,
application of Al- and Fe-treated sludges raised the Mo concentration
in bromegrass from 0.29 to 0.69 and 0.46 mg/kg, respectively. The amount
of Mo added with the Al- and Fe-treated sludges averaged 2.18 and 1.66 kg
per hectare per year, respectively.
Pierzynski and Jacobs (1986b) applied a sludge containing 1500 mg
Mo/kg ft rates of 42 and 94 mt/ha (equivalent to 63 and 141 kg Mo/ha). Dur-
ing the three year study the Mo content of corn seedlings (25-31 cm height)
ranged from 47 to 724 mg/kg for those grown with the higher sludge applica-
tion as compared to a range of 1.9-6.0 mg/kg in those from control plots.
11
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Similar increases were observed for soybean seedling tissue (18-23 cm
height) and diagnostic leaf tissue of both crops. At the end of the study,
soil pH had increased from 4.6 in the control to 6.9 in the 94 mt/ha sludge
treatment. This change in soil pH may explain the increase of Mo con-
centration in plant tissue. The Mo content of corn grain also increased
with time (0.2 to 0.6 mg Mo/kg for control and 2.0 to 6.9 mg Mo/kg for the
high sludge rate) but the effect on the Mo concentration in soybean seeds
was greater than on corn grain (8.9 to 19.9 mg Mo/kg for control and 122 to
242 mg Mo/kg for the high sludge rate). Elevated Mo levels did not affect
growth of either crop.
A greenhouse study has shown that uptake of Mo by ryegrass and white
clover was enhanced more by addition of up to 0.41 kg Mo/ha from sludge
than from Na molybdate (Williams and Gogna, 1983). However. Mo additions
from sludge did not always enhance Mo uptake by corn, soybeans, and alfalfa
compared to Na molybdate, when rates of Mo from 60 to 400 kg Mo/ha were
used (Pierzynski and Jacobs, 1986a). Results from another study indicated
that sludge applications, especially to high pH soils, tended to reduce the
Cu/Mo ratio of the affected vegetation (Soon and Bates, 1985). Under these
conditions the likelihood of Mo induced Cu deficiency in grazing ruminant
animals consuming the forage is enhanced.
Selenium
Sludge application to agricultural soils did not increase Se uptake
by crops (Dowdy et al., 1984; Logan et al., 1987). In these studies, Se
inputs ranging from 0.024 to 66 kg/ha did not result in significant accumu-
lation of Se in plant tissue. Unless additional data become available to
indicate otherwise, Se should not be a limiting factor in land application
of municipal sludges.
Cation Exchange Capacity
Cation exchange capacity has been used as the primary soil property
to govern metal loadings for the past 10-15 years. The basic concept ori-
ginated in England and was adopted to prevent metal toxicities to crops;
however, its use was mainly intended for soils 'where organic matter con-
tributes a significant fraction to the CEC.
Method of Analysis
One problem when using CEC to regulate sewage sludge addition to
soil is that no single method of determining CEC is universally accepted
for its determination. The two most widely used methods are: 1) summation
of exchangeable cations, and 2) saturation with either a buffered or unbuf-
fered index cation. The above mentioned methods can give vastly different
CEC values for the same soil. Hence, the recommended total metal loading
rate and subsequent metal uptake by plants can vary depending upon the
method used to determine CEC.
12
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Criteria developed under 40 CFR part 257 of the Resource Conserva-
tion and Recovery Act (RCRA) state that the method to be used for CEC
analysis should depend upon the type of soil (US EPA, 1979b). For dis-
tinctly acid soils the summation method should be used and for neutral,
calcareous, or saline soils the sodium acetate method should be used (see
Rhoades, 1982). If CEC is to be used as an index for metal loadings,
then the method of analysis must be standardized.
Correlation of CEC and Plant Uptake of Metals
Research on the relationship between CEC and plant uptake of metals
has been minimal and results have been conflicting (CAST, 1980; Logan and
Chaney, 1983). Hinesly et al. (1982) conducted a study to determine the
effect of CEC on Cd uptake by corn. Soil samples of the 81 horizon of the
Ava series and the Ap horizon of the Maumee series were separately mixed
with samples of the Plainfield series to obtain soil mixtures having a
CEC from 5.3 to 15.9 cmol(+)/kg(meq/100 g). Additions of CdCl2 or 100 mt/ha
of dried, digested sewage sludge were used to provide a soil-Cd concentra-
tion of 10 mg/kg. Corn was grown in pots of each mixture and harvested at
3- and 7-week intervals for tissue analyses. The soil CEC inversely
affected the uptake of Cd by corn when Cd was supplied as a soluble salt,
but not when it was supplied as a constituent of municipal sewage sludge.
This conclusion was confirmed in greenhouse studies conducted by Korcak
and Fanning (1985).
In terms of phytotoxicity, research data available indicates that the
maximum metal loadings allowed in the CEC-metal limit approach are conser-
vative. Furthermore, a large degree of safety is provided by the CEC-metal
limit approach. For example, no phytotoxicities have occurred in studies
where the total metal loading equals or greatly exceeds those recommended
in the CEC table at pH 6.5 (Chang et al., 1983; Ellis et al., 1981; Hinesly
et al., 1984a; Vlamis et al., 1985). These observations indicate that the
present practice of using CEC as a basis for establishing metal-loading
limits should be abandoned.
CONCLUSIONS
The following conclusions are supported by previous literature or by
new information reported in this total report.
1. Conclusions on the impact of sewage sludge on trace element uptake by
plants should be based on field studies rather than greenhouse or pot
studies. Plant tissue concentrations obtained in greenhouse or pot
studies may not be representative of those obtained in the field
unless root growth is not restricted and accumulation of soluble
salts is avoided.
13
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2. Concentrations of trace elements in crops grown in soils treated with
metal salts exceed those of crops grown on sewage sludge-amended
soils and should not be used to predict dietary intake.
3. Soil physical properties are related to trace element uptake by plants
but current data does not allow quantification of these relationships.
4. Due to natural variations in soil and crop characteristics, trace ele-
ment content of crops grown on untreated soils differ.
5. The soil pH value used in conjunction with application of sewage sludge
should be measured on the sewage sludge-soil mixture or on the
untreated soil using a 1:1 soil water ratio, realizing that 0.01 M[
CaCl2 is a preferred matrix to compensate for soluble salt levels in
sewage sludge or soils.
6. The impact of the pH reduction on increased metal uptake is more marked
with high metal sludges and crops responsive to metal additions.
7. The relationship of either CEC or texture to metal uptake in sewage
sludge-amended soils has not been conclusively demonstrated under field
conditions. The current guidelines that are based on the use of CEC to
limit metal additions to soils are not supported by current long-term
field experimentation.
8. Trace element deficiencies rather than toxicities are a major concern
in soils containing free CaCOa. Sewage sludge additions have been used
to correct Fe deficiency in calcareous soils. Based on plant uptake,
Mo is the principal metal of concern in calcareous soils treated with
sewage sludge.
14
-------
TABLE 1. METAL AND ORGANIC CARBON CONTENTS, CEC, AND pH FOR SOILS FROM SELECTED SITES IN THE
CONTINENTAL UNITED STATES (FROM HOLGREN ET AL., 1985).*
State
Arizona
Iowa
Missouri
Minnesota
California
Kansas
U. Virginia
Wisconsin
Montana
N.Dakota
Idaho
Ohio
Colorado
Nebraska
Florida
New YorK
Oregon
S.Dakota
Michigan
S.Carolina
Georgia
Alabama
Maryland
N.Carolina
Nt
14
85
33
89
283
38
40
164
33
30
54
81
89
72
89
173
106
44
86
10
146
92
57
242
Cd
Mean
0.24
0.24
0.27
0.30
0.31
0.32
0.32
0.35
0.37
0.37
0.38
0.38
0.39
0.39
0.44
0.45
0.49
0.56
0.94
0.03
0.05
0.06
0.08
0.09
SD*
0.06
0.07
0.08
0.09
0.28
0.07
0.34
0.20
0.07
0.21
0.16
0.15
0.30
0.18
0.28
0.36
0.45
0.12
0.30
0.01
0.05
0.07
0.02
0.07
Pb
Mean
14
14
20
12
12
15
646
12
11
10
11
19
16
14
10
17
11
14
16
10
8
7
11
10
SD
4
4
5
2
12
2
1127
7
2
5
2
4
13
3
10
5
7
3
6
3
5
4
4
6
Zn
Mean
• (mg/kg)
72
62
60
71
93
53
84
59
75
69
68
89
85
58
88
64
71
96
80
12
18
16
31
15
Cu
SD
18
16
9
20
41
10
37
29
13
42
24
41
42
25
67
37
30
25
37
5
19
7
16
14
Mean
39.4
21.3
18.8
22.3
46.6
15.6
96.9
37.7
21.0
22.0
22.0
28.1
19.4
17.3
103.7
74.8
33.4
30.3
111.5
4.1
7.0
8.1
8.1
8.9
SU
11.3
5.7
3.8
4.5
30.2
2.5
143
36.8
4.6
12.9
' 8.0
11.7
8.0
7.7
88.2
77.5
16.5
8.8
75.6
1.7
5.3
5.9
2.6
12.9
Ni
Mean
28.7
28.2
24.8
30.0
74.3
20.4
23.3
16.4
26.1
31.1
25.2
28.2
15.9
21.7
10.3
19.5
27.1
42.3
14.7
4.1
9.0
11.3
12.4
8.6
Su
6.5
8.1
3.5
5.5
63.9
3.4
13.1
9.4
5.5
16.9
7.9
9.7
7.2
12.3
7.7
10.1
6.0
18.8
8.6
1.8
7.9
6.8
4.4
13.1
PH
Mean
7.7
5.9
6.5
5.9
7.2
5.6
5.3
5.9
6.8
7.1
7.4
' 6.4
7.7
6.4
5.8
5.4
6.1
6.5
5.7
4.2
5.9
5.8
5.7
5.1
SU
0.5
0.7
0.7
0.8
0.8
0.9
0.7
0.8
0.9
0.8.
1.0
0.6
0.5
0.8
0.9
0.8
1.0
0.9
0.7
0.3
0.5
0.7
0.7
0.5
Onjanic C
Hdan SIT
(
0.37
2.53
1.80
3.01
1.00
1.14
2.99
14.64
1.41
1.99
1.16
1.83
0.80
1.49
26.80
16.71
3.36
2.62
28.43
2.27
0.74
0.65
0.75
0.69
*)
0.14
0.94
0.61
0.90
0.88
0.18
2.19
16.45
0.38
0.76
0.54
0.54
0.29
0.48
18.11
17.32
5.03
0.49
5.13
1.00
0.26
0.30
0.17
1.74
CEC
Mean SD
(mmol (+)/kg)
143 36
282 77
200 46
342 89
214 140
192 25
141 78
55G 552
171 35
260 151
173 39
189 58
137 49
199 51
970 657
767 769
338 279
300 49
1358 315
81 22
35 15
31 19
44 21
74 84
(continued)
-------
TABLE 1 (continued)
Cd
State
Oklahoma
Virginia
Texas
Delaware
Maine
Arkansas
Illinois
New Mexico
Washington
Pennsylvania
Louisiana
Indiana
Nt
94
46
362
4
31
62
135
41
122
45
133
80
Mean
0.10
0.14
0.16
0.17
0.17
0.18
0.20
0.20
0.20
0.21
0.22
0.23
SD*
0.08
0.07
0.11
0.06
0.03
0.15
0.09
0.07
0.08
0.24
0.14
0.14
Pb
Mean
7
98
9
10
13
15
16
11
9
24
16
13
SD
3
118
5
2
. 2
8
3
3
4
25
16
5
Zn
Mean SD
(mg/kg) - -
33 47
59
40
• 25
74
45
56
47
66
30
64
51
29
27
9
13
33
21
14
19
27
51
?S
Cu
Mean
4.0
9.4
2.2
5.0
0.7
5.5
7.2
6.1
7.3
5.3
2.1
7.0
SD
13.3
28.4
6.9
2.2
24.0
8.8
5.6
5.7
10.5
28.4
16.6
9.8
Mean
14.9
22.3
15.9
6.6
41.5
17.2
20.6
16.9
29.0
10.4
25.3
16.5
N1
SD
14.4
12.0
10.2
4.4
6.4
9.8
7.0
5.0
16.7
7.8
18.7
8.6
pH
Mean
6.4
5.6
7.1
6.3
4.5
5.7
6.0
8.2
6.3
6.1
5.7
5.7
SD
0.6
0.8
1.0
1.1
0.5
0.3
0.9
0.7
0.1
0.9
0.6
0.7
Organic C
Mean
SD
CEC
Mean SD
(1) (mmoii
0.65 0.23 94
2.07
0.78
0.55
2.25
1.07
1.79
0.58
1.48
1.36
1.37
1.35
0.97
0.41
0.22
0.43
0.32
0.77
0.19
2.71
0.59
0.65
0.55
92
153
4
134
145
195
142
141
90
238
130
l+JAg
54
34
105
1
18
97
82
48
59
24
174
57
*So1ls were selected from sites removed from mobile and point source contamination; values reported
for metals may not be representative of U.S. soils in general. Data are expressed on a
dry weight basis.
tN = number of soil sites analyzed
*SD * standard deviation
-------
TABLE 2. TRACE ELEMENT CONCENTRATIONS FOR SOILS FROM SELECTED SITES IN
THE CONTINENTAL UNITED STATES (HOLMGREN ET AL., 1985).*
Mean
Median
Geometric mean
Std. deviation
Maximum
Minimum
50th percent.
95th percent.
Cd
0.27
0.20
0.17
0.26
2.3
0.01
0.20
0.79
Pb
17
11
ll(16)t
141
4,109
0.2
11
26
Zn
57
54
43(48)
39
402
1.5
54
127
Cu
30
19
18(17)
42
735
0.3
19
98
Ni
24
18
16(13)
27
269
0.3
18
56
*Soils were selected from sites removed from mobile and point source con-
tamination; values reported for metals may not be representative of U.S.
soils in general. Data are expressed on a dry weight basis.
tGeometric mean of U.S. soils from Shack!ette et al. (1984).
17
-------
TABLE 3. TRACE ELEMENT CONCENTRATIONS (DRY WEIGHT) IN THE EDIBLE PART OF CROPS GROWN ON UNTREATED
SOILS.*
CD
Crop
Lettuce
Min Max
34 3800
Spinach 160 1900
Potatoes
Wheat
Rice
Sweet corn
Field corn
Carrots
Onions
Tomatoes
Peanuts
Soybeans
*Data are for
fWoln1ck et al
*Wolnick et al
§95th percenti
9 1000
5 220
<1 250
0.5 230
<1 350
15 1200
11 340
45 790
11 660
1 1200
Cdt
Median
435
800
140
36
5
8
4
160
90
220
68
45
95th§
2100
1480
360
125
34
57
67
786
240
610
219
180
crops grown in areas removed
. (1983a,
. (1985)
le
1983b)
Zn*
Pbt
Min Max Median 95th
-
13
17
5
11
7
28
12
3
6
12
17
32
from
- - -
110
200
.1 35
76
.7 23
55
39
.8 61
.1 33
35
63
70
mobile
mgAg
46
43
15
29
15
25
22
20
16
22
31
45
and
78
128
27
48
20
46
30
48
26
29
42
59
point sources
Min Max
36
240
1
1
<1
7
<1
10
2
<1
<1
3
of
1700
2300
2200
770
80
.6 260
3600
1100
720
460
200
350
Medi
ug/'kg
190
530
25
21
5
9
6
55
38
27
8
36
an 95th
994
1180
97
168
26
62
32
236
95
108
27
99
contamination.
-------
TABLE 4. GENERAL CHARACTERISTICS OF SOILS USED IN W-124 STUDY.
Location Soil
AL
AZ
CA(D)
CA(G)
CO
FL
IL
IN
MD*
MI
MN
NE
OH
OR
LIT
Ml
Decatur clay (Rhodic Paleudult)
Pima clay loam (Typic Torrifluvent)
Domino loam (Xerollic Calciorthid)
Greenfield sandy loam (Typic Haploxeralf)
Nocono clay loam (Aridic Argiustoll)
Lake fine sand (Typic Quartzipsamment)
Ipava silt loam (Aquic Argiudoll)
Chalmers silt loam (Typic Haplaquoll)
Christiana sandy loam (Typic Paleudult)
Celina silt loam (Aquic Hapludalf)
Port Byron silt loam (Typic Hapludoll)
Sharpsburg silty clay (Typic Argiudoll)
Celina silt loam (Aquic Hapludalf)
Willamette silt loam (Pachic Ultic Argixeroll
Millville silt loam (Typic Haploxeroll)
Piano silt loam (Typic Argiudoll)
Sand
- - -
240
330
200
100
250
942
-
120
-
510
90
50
230
)360
340
40
Silt
• gAg
340
340
380
270
400
35
-
CIO
•
380
660
610
610
442
530
820
Cation Exch
Clay capacity
. Organic
C
(mmol(+)/kg) (g/kg)
420
330
420
630
350
23
-
270
-
110
250
340
160
198
130
140
91
280
140
90
230
14
266
251
59
120
220
—
120
150
190
197
11.3
11.0
8.9
5.1
13.2
7.0
35.1
23.7
10.5
12.3
24.4
20.3
13.5
13.4
11.6
26.2
*MD(L) and MD(H) refers to unamended and CaCO amended soils, respectively.
-------
TABLE 5. CONCENTRATIONS OF Cd IN DTPA SOIL EXTRACTS AND IN LEAF AND GRAIN
OF BARLEY GROWN IN 15 LOCATIONS.
OTPA Extract
Location*
AZ
CA(G)
CA(D)
CO
FL
IN
HO(L)
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
20
mt/ha/y
1.64
1.59
3.00
3.41
3.52
0.83
0.95
1.45
1.52
2.39
0.75
1.48
2.05
1.95
2.13
NO
0.34
0.50
1.77
1.25
0.76
2.06
2.93
4.35
2.70
NO
NO
NO
NO
NO
NC
0.70
o.ao
2.13
3.54
100
mt/ha
4.86
4.00
4.03
3.52
3.63
3.85
1.35
1.40
1.26
1.18
4.80
3.05
2.40
1.77
1.40
NO
1.65
2. OS
2.29
2.63
4.58
4.50
4.05
5.45
3.70
0.39
0.41
2.64
2.41
5.35
NO
3.75
3.04
3.20
3.13
NPK
0.30
0.03
0.25
0.25
0.19
0.10
0.10
0.10
0.10
0.06
0.10
0.10
0.10
0.10
0.06
NO
0.09
0.13
0.12
0.21
0.06
0.07
0.05
0.15
0.17
0.51
0.16
0.12
0.14
0.24
NO
0.11
0,09
0.06
0.06
Barley Leaf
20
mt/ha/y
0.61
2.88
1.43
1.63
NO*
0.07
0.03
0.03
0.03
0.13
0.03
0.03
0.03
0.03
0.04
NO
0.33
NO
NO
NO
0.44
0.37
0.69
NO
0.15
NO
NO
NO
NO
NO
0.86
0.41
0.22
0.80
0.56
100
mt/ha
-mg/kg
1.19
3.46
2.47
2.13
NO
0.08
0.03
0.03
0.04
0.24
0.07
0.03
0.03
0.03
0.33
NO
0.55
NO
NO
NO
0.67
0.45
0.73
NO
0.19
NO
NO
NO
0.43
0.22
1.22
1.22
0.43
2.65
0.79
NPK
0.46
0.83
1.95
2.00
NO
0.03
0.03
0.03
0.03
0.06
0.03
0,03
0.03
0.03
0.05
NO
0.25
HO
NO
NO
0.33
0.30
0.20
NO
0.07
NO
NO
NO
0.33
0.08
0.13
0.36
0.11
0.28
0.35
Barley Grain
20 100
mt/ha/y mt/ha
0.21
0.05
0.04
0.03
NO
0.08
0.03
0.05
0.09
0.05
0.03
0.03
0.04
0.03
0.09
0.08
0.16
0.11
0.27
0.03
0.11
0.25
0.32
0.27
0.66
NO
NO
NO
NO
NO
0.27
0.21
0.30
0.'54
0.32
0.32
0.11
0.06
0.03
NO
0.16
0.04
0.04
0.04
0.03
0.06
0.03
0.03
0.03
0.08
0.16
0.22
0.33
0.73
0.03
0.13
0.38
0.47
0.37
0.85
0.36
0.86
0.50
0.25
0.19
0.73
0.54
0.32
0.43
0.42
NPK
0.03
0.03
0.05
0.03
NO
0.03
0.03
0.04
0.06
0.05
0.03
0.03
0.03
0.03
0.03
0.05
0.12
0.04
0.03
0.03
0.03
0.06
0.03
0.05
0.16
0.07
0.31
0.15
0.13
0.04
0.07
0.12
0.11
0.07
0.09
(continued)
20
-------
TABLE 5 (continued)
DTPA Extract
Location*
MO(H)
MI
MN
NE
OH
OR
UT
WI
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
4
5
1
2
3
4
5
1
2
3
20
mt/ha/y
NOt
0.91
0.83
2.28
4.09
0.63
1.70
1.55
NO
3.14
0.77
2.27
2.23
2.59
3.61
2.90
0.8S
4.00
4.62
2.55
1.02
2.20
2.42
2.83
3.43
NO
NO
1.77
3.36
1.95
2.08
3.33
3.90
6.58
1.42
1.73
1.43
1UO
nrt/ha
NO
4.09
2.57
3.08
3.34
2.15
3.43
2.47
NO
3.49
3.85
5.58
3.06
4.97
3.50
5.00
1.39
3.89
4.53
3.82
3.30
5.11
3.63
3.10
1.68
NO
NO
1.06
2.75
9.23
4.57
5.68
4.47
6.13
4.16
5.07
5.62
NPK.
NO
0.06
0.05
0.07
0.06
0.28
0.08
0.36
NO
0.38
0.08
0.17
0.20
0.24
0.25
.NO
NO
NO
NO
NO
0.15
0.18
0.25
0.25
0.40
NO
NO
0.27
1.05
0.33
0.22
0.30
0.40
0.57
NO
0.17
0.29
Barley Leaf
20
mt/ha/y
0.49
0.46
0.58
0.60
0.41
0.89
0.82
NO
1.20
1.30
0.46
0.34
0.39
0.33
0.21
0.68
0.07
0.03
0.20
0.14
0.28
0.34
0.38
0.27
0.78
NO
NO
NO
0.36
NO
0.44
0.56
0.74
1.47
0.33
0.25
0.36
100
mt /ha
ing/teg -
1.21
0.92
0.17
0.68
0.27
2.39
1.15
NO
1.13
0.64
1.78
0.65
0.53
0.34
0,21
1.31
0.12
0.03
0.19
0.10
0.81
0.64
0.42
0.22
0.76
NO
NO
NO
0.34
NO
0.57
0.49
0.48
2.79
0.74
0.79
0.79
NPK
0.15
0.18
0.07
0.18
0.18
0.85
0.59
NO
0.61
0.41
0.14
0.14
0.07
0.12
0.08
NO
NO
NO
NO
NO
0.15
0.18
0.23
0.14
0.67
NO
NO
NO
0.26
NO
0.36
0.50
0.55
0.65
0.21
0.15
0.27
Barley Grain
20
mt/ha/y
0.25
0.11
NO
0.40
0.30
0.55
0.93
NO
0.84
1.35
0.12
0.13
0.18
0.23
0.22
0.95
0.25
0.03
0.18
0.06
0.21
0.26
0.15
0.11
0.07
0.23
0.03
0.55
0.21
0.16
0.14
0.18
0.17
0.27
0.21
0.20
100
mt/ha
0.59
0.33
0.26
0.46
0.31
1.08
0.93
MO
0.85
0.91
0.36
0.33
0.21
0.28
0.24
1.70
0.42
0.03
0.18
0.07
0.36
0.32
0.17
0.08
0.05
0.40
0.03
0.66
0.63
0.41
0.23
0.21
0.32
0.47
0.55
0.45
NPK
0.06
0.03
0.20
0.07
0.09
0.65
0.52
NO
0.72
0.43
0.07
0.03
0.07
0.05
0.06
NO
NO
NO
NO
NO
0.12
0.13
0.04
0.03
0.04
0.12
0.03
0.41
0.11
0.08
0.06
0.13
0.11
0.17
0.11
0.14
*See Table 4 for description of soils.
tNO signifies not determined.
21
-------
TABLE 6. CONCENTRATIONS OF Zn IN OTPA SOIL EXTRACTS AND IN LEAF AND GRAIN
OF BARLEY GROWN IN 15 LOCATIONS.
DTPA Extract
Location*
AZ
CA(G) •
CA(0)
CO
a
IN
MO(L)
Year
1
2
3
4
S
I
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
20
mt/ha/y
17.9
19.3
44.2
44.3
46.6
14.7
18.3
18.5
21.4
37.1
13.0
34.0
26.4
26.5
30.8
NO
4.7
6.7
14.5
18.9
11.3
31.3
48.3
60.5
41.1
NO
NO
NO
NO
NO
NO
9.3
10.4
23.7
32.5
100
mt/ha
59.5
45.4
52.9
54.8
55.1
35.0
23.6
19.2
15.8
17.3
43.8
55.9
27.5
22.4
19.0
NO
23.0
28.0
38.9
40.0
74.5
69.5
76.5
76.5
61.8
119.3
33.1
31.0
41.4
68.5
NO
53.6
35.0
39.5
33.1
NPK.
5.1
1.1
4.4
3.5
3.3
2.0
1.8
1.6
1.6
1.6
1.5
2.3
1.5
1.7
1.6
NO
2.2
2.8
2.4
2.6
1.7
2.2
2.5
2.9
2.5
3.6
1.3
2.0
3.3
2.3
NO
2.4
3.0
3.4
1.9
Barley Leaf
20
mt/ha/y
46.4
53.7
35.5
31.4
NOT
36.3
22.0
39.1
32.4
24.9
21.0
25.0
37.1
25.8
26.3
NO
45.4
NO
NO
NO
23.9
66.0
153.1
NO
30.9
NO
NO
NO
NO
NO
25.3
21.4
26.3
54.0
20.0
100
mt/'ha
mg/kg -
58.1
71.2
36.7
36.8
NO
39.3
29.5
33.4
24.5
19.7
34.3
27.8
36.3
23.2
23.6
NO
60.7
NO
NO
NO
33.4
70.8
93.3
NO
28.7
NO
NO
NO
31.4
42.9
69.9
58.7
32.6
112.4
23.0
NPK
30.6
38.9
16.4
19.2
NO
28.8
20.8
32.8
26.6
20.1
21.8
22.5
30.0
20.1
21.5
NO
25.7
NO
NO
NO
13.9
36.0
38.5
NO
20.8
NO
NO
NO
21.0
21.8
17.4
17.0
21.9
17.2
14.9
Barley Grain
20
mt/ha/y
51.5
55.4
55.7
37.4
NO
45.8
34.0
37.2
33.3
32.8
37.8
34.3
41.5
30.6
47.0
57.8
66.5
51.8
4.8
100.0
13.5
77.3
55.3
67.1
85.0
NO
NO
NO
NO
NO
38.6
32.2
37.4
55.6
35.1
100
mt/ha
59.2
58.9
56.4
37.4
NO
55.8
40.5
31.9
39.4
32.4
49.5
37.0
42.0
33.7
39.5
58.8
64.5
66.8
76.1
112.0
18.0
65.3
63.8
73.8
94.1
82.1
60.2
61.6
43.5
44.0
52.1
46.7
38.9
66.1
40.7
NPK
46.7
40.4
46.7
40.3
NO
33.8
26.3
29.8
28.9
27.1
31.3
37.3
32.0
25.8
26.7
51.8
56.0
41.8
47.3
60.5
10.7
41.8
43.0
30.7
50.0
57.5
37.1
35.8
27.0
31.8
22.6
27.6
25.0
34.4
21.2
(continued)
22
-------
TABLE 6 (continued)
Location*
MO(H)
MI
MN
NE
OH
OR
UT
Wl
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
4
5
1
2
3
4
5
1
2
3
07
mt/ha/y
sot
8.4
9.6
23.1
64.5
8.4
21.2
24.3
NO
52.8
32.5
34.0
33.5
35.8
73.7
31.5
18.1
45.5
59.4
54.8
23.9
37.8
41.9
55.8
43.6
NO
NO
31.4
55.3
29.0
29.9
46.5
50.4
78.6
29.6
30.0
23.6
PA Extract
100
mt/ha
NO
54.5
32.4
31.3
30.0
25.8
44.3
35.7
NO
56.4
162.7
85.5
43.3
67.4
56.7
102.0
54.8
43.8
62.4
52.6
69.3
70.2
49.2
36.0
21.9
NO
NO
22.3
40.2
129.8
58.5
75.8
57.5
72.5
74.6
89.8
95.1
NcK.
NO
1.6
1.5
1.8
1.3
1.5
1.8
3.9
NO
5.4
5.0
2.0
2.1
2.3
2.3
NO
NO
NO
NO
NO
9.4
9.5
8.3
19.9
10.1
NO
NO
8.8
18.9
2.5
2.8
3.6
5.4
4.8
3.5
3.7
3.9
Bai
20
mt/ha/y
25.0
19.6
22.4
40.7
20.9
67.9
48.3
ND
59.2
79.5
46.3
38.8
41.1
45.0
39.2
39.0
19.0
ND
22.7
25.6
30.0
32.2
31.0
35.6
19.5
NO
NO
NO
56.3
ND
26.0
29.3
37.3
52.5
61.2
38.0
28.5
-ley Leaf
103
mt /ha
mg/kg -
74.9
32.8
26.7
43.0
23.4
112.3
63.2
NO
52.1
57.5
106.0
52.0
44.3
57.7
34.3
96.0
26.7
NO
18.9
24.7
40.5
32.3
28.2
35. 9
15.6
NO
NO
NO
41.1
NO
32.3
29.3
35.8
108.0
80.4
71.8
42.1
NPK
18.5
11.3
17.4
13.4
14.7
48.7
27.9
NO
43.4
44.0
24.3
28.5
28.9
40.7
25.5
NO
NO
NO
NO
ND
26.0
24.8
24.7
29.6
18.6
NO
NO
NO
57.0
NO
21.5
43.3
22.0
57.5
54.4
57.8
53.5
Barley Graii
~73
mt ,'h a 'y
33.0
27.9
NO
45.3
33.4
64.8
110.0
NO
65.7
113.3
67.0
67.5
69.3
49.4
65.0
94.0
98.1
64.3
75.5
49.7
53.0
50.1
36.0
38.0
24.8
18.3
56.0
53.3
63.2
52.0
65.3
61.5
65.5
57.8
54.4
57.8
53.5
100
40.7
3n. 2
30.5
43.8
35.1
78.5
85.3
NO
64.7
1S5.0
111.8
80.3
70.1
46.4
67.1
118.0
111.0
63.5
69.5
47.7
70.3
49.9
36.0
32.6
23.6
21.9
70.0
57.8
57.6
99.5
77.5
65.0
58.8
62.3
78.4
86.4
68.8
NK
24.4
22.1
20.5
27.6
16.5
47.5
69.5
NO
46.8
121.5
43.5
41.3
52.0
36.0
49.6
NO
NO
NO
ND
NO
47.3
35.8
28.1
27.8
19.9
13.4
52.5
43.3
63.0
48.5
47.5
44.0
71.0
68.3
36.5
36.1
40.3
*See Table 4 for description of soils.
tNO signifies not determined.
23
-------
TABLE 7. CONCENTRATION OF Cu IN DTPA SOIL EXTRACTS AND IN LEAF AND GRAIN
OF BARLEY GROWN IN 15 LOCATIONS.
DTPA Extract
Location*
AZ
CA(G)
CA(0)
CO
Fl
IN
MO(L)
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
20
6.4
8.3
13.8
13.8
14.6
4.7
5.5
5.8
6.0
9.7
4.9
10.1
8.9
7.8
9.2
NO
3.2
4.2
7.2
6.1
4.1
10.5
13.9
14.7
15.7
NO
NO
NO
NO
NU
NO
3.7
4.5
11.8
13.1
100
mt/ha
19.5
15.5
17.7
15.7
15.7
20.5
6.1
5.3
4.3
4.3
26.8
17.9
10.3
7.1
5.9
NO
9.1
12.3
17.2
18.9
26.5
26.2
19.8
23.5
22.8
30.4
J.8
^ 1
18. 0
24.7
NO
1.8
14.9
17.6
13.6
NPK
7.1
2.4
3.8
2.8
2.5
1.0
1.1
1.0
0.9
0,8
1.4
1.8
1.4
1.4
1.2
NO
2.3
2.9
2.5
2.0
0.5
1.3
0.6
0.7
0.5
4 1
2.0
3.2
3.7
3.5
NO
1.1
1.3
1.8
1.0
Barley Leaf
CO
nu/ha/y
8.6
10.4
12.4
10.9
NDt
8.3
6.6
7.8
12.0
10.1
6.7
6.9
10.4
8.3
11.4
NO
9.5
NO
NO
NO
5.5
9.4
11.8
NO
6.9
NO
NO
NO
NO
NO
8.9
5.9
5.7
11.5
6.9
100
mt/ha
- ing/kg
9.0
12.1
11.8
11.8
NO
8.4
7.0
6.1
9.0
8.8
9.1
7.0
8.8
6.3
10.9
NO
11.)
NO
NO
NO
7.2
10.8
9.3
NO
5.7
NO
NO
NO
5.1
6.7
13.1
9.7
7.2
12.5
5.5
NPK
7.6
9.9
12.4
11.9
NO
6.4
5.7
6.2
8.4
8.4
6.1
6.5
7.7
7.7
12.2
NO
9.6
NO
nu
NO
3.0
5.4
4.7
NO
4.7
NO
NO
NO
3.3
5.6
5.0
5.4
5.4
6.3
3.9
Barley Grain
20
nit ,'h a /y
9.1
10.8
13.4
12.7
NO
4.4
2.5
3.9
4.5
9.6
3.6
3.2
3.7
4.6
18.4
12.5
44.4
6.4
6.7
14.2
NC
4.8
4.0
NO
6.5
NO
NO
NO
NO
NO
4.9
4.4
7.7
6.1
5.5
100
mt/ha
9.6
11.8
14.1
13.2
NO
4.2
3.0
3.6
4.7
10.1
4.0
3.9
3.4
6.0
17.0
15.9
3S.7
5.3
6.2
13.1
NO
5.2
4.1
2.4
6.4
5.7
7.4
5.9
5.0
7.1
3.9
5.7
4.4
2.9
5.0
NPK
8.9
9.5
17.2
13.5
NO
2.6
1.9
3.6
2.8
11.3
3.2
4.0
3.2
5.4
15.8
13.8
44.8
5.3
5.6
8.2
NO
3.2
1.8
0.5
2.9
4.6
6.1
4.7
3.4
6.8
2.4
3.6
3.1
4.5
2.4
(continued)
24
-------
TABLE 7 (continued)
DTPA Extract
Location*
MO(H)
HI
MN
NE
OH
OR
UT
HI
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
4
5
1
2
3
4
5
1
2
3
20
mt/ha/y
NDt
4.2
4.7
11.7
14.0
2.8
9.2
7.5
NO
15.3
8.8
8.5
8.1
8.4
15.8
8.6
4.9
10.3
14.2
14.1
8.0
13.1
13.5
14.2
14.7
NO
NO
9.5
16.9
13.2
12.6
17.4
19.3
30.3
9.7
10.1
6.9
100
mt/ha
NO
19.7
13.4
17.5
14.4
9.6
19.8
11.5
NO
17.1
43.3
21.8
11.4
16.8
11.3
24.3
13.2
11.6
15.2
15.9
19.2
27.9
20.0
16.0
7.8
NO
NO
7.0
14.2
54.0
24.2
27.6
22.6
28.8
24.3
29.4
28.7
NPK
NO
0.9
0.9
1.2
0.9
0.6
0.7
1.5
NO
2.0
2.0
1.0
0.9
1.1
1.3
NO
NO
NO
NO
NO
2.9
2.5
2.7
3.5
3.0
NO
NO
2.2
4.7
1.4
1.3
1.3
2.0
1.6
1.3
1.7
1.9
Barley Leaf
20
mt /h a ,'y
8.9
6.2
5.5
12.3
5.4
27.9
13.4
NO
37.0
17.9
10.4
5.7
6.9
8.3
7.4
5.6
5.8
6.3
4.8
4.7
26.8
19.4
21.9
23.9
5.8
NO
NO
NO
9.5
NO
9.7
9.7
12.6
10.1
12.4
9.4
10.5
100
mt/ha
- mgAg
14.2
7.6
6.6
12.8
4.9
27.4
14.0
NO
25.0
18.3
U.I
7.1
7.4
10.1
9.8
8.3
7.2
9.0
5.0
4.6
34.3
16.1
18.1
27.3
5.5
NO
NO
NO
7.5
NO
9.5
9.8
11.4
13.1
12.7
12.2
11.0
NPK
6.7
4.5
4.9
6.4
4.1
31.3
13.2
NO
27.3
13.6
16.8
4.8
6.7
7.4
7.2
NO
NO
MO
NO
NO
24.0
22.1
18.6
25.8
5.5
NO
NO
NO
8.1
NO
8.3
13.0
8.8
8.5
9.6
7.7
9.2
Barley Grain
20
mt/ha/y
5.2
2.6
NO
5.4
4.5
22.3
19.0
NO
18.0
32.4
0.5
0.5
2.5
3.2
6.0
10.2
8.7
4.3
4.1
2.6
5.4
7.3
4.8
3.6
2.7
4.5
NO
4.2
5.0
7.0
7.6
6.1
6.0
5.4
7.1
5.5
5.9
100
mt/ha
5.1
4.5
5.9
7.0
5.2
14.0
23.8
NO
16.1
19.3
0.5
0.5
2.0
3.0
5.9
9.8
13.6
4.3
5.6
3.6
6.4
7.2
4.1
3.3
2.7
5.0
NO
5.1
4.8
12.8
7.6
6.3
5.7
6.0
8.6
7.5
6.8
NPK
3.6
3.7
3.3
4.6
2.8
26.0
22.4
NO
21.1
16.5
3.8
0.5
3.4
3.0
5.9
NO
NO
NO
NO
NO
5.1
5.7
3.8
3.0
2.6
2.3
NO
2.4
4.5
5.8
5.7
5.2
5.2
4.8
5.5
4.8
4.9
*See Table 4 for description of soils,
*NO signifies not determined.
25
-------
TABLE 8. CONCENTRATIONS OF Ni IN DTPA EXTRACTS AND IN LEAF AND GRAIN
OF BARLEY GROWN IN 15 LOCATIONS.
OTPA Extract
Location* Year
AZ
CA(6)
CA(D)
CO
FL
IN
MO(L)
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
20
mt/ha/y
4.9
1.5
2.5
2.3
2.4
1.8
2.5
2.2
1.9
4.1
1.6
2.9
2.4
1.8
3.0
NO
0.8
0.9
1.9
1.4
1.3
2.3
2.8
5.7
4.2
NO
NO
NO
NO
NO
NO
1.6
2.3
6.3
4.5
}OU •
itrt/ha
7.9
3.3
2.3
2.2
2.7
7.6
2.9
1.9
1.2
1.7
9.3
5.8
2.5
1.3
1.8
NO
2.2
2.8
4.8
7.8
19.3
5.3
5.0
5.6
4.5
43.3
4.0
6.9
2.0
2.2
NO
7.2
4.2
7.8
5.2
NPK
1.3
0.1
0.7 '
0.7
0.6
0.6
0.8
0.4
0.4
0.7
0.6
0.6
0.4
0.4
0.8
NO
0.5
0.7
0.6
0.6
NO
0.2
0.2
0.4
0.2
6.8
7.8
1.9
1.7
1.8
NO
1.4
1.0
3.3
0.9
Barley Leaf
20
mt/ha/y
4.1
2.2
7.7
10.2
NOt
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
l.fl
NO
1.3
NO
NO
NO
NO
NO
NO
NO
0.1
NO
NO
NO
NO
NO
0.3
2.6
1.0
1.8
1.2
100
ret. /ha
- mg/kg
4.6
2.3
7.2
4.5
NO -
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
1.0
NO
1.4
NO
NO
NO
NO
NO
NO
NO
0.1
NO
NO
NO
1.1
0.7
0.5
2.8
1.0
1.9
1.5
Barley Grain
NPK 20 100
mt/ha/y mt/ha
3.2
1.3
7.2
5.2
NO
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
1.0
NO
0.7
NO
NO
NO
NO
NO
NO
NO
0.1
NO
NO
NO
1.3
0.5
0.5
2.6
1.5
1.9
0.9
3.5
6.5
1.7
1.7
NO
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
1.0
1.6
1.6
0.9
0.7
0.7
NO
NO
NO
NO
0.1
NO
NO
NO
NO
NO
0.5
0.6
0.4
0.6
1.0
4.5
6.5
1.7
1.7
NO
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
1.0
1.4
2.0
0.8
1.1
3.7
NO
NO
NO
NO
0.1
2.7
1.0
0.6
2.9
0.8
1.0
0.7
0.5
0.7
1.3
NPK
2.9
5.1
1.4
1.4
NO
NO
0.1
2.0
NO
1.0
0.1
0.1
2.0
NO
1.0
1.4
2.1
0.8
0.6
1,0
NO
NO
NO
NO
0.1
1.4
0.4
0.3
1.4
0.3
0.2
0.6
0.4
0.4
0.6
(continued)
26
-------
TABLE 8 (continued)
DTPA Extract
Location*
MO(H)
MI
MN
NE
OH
OR
UT
WI
Year
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
4
5
1
2
3
4
5
1
2
3
20
mt/ha/y
NOt
1.7
1.3
5.0
3.8
0.9
2.7
2.3
NO
3.8
7.5
6.5
4.6
6.2
9.7
3.9
3.5
11.6
5.7
11.1
1.9
3.5
3.2
3.7
3.7
NO
NO
4.4
6.4
3.4
3.0
4.5
4.3
3.9
8.6
8.4
7.9
100
mt/ha
NO
5.7
2.9
5.0
3.8
3.8
5.7
3.4
NO
4.4
24.3
12.3
5.4
11.2
7.8
6.S
8.1
7.8
5.8
9.6
6.7
8.7
4.3
3.5
1.8
NO
NO
2.8
4.2
12.7
5.6
6.4
4.5
5.3
14.6
14.9
14.8
NPK
NO
0.6
0.7
3.0
1.1
0.2
0.5
3.3
NO
0.5
4.1
2.3
2.0
2.4
2.8
NO
NO
NO
NO
NO
0.5
1.0
0.8
0.7
0.9
NO
NO
1.3
2.2
0.7
0.6
0.7
0.6
0.5
5.5
5.0
5.4
Barley Leaf
20
rt/ha/y
0.3
2.5
1.2
2.0
1.0
1.2
1.3
NO
1.1
0.9
1.1
0.5
0.7
1.1
0.8
2.8
1.1
1.2
1.2
10.1
1.5
1.0
2.0
0.6
0.9
NO
NO
NO
0.1
NO
2.0
3.8
2.3
1.8
3.1
2.2
0.8
100
mt/ha
- nig/kg
0.4
2.6
1.2
2.2
1.1
2.3
1.5
NO
1.0
1.0
1.3
0.9
0.8
2.0
0.7
5.0
1.1
5.0
1.1
6.3
1.7
2.3
1.7
0.5
1.0
NO
NO
NO
1.3
NO
2.3
3.6
1.6
2.3
3.5
2.8
1.0
NPK
0.5
2.6
1.3
2.0
1.2
1.2
1.4
NO
1.1
0.7
1.3
0.5
1.0
1.1
0.4
NO
NO
NO
NO
NO
0.9
1.4
l.E
0.5
0.6
NO
NO
NO
0.1
NO
1.9
4.6
2.0
1.6
3.4
2.0
0.7
Barley Grain
20
mt/ha/y
6.0
0.4
NO
0.5
1.3
11.2
1.2
NO
0.3
1.3
0.4
1.4
0.9
0.9
1.1
1.6
1.2
0.3
0.9
0.8
0.5
0.6
0.5
0.3
0.4
3.8
2.0
2.5
0.1
0.3
0.2
0.1
0.3
0.2
2.7
1.8
0.5
100
mt/ha
0.7
0.6
0.3
0.6
1.1
5.3
1.1
NO
0.4
0.9
2.7
3.2
1.1
1.5
0.8,
1.6
4.S
0.5
1.0
1.2
1.2
0.7
0.3
0.2
0.5
5.4
2.0
4.7
1.3
0.9
0.3
0.1
0.4
0.2
4.2
2.8
1.3
NPK
0.5
0.4
0.6
0.3
0.7
13.0
0.5
0.2
0.5
0.3
1.2
0.9
0.8
0.8
NO
NO
NO
NO
NO
0.5
0.5
0.2
0.1
0.7
2.5
2.0
2.5
0.1
0.2
0.1
0.1
0.1
0.1
1.9
1.4
0.4
•See Table 4 for description of soils.
tNO signifies not determined.
27
-------
SECTION 3
EFFECTS OF SLUDGE PROPERTIES ON
ACCUMULATION OF TRACE ELEMENTS BY CROPS
INTRODUCTION
Loading limits for trace elements from municipal sewage sludges
applied to land should be based on sludge and soil characteristics that
affect plant availability of those elements. Current evidence indicates
that the rate at which a plant root absorbs a trace element such as Cd, Zn,
or Cu depends on the activity of the free-ion form of that metal in solu-
tion at the root surface. The activity at the root surface, in turn,
depends on equilibrium reactions between solution and solid phases and
the rate of transport to the root. Therefore, if we can predict the trace
element uptake that a specific application of a given sludge on a particu-
lar soil will produce, we should be able to establish long-term loading
limits, that will assure that additions of trace elements to tha food chain
are within tolerable limits and phytotoxicities of other trace elements are
not a problem.
Sludges by themselves support certain trace element activities when
equilibrated with the soil solution. Absorbing sites on the soil immo-
bilize some of the dissolved trace element ions, causing more ions to be
released from the sludge. If the trace element adsorption capacity of
the applied sludge is small compared to the adsorption capacity of the
soil, the soil properties will be very important in determining the equi-
librium solution activity. However, if the trace element adsorption
capacity of the sludge is high compared to that of the soil (usually
associated with high sludge rates), the soil adsorption sites that can
be filled at the activity supported by the sludge will result in only a
small decrease in solution activity, and the sludge properties will
dominate. Under these conditions the soil's effect on the pH of the
mixture may still be significant, and the pH will affect trace metal
concentrations in equilibrium with the sludge.
The fact that trace element activity, and thus plant uptake of trace
elements from sludged soils, tends to approach a maximum as the sludge
rate increases suggests that this behavior could be used to differentiate
sludges that would support potentially harmful concentrations in plant
tissue from sludges that would not, regardless of the application rate.
Therefore, trace element activity could be used to differentiate sludges
28
-------
that do an do not require regulation in terms of trace element loading
limits. (Fig. 1). In this figure, a constant pH is assumed, and the
dashed horizontal line (C ) represents the maximum concentration of trace
element that would be allowed in a test species based on the maximum
allowable dietary intake calculations or on phytotoxicity. In the case of
Cd, this line would represent the maximum allowable concentration in a test
plant (such as lettuce), based on the assumption that uptake by different
plant species grown on soils amended with sludge will show proportionate
differences in Cd uptake, and the total intake from a "market basket" mix
of species grown on a given sludge treatment can be estimated from the con-
centration determined in the test species. The letters A, P., C, and 0
represent Cd uptake curves derived from sludges that support different
maximum Cd concentrations in plants, and the subscripts 1 and 2 represent
uptake curves for the designated sludge applied to soils vrth low and high
Cd-adsorption properties, respectively (if the maximum plant-Cd concentra-
tion that a given sludge loading would depend on soil properties (curves
AI and A2)). Sludges B, C, and D, at or above the pH usec in the test,
would not require loading limits regardless of the soil properties. In
fact, sludge D represents a sludge that supports a lower plant Cd con-
centration than does the nonamended soil. This is a rare occurrence,
but it has been observed.
Estimates of plant availability of the trace elements in sludges could
be obtained from field or greenhouse studies with a specific variety of
lettuce (or other crop that tends to accumulate the elements of interest)
grown on sludge-amended soils that had been allowed to equilibrate under
aerobic conditions. Later, reliable methods for assessing trace element
supplying properties of sludges and adsorption characteristics of soils
may be developed for use in place of the bioassay. Interpretation of
such tests will require research relating test results to plant uptake.
Use of chelating resins for desorbing trace elements from sludges and
for establishing known trace element activities for soil adsorption
curves appears promising.
FORMS AND AMOUNTS OF TRACE ELEMENTS IN MUNICIPAL SEWAGE SLUDGES
All domestic sewage sludges contain varying amounts of Cd, Cr, Cu,
Pb, Ni, and Zn. Data presented by Sommers (1977) showed wide variations
in metal concentrations and a fairly large number of sludges containing
very high concentrations. With the implementation of the federal
industrial waste pretreatment program as a control on the discharge of
these trace metals into publicly-owned treatment facilities, the metal
loads to municipal wastewater treatment facilities and subsequently the
levels in municipal sludges can be expected to decrease with time. The
federal program, which is likely to generate vast amounts of performance
data in the future, is not mature enough to produce such data at this
time. This can be illustrated by examining trends in sludge metal com-
position data from Chicago, Baltimore, and Philadelphia where local pre-
treatment programs have been implemented.
29
-------
Jrends j_n_ sludge trace-metal concentrations
The Metropolitan Sanitary District of Greater Chicago (MSDGC)
adopted a program in 1969 that was designed with objectives similar to
those of the federal program which prevent? pass-through of pollutants
and produces higher quality effluents. The program specifies concentration
limits for 13 contaminants and nine limiting conditions for the discharge
of industrial wastes to the MSDGC sewerage system. The specific limits
required by this program are as follows (in mg/L):
boron, 1.0; cadmium, 2.0; chromium (total), 25.0; chromium
(hexavalent), 10.0; copper, 3.0; cyanide (total), 10.0; cyanide
(readily releasable at 150°F and pH 4.5), 2.0; iron, 50; lead,
0.5; mercury, 0.005; nickel, 10; zinc, 15.0; fats, oils and
greases, 100 (changed to 250 in 1983); and pH 4.5 to 10 units.
The levels of sewage-borne metals entering the MSDGC sewage treatment
facilities (Tables 9 and 10) have decreased substantially since 1971
(Whitebloom et al., 1978; Lue-Hing, 1985, personal communication). As
an example, for one POTW in the MSDGC system the influent Cd loading
was reduced by 57.5% over the period of 1971 through 1977 (Table 9) and
for another plant in the system by 69.4% over the period of 1971 through
1984 (Table 10). Similar results were obtained with pretreatment in
Baltimore (Table 11) and Philadelphia (Table 12). Once the federal pre-
treatment program has been fully implemented, reductions on the national
level can be expected to approximate those achieved by these programs.
Forms of Metals in Raw Sewage
The solubility of a metal in the soil-sludge mixture is inherently
governed by the particular chemical form in which it occurs in the sludge.
To understand the chemical form of the various metals in municipal sewage
sludge, one must first determine what forms of these metals are affected by
the wastewater treatment process. Each metal will be distributed between
the soluble and solid phase based upon a complex equilibrium controlled by
the wastewater composition. However, in most cases, Cd, Cr, Cu, Pb, and Zn
have been found to be predominantly associated with the solid phase in
wastewater influents.
Elenbogen et al. (1984) compared the raw sewage metals concentration
entering a pilot-scale primary settling tank with the metals concentration
of activated sludge solids (mixed liquor) in an activated sludge pilot
plant. Elenbogen et al. (1984) concluded that the metals in raw sewage
entering primary settling tanks are bound to the wastewater solids in simi
lar proportions to the metals bound to the mixed liquor solids of the acti-
vated sludge process, and that the distribution of metals between the solid
and liquid phases is the same.
Metal adsorption by sludges has been demonstrated by spiking the
sludge with inorganic metal salts. Elenbogen et al. (1984) studied the
adsorptive capacity of the activated sludge process for metals and the
30
-------
strength of the bond between metals and the activated sludge solids. In
batch-scale experiments in Table 13, Elenbogen et al. (1984) "spiked" mixed
liquor with known amounts of CdCl2 up to 30 mg/L. Most of the soluble Cd
was adsorbed to the mixed liquor solids in less than 15 minutes and over
90% v.as adsorbed after 1 hour of aeration. In a separate series of
controlled pH batch experiments, Elenbogen et al . (1984) also studied the
uptake of Cd by mixed liquor spiked with soluble Cd (CdCl2' concentrations
of 2.3 and 5.0 mg/L, and found that uptake was not influenced by mixed
liquor pH in the range of 5.0 to 8.0. Over 90% of the soluble Cd uptake
occurred in 15 minutes for all of the pH levels tested.
Neufeld and Hermann (1975) also reported high adsorptive capacities in
batch-activated sludge reactors dosed with 30, 100, and 300 mg/L soluble
Cd. In their experiments, 65 to 70% of the added soluble Cd was adsorbed
on the activated sludge floe within 1 hour after dosing, even at the 300
mg/L soluble Cd dose. Within 4 hours, 80% of the initial soluble Cd had
been adsorbed on the solids.
Patterson (1979) reported that in Rockford, Illinois, the soluble
fractions of Cd, Cr, and Zn were 24.0, 26.4, and 16.1%, respectively, of
these total metals in the raw sewage. Patterson and Kodukula (1984)
reported that in the raw sewage at a sewage treatment facility of the
MSDGC, Cd was 12.9% soluble, Cr was 1.7% soluble, Cu was 5.0% soluble, Pb
was 16.9% soluble, Ni was 28.3% soluble, and Zn was 12.1% soluble.
Similarly, Lester et al, (1979) reported that 72% of the Cd, 70% of the Cu,
and 73% of the Pb was associated with the primary settled solids at the
Oxford, England treatment plant. In a companion study, Stoveland et al.
(1979) reported that 73% of the Cr and 74% of the Zn was associated with
the primary solids at the Oxford plant.
In general, therefore, studies of raw sewage metal speciation indicate
that most metals are associated with the solid phase. This, coupled with
the demonstrated affinity for soluble metals shown by the activated sludge
process, would indicate that most of the metals contained in municipal
sludge are associated with the solid phase rather than the liquid phase.
Forms of Metals in Sludges
Because the chemical composition of municipal raw sewage and the types
of metal compounds that may enter a wastewater treatment plant vary widely
the chemical transformations that will occur in the plant are difficult to
predict. However, a general understanding of aqueous metal chemistry would
suggest that metals would be present in both organic and inorganic forms.
Metals associated with organic matter are probably bound strongly to
complexing sites. Inorganic forms could include metallic particles, rela-
tively pure precipitates (phosphates, carbonates, sulfides, or silicates),
solid solutions resulting from coprecipitation with precipitates of Fe, Al,
or Ca, or as metal ions strongly adsorbed on surfaces of Fe, Al, or Ca
minerals (Corey, 1981). If metals such as Cd or Zn enter the treatment
plant in aqueous form, coprecipitation with phosphates, hydrous oxides, or
31
-------
sulfides of Fe and Al, and with phosphates and carbonates of Ca would be
expected (CAST, 1980; Logan and Chaney, 1983).
The scientific literature contains little specific analytical data
on the various species or forms of metals contained in municipal sewage
sludge. Investigators have focused on a determination of sludge metal
forms through the use of various extractants. The amount of metal found
in these various extractants is an indicator of the form of the metal in
the sludge.
Stover et al. (1976) developed a sequential extraction scheme for
fractionating Cd, Cu, Pb, Ni, and Zn in anaerobically digested sludge.
In their scheme they suggest that KN03 extracts exchangeable metals, KF
extracts adsorbed metals, Na4P207 extracts organically bound metals,
EDTA extracts metal carbonates, and HN03 extracts metal sulfides. For
the 12 sludges they studied, Stover et al. (1976) found that Zn was
predominantly found in the organically bound (Nat»P207) form, Cu in the
sulfide (HNOo) form, and Pb in the metal carbonate (EDTA) form. Nickel
was distributed in many forms, and Cd was predominantly in the metal
carbonate (EDTA) form.
A similar extraction procedure, incorporating 0.5M KN03, "ion-exchange
water", 0.5M NaOH, 0.05M Na2EDTA, and 4.0M HN03 has been employed to
fractionate Cd, Cu, Ni, and Zn in anaerobically digested air-dried sludge
into forms designated as exchangeable, adsorbed, organically bound, car-
bonate, and sulfide/residual, respectively (Emmerich et al., 1982). While
the Cd, Ni, and Zn occurred in sludge predominantly in carbonate form, the
major forms of Cu extracted were in the order: organically bound > car-
bonate > sulfide/residual.
Six types of sludge from the MSDGC's West-Southwest Sewage Treatment
Works were subjected to a sequential chemical extraction procedure in an
effort to characterize the metal forms present in the sludges (Elenbogen,
et al., 1983). The following conclusions were reached:
1. Lagoon sludge, waste-activated sludge, and filter cake had similar
chemical distributions of Cd, Cu, and Zn with the predominant
species (48 to 69%) of these metals being in the water soluble
and readily exchangeable (KN03 extractable) forms. These values
seem very high compared with those of other studies.
2. Digested sludge had the highest percentage (22.5 to 25.4%) of Cd
and Zn in the sulfide form (1M_ HN03) compared to the other sludges.
3. Heat-dried sludge and Nu Earth (air-dried MSDGC sludge) had similar
chemical distributions for Cd and Zn, with a relatively small
percentage (less than 10%) of these metals found in the water
soluble form when compared to the other sludges (21 to 56%), and
the greatest amount (34 to 75%) of Cd and Zn being recovered in
the organically bound form (Nai»P207 extractable) for Nu Earth.
However, in the case of heat-dried sludge, the greatest amount
32
-------
(29%) of Cu was found in the highly insoluble (concentrated
extractable) form, with considerably less (17%) Cu being found in
the organically bound form (Na^Oy extractable) compared to the
Nu Earth.
Metal Speciation j_n_
Metals in soils may be present in many forms. The application of
sewage sludge to soils may alter the speciation of a metal, which, in turn,
may affect its availability to plants.
The use of chemical extractants in studying metal speciation in soils
has been focused mainly on the so-called plant available forms. Metals
have frequently been extracted with simple aqueous solutions to determine
plant available forms (Adams, 1965; Gupta and MacKay, 1965). In all cases,
metal concentrations in water extracts were low.
Sequential chemical extraction schemes, considered to be of greater
value than single extractants in determining metal distribution in
wastewater sludge (Stover et al., 1976), have frequently been applied to
fractionate trace metals in sludge-amended soils. A modified version of a
sequential extraction procedure developed by Stover et al. (1976) was used
by Emmerich et al. (1982) to determine the chemical forms of metals in
loamy soils amended with anaerobically digested sludge. Emmerich et al.
(1982) observed that less than 3% of the total Cd, Cu, Ni, and Zn in a
sludge-amended loam soil were extracted by 0.5M KN03 and "ion-exchange
water". Sposito et al. (1982) extracted 1.1 to 3.7% of these same metals
using the same extractants. These results are consistent with
exchangeable-plus-adsorbed forms of Cd, Pb, and Zn in sludges (Stover et
al., 1976), and with water-soluble plus-exchangeable forms of Cd, Cu, Pb,
and Zn in silt loam soils amended with digested sludge (Silviera and
Sommers, 1977).
The diversity of reagents used to extract specific metal forms in soils
make comparison of such studies difficult. Even if the reagent used is the
same, the rate of leaching will be a function of the sample size, duration
of extraction, temperature, and other factors (Sterritt and Lester, 1984).
Speciation of the metals in soils which receive sludge application
is also important, as it will determine availability (Sterritt and Lester,
1984). However, Lake et al. (1984) conclude that no comprehensive or
reliable speciation schemes for determining discrete heavy metal species or
groups in sewage sludge and soil-sludge mixtures has yet been developed.
Plant-Availability £f_ Sludge-Borne Trace Elements
The rate at which an element is taken up by a plant root appears to be
a function of the activity of the free ion at the root surface (Checkai et
33
-------
al., 1982; Baker et al., 1984). However, as the concentration at the root
surface decreases because of uptake, transport to the root may limit the
rate of uptake.
The interacting factors that determine the rate of element uptake are
most easily presented in a mathematical model. As most trace elements,
particularly at low loadings, are delivered to the root surface primarily
by diffusion (Barber, 1984), a diffusion model is used for illustrative
purposes.
Factors Controlling Trace Element Uptake—Theoretical Considerations
Soil factors that affect diffusive transport of a solute include
water content, solute concentration in solution, and the ability to
resupply absorbed solute (buffer power). Important plant factors include
root geometry (root radius, presence of root hairs/mycorrhizae) and root
uptake physiology, i.e., root absorbing power and effects of root exudates.
How these factors interact is shown in Eq. (1), which is a modification of
an uptake equation derived by Baldwin et al. (1973) that describes the
diffusive radial flux of solute from an isotropic medium (soil) to a
cylindrical sink (plant root), assuming depletion of a cylindrical volume
of soil surrounding each segment of root.
(1)
- exp.
b(l + °Air° in 'h
^ Dief 1.65
}
i
ro J
Soil factors:
C,. = initial concentration (mol/cm3) of nutrient in soil solution
b = buffer power—the change in concentration of total labile
form [adsorbed + dissolved] (mol/cm3 soil) per unit of
change in concentration of dissolved form (mol/cm3 soil
solution)
A, = fractional area of soil solution
6 = volumetric water content (cm3 water/cm3 soil)
D, = diffusion coefficient in soil solution (cm2/sec)
34
-------
Plant factors:
U = uptake per unit volume of soil in time, t (mol/cm3 soil)
a = root absorbing power (uptake flux density mol/cm2 root-sec)/
(concentration mol/cm3 soil solution)
t = time (sec)
r. = half-distance between roots (cm)
r = root radius (cm)
L = root density (cm root/cm3 soil)
f = conductivity factor
it = 3.1416
The conductivity factor, f, decreases with a decrease in e because of
greater tortuosity of the diffusion path at lower water contents. The
buffer power, b, is equal to the change in concentration of total labile
solute per unit change in concentration of that solute dissolved in the
soil solution. The labile form includes dissolved and reactive adsorbed
forms. Soils with high adsorption capacities for specific solutes gen-
erally show high buffer powers for those solutes. Commonly found ranges
in buffer power for specific nutrients range from less than 1 for nonad-
sorbed species to more than 1000 for strongly adsorbed species, and gen-
erally decrease with increasing saturation of the adsorbing sites with a
particular solute (Nye and Tinker, 1977; Barber, 1984).
The root density, Lv, is equal to the length of root per unit volume
of soil. The value of Lv is readily determined for roots without root
hairs or mycorrhizae, but their presence makes the geometry of the nutrient
absorbing system more difficult to describe quantitatively. The root
absorbing power, a, is equal to the uptake flux density divided by the
nutrient concentration at the root surface. In some cases, a can be de-
scribed by a Michaelis-Menten plot of flux density (mole per cm2 per sec)
vs. concentration at the root surface (mol/cm3). This relationship has been
shown to depend on the pre-existing nutrient status of the plant (Lauchli,
1984), speciation of dissolved solute (Checkai et al., 1982), and antago-
nistic effects of other metals (Logan and Chaney, 1983). A confounding
factor is the effect of root exudates on rhizosphere pH (Marschner et al.,
1982) and possible complexing of trace metals.
Sludge appli'ations affect both Cii and b in a soil. As the sludge
application rate increases to the point where soil adsorption sites that
can be filled at the activity supported by the pure sludge are nearly
saturated, further increase in sludge application results in little addi-
tional change in either GI-J or b, and U should approach a maximum. The
maximum uptake rate obtained with a given sludge should differ from soil-
to-soil because pH differences affect both C]-j and b, and 9 and f vary.
35
-------
Similarly, uptake will vary with plant species because of differences in a,
Lv, r0, and the nature of root exudates.
Most trace elements, particularly trace metals, added to soils appear
to be immobilized mainly by adsorption reactions, which can usually be
described by a Langmuir or Freundlich adsorption isotherm (Cavallaro and
McBride, 1978; Garcia-Miragaya and Page, 1978; McBride et al., 1981;
Kotuba, 1985). If the solute adsorption curve (adsorbed concentration vs.
concentration in solution) for the soil and the desorption curve for the
sludge have been determined, the equilibrium solute activity for any mix-
ture of sludge and soil can be calculated. For example, if both curves
can be described mathematically, in this case, by a Langmuir equation,
the variables CT-J and b in the uptake equation can be calculated in the
following way for a trace metal:
MT C M K
M = — ! — or C = - (2)
K + C MT - M
where M is metal adsorbed, Mj is the metal adsorption capacity, K is a
constant equal to the dissolved metal concentration at one-half saturation
of the adsorption sites, and C is the equilibrium metal activity. If a
given amount of sludge is added to a given amount of soil, an amount of
adsorbed metal, X, will be transferred from the sludge to the soil (if the
sludge supports a higher metal activity than the soil), and a new
equilibrium metal activity, CM will result. If the amount of metal in
solution is insignificant compared with that adsorbed, the reaction can be
represented by the following equation, where the subscripts A and B repre-
sent soil and sludge, respectively.
CM = - = - (3)
MTA - (MA + X) MTB - (MR - X)
At equilibrium, equation (3) can be used to solve for X and CM- If X is
small compared with MB, the equilibrium metal activity will be very close
to that for the sludge alone. In theory this approach would permit esti-
mation of both metal solution activity and buffer power for input into
an uptake model. The fact that sludge properties change with time presents
some difficulty in practice.
Experimental Results
Few, if any, investigators have evaluated in a single study the in-
teractions among plant uptake and sludge properties, sludge rate, and metal
36
-------
activity in the soil solution. Fujii (1983) found that application of a
sludge containing 180 mg Cd/kg on sand and silt loan soils at pH 6 + 0.3
maintained Cd activities in the sand 2.5 to 4 times those in the silt loam
at rates up to 18.4 kg 01/ha. Concentrations of Cd in corn tissue grown on
these soils in the greenhouse were 1.5 to 2 times higher in the sand than
the silt loam (Shammas, 1978). Adsorption characteristics of the sludge
and soil were not studied.
Chelating resins have been used for determining Cd-adsorption charac-
teristics of a muck and a sandy soil (Turner et al., 1984), and for charac-
terizing dissolved metal complexes (Henderson et al., 1982; H^ndrickson and
Corey, 1983). Because of the large metal-ion buffering power of these
resins, metal ions can be adsorbed on or desorbed from soils or sludges
without significantly changing the metal-ion activities supported by the
resin, if the proper ratio of resin to soil or sludge is used. Adaptation
of this cheloting-resin methodology to the routine determination of metal
adsorption/desorption characteristics of soils and sludges appears pro-
mising.
Factors affecting the lability of metals in sludges have not been
determined directly, but rather inferred from theoretical considerations,
fractionation studies, or from greenhouse or field experiments with sludges
of different chemical compositions. Greenhouse and field studies have
generally supported the hypothesis (Corey, 1981; Corey et al., 1981) that
much of the immobilization of trace metals in sludges is caused by copre-
cipitation with Fe, Al, and Ca precipitates during the treatment process,
but no way of quantifying this effect has yet been devised.
In comparing the Cd uptake from equal rates of two noncalcareous
sludges in the greenhouse, Cunningham et al. (1975a) found that the average
concentration of Cd in plant tissue was about the same for the 2 sludges
(1.5 vs. 1.4 mg/kg), even though the Cd content of the sludges differed by
a factor of 3 (76 vs. 220 mg/kg). The sludge with the lower Cd content had
a lower Fe content (1.2 vs. 7.9%) and also a lower P content (2.9 vs.
6.IS). Thus, the effect of the higher Cd content in the one sludge may
have been offset by a relatively high content of substances such as
FePOi, with which Cd could coprecipitate. In a field study, the Cd con-
centratior in corn leaves from plots treated with a sludge containing
229 mg Cd/kg, 3.0% Fe, 1.1% Al, 4.7% Ca, and 1.6% P was nearly 3 times as
high (1.7 vs. 0.6 mg/kg) as in corn leaves from plots treated with the
same amount of Cd supplied by a sludge containing 180 mg Cd/kg, 7.8% Fe,
2.5% Al, 1.5% Ca, and 3.0% P (Keeney et al., 1980). The isotopically
exchangeable Cd was also found to be 3 times higher for the sludge low
in Fe and P, even though the total Cd concentrations in the 2 sludges
were similar.
In a greenhouse study, B?tes, Soon and Haq (19/9, personal communica-
tion) added sludges to soils cropped to annual ryegrass over a period of
about 5 years. Fourteen successive crops of ryegrass were grown, with
sludge being added prior to seeding each crop. The cumulative Cd loadings
were 10.6 kg/ha for the Sarnia sludge and 12.1 kg/ha for the Ruelph sludge.
37
-------
The sludges had similar ratios of P to Cd at the start of the fourteenth
crop, but the ratios of Fe to Cd were 889 and 195 for the Sarnia and
Guelph sludges, respectively. The average Cd concentrations in the four-
teenth crop of ryegrass were 1.35 mg/kg for the Sarnia sludge and 2.35
mg/kg for the Guelph sludge. With nearly equal additions of total Cd, the
lower Cd availability was associated with the sludge having the higher Fe
content. In fact, there was a measurable, though not statistically signi-
ficant, decrease in plant-Cd concentration compared to the control treat-
ment with a sludge in which the Fe and P contents were 8 and 5%,
respectively, even though the total sludge-applied Cd was 1.63 kg/ha
(Bates, 1986, Personal commununication).
Bel!, et al. (1985, Personal communication) added 2 sludges with equal
Cd but different Fe concentrations (sludges A and 8 in Table 14) to a fine
sandy loam at rates high enough to show maximum Cd concentration in tobac-
co. The sludge with higher Fe showed lower Cd uptake even though the pH
was slightly lower with that sludge.
Additional evidence that metal concentration in plants may be affected
by the form of metals in sludge can be implied from the work of King and
Dunlop (1982). Sludges from Wilmington, North Carolina (13 mg Cd/kg) and
Fhi-ladelphia, Pennsylvania (225 mg Cd/kg) were applied to several soils in
which corn was grown in the greenhouse. Sludges were applied at rates to
supply equal amounts of Cd. The effect of sludge type was significant, as
evidenced by different slopes in models of Cd concentration in corn stover
regressed on Cd loading rate:
Wilmington: plant Cd (mg/kg) = 0.11 + 0.18 Cd rate (kg/ha)
Philadelphia: plant Cd (mg/kg) = 0.18 + 0.45 Cd rate (kg/ha)
The relationship between sludge rate and metal uptake by plants has
been investigated by many researchers. In general, for Cd and Zn the metal
concentration in tissue approaches a maximum and has shown a logarithmic or
Langmuir-type relationship with sludge rate. In many cases, Cu uptake is
not affected significantly. In studies when the sludge addition was not
high enough to approach a constant metal activity in solution, the rela-
tionship between sludge rate and tissue concentration often approached
linearity. For example, Pietz et al. (1983) and Hinesly et al. (1984a)
found a near linear relationship between Cd or Zn in corn leaves and Cd
application rate up to 111 kg/ha applied to a calcareous strip mine spoil
in a sludge containing about 300 mg Cd/kg. The 3ludge was applied over a
period of 6 years. When the same sludge was applied for 12 years to an
acid Blount soil, the year-to-year variability in leaf analyses obscured
any relationship to cumulative additions (Hinesly et al., 1984a). Vlamis
et al. (1985) also noted a linear response with Cd and Zn in barley with 2
sludges applied at rates up to 225 mt/ha on an acid soil. However, metal
uptake at the high sludge applications may have been augmented by the
effects of lower pH found in these treatments.
In contrast to the linear responses reported above, Soon et al. (1980)
found that Cd in corn stover was logarithmically related to sludge rate
38
-------
(up to 4 kg Cd/ha) for 3 sludges receiving either Fe, Al, or Ca additions
during treatment. All relationships were logarithmic, but the plots of the
Cd concentration in stover and the log of Cd applied differed in slope by
a factor of 3, emphasizing the effects of sludge properties on Cd avail-
ability.
In a field study, Chaney et al. (1982) used sludges with different Cd
concentrations to determine the effect of concentration and application
rate on Cd concentration in lettuce. The first increment of low-Cd sludge
(13 mg/kg) increased Cd concentration in the lettuce slightly, but higher
rates had no further effect on Cd concentration. The first increment of
high-Cd sludge (210 mg/kg) had a pronounced effect on Cd concentration, but
the response to additional increments was less pronounced, indicating a
logarithmic response (Figure 2). Unpublished data on Cd accumulation in
lettuce (Chaney, 1985, Personal communication) (Figure 3) also show a
plateau effect along with an effect of pH and sludge composition.
In another field study (Bell et al., 1985, Personal communication),
tobacco was grown on sludge-treated soil. Copper, Cd, and Zn contents
of the tobacco were affected markedly by the first increment of sludge,
Additional increments had no effect on Cu content, and only slightly
increased Zn and Cd content.
Sommers (1985, Personal communication) presented data in which 3
sludges containing high concentrations of Cd (284, 1210, and 247 mg Cd/kg)
were applied to a Chalmers soil at linearly increasing rates for 2 sludges,
and logarithmically increasing rates for the third (Table 15). Over a
period of 8 years, oats, winter wheat, soybeans, and corn were grown on
these plots. In almost all cases, the relationship between tissue con-
centration of Cd or Zn and rate of metal applied in the form of sludge
was logarithmic or approached a constant value at high sludge rates (Table
15). This was also the case with vegetable data from the Metropolitan
Sanitary District of Greater Chicago (Table 16) and of Hinesly et al.
(1984b). Crops studied by Hinesly et al. (1984b) included corn (Figure
4) and many other grass species (Table 17) grown for 3 years following
sludge application. One interesting aspect of this latter study was the
decrease in Cd concentration in corn tissue with time after application,
particularly at the high rate (Figure 4). This effect is further illus-
trated in data from Dowdy et al. (1984) which show uptake by corn silage
in grams per hectare over a period fron 1979-1984 (Figure 5). These
studies agree with the conclusions of CAST (1980) and Logan and Chaney
(1983), that bioavailabi1ity of metals remains constant or decreases
over a period of years at a constant pH. The marked decrease in metal
uptake at the high rate after 1 year suggests that exposure of anaero-
bically-digested sludges to an aerobic environment, and/or interactions
with soil may produce marked changes in lability of the mete.ls during
the first year following application.
In addition to metal forms and concentrations in sludges, the effects
of sludge additions on soil pH must also be considered. Lime-stabilized
sludges function as liming materials (Soon et al., 1980; Chang et al.,
39
-------
1980). Noncalcareous sludges may either raise or lower soil pH, depending
on such factors as amount of NH4-N nitrified or sludge pH, and pH buffering
capacity in relation to the pH and buffering capacity of the soil. Gen-
erally, plant uptake of metals increases with increasing acidity (CAST,
1980; Logan and Chaney, 1983).
CONCLUSIONS
1. Trace metals in the influent to a sewage treatment plant are asso-
ciated mainly with the solids, and they remain associated with
solids in the sludge following treatment.
2. Concentrations of trace elements in many POTW sludges have decreased
markedly in the past decade as a result of industrial waste pre-
treatment, and this trend is expected to continue.
3. Uptake of solutes by plants is influenced by soil and plant fac-
tors, and a simplified mathematical model is presented to indicate
how these variables interact in affecting solute uptake.
4. The relevant soil variables related to solute uptake affected most
by sludge application are concentration in solution, concentration
of the labile adsorbed form, and distribution of dissolved species
between free-ion and complexed forms.
5. The relevant plant variables related to solute uptake affected most
by sludge application are root adsorbing power (related to specia-
tion in solution and concentrations of other ions competing for
uptake sites) and possibly root geometry.
6. The equilibrium trace element concentrations that a sludge supports
depend on the chemical properties of the sludge, particularly the
presence of trace-element precipitates, whether relatively pure or
coprecipitated with Fe, Al, or Ca precipitates, the strength of
bonding to organic and mineral adsorption sites, the proportion of
potential adsorbing sites filled, and the presence of dissolved
ligands capable of complexing the trace metals. If sludge matrix
is constant, plant availability of a trace element increases with
increasing concentration of that trace element in the sludge.
7. If a sludge supports a higher equilibrium solution concentration of
an element than does a soil, mixing the 2 will result in an equili-
brium concentration intermediate between the 2 that should be pre-
dictable if the desorption characteristics of the sludge and
adsorption characteristics of the soil are known. This hypothesis
has not been tested experimentally.
8. As increasing amounts of sludge are added to a soil, trace-element
adsorption sites on the soil become progressively saturated (or
40
-------
desaturated) to the point that the equilibrium concentration approaches
tnat of the sludge alone. Further sludge applications above a parti-
cular level depending on soil properties should result in little, if
any, change in equilibrium concentration. Below this critical sludge
rate, soil adsorption characteristics affect the equilibrium con-
centration supported by a given addition of sludge. Above that
critical sludge rate, the equilibrium concentration characteristic
of the sludge should be maintained (sludge controls).
9. If the equilibrium trace-element concentration (and buffer power)
supported by the sludge :s less than that which will result in
excessive concentrations in plant tissue or damage to the plant,
there is no need to limit application rates of that sludge en the
basis of metal content.
10. If the equilibrium metal concentration (and buffer power) supported
by the sludge at a specified pH is high enough to cause excessive
concentrations in plant tissue or plant damage, determining maximum
loading rates based on both soil and sludge characteristics will be
required.
11. Most research indicates that plant availability of sludge-derived
metals stays the same or decreases with time following application.
Therefore, any testing procedures developed to estabish long-term
metal-loading limits should be run after the sludge has been
allowed to equilibrate with the soil. Presently the time(s) re-
quired to equilibrate sludges with soils are not precisely known,
but limited data suggest a minimum of two cropping seasons.
12. Methods 'involving chelating resins for obtaining metal desorption
curves for sludges and metal adsorption curves for soils appear
promising.
13. Addition of Fe or Al salts or lime during the sewage treatment
process appears to reduce equilibrium metal activities supported by
sludge; however, research designed to test this hypothesis has not
been done.
41
-------
SLUDGE A
en
.*:
CJ>
E
z~
g
5
cr
\-
z
LJ
CJ
2
O
o
t-
2
LJ
^
UJ
_l
UJ
LJ
O
<
cc
s, s2
SLUDGE APPLICATION, Mt/ho
Figure 1. Basis for differentiating sludges that do not require loading
limits to prevent harmful trace element accumulations in
plants (sludges B, C, and D) from one that does (sludge A).
The two curves for each sludge represent that sludge applied
to a soil of relatively low adsorption capacity (subscript 1)
and a soil of higher adsorption capacity (subscript 2). C0,
is the concentration of a given element in plant grown on
the unamended soil, is shown as being the same for both
soils. Cc is the critical concentration in the plant, and
S and S are loading limits for sludge A applied to soils
(1) and ?2), respectively).
42
-------
2.5
a. .2.0
E
Ol
u
3
4-1
J->
-------
20
6
oo
H
O
O
I
00
UJ
O
D
1-
H
LJ
TD
CJ
15
10
0
LOWER pH
SLUDGE B
HIGHER pH
6 SLUDGE A
LOWER pH
HIGHER pH
0 50 100 150 200
SLUDGE APPLIED, mt/hcu
Figure 3. Effect of sludge application rate on Cd in lettuce leaves.
Sludge A (13.4 mg Cd/kg) and 8.3% Fe) applied in 1976 and
lettuce grown in 1976 to 1983; sludge B (210 mg Cd/kg) and
2.5% Fe) applied in 1978 and lettuce grown in 1978 to 1983.
Results shown are geometric means over years ± standard
error (Chaney, 1985, Personal communication).
44
-------
c
N
1979
1980
1981
0 224 448 896
SLUDGE APPLIED (mt/ha)
CADMIUM
1979
CP
en
UJ
_J
2
O
2
O
O
•a
0 0 224 448 896
SLUDGE APPLIED (mt/ha.)
Figure 4. Effect of a one-time application of municipal sewage sludge
containing 4230 mg Zn/kg and 3UO mg Cd/kg on the Zn and Cd
contents of corn leaf tissue in each of 3 years after
application to a calcareous strip-mine spoil. Data for
1979 and 1980 are from Hinesly et al. (1984c). Data for
1981 are from Table 17.
45
-------
100
80 -
Cd DEPLETION
o
x:
LJ
h-
Q_
TD
O
a CONTROL
o LOW
• MEDIUM
A HIGH
YEARS
Figure 5. Decrease In Cd uptake by corn silage with time after application of sewage sludge
at three rates in 1979 (Dowdy et al., 1984).
-------
Table 9. METAL LOADINGS AND CUMULATIVE PERCENT REDUCTIONS TO CHICAGO
AREA TREATMENT FACILITIES, 1971 THROUGH 1977.
1971
1972
1973
1974
1975
1976
1977
Cumulative
% reduction
Cd
398
343
301
213
113
132
168
57.7
*From Whitebloom et
Table 10.
1971
1984
Cumulative
% reduction
Cr
5,197
3,321
2,463
1,894
1,522
1,527
1,422
72.6
al. (1978)
Cu
2,166 2
1,996 1
961 1
652
538
685
588
72.9
•
Pb
,049
,793
,063
735
497
368
536
73.8
Ni
2,443
1,377
957
643
386
416
436
82.2
METAL LOADINGS AND CUMULATIVE PERCENT REDUCTIONS
AREA TREATMENT FACILITIES, 1971 THROUGH 1984.*
Cd
875
267
69
Cr
11,434
2,607
77
Cu
4,765 4
2,088
56
Pb
,508
871
81
Ni
5,374
1,545
71
Zn
6,972
4,641
4,260
3,403
2,537
2,400
2,587
62.9
TO CHICAGO
Zn
15,338
5,109
67
*Lue-Hing (1985, personal communication). Data in Tables 9 and 10 are
from two different POTWs within the MSDGC system.
47
-------
Table 11. RESPONSE OF METALS CONCENTRATIONS IN DIGESTED SLUDGE FILTER
CAKE AT THE SACK RIVER POTW, BALTIMORE, MARYLAND IN RESPONSE
TO PRETREATMENT EFFORTS.*
Year
1980
1981
1982
1983
1984
1985
Cd
18
19
18
23
26
22
Cu
2840
2070
1110
1060
1010
681
Pb
433
493
398
324
372
346
Ni
381
374
193
214
266
126
Zn
3400
3410
2360
2620
2750
2030
*Source identification began in 1980, and source reduction began in
1981. Based on monthly coirposites in early years, then biweekly and
weekly. Spencer, E. (1985, Personal communication).
48
-------
TABLE 12. RESPONSE OF METALS CONCENTRATIONS IN SLUDGES AT TWO
PHILADELPHIA POTWs IN RESPONSE TO PRETREATMENT PROGRAM.*
Year Cd Cu Pb Ni Zn
_--_-_____ mg/kg dry weight ---------
Southwest
1974 31 825 1540 100 3043
1976 27 1110 2710 103 2650
1977 27 1400 2170 185 3940
1978 16 1020 1800 275 4050
1980 18 986 740 98 2780
1981 25 971 562 117 2300
1982 20 940 1030 113 2440
1983 12.5 736 421 79 1700
1984 14.3 1140 427 111 1830
1985 15.0 880 373 80 1730
Northeast
1974 108 1610 2270 391 5391
1976
1977
1978
1980
1982
1983
1984
1985
97
71
57
26
14
10.9
12.4
17.3
2240
232U
1240
1210
985
1020
1200
1270
2570
2680
1620
728
423
351
360
382
372
459
319
275
185
130
130
187
5070
3920
5910
3890
2=70
2110
1980
2100
*Source identification began in 1976. Liquid sludge analyzed until
1982, and sludge filter cake in 1983 and later. Semske, F. (1985,
Personal communication).
49
-------
TABLE 13. CADMIUM UPTAKE OF MIXED LIQUOR SEWAGE SLUDGE (MLSS) AT
VARYING SOLIDS TO CD RATIOS.*
Run
A
B
C
D
Cd Time of
addedt aeration
mg/L min
1 0
30
60
2 0
15
60
120
180
10 0
15
30
60
30 0
60
120
960
MLSS
mg/L
1900
1900
1900
1000
1000
1000
1000
1000
9680
9680
9680
9680
2600
2600
2600
2600
MLSS
to Cd
ratio
1900:1
1900:1
1900:1
500:1
500:1
500:1
500:1
500:1
968:1
968:1
968:1
968:1
87:1
87:1
87:1
87:1
Soluble Cd
remaini ng
mg/L
0.0153
0.0189
0.0138
0.375
0.186
0.122
0.112
0.066
0.49
0.31
0.15
0.14
7.50
2.28
1.82
0.78
Cd
uptake
%
98.5
98.1
98.6
81.2
90.8
93.9
94.6
96.7
95.1
96.9
98.5
98.6
75.0
92.4
94.0
97.4
*From Elenbogen et al. (1984).
tAdded in the form of CdCl .
50
-------
TABLF 14. EFFECT OF SLUDGE PROPERTIES ON PLATEAU CONCENTRATIONS OF
CD IN TOBACCO LEAVES GROWN IN THE FIELD LONG AFTER SLUDGE
APPLICATION.*
Concentration
Sludget
A
B
in si
Cd
mg/kg
13.2
13.4
13.4
jdcje
Fe
%
2.5
8.3
8.3
Maximum
appl ication
mt/ha kg
224 2
224 3
224 3
Cd/ha
.90
.00
.00
Soil
pH
5.4
5.2
5.8
Cd concentration
above
mg Cd/kg
7
2
0
control
dry wt
.5
.4
.2
*
*Bell, et al. (1985, Personal communication).
tSludge A applied in 1972 to Beltsville silt loam. Sludges B applied
in 197d to Christiana fine sandy loam. Tobacco ('Maryland 609')
grown in 1983 and 1984 for Sludge A, and 1984 for Sludge B.
51
-------
TABLE 15. EFFECT OF SLUDGE RATE AND YEAR AFTER SLUDGE APPLICATION ON
CONCENTRATIONS OF CADMIUM, ZINC, COPPER, AND NICKEL IN OAT
STRAW AND LEAVES OF WINTER WHEAT, SOYBEAN, AND CORN.*
Leaf metal
Sludge
Metal
kg /ft a
Oats
nr
concentrate on
Winter wheat Soybean
(2)
(rf)
(1)
mg/kg -
la)
Corn
(I)
(3)*
Cadmi urn
A
FK
MA
A
FK
MA
0
Ib
32
64
127
0
68
136
203
0
14
28
42
0
381
762
1523
0
106
213
319
0
291
582
875
0.9
1.3
2.0
2.2
3.3
0.9
9.9
15.9
20.3
0.9
0.9
1.1
1.1
20.2
30.3
41.4
48.9
20.2
27.0
30.3
32.0
20.2
20.2
26.0
22.6
0.5
1.5
2.0
5.4
6.5
0.5
12.1
14.6
15.8
0.5
1.1
1.0
1.4
21.9
56.3
67.4
63.5
21.9
52.8
50.5
48.8
21.9
38.0
33.1
30.3
0.3
0.3
0.4
0.5
0.5
0.3
1.2
1.4
1.5
0.3
0.3
0.3
0.3
35.3
38.1
44.2
44.4
35.3
40.1
36.9
40.1
35.3
32.8
38.5
35.6
1.6
2.2
1.8
1.8
2.4
1.6
4.6
5.0
6.0
1.6
2.1
1.7
2.1
Zinc
41.6
53.0
66.8
55.0
41.6
54.4
59.1
63.2
41.6
44.1
48.4
51.2
1.4
1.8
1.9
3.4
4.9
1.4
5.0
8.9
11.0
1.4
1.2
1.3
2.4
72.2
103.5
92.6
110.0
72.2
79.1
80.1
82.9
72.2
76.7
88.5
86.7
1.3
1.6
1.5
1.6
1.9
1.3
5.1
7.8
—
1.3
1.1
1.4
0.9
25.7
39.1
53.7
48.7
25.7
50.5
48.5
—
25.7
44.4
44.7
52.7
0.6
1,2
1.0
1.0
1.1
0.6
5.6
4,7
0.6
1.1
1.1
0.8
69.8
62.7
71.3
77.0
69.8
56.2
54.1
--
69.8
78.1
67.8
83.9
(continued)
52
-------
TABLE 15 (continued)
Leaf metal concentration
Sludge
A
FK
A
Metal
kg/ha
0
67
134
269 '
538
0
74
149
223
0
25
50
76
Oats
(1)
Winter
(2)
wheat
(8)
Soybe
(1)
L- n
an
(3)
Corn
(1)
(«)
2.0
2.2
3.0
4.9
6.0
2.0
2.6
4.2
3.7
2.0
2.5
2.5
2.6
4.0
4.1
5.0
13.0
7.8
4.0
4.6
4.3
4.5
4.0
3.7
4.9
4.0
Cop
2.6
2.5
3.4
4.0
4.8
2.6
4.8
3.7
4.7
2.6
3.2
3.1
2.7
per
7.4
8.7
8.1
7.7
7.4
7.4
9.8
10.1
10.3
7.4
8.2
8.4
10.0
9.1
9.4
9.4
9.7
10.2
9.1
10.1
10.6
11.2
9.1
10.0
10.9
10.2
8.3
8.2
9.2
9.4
10.3
8.3
11.4
10.6
--
8.3
7.9
8.9
9.6
5.5
5.9
6.4
7.5
7.7
5.5
6.7
6.8
--
5.5
7.1
6.7
4.7
Nickel
A
FK
A
0
114
228
451
914
0
24
48
72
0
12
24
36
1.1
2.0
3.3
5.1
12.5
1.1
1.6
2.5
3.4
1.1
1.1
1.2
1.3
2.9
3.2
4.0
9.8
7.5
2.9
4.1
2.8
3.6
2.9
2.5
2.7
2.7
0.3
0.3
0.4
0.4
0.8
0.3
0.4
0.6
0.5
0.3
0.4
0.5
0.4
49.3
18.5
20.2
28.5
20.8
49.3
44.1
28.4
19.2
49.3
21.3
24.2
11.4
5.7
9.5
9.3
10.9
16.6
5.7
6.9
8.6
9.2
5.7
3.7
5.2
4.2
3.1
3.9
1.6
5.9
2.5
3.1
2.3
2.6
--
3.1
1.3
6.8
1.4
0.2
0.3
0.2
0.3
0.3
0.2
0.3
0.2
—
0.2
0.5
0.5
0.4
*Sommers (1985, Personal communication).
tLeaf tissue for winter wheat, soybean and corn; straw for oats.
^Numbers in parentheses denote crop year following sludge
application.
53
-------
TABLE 16. CADMIUM, ZINC, COPPER, AND NICKEL CONCENTRATIONS IN EDIBLE
PARTS OF VEGETABLES GROWN AT WEST-SOUTHWEST SEWAGE TREATMENT
WORKS, METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO.*
Crop
Beets
Tomatoes
Swiss
chard
Carrots
Green
beans
Spinach
Beets
Tomatoes
Swiss
chard
Carrots
Green
beans
Spinach
Year
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
(1982)
1979
1983
19/9
1983
1979
1983
1979
1983
1979
1983
1979
1983
(1982)
0
0.2
0.7
1.1
2.0
2.3
1.3
0.7
1.3
0.4
0.1
6.4
8.5
10.3
34
39
27
27
69
62
20
31
32
38
147
209
201
Sludge
60
Cadr
1.4
1.8
1.8
2.2
8.0
4.0
1.4
1.8
0.3
0.1
12.6
21.4
11.3
Zinc
45
55
30
32
129
91
22
33
33
35
249
433
276
added, mt/ha
120
/kg edible
nium
1.6
2.0
2.4
2.1
12.2
8.1
1.2
2.8
0.4
0.2
10.3
28.3
17.2
62
59
30
31
176
120
25
30
37
33
265
404
315
240
tissue
2.7
1.8
2.2
2.6
16.8
8.4
1.9
3.4
0.4
0.1
14.4
31.7
10.6
93
80
34
29
237
129
27
31
37
35
309
451
226
300
2.9
4.9
3.4
2.9
22.1
12.2
2.3
3.1
0.5
0.2
12.1
33.8
11.8
90
97
35
32
302
251
32
33
37
35
311
472
258
54
(continued)
-------
TABLE 16 (continued)
Sludge added, mt/ha
Crop
Beets
Tomatoes
Swiss
chard
Carrots
Green
beans
Spinach
Beets
Tomatoes
Swiss
chard
Carrots
Green
beans
Spinach
Year
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
1979
1983
0
8.8
9.7
13.2
10.4
23.7
25.2
5.4
7.9
8.6
8.5
13.8
12.3
0.5
2.1
1.1
6.8
1.3
0.8
0.6
1.9
3.3
2.3
1.4
10.6
60
Copper
10.4
11.9
16.6
12.4
20.8
26.6
6.0
7.8
8.9
9.1
14.2
14.2
Nickel
0.6
2.6
1.3
7.1
1.4
2.3
1.1
0.7
1.2
2.1
1.5
5.8
120
metal/kg edible
9.8
12.3
14.5
11.9
25.6
27.6
5.8
7.5
9.2
7.6
17.3
15.1
0.9
2.8
1.4
27.1
2.5
2.4
•1.4
0.8
2.4
2.9
1.7
8.8
240
tissue
11.1
14.2
16.2
11.0
30.9
26.7
5.9
7.8
8.2
8.6
18.9
16.3
1.4
3.3
4.1
7.2
3.5
2.1
2.2
1.2
3.6
5.1
2.7
6.0
300
12.8
14.1
16.6
12.0
29.2
29.4
6.5
7.7
8.5
7.9
19.1
17.4
1.5
6.6
2.7
8.4
4.3
3.3
2.9
1.0
3.3
4.7
2.6
10.0
*Nu Earth was applied from 1977 through 1979 in three equal applications
(C. Lue-Hing, 1985, Personal communication).
55
-------
TABLE 17. EFFECT OF SLUDGE RATE APPLIED IN 1979 ON CONCENTRATIONS OF
CADMIUM, ZINC, AND COPPER IN WHEAT, RYE AMD FOUR GRASSES
IN 1981.*
Sludge rate, mt/ha
Crop
Wheat (leaf)
Rye (leaf)
Redtop
Brome
Orchard grass
Western wheat grass
Reed canary grass
Perennial rye
Timothy
Tall fescue
Wheat (leaf)
Rye (leaf)
Redtop
Brome
Orchard grass
Wetern wheat grass
Reed canary grass
Perennial rye
Timothy
Tall fescue
Wheat (leaf)
Rye (leaf)
Redtop
Brome
Orchard grass
Western wheat grass
Reed canary grass
Perennial rye
Timothy
Tall fescue
0
<0.1
0.1
0.1
0.1
0.2
<0.1
0.1
<0.1
0.1
0.1
15
20
19
17
21
19
28
17
23
23
7
10
5
5
4
4
6
4
5
5
224
Cadmium
0.7
0.4
0.3
0.8
0.5
0.4
0.2
0.1
0.1
0.4
Zinc
26
42
45
29
32
35
62
40
50
35
Copper
8
13
9
7
6
7
9
6
9
7
448
tissue
1.6
O./
0.8
1.0
1.4
0.8
0.6
0.9
0.2
0.9
39
71
68
40
39
41
104
90
65
48
9
18
12
8
7
S
11
10
10
8
896
1.5
0.9
1.2
1.6
1.7
0.7
O.H
0.7
0.8
1.8
46
61
86
48
49
44
121
88
74
62
9
18
14
10
9
8
13
17
12
10
*Hinesly and Redborg (1984b)
56
-------
SECTION 4
EFFECTS OF LONG-TERM SLUDGE APPLICATION ON
ACCUMULATION OF TRACE ELEMENTS BY CROPS
INTRODUCTION
Since the last comprehensive review of elemental uptake by plants
grown on sludge treated soils (Logan and Chaney, 1983), considerable data
from long-term field experiments have become available, ilost experiments
were designed to assess the effects of sludge applications on plant accu-
mulation of metals (e.g., Cd, Cu, Ni, Zn, etc.). This report will con-
centrate on newly available long-term field data in terms of their
implications on land application of sludges.
In the following sections, we will attempt to answer:
(1) What is the qual ty of experimental data?
(2) Do repeated annual sludge applications affect the metal accu-
mulation in plant cissue?
(3) Do the plant tissue metal accumulation patterns of a single
sludge application differ from those of multiple sludge appli-
cations having equal total metal input? and
(4) Does metal uptake by plants change following termination of
sludge application?
Nature of_ the Experimental Data
The data used for the analyses and the results presented in this
report are, for the most part, derived from replicated field experiments.
Logan and Chaney (1983) pointed out that common errors in the study of
toxic element uptake by plants grown i,i sludge treated soils are (1) sub-
stituting inorganic metal salts for sludge or spiking the sludge with
inorganic salts in preparing the growth medium; (2) relying on short term
small pot experiments in the greenhouse rather than field observations to
57
-------
predict metal concentrations in plants. Recently data from field studies
have become available which allows us to greatly reduce our reliance upon
information flawed by the above mentioned errors. During the course of
our deliberation, only in the absence of field data did we draw upon
"large" pot, greenhouse or growth chamber findings. It has not been
necessary to use any data derived from studies that used "salts" as the
metal source.
The drawing of "general" conclusions from a pool of information
derived from unrelated field studies have limitations that must be
recognized (plant species exhibit different abilities to accumulate
metals). Only plant species that showed a positive metal uptake result-
ing from sludge applications can be considered for evaluation of factors
that affect response. Environmental factors that influence the metal
accumulations are reviewed in detail in Sections 2 and 3. Where pos-
sible, these differences have been recorded along with data presented.
The recognition of these constraints served as the impetus for the
USDA, CSRS Regional Technical Committee, W-124, to conduct a "uniform"
field study at 15 locations across the United States in 1979 (see Sec-
tion 2 for details). Data from this study were used in our delineation.
CUMULATIVE EFFECTS FROM ANNUAL SLUDGE APPLICATIONS
From the data provided by several researchers (VIamis, et al.,
1985; Soon and Bates, 1981; Chang et al., 1983; Hinesly et al., 1984) it
was apparent that cumulative effects from annual sludge applications may
be broken down into two categories, according to the metal inputs, name-
ly: (1) zinc and cadmium when introduced with sludge at high levels (>100
kg Zn/ha/yr and >1 kg Cd/ha/yr) resulted in an increase in plant tissue
metal over the years of sludge application, but the rate of increase
decreased with time; and (2) typical sludges applied at agronomic rates
to satisfy N requirement for crop growth cause Cd and Zn concentrations
in plants to become greater than those of the control but Cd and Zn con-
tents of plant tissue remained at a low, nearly constant level with each
successive sludge application.
When sludges were applied to barley at rates equivalent to 8.6 kg
Cd/ha and 714 kg Zn/ha annually over a 7-year period, the concentration
of Cd in the barley straw increased from C.26 to 3.39 mg/kg (Table 18,
Vlamis et al., 1985). At the the same time the Zn concentration of the
plant tissue increased from 113 to 820 mg/kg. During the experiment,
the pH of the sludge-treated soil decreased from 5.5 to 4.8 which could
account for some of the increase in metal accumulations by the barley.
While the Cd and Zn accumulation in the vegetative part of barley was
substantial, the barley grain harvested from sludge-treated soils con-
tained considerably lower levels of Cd and Zn and frequently were not
significantly different than those of the control. Swiss chard shows a
similar Cd and Zn uptake response, except in greater amounts. With an
58
-------
average input of 8 kg Cd/ha annually, Swiss chard took up 0.9 mg Cd/kg
plant tissue the first year and increased to 18.0 mg Cd/kg by the tenth
year. Again, as with the barley/sludge system, the pH decreased from its
original 7.0 to 6.5. The long-term effects of sludge applications on the
Cd and 2n levels in affected soils and Swiss chard are illustrated in
Fig. 6 and 7 (Chang and Page, 1985, Personal communication). Soon and
Bates (1981) measured Cd and Zn contents of corn and bromegrass on
sludge-treated plots with a total accumulative Cd and Zn additions of 5.6
and 680 kg/ha, respective^, over an 8-year period. As with barley and
Swiss chard, addition of sludge resulted in an increased metal content in
the corn and bromegrass. Although the Cd and Zn inputs were high the
successive additions of sludge did not result in a continuous increase of
Cd and Zn concentrations in plants. The use of iron (Fe++J") and aluminum
(Al~H"f) treated sludges in this experiment might have affected the
results.
Table 19 summarizes the Cd and Zn contents in crops that were
grown with sludges applied to satisfy nitrogen requirements of plant
growth. In all cases, the concentration of Cd and Zn in the affected
plant tissue remained constant over the years of application. The levels
of Cd and Zn were greater for plants in the sludge-treated plots than the
control plots.
There appeared to be a slight but statistically significant
increase of Cu and Ni in plants grown on sludge-treated soils when they
were compared to plants grown on untreated soils. Their levels did not
appear to rise annually with the successive sludge inputs (Soon and
Bates, 1981, Table 20). The crops (corn and bromegrass) were grown on
calcareous soils which undoubtedly reduced plant availability of the
added metals. An earlier report (Vlamis et al., 1978) on sludge applica-
tion to a noncalcareous soil, however, supported the observations that Cu
and Ni are generally not accumulated in plant tissue. In this study 324
kg Cu/ha and 97 kg Ni/ha were applied in the form of sludges over a
three-year period and the barley grown on sludge-treated soils did not
accumulate significant amounts of Cu and Ni. Studies by other investiga-
tors (Chaney, 1985, Personal communication) also showed little detrimen-
tal effect to plants at Cu and Ni input levels considerably higher than
those reported by Soon and Bates (1981) and Vlamis et al. (1978). In
sludge treated soils maintained at pH > 6.0, phytotoxicity from sludge
applied Cu and Ni accumulation has rarely been reported (Marks et al.,
1980).
From the data reviewed, there are pathways in the sludge-soil-
plant system by which potentially harmful metal elements can accumulate
in plant tissue through land applications of sludge. Amounts absorbed
by plants are small and usually accounted for
-------
SINGLE VS. MULTIPLE APPLICATION
Depending on the way sludges are applied, plants often respond to
Cd and Zn introduced into soils in a different manner. Response curves
(i.e., metal input from sludge applications vs. metal levels in plants)
yenerated from single sludge additions usually have steeper slopes than
response curves generated from multiple sludge additions which have the
same total input spanned over a period of tine. This would imply that
the relationship between total applied metal and the resulting metal con-
tent in plants is not necessarily unique. Based on tne results of a
greenhouse pot experiment, the relationship appeared to be a function of
the annual application rate (Ryan, 1982).
Results from the W-124 experiment were used to illustrate the pat-
terns of Zn and Cd concentrations in plants with multiple sludge applica-
tions and a single sludge addition which had the equal total input. To
summarize the data from various locations into a single diagram, we con-
verted metal concentrations in plant tissue into "relative metal incre-
ment of plant tissue" (RMI) which is the ratio of metal increment of
plants for a given year (i.e., metal concentration of affected plant
tissue minus metal concentration of the control plant) to the first year
metal increment of plants receiving 20 mt/ha treatment.
The graphic illustration of the data may be divided into several
regions. Under the multiple sludge applications, the line of RMI=0 re-
presents the metal concentration of plants equal to the background metal
concentration (Fig. 8). The line RMI=1 represents non-additive effect
which indicate, with subsequent sludge inputs, the increment of metal
concentration in affected plant tissue are equivalent to that of the
first year. The additive effect of multiple sludge inputs on metal
contents of plant tissue is represented by the 1 to 1 line that passes
through RMI=0. There was a wide range in the relative metal increments
of each location, and in one occasion the RMI even exceeded the strictly
additive regime. The mean annual RMI for all locations, however, were
approximately 1 (0.86-1.08) indicating non-additive effects due to
multiple sludge applications. Sometimes, the relative metal increments
of the plant tissue in subsequent years was significantly lower than
increments of the first year.
A large single sludge application (100 mt/ha in this case) pro-
duced a high plant tissue metal concentration in the crop immediately
following the sludge application (Fig. 9). This large single sludge
application produced a sharp rise of Zn levels in plant tissue. In 3 out
of the 11 cases, the first year metal increment of plant tissue exceeded
those calculated by the strictly additive rule with first year metal
increment of the 20 mt/ha/yr as the reference point. The RMI of suc-
cessive crops from the single sludge addition, however, decreased. By
the time when inputs from the multiple applications had reached the same
amounts as with the single application (year 5 in this case), the plant
tissue metal increment of the single sludge application was not signifi-
cantly different from that of the multiple sludge applications.
60
-------
METAL ACCUMULATIONS FOLLOWING TERMINATION OF SLUDGE APPLICATIONS
In the early days of land application studies, several researcher1:
hypothesized that organically complexed metals in soils were less avail-
able to plants than uncomplexed metals. When sludge applications were
terminated, soil microbial activity would reduce organic matter levels of
the sludge-amended soils resulting in a higher availability of sludge-
borne metals (Chaney, 1973; Haghiri, 1974; Brown, 1975). Rut the long-
term observations made in field experiments show that the plant
availability of metals in sludge-treated soils either remained unchanged
or was reduced with time after cessation of sludge applications (Touchton
et al., 1976; Dowdy et al., 1978).
Data from a field experiment in Illinois showed that where sludge
was applied annually for three consecutive years at the agronomic nitro-
gen rates on silt loam soils, Cd and Zn concentrations in leaves, stover
and grain of corn were increased significantly by the sludge addition.
After sludge applications were terminated, concentrations of these metals
in aerial parts of corn plants, although still higher than the control,
decreased with each successive corn crop (Hinesly et al., 1979). Three
years after sludge additions ceased, Cd concentrations of corn grain from
the sludge-affected soils had receded to levels similar to those from
control plots and levels of the metals in leaves and stover from sludge-
treated plots were slightly higher than those from control plots. Webber
and Beauchamp (1979) and Dowdy et al. (1978) reported similar patterns
of metal accumulation in plant tissue.
Crops grown on a soil which received annual sludge applications
exhibited a slight but significant increase in Cd and Zn concentrations
of plant tissues (Hyde et al., 1979) irnmed; .1ly following the termina-
tion of sludge applications at this location. Chang et al. (1982) grew
two winter wheat crops and observed that Cd and Zn concentrations of
wheat grain and straw from sludge-treated plots were slightly higher
than those from control plots. Concentrations of these metals, however,
were well within normal ranges of concentrations found in wheat grown on
uncontaminated soils. Similar results were found by Hinesly (1985) for
Cd, Cu, Ni, and Zn contents in soybeans and wheat grown on plots of silt
loam soil where sludge applications were terminated after four and six
years of annual applications.
Even for soils that received repeated heavy sludge applications
and for plants that were sensitive to metals in the soil, there was
little indication that the availability of sludge-borne heavy metals
would rise upon termination of sludge applications. In one field trial,
the spring and fall split applications of composted sludge at rates
ranging from 22.5 to 180 mt/ha/yr on one-half of the experimental field
was discontinued after the 6th year. The Cd and Zn contents of plants
(Swiss chard and radish) harvested from the area no longer receiving
sludges remained elevated but concentrations were lower than those
obtained from the area where sludge applications continued (Chang and
61
-------
Page, 1985, Personal communication). For the six croppings (3 years)
following the interruption of sludge applications, the metal concentra-
tions of harvested plants remained at levels similar to or less than
those at the time sludge application was terminated (Tables 21 to 26).
Based on the data, there is no evidence that the bioavailabi1ity
of metals in sludge-treated soils will rise with time after terminating
the sludge application. Unless chemical conditions of the sludge-treated
soils are altered or a metal sensitive plant species is planted, there is
no indication that pla.it uptake of metals should increase with time
following termination of sludge application.
CONCLUSIONS
1. Application of Cd and Zn to soils from municipal sludge will cause
the Cd and Zn concentration of plants grown on these soils to exceed
those of the untreated controls. When the sludge is applied at
rates to satisfy the N requirement of the crop grown the Cd and Zn
contents of plant tissue remain at nearly constant levels with
successive sludge applications.
2. In sludge treated soils maintained at pH >6.0, Cu and Ni contents
of the tissue from plants grown on these soils may become slightly
elevated. Phytotoxicity from sludge-applied Cu and Ni, however, has
rarely been reported.
3. Given adequate time for sludge to equilibrate.- with the soil, metal
concentration of the affected plant tissue would be determined by
the total amounts of metals in the soil and would not be affected
by the methods of sludge application (e.g., single addition vs.
multiple applications to yield the same total application as the
single addition).
4. Plant availability of sludge-borne metals is highest during the
first year sludge is applied. Using the first year response curve
generated by a large single sludge addition will overestimate metal
accumulation in vegetative tissue from plants grown in well sta-
bilized sludge/soil systems.
5. There are no field data to indicate that trace element concentra-
tion in plant tissue will rise after the termination of sludge
applications if chemical conditions of the soil remain constant.
Cadmium and zinc levels of plants grown in soils which are no
longer receiving sludges either were not significantly different
from the pretreatment levels or decreased with time.
-------
en
CO
SLUDGE
TRtATMENT:
Q (control)
22.5
90
180
10
_J
o >
CO 5. 14
2 cf 10
l± O>
< J. 6
O
2
_ 000
-1 =J
0 -o
<^ 600
— C7>
0 ^400
S E
200
^OmrTTTTEa
rmmifllTm
-
4U±w:
T f I r^
Tff
r-T
tffflirfiTII
if
_
1
riT
1 — \~ •
rffl"
» —
[-,
i —
r-
j- -, 1
-r
-
•
*
-
iH
-
-
-1
- 1
r
f
1 —
r-
j—
/J
[
r~
-
~
"Tl
-
-
PI
_ X
p
1
j-
I-"
n "
-f-T
rr-
-
1
r-i
L
YEAR !9T6| 78 ( 00 |
79 81
jr 31 sr ^r ;,r i ji *_,t -jt if bh if -jt b if if bl- bf bh bf bl S ot jf bl- bF bF bF bl 5 M 'if \A '.I i>l jf
78 | 00 | 82 76 | 78 | 80 | 82 76 , 78 , 80 | 02 76 , 78 | 80 | 82 76 | 78 | 80 ( I
7 79 fll 77 7Q Ri 77 79 81 77 79 81 77 79 81
77 79 81
Fig. 6. Cd and Zn concentrations of composted sludge treated Ramona sandy loam (Chang and Page, 1985).
-------
SlUDGC .
TRf.ATMr.NT: (mt/ha/yr)
0 (control)
225
IG
n_
a.'
800
f)0°
--- -100
'" t"
i |
RANGE it i— MfAN
' P
90
100
Jl.
St Sf Si SI :J SI .1 Si
i.
SF'SI sT'sF'sF'sfGF'SF' si'si sr
ft
it
- H--1 ,
SI SI Sf 51 Si
*n
w
• *
Yf'AH I9/'G 70 BO 02 76 78 80 82 76 78 80 82 76 78 80 02
77 79 8! 83 77 79 81 83 77 79 81 03 77 79 81 83
'51 V'.l MM 'Sf SI M
7G 70 00 82
77 79 ft I n
Fig. 7, Cd and In content of Swiss chard harvested from soils receiving biannual (spring and fall)
sludge application from 1976-1983 (Chang and Page, 1985).
-------
STRICTLY
ADDITIVE
NON
ADDITIVE
BACKGROUND
20 40 60 80 100
SLUDGE INPUT (rut/ha)
0 1
z
3 4
YEAR
5
Fig. 8. Relative Zn increments of barley leaf receiving annual sludge
addition of 20 mt/ha for five years (calculated with data from
11 of the 15 experimental sites of W-124).
65
-------
6
1 5
1 4
0.
Z
0 3
M
z 2
UJ
UJ
Z 1
2 0
Ul
< -i
_j
UJ
cr
-2
8.5'
•
-
\
\
\
\
\
\
\
STRICTLY
ADDITIVE
Tt
RANGE
MEAN'1
-L
\
Ns T REFERENCE
"•"'-._____ AT20i»t7ho
-
• 111!
31 2345
YEAR
Fig. 9. Relative In increments of barley leaf receiving 100 r. ;/ha one-
time sludge application (calculated with data from 11 of the
15 experimental sites of W-124).
66
-------
TABLE 18. CADMIUM AND Zn CONTENTS OF PLANT TISSUES WHEN SLUDGES WERE APPLIED ANNUALLY AT HIGH RATES.
Metal/Crop
Cd/Oarley
Barley
Corn
Brou-
grass
Swiss
chard
Swiss
chard
Swiss
chard
Zn/Barley
Barley
Corn
Brom-
grass
Sw1rs
chard
Swiss
chard
Sw\SS
chard
Plant
parts
straw
straw
stover
above
ground
above
ground
above
ground
above
ground
straw
straw
stover
above
ground
above
ground
above
ground
above
ground
Total
metal
Inputs
(kg/ha)
60
0
5.44
6.08
80
20
0
5000
0
680
672
6400
1600
0
pH
Initial/
final
5.5/4.8
5.5/5.5
7.5/6.7
7.4/7.2
7.0/6.2
7.1/6.5
7.2/7.5
5.5/4.8
5.5/5.1
7.5/6.8
7.4/6.9
7.0/6.2
7.1/6.5
7.2/7.5
1
0.26
0.09
0.38
0.09
0.9
0.5
0.3
113
72
41
28
105
79
67
2
0.23
0.04
0.54
0.39
2.7
07
0.3
150
58
69
41
191
90
50
No.
3
0.55
0.07
0.80
0.23
3.2
1.2
0.2
248
71
103
39
216
111
40
of successive annual applications
4
Met at
0.63
0.06
0.70
0.20
4.2
1.0
0.1
341
51
88
34
249
116
39
5
In plant
0.85
0.04
0.53
0.28
6.9
2.0
0.4
402
37
85
40
324
110
66
6 T
tissue (mg/kg)
1.61
0.10
0.36
0.27
7.1
3.3
0.9
455
116
77
42
209
155
67
3.39
0.06
0.39
O.M
9.4
5.5
1.2
820
6B
74
44
275
146
56
8
.
-
0.57
0.45
4.4
3.2
0.6
_
-
65
65
372
261
52
9 10
Reference
.
VI amis
Soon 4
Soon I
13.1 18.0 Chang
7.2 8.7 Chang
0.8 1.7 Chang
Vlamis
-
Socn i
Soon 1
. 844 907 Chang
345 567 Chang
68 34 Char.g
et al. N8S
Bj'es 198)
Bates lOfll
S Page 1985
i Page 1985
4 Page 1985
et a). 1085
Bates 1081
Bates 1081
i Page 1985
4 Page 1085
I Page 1085
-------
TABLE 19. CADMIUM AND Zn CONTENTS OF PLANT TISSUE WHEN SLUDGES WERE APPLIED AT AGRONOMIC RATES.
Metal/Crop
Cd/Barley
Barley
Corn
Brome-
grass
Barley
Barley
en
00 Barley
Barley
Zn/Barley
Barley
Corn
Bron-
yrais
Barley
Barley
Barley
barley
Plant
parts
straw
straw
stover
whole
plant
grain
grain
grain
grain
straw
straw
stovi r
whole
plant
leaf
leaf
le^f
leaf
Yrs. of
sludge Total pli
appltca- netal Initial/
tlon Inputs fln/l
7
7
B
B
6
6
6
6
7
7
8
B
6
6
6
6
2
0
0.72
1.6
5.5
0
5.5
0
133
0
112
192
BO
0
80
0
5.5/7.0
5.5/5.8
7.4/7.3
7.4/7.4
6.1/6.7
6.3/7.1
7.1/7.1
7.1/7.1
5.5/7.0
5.5/5.8
7.5/7.3
7.4/7.4
6.1/6.7
6.3/7.0
7.1/6.9
7.1/7.1
1
0.23
o.oa
„
0.04
0.07
0.0?
0.06
0.03
66
45
26
20
19
16
24
20
No.
2
0.07
0.04
0.30
0.16
0.05
3.04
0.02
0.02
46
41
23
24
22
13
20
14
of successive annual applications
3 4
Metal In plant
0.16
0.06
0.29
0.08
0.04
0.01
0.01
0.05
52
52
35
25
23
25
17
IB
0.20
0.08
0.27
0.12
0.04
0.04
0.04
0.04
46
36
30
23
32
21
29
22
5 6
tissue (tng/kQ)
0.12
0.09
0.25
0.11
0.04
0.04
0.04
0.04
44
30
31
27
32
18
25
21
0.26
o.oa
0.17
0.08
0.05
0.04
0.05
0.04
93
98
30
24
47
22
26
21
7
0.24
0.04
0.16
0.12
.
-
-
-
54
57
29
25
.
-
.
-
8
Reference
VI amis et al.
-
0.18 Soon 1 Bates
0. 11 Soon t Bates
Chang et al .
-
Chan; et al.
-
VI amis et al.
-
27 Soon I Bates
32 Soon i Bates
Chang et al.
-
Chang et a! .
-
1905
1981
1981
19S3
1983
1985
1901
1981
1983
1983
-------
TABLE 20. CADMIUM AND N1 CONTENTS OF PLANT TISSUES FROM SLUDGE-TREATED SOILS.
Metal Crop
Nt
Cu
Corn
Cora
BriM-
grasi
Bron-
yrass
Corn
Corn
Broa-
yrass
Bro»-
grass
Plant
parts
Stover
stover
whole
plant
whole
whole
stover
stover
whole
plant
whole
plant
Yrs. of
sludge Total
appllca- metal
tton
8
8
8
8
8
8
8
a
Inputs
507
63
624
156
354
88
3J2
98
pit 1
Initial/
final
7.5/8.
7.5/7.
7.4/8.
7.4/7.
7.5/6.
7.5/7.
7 5/6.
7.4/7.
No.
2
of successive
3 4
Metal In plant
0
8
0 -
7 -
7 -
3 -
7
3 -
1.5
i.O
0.2
0.3
12
8
11
8
1.5 0.5
1.6 0.4
1.2 0.6
1.6 0.5
10 7
8 6
15 14
10 9
annual
5
tissue
2.3
1.9
6.0
3.5
11
9
10
10
appl (cations
6
7 8
(mg/kg) Reference
1.0
0.7
4.3
2.0
8
6
15
10
1.2 1.9 Soon 1 Bates 1981
0.6 0.7
4.2 4.8 Soon S Bates 1981
2.2 1.9
9 8 Soon J Bates 1981
6 6
14 14 Soon 1 Bates 19BI
7 8
-------
TABLE 21. CADMIUM CONCENTRATIONS (mg/kg) OF SWISS CHARD GROWN ON SLUDGE-TREATED SOILS
(CHANGE AND PAGE, 1985).
22.5 •t/ha/yr"
Year
1976 '
1977
1978
1979
1980
1981
1982
1-183
NB4
14115
Season
Spring
Fall
Spring
Fall
Spring
fall
Spring
fall
Spring
Fall
Spring
fall
Spring
Fall
Spring
Tall
Spring
Fall
Spring
Fall
Control
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
)
1
.72
.28
.20
.25
.20
.20
.28
. 1?
Si
.42
.50
.90
.50
.20
.70
.50
.40
.8
.4
.'>
Continued lerni-
Appllcation nated
1.
0.
0.
0.
0.
0.
0.
c.
0.
0.
1.
1.
1.
2.
3.
2.
4.
3.
3.
4.
05
35
58
40
48
50
62
52
90
72
45
75
35 1.70
68 2.30
18 2.00
02 1.30
82 2.30
00 1.40
30 1.00
10 2.80
45 mt/ha/yr*
Continued Termi-
Applicatton nated
l.ZB
0.52
1.35
0.72
1.60
1.20
1.55
0.98
3.05
1.95
3.15
3.30
3.15
5.50
3.72
3.32
5.68
7.20
11.3
8.70
-
-
.
-
.
-
.
-
.
-
.
-
3.80
5.20
3-BO
2.50
5.60
4.80
3.60
5.60
90 mt/ha/yr*
Continued Termi-
Applicatlon nated
l.X
0.88
1.75
1.78
3.38
2.58
3.75
3.48
6.85
3.80
5.40
6.32
5.75
7.45
5.29
3.65
6.30
9.80
18.30
13.60
-
-
.
-
.
-
-
-
.
-
.
-
6.10
6./0
4.60
3.80
6.P.O
7.40
10.90
8.60
1110 ml/hi/yr"
Continued U-r.ai-
Appl teuton njted
-
0.88
3.28
2.72
5.12
3. IB
4.02
4.15
7.75
6.88
7.35
7. 12
8.32
9. Jd
7.65
4.38
9.32
13. 10
21.60
ID. 00
-
-
_
-
_
-
_
-
.
-
.
-
11. m
a. ;o
7.20
3.70
5.80
10. 70
17.20
9. SO
*l iperlmenttl Held was split after Fall 1981
received sludge but was cropped.
where one-h»lf continued to receive sludge and the other half no longer
-------
TABLE 22. ZINC CONCENTRATIONS (mg/kg) OF SWISS CHARD GROWN ON SLUDGE-TREATED SOILS
(CHANG AND PAGE, 1985).
fear
1976
,977
W78
1979
1980
1981
1982
1983
1984
1985
Season
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Spring
Fall
Control
65
67
45
50
48
40
51
39
81
66
76
67
61
67
52
54
84
66
73
37
22.5 iBt/ha/yr*
Continued Ternil-
Appl Icatlon nated
167
67
72
60
62
47
85
78
101
71
152
96
107
106
203
138
202
188
232
209
_
.
-
-
.
-
127
88
If; 3
94
95
98
101
99
45 *t/h»/yr*
L ,nl Inued
Appl Icatlon
170
79
124
90
127
ill
149
116
301
110
297
155
251
146
320
261
176
345
389
567
Termi-
nated
-
.
.
.
_
.
278
174
268
225
218
290
252
218
90 Bt/ha/y
Continued
Application
229
105
215
189
241
172
332
289
550
192
368
322
3B2
213
361
319
554
725
768
Terml -
nated
„
-
.
,
_
-
337
240
313
1)6
348
554
305
510
1BO mt/ha/
"Continued
Application
105
215
191
432
216
378
249
633
3?4
366
2VO
475
275
490
3/2
373
844
1000
9') 7
*£-,
Terml -
rated
.
-
-
-
-
-
465
2«2
404
31)4
23(1
71)
548
562
"experimental Meld was split after Fall 1981 where one-half continued to receive sludge and the other half no longer
received sludge but was cropped.
-------
TABLE 23. CADMIUM CONCENTRATIONS (mg/kg) OF RADISH LEAF GROWN ON SLUDGE-TREATED SOILS
(CHANG AND PAGE, 1985).
fear
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
Season
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Control
0.2
0.2
0.3
0.5
0.2
0.3
0.5
0.7
1.0
0.6
1.1
1.7
0.8
1.8
1.4
U.8
0.9
0.6
I,.?
0.6
22.5 urt/ha/yr v
Continued Terml-
Appllcatlon nated
0.4
0.6
0.6
0.7
0.2
1.0
2.0
2.5
1.4
1.8
1.8
2.3
2.1 1.2
3J 3.1
?.a 2.1
2.2 1.5
2.5 1.2
2.8 1.1
4.2 1.7
3.4 1.6
45 mt/hj/yr'
Continued Terml-
Appllcatlon nated
0.4
0.9
0.9
1.9
1.2
1.4
2.5
3.6
2.0
3.8
2.7
4.2
3.1 1.9
5.6 3.5
3.7 2.7
2.H 2.2
6.6 2.6
6.7 2.1
11.8 3.7
5.5 3.2
90 mt/ha/yr*
Continued Terml-
Applicalion nated
0.5
1.1
1.5
2.8
1.4
2.0
3.1
5.9
3.2
3.8
5.4
6.1
5.9 2.9
7.2 4.8
4.9 3.6
3.7 2.4
8.0 3.2
8.5 3.6 •
13.7 9.5
7.9 4.7
180 mt/ha/yr*
Continued Terml -
Application nated
_
1.5
3.4
5.0
1.9
3.2
3.9
7.4
5.2
B.i)
7.0
8.4
6.6
6.2
6.8
5.3
s.n
14.2
14.9
10.11
.
-
.
-
_
-
.
-
_
-
_
-
6.3
3.0
6.1
3.7
7.1
7.5
11.3
7.4
*£
-------
TABLE 24. CADMIUM CONCENTRATIONS (nig/kg) OF RADISH TUBER GROWN ON SLUDGE-TREATED SOILS
(CHANG AND PAGE, 1985).
»eir
1976
1977
1978
1979
I9HO
1-IHI
I-JH2
I'll) 3
l')U4
I'M
Season
Spring
Fill
Spring
Fill
Spring
Fill
Spring
Fill
Spring
Fill
Spring
Fall
Spring
Fill
Spring
Fill
Spring
Spring
Fall
Control
0.2
Q.I
0.1
0.2
0.2
0.1
0.2
0.3
0.3
0.3
0.3
0.5
0.4
0.4
0.8
0.6
0.3
0.3
0.6
0.3
22.5 mt/hi/yr*
Continued Termi-
Appltcitton nated
0.2
0.2
0.3
0.4
0.3
0.5
0.4
1.0
0.5
0.8
0.4
0.5
0.6 0.4
0.5 0.4
0.7 0.7
1.1 0.9
0.9 1.0
1.1 0.6
1.1 1.0
1.9 1.1
45 mt/h«/yr*
Continued Terml-
Appllcitlon nited
0.2
0.3
0.3
0.7
0.4
0.7
0.5
1.1
0.5
1.4
0.6
0.6
1.0 0.7
0.8 0.5
0.8 0.7
1.6 1.1
1.0 0.8
1.6 1.0
1.0 1.1
3.1 1.9
90 mt/hi/yr*
Cont Inued
Application
0.2
0.4
0.4
0.9
0.5
1.2
0.7
1,5
0.8
2.5
0.9
0.8
1.4
1.3
0.7
2.1
1.2
1.9
2.5
4.0
Tennl -
nited
_
.
-
.
-
.
1.0
0.9
0.7
1.5
0.9
1.2
1.3
3.8
ISO mt/ha/yr*
Cont i nutd Ternti -
Application nated
0.7
0.9
1.9
0.7
1.8
1. 1
2.2
1.0
2.7
1.0
0.9
1.4 1.4
1.4 1.2
C.9 0.7
2.2 2.1
1.2 1.0
2.7 2. 3
3.5 2.6
5.6 4.3
*fiperimcnta I field was split after Till 1981 where one-half continued to receive sludge and the other half no longer
received sludge but was cropped.
-------
TABLE 25. ZINC CONCENTRATIONS (mg/kg) OF RADISH LEAF GROWN ON SLUDGE-TREATED SOILS
(CHANG AND PAGE, 1985).
22.5 at/ha/yr*
Year
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
Season
Spring
Fill
Spr'ng
Fill
Sprtng
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fill
Control
55
42
45
55
46
30
38
4.7
42
40
46
50
45
42
41
48
50
70
32
44
Continued
Application
56
53
46
82
46
64
52
95
58
66
73
84
74
79
74
95
97
147
103
106
Termi-
nated
_
-
„
.
_
..
56
63
51
57
62
73
53
62
45 mt/ha/yr*
Continued
Application
62
75
56
64
71
90
74
232
81
121
117
134
109
142
107
1C9
195
262
186
166
Termi-
nated
-
-
.
.
-
-
78
82
76
90
97
120
as
93
90 mt/ha/yr*
Continued
Application
55
7U
73
102
93
134
1?9
223
129
201
216
176
206
192
167
2X
316
3B3
305
232
Termi-
nated
.
.
-
.
.
-
120
116
110
133
iao
171
143
12(1
ian mt/ha/
Com 1 fined
Appl teat ion
173
79
lil
121
177
198
254
193
294
266
275
234
2B3
275
354
421
62/
452
353
yr*
Termi -
nated
_
_
-
_
-
_
200
1U4
196
225
?44
?H6
231
1/9
*F.«perimental field was sp'.lt after Fall 1981 where one-half continued to receive sludge and the other half no longer
received sludge but was cropped.
-------
TABLE 26. ZINC CONCENTRATIONS (mg/kg) OF RADISH TUBER GROWN ON SL'JDGt-TREATED SOILS
(CHANG AND PAGE, 1985).
22.5 mt/ha/yr*
Year
H76
1977
1978
,979
1980
1981
1982
l'J83
1S84
N85
Season
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Spring
Fall
Control
34
48
3B
31
20
42
36
37
34
49
33
37
42
31
30
46
31
40
24
42
Continued
Application
38
57
31
46
32
63
59
46
41
58
39
40
50
40
42
58
44
84
3d
78
Termi-
nated
-
.
.
-
-
46
30
36
39
40
50
33
52
45 at/ha/
Continued
Application
39
70
37
56
57
86
56
71
51
82
52
52
71
53
44
75
69
118
68
88
yr*
Terml-
nated
_
.
.
.
.
_
57
38
40
51
48
68
39
64
90 nt/ha/y
Continued
Application
39
47
51
62
94
124
71
97
63
131
70
67
99
80
60
101
89
154
94
110
r*
Ternil-
nated
_
-
-
-
-
.
73
46
41
76
63
90
49
79
1110 mt/ha/yr*
Continued
Appl icat ion
92
61
84
54
158
88
13b
76
144
77
79
105
95
82
117
\"
116
132
Termi-
nated
_
-
-
_
-
_
93
72
SB
101
76
IS?
7?
(14
*£jcperlmental field was split after Fall 1981 where one-half continued to receive sludge and the other half no longer
received sludge but was cropped.
-------
SECTION 5
TRANSFER OF SLUDGE-APPLIED TRACE ELEMENTS TO THE FOOD CHAIN
INTRODUCTION
Assessment of the likelihood of risks to humans, livestock, and
wildlife from potentially toxic constituents in sewage sludge applied to
land requires a knowledge of the potential for transfer of each ccnstiuent
from the sludge or sludge-soil mixture to crops and to animals (including
humans) which ingest sludge, sludge-soil mixture, or crops grown on the
sludge-amended soil. Transfer of sludge constituents from soil to crops is
predominantly a function of: (1) the constituent; (2) soil pH; (3) charac-
teristics of the applied sludge and cumulative sludge application rate; and
(4) the crop species and cultivar grown. Each of these factors can be
associated with a 2-fold or greater change in plant concentration of some
trace elements.
Earlier attempts to estimate food-chain transfer have used plant
uptake slopes obtained by linear regression of the constituent's concentra-
tion in edible crop tissue and the amount of the constituent applied [(mg
constituent/kg dry crop) per (kg constituent applied/ha)]. In the long-
term, plant uptake of sludge-applied Cd and Zn is a curvilinear
(plateauing) response to the cumulative application rate of applied consti-
tuent in a sludge. Further, the plateau reached is a function of the con-
centration of the constituent in sludge and other sludge properties such as
Fe added during sludge processing.
Estimation of food-chain transfer is critical to valid estimation of
the potential for risk. At present, these estimates are best made by con-
sidering (1) the relative increased uptake of constituents by various crops
from sludge-amended soil under responsive conditions; (2) the rate of
ingestion of different crops by the U.S. population (e.g. Pennington,
1983); (3) the demonstrated bioavailability of the increased amounts of an
element in sludge-grown crops or ingested sludge; and (4) an appropriate
transfer coefficient from sludge-amended soil to edible crop tissues [i.e.,
the increase in crop trace element residue (above that in the same crop
grown on background soils) at the plateau reached on sludge-amended soil],
Ryan et al. (1982) developed an approach for estimating food-chain
transfer of sludge-applied Cd. While this model has to be modified to
76
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account for curvilinear response to sludge-applied Cd, many other parts of
the approach remain valid. In particular, the aggregate increased food-
chain exposure to a sludge-borne constituent for the exposed population can
be expressed in terms of a constant times the element transfer coefficient
(height of the plateau above that for untreated soil) for an indicator crop
such as lettuce. Individuals who grow, on acidic sludge-amended soils, a
significant portion of the garden vegetables they ingest are generally
believed to be the individuals most likely to have increased dietary Cd due
to land application of sludge. For chronic lifetime (50 year) Cd exposure,
estimation also relies en U.S. food intake estimates (g fresh weight/day)
from Pennington (1983), and solids content of foods from USOA data bases
(Adams, 1975). Because response curves or plateaus have not yet been eva-
luated for every crup consumed by the U.S. population, uptake by various
food crops must be represented by the FDA food groups. For Cd, based on
many data sources, the response of minor food crops regains well repre-
sented by the FDA food groups.
On the other hand, the use of a "Cd-accumulator" crop to represent
increased Cd uptake by all crops in a food group has been criticized. For
example, lettuce and broccoli were both listed in the leafy vegetable food
group, bjt have at least 10-fold different response slopes. Root vege-
tables and garden fruits also include high and low element accumulating
crops. These wide crop differences have caused an excessive estimated
increase in food-chain Cd transfer (providing a hidden safety factor).
Thus, food group aggregate transfer response slopes have to be adjusted for
the proportion of low and high accumulating crops in each foou group. Each
food group can still be represented by a constant times the response of
lettuce. This approach appears to be appropriate based on the findings of
this workshop.
Many studies have shown significantly higher uptake of Cd, Zn, and
Ni at lower soil pH compared to neutral soil pH (see Logan and Chaney,
1983; CAST, 1980). Exceptions were reported by Pepper et al. (1983) and
Hemphill et al. (1982) in which corn silage was unchanged or slightly
higher in Cd on limed sludge-amended soil. One possible reason for this
exception is that corn differs from other crops in its mechanism of
obtaining Fe from soil. Recent research on the mechanism plants use to
obtain Fe from soil has shown that the Graminae (corn, wheat, barley,
rice, oat, sorghum, etc.) excrete an organic chelating agert which
facilitates Fe diffusion to the root and Fe uptake (Sugiura and Nomoto,
1984; Romheld and Marschner, 1986), while plants in other families do not
excrete chelators. These compounds also chelate Cd, Cu, Zn, and other
microelements in the presence of Fe (unlike bacterial siderophores, which
have very high selectivity for ferric iron). Non-specific chelating agents
added to soils are also known to facilitate diffusion and plant uptake of
Zn, Cd, and other elements. Thus, Cd uptake by Graminae can have a lesser
response to soil pH change than other species, depending on the avail-
ability of soil Fe.
Most studies of soil pH effect on metal uptake by crops have studied
the pH range from about 5.0 to 7.5. In a report by Francis et al. (1985),
77
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S in a coal gasification waste caused soil pH to fall to 4.0, and tne
ryegrass crop grown on this extremely acidic soil was stunted and very high
in metals even though metals in the soil and coal waste were not very high.
Extreme acidic soil pH levels associated with severe pH mismanagement may
allow crop metal residues not otherwise considered in this report.
Important problems remain in estimating the variance in potential
risk due to unusual individual dietary selection patterns, and to indivi-
dual variation in retention of potentially toxic, constituents in foods.
For example, it would be useful to know the statistical distribution of
increased Cd intake among individuals consuming self-selected diets using
crops grown on sludge-amended acid gardens. If these data were available,
one could design Cd limits to protect individuals with the 95th percent! le
of increased exposure. Several papers have noted that the relevant infor-
mation needed on variation in food intake for evaluation of chronic risk
from food Cd is lifetime (50-yoar) variation in intake of foods, rather
than the 1-day variation now available (Dean and Sue^s, 19R5). Although
the mean 1-day ingestion of foods for a population is estimated well by a
large survey of individual 1-day intakes, the variance in long-term average
daily intake is greatly over-estimated by the variance of 1-day intakes v'or
a population (Beaton et al., 1983; Todd et al ., 1983; Block, 198?). Beaton
et al. (1983) and Sempos et al. (1985) found that intra-individual variance
was greater than the inter-individual variance for multiple 1-day obser-
vations. Much smaller variances among individuals are associated wi*h
long-term dietary intakes, especially if one considers major dietary y.ib-
groups (e.g. vegetarians) separately. Thus, present approaches for esti-
mating the fraction of the population ingesting more Cd than some limit
(e.g., 95th percentile, or fraction > 71 uy Cd/day), based on variances in
population 1-day food intakes, would greatly overestimate the lifetime Cd
intake by individuals.
Further, the protection of individuals varying in retention of
ingested elements must consider the effects of important nutritional
interactions on element bioavailability. There are several clear examples
of this source of error in estimating risk. One is the health effects to
Japanese farmers who ingested rice grown in soils rich in Cd and Zn due to
contamination by Zn-ore wastes. In contrast to essentially all other food
crops, rice is grown in flooded soils. Cadmium and Zn uptake by rice is
normally kept very low because insoluble metal sulfides are formed in the
soil. However, some metal uptake occurs because the roots obtain oxygen by
air channels within the plants. It was found that rice metabolized Cd and
Zn differently in these anaerobic rice soils than patterns common to other
food crop species in aerobic soils. Although both soil Cd and soil Zn were
greatly increased (up to 10 mg Cd/kg and 1200 mg Zn/kg), rice grain Cd rose
up to 100-fold while grain Zn was unchanged (Tsuchiya, 1978, page 237).
Further, during preparation of polished rice, much of the Ca, Zn, and Fe in
brown rice is removed during milling, while a much lower fraction of the Cd
is removed (Pedersen and Eggum, 1983; Chi no, 1981; Chi no and Baba, 1981,
Yoshikawa et al., 1977). Lastly, rice Fe has very low bioavailabi1ity
(Hallberg et al., 1974, 1977). All these factors [crop metal uptake
characteristic, food processing, and effect of nutrient (Fe, Zn, and Ca)
73
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status on human Cd retention] favored Cd retention by the farmers.
Bioavailability of Cd was thus high, and human disease resulted.
In another Cd exposure case, individuals who consumed large amounts
of Cd-rich oysters had higher dietary levels of Zn, Fe, and Ca, levels
which were more like those in the normal U.S. diet. The oyster Cd had very
low apparent bioavailability based on Cd in blood and urine compared to the
effect of smoking on Cd in blood and urine (Sharma et al., 1983; McKenzie
et al., 1982). These findings suggest that predictions of human retention
of Cd from Western-type diets i,-ay be less than values currently in use.
Another example comes from the availability of sludge Cu to li«e-
stock. In contrast to Cu salts mixed with diets, Cu in sludge fed to
livestock has low bioavailability. Generally, ingested sludge lowers
liver Cu stores rather than causing Cu toxicity, even though equal levels
of soluble Cu salts would poison the animals (Decker et al., 1980; Bertrand
et al., 1981; Baxter et al., 1982).
MODELING THE EFFECT OF CROP VARIATION IN INCREASED TRACE
ELEMENT ACCUMULATION IN RESPONSE TO SLUDGE APPLICATION
The extent of increase in trace element concentration above control
for crops grown on a sludge-amended soil is very strongly affected by crop
species. Besides crop species variation in response, sludge Cd concen-
tration and soil pH very strongly affect the plant Cd:soil Cd relationship.
Other factors, such as crop cultivar and Fe level in the sludge, may have a
substantial effect on the plant Cd:soi1 Cd relationship, while many other
factors have affected results in some studies (soil organic matter, soil
sesquioxides, pH buffering capacity of the soil, soil fertility, crop
mycorrhizal infection, type of N fertilizer, and climatic factors).
An approach to estimate the relation between sludge-applied Cd, for
example, and increased dietary Cd exposure is to integrate all crop
response in terms of Cd uptake by a responsive reference crop such as let-
tuce. Relative to the responsive crop, the increased Cd uptake among crops
due to sludge application has been reasonably consistent. However, few
individual experiments have included a large number of crop species in a
responsive sludge treatment to provide the relative increases in crop
levels of potentially toxic constituents needed for dietary exposure
assessments. The studies by Davis and Carlton-Smith (1980) and Carlton-
Smith and Davis (1983) report the response of many crop species in one
experiment. The conditions of these studies meet the constraints for
appropriate techniques for sludge trace element risk assessment. They grew
many crop species (some with multiple cultivars) on 2 soils collected from
long-term sludge farms in England. They used large pots of soil (10 kg) in
the greenhouse. Soil A had pH 6.7 and contained 5.8% organic matter and
7.4 mg Cd/kg soil. Soil B had pH 6.8 and contained 26% organic matter and
68.7 mg Cd/kg soil. Crop Cd ranged from near zero to about 8 mg/kg dry
79
-------
weight. Relative crop Cd concentrations were similar between these 2 soils,
and in good agreement with other research results.
In an effort to make maximum use of these data, Davis and Carlton-
Smith developed tables of relative element concentrations for Cd, Zn, Cu,
Ni and Pb. The concentration in each crop was expressed as a percentage of
that in the crop with highest uptake of a given element, and the data were
averaged across the 2 soils. The raw data for this study were obtained
from Dr. R. D. Davis. In evaluating the raw data, it was noted that
several data points were outliers, and these data points were deleted.
The geometric mean element concentrations for the 2 soils (Table 27) were
calculated; then a normal background Cd concentration in each group was
subtracted from the geometric mean Cd level in that crop, and the ratio
of Cd in crop X to the mean level of Cd in lettuce [(Cd in Crop X):(Mean
Cd in lettuce)] was calculated (Table 28). The background Cd levels were
estimated for crop groups, mainly relying on Wolnik et al. (1983, 1985);
other field results were also considered and summarized by Korcak (1986,
Personal communication).
Table 27 shows the geometric mean concentration of Cd, Ni and Zn
in edible crop tissues of vegetable and grain crops. Similar results
for relative uptake for total shoots of forage crops grown on 2 sludge-
amended soils and 1 control soil are presented for Cd, Cu, Mo, Ni, and
Zn in Table 29 from Carlton-Smith and Davis (1983). (We do not report
their Pb data because the crops were grown near an urban area, and the
Pb results are not representative of agricultural production areas).
The relative crop uptake tables remove factors other than crop
species and cultivar. From the summarized data, it is not possible to
ascertain the effects of other parameters (such as soil organic matter,
soil pH, or sludge application rate) on relative metal uptake among crops.
Relative Cd uptake by crops was also evaluated in areas of naturally
Cd-rich soils in Salinas Valley, Monterey Co., California (Table 30; Burau,
1980). Many paired samples of mature vegetable produce were obtained along
with plow layer soil. The slope of the relationship between crop and soil
Cd was reported for crops for which linear regression showed a significant
slope. The Cd-enriched soils have quite similar properties, with Cd coming
from geologic sources rather than sludge. Table 30 shows slopes and a
relative uptake calculation similar to those used in Tables 28 and 29, with
leaf lettuce set = 100.
Giordano et al. (1979) reported crop uptake of trace elements as
affected by sludge application rate and soil heating. They continued the
study for 2 years following application. Their results (unheated soil
data) corroborate the extremely low increase of Cd in beans, cabbage,
pepper, tomato, and the curcurbit family and low Cd increase in potato.
Although it has been clearly shown that crops differ in uptake of
trace elements from the same soil, the biochemical/physiological basis for
crop differences has not been explained. Basic research by Jarvis et al.
80
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(1976) indicated that crops differed in Cd uptake by roots, and also dif-
fered in the fraction of root Cd translocated to shoots. Recently, Grill
et al. (1985) found that many plant species made a family of cysteine-rich
peptides (related to glutathione) which strongly chelate Cd, Zn, Cu, Pb,
and Zn. Their "phytochelatins" may be synthesized in the fibrous roots and
chelate absorbed metals, and thereby protect root metabolism and reduce
trace element translocation to edible plant tissues (Grill et al., 1985;
Rauser and Glover, 1984).
CROP CULTIVAR DIFFERENCE IN METAL UPTAKE FROM SLUDGE-AMENDED SOIL
Cultivars (also referred to as varieties, genotypes, selections or
strains) within a crop species vary significantly in uptake of sludge-
applied trace elements. Cultivar variation in Cd and other element uptake
was evaluated because in agronomic management unrelated to sludge use (Foy
et al., 1978) this source of variation had been found to be important in
correction of trace element deficiencies (Fe, Cu, Mn, Zn) and in tolerance
of plants to trace element toxicity (Al, Mn, Zn). The expected benefits
from cultivar difference in tolerance or uptake of slutlge-borne trace ele-
ments include: (1) the ability to select relatively metal-tolerant or
metal-excluder (non-accumulator) cultivars for use in management of
designed sludge farms; (2) determination of whether cultivar differences
are great enough to require adjustment of dietary element risk assessments;
and (3) identification of cultivars which could be used to reduce
background levels of element ingestion from the general food supply.
At this time, a few crops have been studied under the conditions
which generate results considered reliable for evaluation of the long-term
effects of sludge-borne trace elements. Cadmium uptake by cultivars of
corn, soybean, and lettuce have been studied in appreciable detail. Car-
rot, wheat, and some forage species have been studied, but to a lesser
extent. Other studies are needed, particularly for crops which strongly
absorb or exclude particular trace elements. As a general rule, cultivars
have been found to vary by at least 2- to 5-fold from lowest to highest
uptake response. However, a 30-fold variation was found in corn inbreds.
An extensive characterization of relative corn cultivar variation
in uptaice of a sludge-applied trace elements was reported by Hinesly et al.
(1978, 1982). Uptake of Cd and Zn by 20 corn inbreds grown on long-term
sludge-amended soils in the field were reported. These soils provided
substantially increased plant-available Cd and Zn. The relative Cd and Zn
concentration in the cultivars were recalculated as the geometric mean for
three sludge rates. Leaf Cd ranged from 0.88 mg Cd/kg dry weight in inbred
R805 to 30.3 mg Cd/kg dry weight in inbred B37. Grain Cd ranged from 0.05
mg Cd/kg dry weight in inbred H96 to 1.81 in inbred B37. The grain and
leaf Cd concentrations were highly correlated as were the ranks among
inbreds of grain Cd concentration and leaf Cd concentration. However, the
grain Cd to leaf Cd concentration ratio of an inbred varied from 1.8 to
10.4. This wide range 1n grain Cd to leaf Cd ratio indicates that one
81
-------
should not base a breeding program to lower grain Cd concentrations only on
measuring seedling leaf Cd concentrations, nor should one use grain Cd
results alone to select for Cd-excluder silage corn cultivars. On these
same field plots, corn leaf Zn ranged from 44.2 to 152 mg/kg dry weigH and
grain Zn varied from 31.5 to 58.4 mg/kg. Although ranks and concentration
of both Cd
-------
Other less intensive studies with sludge-amended soils confirm this
relatively narrow range (Giordano et a!., 1979; Davis and Carlton-Smith,
1980 [Table 27]; Feder et al., 1980 [see CAST, 1980, Tab'e 8] for leafy
type lettuces. Head lettuce had approximately half the Cd concentration
found in leafy lettuces grown in Salinas Valley (Burau, 1980) (Table 3D).
Chaney and Munns (1980, unpublished) cested the effect of sludye source and
soil pH on Cd uptake by 5 lettuce cultivars. They also found cultivar dif-
ferences in Cd uptake were small. Relative cultivar response was similar
on lower and higher pH soils, but the range was much narrower on limed
soils. Oavies and Lewis (1985) and Crews and Davies (1985) compared trace
element concentration in eoible tissues of lettuce cultivars grown on metal
rich soils contaminated with mine wastes in Great Britain. They found that
relative cultivar response was similar on different soils, and the range of
lettuce Cd concentration was about 2- to 3-fold on the several soils.
The Cd concentration in potato tubers did not vary significantly
among 6 cultivars grown on a metal-rich soil at a long-term sludge utili-
zation farm (Harris et al., 1981). The soil was pH 6.6 and contained 19.6
mg Cd/kg, while the mean Cd level for the washed unpeeled potato tubers was
0.28 mg Cd/kg dry weight [slightly greater than background Cd level in U.S.
potatoes, 0.165 mg/kg dty weight (Wolnick et al., 1983)].
Meyer et al. (1982) found substantial differences among wheat types
grown on U.S. sells containing background Cd levels. Durum type cultivars
contained 0.140 mg Cd/kg dry grain, while soft red spring, soft red winter,
hard red spring, and white wheat cultivars co:.tained only 0.044 mg Cd/kg.
Grain Cd was not significantly correlated with soil total Cd across all
wheat cultivars, but was correlated if wheat typ^s grown on similar soils
were examined. Additional information has beer, provided by Hinesly (1986,
Personal communication) on grain Cd in different cultivars of wheat grown
on sludge-amended soil. 'Beau1 grain contained 3.4 mg Cd/kg, while 'Argee1
contained only 2.4 mg Cd/kg (strongly acidic soil, pH 5.5; 0.1 M
HCl-extractable soil Cd about 33 mg/kg).
In a cooperative field trial on sludge metal availability, 4 barley
cultivars from different regions of the U.S. were compared in a greenhouse
experiment (Chang et al., 1982); no significant differences were found
among the cultivars in Cd or Zn uptake to leaves or grain from plants grown
on sludge-treated soil.
The effect of sewage sludge and carrot genotype on Cd accumulation
in edible carrot roots was reported by Harrison (1986b). Two sludges were
applied to 1 soil in 3 bed configurations. The mean Cd level was 0.38 mg
Cd/kg for the control carrots, 0.50 mg Cd/kg for carrots grown on the lower
Cd level sludge, and 0.77 mg Cd/kg for the higher Cd sludge. Cultivars
differed less than 2-iold in Cd accumulation. Differences among hybrid
selections were significant for Cd, Zn, and otr.=>r elements, although not
all elements were increased due to sludge application.
83
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ESTIMATING MAXIMUM ALLOWABLE SOIL Cd LOADING
BASED ON PREDICTED INCREASE IN DIETARY CD
Several methods have been used in different nations and at different
times to estimate the maximum cumulative Cd app^cation which protects the
health of individuals (Dean and Suess, 1935). This is a very complex
issue, as has been noted by Ryan et al . (1982) and Logan and Chaney (1983).
The analysis given in Ryan et al . (1982) was considered when the US EPA
proposed the existing regulations on land application of sludge in 1979
(Environmental Protection Agency, 1979a). A background document (Environ-
mental Protection Agency, 1979bl reporting the scientific basis for the
regulations was released at the time the interim final regulations were
published.
Based en FDA dietary Cd intake estimates (36 yg Cd/day) and WHC/FAO
recommendations for maximum tolerable weekly Cd intake (52-71 yg Cd/day),
EPA (1979a) concluded that sludge could safely add no more than 30 pg
Cd/day to an individual's diet. The high-risk or hiQh-exposure individual
was to be protected by the regulation: "That high-risk situation is one
where an individual receives 50% of his vegetable diet from sludge-amended
soils for a period of 40 to 50 years." The U.S. EPA recognized the strong
effect of soil pH on Cd uptake by crops. For soils with low background pH,
it was considered likely that soil pH would fall (from the pH 6.5 required
during the permitted period of sludge application) to background soil pH.
Thus, data from crops grown on acidic sludge-amended soils were used to
estimate the relative Cd uptake by different food groups. The background
document cites work by Dowdy and Larsen (1975), Giordano and Mays (1977),
Chang et al . (1978), Chaney and Munns (1986, Personal communication), and
a pot study by Furr et al . (1976). EPA calculated the increase above
control, relative to that for lettuce, for each sludge application rate.
The relative increases were averaged across rates; radish and carrot were
averaqed to obtain 1;root vegetables", and pea fruits and pea pods were
averaged to obtain "legume vegetables." Lettuce represented "leafy vege-
tables" and tomato represented "garden fruits."
31 summarizes the presumed relative increased Cd uptake by
crops in *he relevant FDA food classes, and daily food intakes for the
teenage male diet model used by EPA in 1979 (Environmental Protection
Agency, 1979b). If one multiplies food intakes (g dry/day, column B)
times relative increased Cd uptake (column D), one obtains relative
increased daily Cd intakes (column E). Thus, if lettuce is increased
by 1 mg Cd/kg dry weight, garden foods are increased by 7.90 ug Cd/day
for 100%, or 3.95 ^g/day for 50% of garden foods grown in acidic sludge-
amended garden for 40-50 years. EPA judged that strongly acidic soils
(pH 5.4 to 6.2) would not cause greater than 30 ug Cd increase/day,
although very acid soils (4.3) caused larger increases.
Several groups evaluat d the 19/3 regulations, and other research
provided new information on and a better understanding of Cd transfer and
84
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food consumption. By 1981, when U,S. EPA's Office of Solid Waste was pre-
paring regulations under The Clean Water Act Section 405d, it was clear
that average adult dietary intake data rather than teen-aged male dietary
intakes should be used. Pennington (1983) provided an early draft of her
results, and these were summarized into food groups by Flynn at EPA (1986,
Personal communication). Leafy vegetables included lettuce, spinach,
collards, cabbage, coleslaw, and sauerkraut. Potatoes included french
fries, mashed, baked, boiled, scalloped, and sweet potatoes, and potato
chips. Root vegetables included carrots, onions, beets, radishes, onion
rings, mushrooms, and mixed vegetable. Legume vegetables included pinto,
lima, navy, green (snap), and red beans, pork and beans, cowpeas, peas,
peanuts, and peanut butter. Garden fruits included cucumber, pickles,
tomatoes, tomato sauce and juice, catsup, cream tomato soup, squash, and
vegetable soups; broccoli, celery, asparagus, and cauliflower were included
here by Flynn because they have Cd response more similar to garden fruits
than leafy vegetables, which had been classified in the 1979 teen-age male
diet mcdel.
The 36 pg Cd/day average intake (from FDA) was subtracted from the
71 yg/day WHO/FAO limit yielding 35 yg Cd/day allowed incr?ase. Using the
average adult rather than the teenage male dietary intakes reduced the pre-
dicted increase from 7.90 to 3.79 yg Cd/day (for 100% of garden vegetable
foods grown on acidic sludge amended soil) when lettuce is increased by 1
yg Cd/day dry weight (Table 31). If one divides 35 yg Cd/day by 3.79 yg
increased dietary Cd (per 1 yg Cd increase/g dry lettuce)-, one finds leafy
vegetables could safely reach 9.23 yg Cd increase/g for 100% of diet; or
18.5 yg Cd increase/g lettuce for 50% of diet; or 27.7 yg Cd increase/g for
33% garden foods diet grown on acidic sludge-amended soils.
EPA then attempted to connect these leafy vegetable Cd increases to
cumulative soil Cd loadings. Results for cumulative soil loading versus
leafy vegetables were separated into acidic (pH 5.4-6.2) [Y(lettuce Cd) =
0.48X(kg Cd/ha) + 5.6; R2 = 0.11] and very acidic (pH 5.3) [Y(lettuce Cd) =
8.1 X(kg Cd/ha) - 1.1; R2 = 0.50]; each had low R2. They then tested the
annual soil Cd loading results for acidic soils and got a better correla-
tion [Y(lettuce(Cd) = 1.24X(kg Cd/ha) + 0.12; R2 = 84]. Thus, using this
equation, and 33% of garden foods, one calculates that soil could contain
22.2 kg added Cd/ha, or about 10 mg/kg.
The effect of soil pH on relative increased Cd uptake by garden
crop? is demonstrated by the data in Table 32. Strongly acidic soil pH
causes much greater Cd uptake than near neutral soil pH, especially for
the Cd-accumulating leafy vegetables. The relative increased Cd uptake is
greater for carrot, potato, and peanut at the higher soil pH. Because high
crop uptake at acidic soil pH is required for appreciable risk from nearly
all sludges, relative increased Cd uptake for acidic soils should be used
for risk assessment. However, this source of variation should be considered
in evaluating different sources of data on relative Cd uptake by crops.
Relative increased Cd uptake by food groups from studies reported
above are summarized in Table 33. Results varied among studies due to soil
85
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Fe level. The 2 sludges differed strongly in solids content, and much more
sludge adhered at 7.6% solids than at 2.0% solids. This study was done
during the active growing season, and growth rapidly diluted the sludge
content of forage. Although orchardgrass had slightly higher sludge
adherence initially, either more rapid growth diluted adhering sludge on
orchardgrass than on the tall fescue, or sludges did not adhere as long on
orchardgrass.
In the second study, 1 sludge was applied at 2 rates to undipped
or clipped stands of 5 forage crop species, and forage samples were har-
vested at 6 times until after the normal harvest age of the clipped areas
(Table 37). Statistical analysis showed that the harvest date was the most
significant treatment variable, although the highest significant interac-
tion term was clipping-x-species-x-harvest date. Alfalfa had the highest
sludge content initially, but the lowest by the final harvest. Bluegrass
had the second highest content initially, and retained the highest content
during growth. Alfalfa's growth pattern is different from that of the
grasses; the new growth of cut alfalfa comes from the highest axillary
nodes, and all new growth emerges well above the thatch layer and contains
no sludge. Treated parts of the grasses rise as new growth occurs at their
base; new leaves emerge at the base and grow through the thatch layer.
Thus, alfalfa and other dicotyledonous forage species are unlikely to allow
much sludge transfer to the food chain under good management practices.
Bluegrass forms very tight bunches, and sludge particles are trapped wit'iin
the harvestable portion of the crop. These studies, taken together, indi-
cate that present advice of "clip before spray application, avoid high
solids content sludges, and wait for normal regrowth of the crop before
harvest or grazing" continues to reflect research findings. Bluegrass is a
species particularly inappropriate for spray application of sewage sludge.
Application rate, although statistically significant, was the least impor-
tant factor studied.
Although forages can reach 15-30% sludge (dry matter basis) imme-
diately after application, Environmental Protection Agency regulations
(i979a) now require a 30-day waiting period before grazing; users are
advised to apply sludge to well grazed or clipped forages. This require-
ment reduces initial adherence and growth rapidly dilutes the adhering
sludge. Decker et al. (1980) and Bertrand et al. (1981) found sludge
comprised only 2-3% of the dry diet (based on forage and feces analyses)
[Table 39] in practical grazing management. Injection of sludge in the
plow layer soil prevents sludge adherence to forage crops, and greatly
reduces potential Ingestlon of sludge from the soil surface.
Ingestlon of sludge from the soil surface was estimated for a
compost amendment which did not adhere to the crop (Decker et al., 1980).
Cattle consumed about 1-3% compost when the forage had no detectable com-
post adhering (Table 39). Lower compost Ingestlon occurred 1n 1978 when
compost was applied only once during the growing season. Others have eva-
luated soil consumption by well managed dairy cattle, sheep and swine
(Fries et al. 1982, Fries and Marrow, 1982). Up to 8% soil was Ingested
from pasture, and less from bare soil. Hogue et al. (1984) reported metal
83
-------
residues in sheep tissues after the sheep grazed 152 days on a grass-legume
pasture established on soil in which 224 mt/ha metal-rich sludge had been
incorporated. Although the forage was increased in Cd, kidney Cd of sheep
was not increased. Other element residues were not influenced by sludge
incorporation. Similar results were obtained when sheep grazed pastures
which received surface-applied high Cu swine manure during the previous
grazing season. Neither liver Cu nor fecal Cu was consistently affected by
previous manure application (Poole et al., 1983).
Ingestion of sludge-borne trace elements does not necessarily cause
the health effects which are expected based on traditional toxicological
studies with added metal salts. Sludge feeding studies ha/e been conducted
to evaluate element deposition in tissues of cattle, sheep, and swine. Low
metal concentration sludges have not increased Cd, Zn, Pb, etc. in animal
tissues in several studies (Decker et al., 1980; Baxter et al ., 1932; Evans
et al., 1979); while high Cd sludges have increased Cd in liver and kidney
(Bertrand et al., 1980; Fitzgerald, 1080; Johnson et al., 1981; Kienholz et
al., 1979; Baxter et al., 1982; Hansen et al., 1931) (see review in Hansen
and Chaney, 1983). The most consistent potential problem resulting from
sludge ingestion is reduced Cu concentration in the liver. Sludge Zn, Cd,
Fe, and possibly Mo could interfere with Cu absorption. Ingestion of
sludge rich in Fe induced Cu-deficiency in cattle in the only sludge
feeding or sludge grazing study where animal performance or health was
negatively affected (Decker et al., 1980). When ingested sludges are rich
in Cd, Hg, F, or Pb, deposition occurs in bone or liver, but little change
has been found in livestock tissues used as food (Hansen and Chaney, 1983).
Crops grown on sludge-amended soils can transfer trace elements to
feeds and foods. However, the extent of increases of trace elements in
crop tissues, and the bioavailability of these to animals varies with
sludge properties. Crops grown on soils amended with low metal sluu'ges had
little effect on kidney Cd in several studies; however, high Cd sludges
increased Cd in crops, which increased Cd in kidney and liver (Decker et
al., 1980; Bertrand et al., 1980; Rundle et al., 1984; Miller and Boswell,
1979; Chaney et al. 1978a, 1978b; Boyd et al, 1982; Bray et al., 1985;
Bablsh et al., 1979; Haschek et al., 1979; Heffron et al., 't980; Lisk et
al., 1982; Tel ford et al., 1982, 1984; Williams et al., 1978).
Much of this work has focused on Cd, because Cd can be mobile in
*ood chains. Humans and laboratory animals have been used to characterize
Cd bioavailabi1ity. Problems have been identified with the experimental
methods used in this research. The early studies (Rahola et al., 1973;
Yatr.agata et al., 1975) measured retention after only a few days or weeks.
McLellan et al . (1978) found that part of the diet Cd was absorbed by
intestinal mucosal cells which were subsequently sloughed into the
intestine and the diet Cd repeatedly recycled in intestinal cells for a
prolonged time. This delayed excretion allowed true absorption long after
the test diet was fed and other parts of the test meal excreted. Flanagan
et al. (1978) found that Fe deficiency very strongly affected Cd retention.
The Fe deficiency Increased Cd absorption into the intestinal mucosal cells
where it was largely trapped as Cd-metallothionein. Fox et al. (1984)
89
-------
showed this aspect of Fe deficiency allows increase in true Cd absorption
ar.d movement to kidney long after the test diet residue is excreted.
Shaikh and Smith (1980) were able to study subjects up to 800 days after
the test dose (using 109Cd), and resolved whole body Cd into 3 Cd pools,
now including the slowly excreted intestinal Cd turnover pool. The biolo-
gical half-life of the slowest pool was 18 years to infinity rather than
100 days as previously reported for the shorter-term human studies. Again,
Fe deficiency affected retention of dietary Cd, but the apparent retention
was appreciably lower than in earlier studies. These tend to support the
findings of Newton et al. (1984) and Snarma et al. (1983) that only low
amounts of Cd are retained by humans ingesting Western-type diets.
CONCLUSIONS
1. Conditions for valid assessment of relative increased crop concentra-
tion of an element due to sludge utilization are limited to long-term
sludge amended soils, preferably 4 or more years after sludge is
applied. Metal salts and metal salt-amended sludges do not provide
valid data for assessment of food-chain element transfer.
2. Some trace elements can be increased in edible crop tissues when
sewage sludges rich in the element are applied to acidic soils (Cd,
Zn, Ni), or alkaline soil (Mo). Under these conditions which allow
substantial increase of a trace element in crops (responsive
conditions), the relative increase 1n element concentration among crop
species are suffiriently consistent to be relied upon in dietary expo-
sure modeli-q. Some variation in relative increased traca element
concentration among crops may result from high soil organic matter, or
from calcareous vs. acidic soil conditions. High organic matter and
high soil pH both reduce element uptake (except for Mo and Se).
3. Except for corn inbreds, cultivar variation in element concentration
has been found to be approximately 2- to 5-fold. Because of inclusion
of various cultivars 1n the food supply, this variation would not
significantly alter chronic exposure due to increased crop uptake of
sludge applied elements. However, cultivar selection can be used to
reduce food-chain transfer of elements from well managed sludge utili-
zation farms.
4. If the FDA food groups are used in dietary Cd modeling, they should be
adjusted for relative high and low Cd accumulating crop types (lettuce
vs. cabbage; carrot vs. beet) within a food group. Food intakes
should represent average adult intake for 50 years, not the maximum
intakes of teen-age males. For evaluation of potential chronic Cd
exposure from acidic sludge-amended garden soils, the adult food inta-
kes reported by Pennington (1983) can be used, and the relative
Increases in Cd 1n crops or food groups summarized in this report.
Increased Cd uptake by all garden foods can be integrated in terms of
Increased Cd uptake by a reference crop such as lettuce. Dietary Cd
90
-------
increase can be predicted by the response of Cd concentration in let-
tuce grown in test soils (height of the plateau in lettuce Cd on
sludge-amended soils above the control, as affected by sludge Cd con-
centration and other factors) times the integrated garden foods Cd
intake factor. Thus, increase in dietary Cd due to growing 100% of
consumed garden vegetables on sludge-amended acidic garden soils was
estimated as 2.20 ug Cd/d when lettuce is increased above background
by 1 mg/kg dry lettuce.
5. Prediction of changes in kidney Cd due to increases in dietary Cd from
foods grown in acidic sludge-amended gardens should consider effects
of nutritional status and nutrients in the garden crops on Cd reten-
tion by humans.
6. Ingestion of sludge can allow exposure and/or risk which can be pre-
vented by incorporation of sludge below the soil surface, or by til-
ling sludge into the soil. For some elements (e.g., Fe, F, Cu, Zn,
Pb), this pathway may allow sufficient exposure to sludge-borne ele-
ments to cause risk, at least for element-rich sludges. Bioavail-
ability of many elements in ingested sludge is very strongly influ-
enced by concentration of the element and other elements present,
sludge carbonate content, and sludge redox potential. For many ele-
ments which comprise potential risk if sludqe is ingested, median
quality sludges have not caused any problems with livestock at common
exposure rates from surface-applied sludge.
91
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TABLE 27. TRACE ELEMENT CONCENTRATION IN EDIBLE PLANT TISSUES, AND RELATIVE
Cd CONCENTRATIONS IN EDIBLE TISSUES OF CROPS (DRY WEIGHT BASIS);
GEOMETRIC MEANS FROM EACH OF 2 LONG-TERM SLUDGE-AMENDED SOILS)
(DAVIS AND CARLTON-SMITH, 1980).
Crop Cultivar
Cd
Ni
Relative Cd
Zn Concentration
— mg/kg dry weight —
Lettuce
Lettuce
Lettuce
Spinach
Kale
Cabbage
Wheat
Mangold
Turnip
Leek
Wheat
Turnip
Rape
Onion
Beetroot
Tomato
Sugarbeet
Bettroot
Carrot
Radish
Barley
Parsnip
Barley
Swede
Potato
Oat
Squash
Sweet corn
Sunflower
Maize
French bean
Pea
Tom Thumb
Webbs
Paris White Romaine
Bloomsdale
Maris Kestrel
Greyhound
Spartacus
Yellow Globe
Bruce
Musselburgh
Sappo
Snowball
Crpal
White Lisbon
Detroit
Moneymaker
Sharpes Klein Monobeet
Boltardy
Standard Improved
French Breakfast
Julia
Giant Exhibition
Ark Royal
Acme
Desi ree
Leander
Zucchini
Golden Earley
Tall Single
Caldera
Canadian Wonder
Onward
8.1
6.9
6.2
5.0
1.3
0.97
0.88
0.74
0.74
0.73
0.62
0.58
0.54
0.52
0.41
0.40
0.35
0.34
0.33
0.33
0.31
0.26
0.25
0.24
0.20
0.18
0.17
0.16
0.15
0.13
0.08
0.05
1.2
2.2
4.0
1.4
6.0
5.7
6.4
2.2
1.9
0.91
4.9
2.0
8.2
0.81
2.3
2.0
2.1
2.1
1.5
3.1
4.2
3.2
7.8
1.2
0.66
7.2
5.8
0.37
11.4
1.0
9.9
4.1
95.
96.
82.
391.
105.
105.
75.
131.
45.
28.
75.
37.
54.
40.
103.
22.
130.
76.
38.
48.
67.
34.
69.
28.
20.
53.
80.
41.
41.
37.
31.
63.
100.
85.
77.
62.
16.
12.
11.
9.1
9.1
9.0
7.7
7.2
6.7
6.4
5.1
4.9
4.3
4.2
4.1
4.1
3.8
3.2
3.1
3.0
2.5
2.2
2.1
2.0
1.9
1.6
1.0
0.6
92
-------
TABLE 28. RELATIVE INCREASED Cd CONCENTRATION IN EDIBLE TISSUES OF CROPS
GROWN ON LONG-TERM SLUDGE-AMENDED SOILS. MEAN CROP Cd FROM
TABLE 27 WAS CORRECTED FOR NORMAL BACKGROUND LEVELS OF Cd
IN CROPS. ALL INCREASED Cd CONCENTRATIONS WERE DIVIDLD BY
6.37, THE MEAN CORRECTED Cd CONCENTRATION IN 3 CULTIVARS LETTUCE
(BASED ON DATA FROM DAVIS AND CARLTON-SMITH, 1980).
Crop
Lettuce
Lettuce
Lettuce
Spinach
Kale
Wheat
Cabbage
Wheat
Mangold
Turnip
Leek
Rape
Turnip
Onion
Barley
Beetroot
Barley
Sugarbeet
Bettroot
Radish
Oat
Carrot
Tomato
Potato
Sunflower
Squash
Parsnip
Sweet corn
Maize
Swede
French bean
Pea
Cultivar
Tom Thumb
Webbs
Paris White Romaine
Bloomsdale
Maris Kestrel
Spartacus
Greyhound
Sappo
Yellow Globe
Bruce
Musselburgh
Orpal
Snowball
White Lisbon
Julia
Detroit
Ark Royal
Sharpes Klein Monobeet
Boltardy
French Breakfast
Leander
Standard Improved
Moneymaker
Desiree
Tall Single
Zucchini
Giant Exhibition
Golden Earley
Caldera
Acme
Canadian Wonder
Onward
Crop
Cd
8.1
6.9
6.2
5.0
1.3
0.88
0.97
0.62
0.74
0.74
0.73
0.54
0.58
0.52
0.31
0.41
0.25
0.35
0.34
0.33
0.18
0.33
0.40
0.20
0.15
0.17
0.26
0.16
0.13
0.24
0.08
0.05
Back-
ground
Cd
/ a arj
0.7
0.7
0.7
0.7
0.27
0.08
0.27
0.08
0.21
0.21
0.27
0.08
0.21
0.21
0.08
0.21
0.08
0.21
0.21
0.21
0.08
0.25
0.32
0.13
0.08
0.11
0.21
0.11
0.08
0.21
0.06
0.06
Increased
Crop Cd
i we* "i n h 't1
7.4
6.2
5.5
3.7
1.0
0.80
0.60
0.54
0.53
0.53
0.46
0.46
0.37
0.31
0.23
0.20
0.17
0.14
0.13
0.12
0.10
0.08
0.08
0.07
0.07
0.06
0.05
0.05
0.05
0.03
0.02
-0.01
Relative
Increased
Cd Uptake
116.
97.
86.
58.
16.
13.
9.4
8.5
8.3
8.3
7.2
7.2
5.8
4.9
3.6
3.1
2.7
2.2
2.0
1.9
1.6
1.3
1.3
1.1
1.1
0.9
0.8
0.8
0.8
0.5
0.3
-0.2
Background Cd concentrations were based on field grown control crops reported
in many studies, but mainly Wolnik et al. (1983, 1985); Korcak (1986, Per-
sonal communication) summarized these results 1n a draft report to EPA.
93
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TABLE 29. RELATIVE UPTAKE OF TRACE ELEMENTS TO TISSUES OF FORAGE CROPS
(DRY WEIGHT BASIS) (CARLTON-SMITH AND DAVIS, 1983).
Crop Cultivar
Agrostis tenuis '
Agrostis tenuis '
Dactyl is glomerata '
Dactyl is glomerata '
Dactyl is glomerata '
Festuca arundinacea '
Festuca pratensis '
Festuca rubra '
Festuca rubra '
Lolium multiflorum '
Lolium multiflorum '
Lolium multiflorum '
Lolium multiflorum '
Lolium multiflorum '
Lolium perenne '
Lolium perenne '
Lolium perenne '
Lolium perenne '
Lolium perenne '
Lolium perenne '
Phleum pratense '
Phleum pratense '
Phleum pratense '
Avena sativa '
Hordeum sativa '
Triticum aestivum '
Zea mays '
Zea mays '
Medicago sativa '
Tri folium pratense '
Tri folium pratense '
Tri folium repens '
Tri folium repens '
Tri folium repens '
Brassica oleracea '
Brassica rapa '
Beta vulgaris '
Beta vulgaris '
Highest concentration
Goginan1
Parys1
S261
S371
S1431
S1701
S2151
Merlin'
S59'
Aubade'
RVP1
S221
Sabalan'
Sabrina'
Cropper1
Melle'
S231
S241
S321'
Talbot1
S481
S511
S3521
Trafalgar'
Julia1
Sappo1
Caldera'
Maris Carmine'
Europe1
Hungarapoly'
S1231
Kent Wild White'
S100'
S184'
Man's Kestrel '
The Bruce'
Sharpes Monobeet
Yellow Globe'
among crops
(mg/kg dry weight)
% of crop with highest concentration
Cd
15
12
39
15
12
52
37
10
29
15
17
15
15
11
16
15
14
14
19
14
31
31
32
9
9
7
13
32
14
7
7
8
5
5
16
50
1 100
95
1.41
Cu
49
55
100
57
47
76
78
51
51
68
72
73
67
89
86
86
86
90
90
89
96
95
88
29
48
38
30
31
35
53
57
43
51
38
21
35
66
81
15
Mo
38
50
„_
--
__
23
...
__
__
29
28
29
25
29
37
27
33
29
29
35
25
24
21
16
16
16
11
12
34
62
62
100
79
71
41
38
19
26
14
Li
73
85
57
33
30
63
91
34
47
44
55
46
59
60
80
92
68
100
80
82
73
73
80
42
16
17
16
16
31
44
48
34
36
40
30
33
57
57
1.4
Zn
36
44
17
10
11
32
32
19
22
24
25
26
21
26
31
27
30
30
30
32
30
28
33
8
15
10
10
14
11
14
16
18
20
21
13
19
83
100
417
Concentration in plant shoots normalized across control and 2 sludge
treatments. For the crop with the maximum normalized concentration,
(100) = the listed mg element/kg dry matter.
94
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TABLE 30. RELATIVE Cd CONCENTRATION IN CROPS GROWN ON NATURALLY Cd
RICH SALINAS VALLEY SOILS (BURAU, 1980).*
mg Cd/kg wet weight % dry mg Cd/kg dry weight Relative
Crop irg Cd/kg dry soil weightt
Spinach
Endive
Lettuce, leaf
Lettuce, romaine
Lettuce, head
Chili pepper
Carrots
Artichokes
Potatoes
Garlic
Sweet corn
Cucumber
Squash, zucchini
Red beets
Onions
Caul i flower
Parsley
Tomatoes
Broccoli
Beans, white
0.70
0.24
0.16
0.16
0.07
0.10
0.13
0.14
0.09
0.17
0.11
0.02
0.02
0.04
0.03
0.02
0.03
0.01
0.01
0.08
9.3
6.9
6.0
6.0
4.5
8.0
11.8
13.5
20.2
38.7
27.3
4.9
5.4
12.7
10.9
9.0
14.9
6.5
10.9
89.1
mg Cd/kg soil
7.5
3.5
2.7
2.7
1.6
1.2
1.1
1.0
0.45
0.44
0.40
0.41
0.37
0.31
0.28
0.22
0.20
0.15
0.092
0.090
uptake
280
130
100
100
59
44
41
37
17
16
15
15
14
11
10
8
7
6
3
3
*Soils were between pH 6-8 and contained 1-10 mg Cd/kg, and about 1.5%
organic matter.
tFrom Watt and Merrill (1963).
95
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TABLE 31. CADMIUM EXPOSURE MODEL FROM THE 1979 ENVIRONMENTAL PROTECTION
AGENCY SLUDGE APPLICATION REGULATION AND BACKGROUND DOCUMENT
(EPA, 1979a, 1979h), AND THE 1981 DRAFT BACKGROUND DOCUMENT.
TABLE SHOWS INTAKES OF FDA FOOD CLASSES BY THE HYPOTHETICAL
TEENAGED MALE DIET MODEL (1979) OR AVERAGE ADULT DIET MODEL
(1981), AND RELATIVE Cd UPTAKE BY FOOD GROUPS (EPA, 1979b).
Food Group
9
1979 Diet Model
Leafy vegetables
Potatoes
Root vegetables
Legume vegetables
Garden fruits
A
Food
wet/da.)
55
183
33
69
69
B
Intake
i g dry/daj
4.95
43.9
2.64
13.1
5.52
C
H20
f %
91
76
92
81
92
D
Relative
Increased
Cd Uptake
1.00
0.02
0.23
0.04
0.17
E = (B x D)
Relative
Daily Cd
ug C/day
4.95
0.88
0.61
0.52
0.94
7.90
If 100% of garden foods diet were grown on acidic sludged land, diet would
be increased 7.90 yg Cd/day when lettuce increased by 1 ug Cd/g dry weight.
If 50% of garden vegetables, diet increases by 3.95 yg/day when lettuce
increases 1 ug Cd/g dry weight.
1981 Diet Model
Leafy vegetables
Potatoes
Root vegetables
Legume vegetables
Garden fruits
26
64
13
38
60
2.34
15.36
1.04
7.22
3.60
9
24
8
19
6
1.00
0.02
0.23
0.04
0.17
2.34
0.307
0.239
0.289
0.612
3.79
If 100% of garden foods diet were grown on acidic sludged land, diet would
be increased 3.79 yg Cd/day when leafy vegetables increased by 1 yg Cd/g dry
weight. If 50%, diet increases by 1.90 ug/day; and if 33%, 1.26 yg Cd/day.
96
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TABLE 32. EFFECT OF SOIL pH ON RELATIVE INCREASE ABOVE CONTROL OF Cd
IN EDIBLE CROP TISSUES (CHANEY, 1985. PERSONAL COMMUNICATION)
Crop
Lettuce
Carrots
Potatoes
Peanuts
Increased
Acidic
— mg Cd/kg
29.3
2.15
1.17
0.54
Crop Cd
Limed
dry —
5.73
1.48
1.02
0.41
Relative
Acidic
1.00
0.073
0.040
0.018
Increase
Limed
1.00
0.26
0.18
0.072
Sludge containing 210 mg Cd/kg applied at 50 and 100 rot/ha in summer,
1978. Carrot and lettuce results from 1979; potato and peanut results
from 1980.
97
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TABLE 33. COMPARISON OF RELATIVE INCREASED Cd UPTAKE BY FOOD GROUPS BASED
ON DIFFERENT DATA SOURCES SUMMARIZED ABOVE.
Reference*
Food Group
Leafy Vegetables (lettuce)
Potato
Root Vegetables
Legume Vegetables
Garden Fruits
EPA
1979
1.00
0.02
0.23
0.04
0.17
Davis
(2)
1.00
0.020
0.07
0.01
0.020
Dowdy
Larson
1975
1.00
0.052
0.36
0.022
0.15
Giordano
et al .
1979
1.00
0.00
0.37
0.017
0.18
Burau
(4)
1.00
0.17
0.21
0.03
0.12
Chaney
Ac i d i c
(6)
1.00
0.040
0.073
0.014
—
"^Numbers in parentheses indicate table in text where data are contained.
98
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TABLE 34. AVERAGE ADULT DAILY INTAKES OF FOODS AGGREGATED INTO FOOD GROUPS
ON WET WEIGHT AND DRY WEIGHT BASIS. AVERAGE WET G/DAY FOOD IN-
TAKES OBTAINED FROM PENNINGTON (1983); SIX MALE AND FEMALE
DIETS, FOR AGES 14-65, WERE AVERAGED. CONVERTED TO DRY WEIGHT
USING DATA FROM ADAMS (1975).
Pennington Data
Food
g wet/day
Adams Data
% dry wt.
Adult Food Intake
g dry/day % dry
Leafy Vegetables - High Cd Uptake:
Lettuce
Spinach
Spinach
Leafy Vegetables
Collards
Cabbage
Coleslaw
Sauerkraut
Broccoli
Celery
Asparagus
Cauliflower
Potatoes:
French fries
Mashed
Boiled
Baked
Chips
Scalloped
Sweet
Sweet
Root Vegetables -
Carrots
Root Vegetables -
Onions
Mixed veg.
Mushroom
Redbeets
Radish
Onion rings
19.231
0.816
2.329
22.376
- Low Cd Uptake
1.715
2.849
2.530
0.939
2.403
0.922
0.836
0.772
12.966
20.026
16.232
12.202
6.859
2.963
5.941
1.541
0.674
High Cd Uptake
3.401
Low Cd Uptake:
2.473
5.154
0.787
1.069
0.402
0.710
10.595
4.8
8.6
8.0
10.4
6.1
19.4
7.2
8.7
5.9
6.4
7.2
55
20
20
24.9
98.2
28.9
36.3
40.0
17.8
10.9
17.4
9.C
10.7
5.5
8.2
0.178
0.174
0.491
0.068
0.209
0.054
0.054
0.056
11,
3.
2.
1.
2.
1.
.074
.360
.465
.708
.901
.717
0.559
0.270
24.054
0.605
0.270
0.897
0.076
0.114
0.022
0.058
T74~37
5.3
9.9
36.2
17.8
13.6
(continued)
99
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TABLE 34 (continued)
Pennington Data Adams Data Adult Food Intake
Food g wet/d % dry wt.
-------
TABLE 35. FOOD GROUP AGGREGATION OF FOOD INTAKE RESULTS FROM PENNINGTON
(1983). DATA FOR SIX AGE-X-SEX GROUPS (AGES 14-65) WERE
AVERAGED; WET WEIGHT CONVERSION TO DRY WEIGHT CONDUCTED ON
INDIVIDUAL FOOD BASIS USING DATA FROM ADAMS (1975). FOODS
FROM THE PENNINGTON LISTS WERE THE SAME AS LISTED BY FLYNN
EXCEPT STALK VEGETABLES WERE MOVED TO LEAFY VEGETABLES -
LOW CATEGORY, AND SWEET CORN AND MELONS WERE ADDED TO GARDEN
FSUITS - LOW.
Food
Food Intakes Dry
wet g/d dry g/d Weight
Relative
Increased
Cd Uptake
Relative
Increased
Cd Intake
Leafy Vegetables-High 22.376 1.121 5.0 1.00
Leafy Vegetables-Low 12.966 1.284 9.9 0.13
Potatoes 66.438 24.063 36.2 0.020
Root Vegetables-High 3.40 0.605 17.8 0.20
Root Vegetables-Low 10.60 1.437 13.6 0.052
Legume Vegetables 42.39 12.640 29.8 0.010
Garden Fruits-High 35.537 3.319 9.3 0.020
Garden Fruits-Low 31.949 4.671 14.6 0.010
1.121
0.167
0.481
0.121
0.075
0.126
0.066
0.047
2.20
y Vegetables - High includes lettuce and spinach.
Leafy Vegetables - Low includes cabbage, kale, broccoli, etc.
Root Vegetables - High includes carrots.
Root Vegetables - Low includes radish, turnip, beet, onion, and leek.
Garden Fruits - High includes tomato products and pepper.
Garden Fruits - Low includes cucurbits, sweet corn, and strawberries.
101
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TABLE 36. COMPARISON OF FOOD INTAKES, RELATIVE INCREASED Cd UPTAKE, AND
ESTIMATED INCREASED DIETARY Cd IN THE EPA (1979b), 1981 EPA
DRAFT, AND PRESENT DOCUMENT.
Food Group
EPA, 1979 EPA, 1981
, g
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TABLE 37. EFFECT OF SLUDGE SOURCE, AMD TIME AFTER SLUDGE APPLICATION ON
SLUDGE ADHERENCE TO TALL FESCUE AND ORCHARDGRASS (CHANEY AND
LLOYD, 1986, PERSONAL COMMUNICATION).
Sludge
City 1
City 23
% Solids Crop
2.0 Tail Fescue
Orchardgrass
7.6 Tall Fescue
Orchardgrass
Days
0
*f
3.0
7.4
10.2
11.9
After Sludge
7
3.1
4.4
6.2
6.9
Appl icati
14
1.5
?.«
3.1
2.1
on
20
0.82
0.90
2.7
1.0
Forages were not clipped; sludge applied at 94 m3/ha using watering cans.
Sludge content calculated based on increased levels of 6 elements above
levels present in unsprayed control forage samples.
Anaerobically digested sludge from City 1 contained (in mg/kg dry solids):
Zn, 3030; Cd, 549; Pb, 495; Cu, 665; Ni, 68; Fe, 11,000.
Anaerobically digested sludge from City 23 contained (in mg/kg dry solids)
Zn, 750; Cd, 7.2; Pb, 170; Cu, 195; Ni, 27; Fe, 123,000.
103
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TABLE 38. EFFECT OF FORAGE CROP 3PECIES, CLIPPING CROP BEFORE SLUDGE
APPLICATION, AND TIME AFTER APPLICATION ON ADHERENCE OF
SPRAY-APPLIED FLUID SLUDGES TO FIVE FORAGE CROP SPECIES
(CHANEY AND LLOYD, 1986, PERSONAL COMMUNICATION).
Crop Harvest Date
Tall Fescue
'Kentucky 31'
Orchard grass
'Potomac'
f
Kentucky bluegrass
'Merion'
Smooth bromegrass
'Saratoga'
0
7
14
28
43
70
0
7
14
28
43
70
0
7
14
28
43
70
0
7
14
28
43
70
Uncl ipped
_ _ * c 1 i iri
3.fi9 d-i
3.02 f-1
2.79 h-n
1.89 m-q
2.85 h-m
1.01 q-w
2.68 i-o
2.27 1-p
2.34 k-p
1.61 p-t
1.32 p-v
1.11 q-x
6.36 b
4.18 cde
4.73 c
4.37 cd
2.64 j-o
1.81 n-q
3.63 d-j
3.29 e-1
2.75 h-n
1.45 p-u
1.56 p-t
0.77 r-x
Cl i pped
1r\ t An ^ A F ;* n Q • .. _ — _ -»
4.44 cd
3.77 c-h
2.61 k-o
1.19 q-v
0.53 u-x
0.30 vwx
4.53 cd
3.67 d-i
1.67 o-s
0.60 t-x
0.40 vwx
0.13 wx
5.68 b
3.99 c-f
3.33 e-k
2.97 g-1
1.32 p-v
0.52 u-x
4.26 cde
4.31 cde
3.97 c-g
1.70 o-r
0.62 t-x
0.45 u-x
(continued)
104
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TABLE 38 (continued)
Crop
Harvest Date
Uncl i pped
Cli pped
Alfalfa
'Saranac'
0
7
14
?8
43
70
%c 1 1 1 H n c>
8.48 a
6.17 b
3.67 d-i
1.21 q-v
0.66 s-x
0.09 wx
5.P8 b
4.30 cde
1.82 n-q
0.51 u-x
0.13 wx
-0.05 x
Forages were established in spring, 1976 on methyl-bromide treated field
plots. After establishment, sludge was applied on May 11, 1977, at 51
and 103 m3/ha, to undipped and clipped (to 10-15 cm as recommended for
species, with clippings removed) crops in three replications. Forage was
harvested to 5 cm after 0-70 days growth. Normal harvest of the clipped
forage would have occurred about day 43.
Sludge was 1.4% solids and contained (in ing/kg dry solids): Zn, 1140;
Cu, 432; Pb, 394; and Fe, 36,000. Sludge content was estimated Dy increased
levels of Zn, Cu, Pb, and Fe in sprayed forage. The speciesx-clipping-x-
harvest date was the highest significant interaction in ANOVA. Sludge
content results followed by the same letter were not significantly different
(at P < 0.05) according to the Duncan Multiple Range Test.
105
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TABLE 39. Adherence of spray-applied liquid sewage sludge to tall
fescue (Decker et al., 1980) or 'Pens cola1 bahaigrass
(Bertand et al., 1981) and sludge content of feces of
cattle which rotationally graze these pastures.
Study and Treatment
Sludge
Solids
Appli-
cation
Rate
Sludge
in/on
Forage
Sludge
i n
Feces
% cm % %
Decker et al. (1980)*
1976 - 21-day sludge 4.4 20 x 0.51 5.39 7.1
1976 - 1-day sludge 4.8 20 x 0.51 22.3 18.6
1977 - 21-day sludge 2.9 20 x 0.51 2.18 7.7
1977 - compost (0.74)f 6.5
1978 - 21-day sludge 3.7 24 x 0.51 2.91 6.1
1978 - compost (0.50)* 2.0
Bertrand et al. (1981)*
1979
1979
- 7-26-day
- 7-13-day
sludge
sludge
2.
2.
1
1
9
18
x
x
0.84
0.84
2
5
.17
.17
4
5
.6
.8
*Four paddocks grazed on a rotation system; sludge was applied to
clipped pasture 21 days before grazing (21-day sludqe), or regrown
pastures 1 day before grazing (1-day sludge). Compost applied 3
times in 1977 and 1 time in 1978, with at least 21 days before
grazing began.
^Estimates based on individual elements were not in close agreement;
no significant sludge content.
*0ata of Bertrand et al. (1981) recalculated using results for Cu, Fe,
Pb, and Zn, elements substantially increased by sludge application.
Two paddocks were grazed in rotation. Rotations were made every
12-14 days; depending on forage growth and weather, the sludge
application occurred 7 to 13 days before grazing commenced. The
two sludge treatments differed in number of sludge applications
made during the grazing season.
106
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SECTION 6
EFFECTS OF TRACE ORGANICS IN SEWAGE SLUDGES ON SOIL-PLANT
SYSTEMS AND ASSESSING THEIR RISK TO HUMANS
INTRODUCTION
Describing the impact of trace organics in sludge on soil-plant
systems can be an even greater challenge than is faced with trace elements.
One reason is the sheer number of compounds potentially involved. Liter-
ally thousands of trace organics exist and many, if not all, can be
expected in sewage sludge at highly variable concentrations. At the same
time, the literature discussing the effects of trace organics on soil-plant
systems is much less voluminous than the trace element literature. Un-
doubtedly, the paucity of scientific studies on trace organics is due to
the complexity of studying these chemicals and the expense of trace organic
analyses.
An important difference between trace metal and trace organic addi-
tions to a soil is the time each may reside or persist in that soil. The
half-life of the most persistent organics (e.g., PCBs) in soil was conclu-
ded to be 10 or more years (Fries, 1982), whereas the residence time for
most metals was estimated to be a few thousand years (Bowen, 1977).
Studies of trace organic behavior in soils must also consider assimilation
mechanisms such as degradation (biotic and abiotic) and volatilization, in
addition to factors such as solubility, adsorption/desorption, leaching and
plant uptake. While these additional mechanisms make trace organic studies
more challenging, they also lend themselves to management alternatives not
available for trace elements. For example, long-term application programs
with organics (e.g., food processing and petroleum wastes) attest to the
soil's ability to receive and successfully assimilate wastes over time.
This attenuation capacity suggests that 'limiting the addition of
trace organics to soils via sludge application siould be based on "matching
the total loadings of an organic(s) with the soil's assimilative ability"
rather than "a specified concentration present in the sludge". Such an
approach allows more flexibility to consider environmentally sound options
on a case by case basis for local circumstances.
107
-------
Some analogies of trace organics to agricultural pesticides can be
made. But the influence of the sludge organic matter matrix in combination
with a specific organic, when added to the soil, is poorly understood.
To facilitate discussion, the large number of organic chemicals were
divided into groups which tend to have similar chemical and physical pro-
perties. Various organics could then be discussed by groups relevant to
their prevalence in sludge, fates in the soil-plant system, and recent
efforts at assessing the risk of trace organic additions to the soil via
sludge application.
The following discussion focuses on the impact of trace organics to
soil-plant systems. The toxicity of trace organics to soil organisms, ani-
mals or humans as a result of their addition to soils and potential path-
ways, whereby exposure of soil-applied organics to animals and humans might
occur, are listed and briefly discussed.
PREVALENCE OF TRACE ORGANICS IN SLUDGES
Any program to assess the risk from trace nrganics must begin by
determining (1) ,>vhich chemicals are the most likely to be present in sewage
sludge and (2) what quantities may be added to soils by the application of
sludges containing these trace organics. To assess the potential impacts,
priority should be given to substances shown to be prevalent in sewage
sludge through residue analysis and which have certain physical-chemical
properties that could lead to unacceptable toxicological or environmental
effects. The next priority are those chemicals heavily used in society,
possessing similar undesirable physical-chemical properties but not yet
identified in sludges. With the current data base only the first priority
can be effectively considered.
Since municipal raw sewage contains virtually all the wastes from
man's activities, one could expect the sludge resulting from the treatment
of this sewage to also contain these same products. Because as many as
15,000-20,000 man-made chemicals (with an array of functional groups) exist,
analyzing all the chemical constituents in a sewage sludge is impossible.
Sludges have been analyzed according to predetermined lists of specific
organic chemicals such as the organic priority pollutants list (NRDC,
1976). Another approach is to separate the organics into "chemical groups"
which have similar physical-chemical properties and focus on selected
groups anticipated to have a greater toxicological and/or environmental
risk. With either approach, the wastewater treatment plant should first
determine what organics are being discharged by users, particularly
industry. This information can then be used as guidance for identifying
which organic compounds should be tested to check for any unusually high
concentrations in sewage sludges.
A third approach is to use short-term bioassays to test sludges or
sludge-amended soil for mutagenicity (Brown et al., 1982; Hopke and Plewa,
108
-------
1984; and Peters, 1985). Sludges failing such a test would then be eva-
luated more rigorously and analyzed for selected organics. This approach
requires additional research on suitable bioassays followed by calibration
of these bioassays with experiences in the field, before it could realisti-
cally be used.
Only a few studies have reported the analyses of trace organics in
sewage sludges. These studies confirm the wide variety of trace organic
compounds that can occur in sewage sludge, but significant problems exist
in the analysis and interpretation of these data:
Sludges are heterogenous and obtaining a representative sample
can be difficult.
• Day-to-day variations in composition occur.
Analytical protocols vary widely in extractions, separations and
cleanup procedures which in turn affect the number and types of
compounds recovered.
For some groups, recoveries from a complex matrix like sludge can
be poor.
• Data are reported in various units (ug/1, mg/kg, etc., some on a
wet weight basis, and others on dry weight).
• Limits of detection in some cases are poor or are not reported.
• Confirmation of each organic, if any was done, is not reported.
Because of these problems and a very limited data base, definitive
statements concerning the prevalence of organic chemicals in sewage sludge
can not be made. To rectify this situation, the following information and
data are suggested as a minimum for reporting on the organic content of
sewage sludge: (a) type of sludge, (b) percent dry solids, (c) number of
samples analyzed, (d) number of "positive" samples above detection limit,
and the following based on dry weight —maximum and minimum < ..ncentration
(range), (e) detection limit, and (f) the median concentration of all
samples tested. This information would provide a means of standardization
for comparing data sets.
Residual levels of trace organic compounds found in sewage sludge
analysis surveys are listed in Table 40. The majority of these data come
from two sources (Burns and Roe, 1982; and Jacobs and Zabik, 1983 ) but are
supplemented by several others. Studies reporting organic concentrations
for fewer than 9 sludges were not included in this summary, except for one
which provided data for dioxins and furans (Weerasinghe et a!., 1985).
Some limitations of the data reviewed (Table 40) are that detection limits
were not reported, some data were reported on a wet weight basis without "%
solids" values given, and median concentrations for all samples were not
provided.
109
-------
Compounds were listed under the following major groups based on similar
physical-chemical characteristics:
•phthalate esters -halogenated aliphatics (short chain)
•monocyclic aromatics -triaryl phosphate esters
•polynuclear aromatics (PAH's) -aromatic and alky! amines
•halogenated biphenyls (PCB's) -phenols
•dioxins and furans -chlorinated pesticides & hydrocarbons
•miscellaneous compounds
These data show that sewage sludges can be highly contaminated with
organic chemicals. Unusually high concentrations, such as the maximum
levels shown for butylbenzylphthalate, bis(2-ethylhexy1) phthalate,
toluene, methyl bromide, chloroethane, vinyl chloride, pentachlorcphenol
and others, suggest a high degree of industrial contamination. Sludges
containing these "maximum concentrations" could have a significant impact
on soil-piant systems, depending on the rate of sludge applied.
Concerns about organic chemicals in sludges must be kept in perspec-
tive, however. Of the 219 organic chemicals collectively measured in
sludges, 70 (or 32%) were below detection limits (Table 41). About one-
fourth (53) of these organics were present in >50% of the sludges (Table
41). The presence of "background concentrations" of many organics in
purely domestic sewage sludges is not unexpected, given the wide variety of
synthetic organic chemicals found in many household products (Hathaway,
1980). The fact that domestic septic tank effluents contain greater than
100 trace level organics provides additional evidence for their presence in
household wastewaters (DeWalle et al., 1985; Tomson et al., 1984).
More important than the presence of an organic(s) in sewage sludge
is the total amount which may get applied to the soil-plant system by
application to land. Table 42 summarizes that part of the analysis data
from Table 40 which had median concentration values. This summary suggests
that about 90% of the organics in sludges will be present at concentrations
less than 10 mg/kg. About 10% of the organics tested had median con-
centrations of 10-100 mg/kg, and only one organic had a median value of
>100 mg/kg (Table 42).
To put potential organic chemical loadings into perspective, one
can make a comparison with agricultural pesticides. Many pesticides used
today are organic chemicals which are added to soil-piant systems at rates
of 0.2-4.0 kg of active ingredient per hectare. Assuming an agronomic
rate of sludge application of 10 mt/ha (dry weight basis) the organic
chemical loadings expected for organic concentrations in sludges o* 1, 10,
and 100 mg/kg are 0.01, 0.1 and 1.0 kg/ha. At rates used to reclaim
drastically disturbed land, 100 mt/ha, the organic loading for sludges
containing 1, 10, and 100 mg/kg organic concentration would be 0.1, 1.0,
and 10 kg/ha, respectively. For agronomic rates organic chemical con-
centrations of sludges approaching 100 mg/kg must be viewed as potentially
having an impact on the soil-piant system, depending on the chemical/
toxicological properties of that organic. At high sludge rates (e.g.,
110
-------
100 mt/ha), concentrations approaching 10 mg/kg in sludge could be
expected to add amounts of an organic comparable to quantities of pesti-
cides added in agricultural operations.
Based on the prevalence of organics in sludges and potential loadings
to soils, agronomic or environmental risk due to the application of
domestic sewage sludge to agricultural soils appears to be minimal. In
addition, many organics will be bound by soil organic matter and biolo-
gically degraded by soil microorganisms (Kaufman, 1983). However, per-
sistent compounds like PCBs and the chlorinated pesticides could accumulate
in soils from repeated sludge applications and can be a concern for food
crop production.
TRACE ORGANICS IN SOILS
Limited infcrmation is available regarding residual effects of sludge
organics in soils. Monitoring for 22 persistent organics in unamended and
sludge-amended soiis (Baxter et al., 1983) showed trace levels of chlordane
(<0.12 mg/kg), dieldrin, p,p'-DDE and PCBs present in untreated and treated
soils. None of the other 22 organics were detected in any of the soil
samples. The authors concluded that sludge applications had not measurably
increased the level of persistent organics above the levels normally found.
In a Michigan study (Singh, 1983), sludge-treated and untreated soils
were collected from 15 sites around the state ana analyzed for 10 organic
compounds: benzene, trichloroethylene, tetrachloromethane, PCBs, pentach-
loronitrobenzene, pentochlorophenol, chlorpyrifos, di-n-butylphth^lale,
bis(2-ethylhexyl) phthalate, and toxaphene. All results for soil analyses
were reported as "none detected" except at two sites PCBs were found at 0.8
mg/kg for untreated and sludge-treated soils at one site, and 0.02 mg/kg
pentachlorophenol was detected in sludge-treated but not in control soils
at another site.
While these two studies suggest that sludge organic chemical loadings
to soils will result in little or no residues ir. soils receiving sludges,
additions of persistent organics can potentially be a concern. Two food
processing companies were contacted to determine what level(s) of organic
residues in soils they use to reject fields for use in growing vegetable
crops. One company indicated that concentrations above 0.1 mg/kg of
aldrin/dieldrin, chlordane, toxaphene, or lindane in mineral soils would be
of concern. For muck soils, 1.6 mg/kg of aldrin/dieldrin or 0.5 mg/kg of
chlordane, toxaphene or lindane could be tolerated. A second vegetable
crop processing company provided the guideline information 1n Table 43.
To assess the potential impact of sludge organic loadings to agri-
cultural soils, the theoretical residue levels can be determined. Using
the highest median concentration for aldrin or dieldrin from Table 40 of
about 1 mg/kg and assuming an agronomic rate of sludqe is Applied (10
mt/ha) for 10 years, the total amount of aldrin or dieldrin added to a soil
111
-------
would be: 0.01 kg/ha x 10 (yr) = 0.1 kg/ha. To determine what the soil
residue concentration would be, one can assume an average bulk density for
soil of 1.3 g/cm3 (1,300 kg/m3) and a 20 cm depth of nixing, so one hectare
(10,000 m2) of soil would weigh 2,600,000 kg (10,000 m2 x 0.2 m x 1,300
kg/m3). Assuming no loss of the organic chemical applied, the soil residue
concentration would be: 0.1 kg (or 100,000 mg) of organic/ha * 2,600,000 kg
of soil/ha = ~0.04 mg/kg.
Under these conditions, sone margin of safety would still be provided
relative to the 0.1 mg/kg guideline level (Table 43) used for most sensi-
tive root crops. However, if the sludge organic concentration was 10 mg/kg
instead of 1 mg/kg, then the same sludge loading would give a soil residue
level of 0.4 mg/kg and cause such a soil to be excluded for growing vege-
table root crops. But a sludge with 10 mg/kg of aldrin or dieldrin would
still be acceptable if 1 ton per hectare per year was applied for 10 years
instead of 10 ton per hectare pe^ year. Therefore, the total amount
applied to a soil is the critical factor rather than the concentration in
the sludge. Again, as noted above, these examples assume no loss of the
organic chemical by volatilization, degradation, etc. from soil.
EXTRACTION/LEACHING PROCEDURES
Under the Amendments to the Resource Conservation and Recovery Act
of 1985 [Hazardous Waste Management System; Definition of Solid Waste;
Final Rule (40 CFR Parts 260, 261, 264, 265 and 266), January 4, 1985], the
U.S. EPA was directed to improve the ability to characterize hazardous
waste. The Extraction Procedure Toxicity Characteristic (EPTC), or EP
toxicity test, currently used entails a leaching test to measure the ten-
dency of a waste to leach, coupled with extract concentrations above which
the waste is to be regulated, and defined as a hazardous waste. This test
was developed on the premise that a potentially hazardous industrial waste
might be sent to a sanitary landfill, resulting in a high potential for
groundwater contamination. The constituents currently included as part of
this test were those for which National Interim Primary Drinking Water
Standards have been established. These standards addressed 8 inorganics
and 6 organic compounds (2,4-dichlorophenoxyacetic acid, endrin, lindane,
methoxyclor, toxaphene, and 2,4,5-trichlorophenoxyacetic acid).
As part of the effort to improve the characterization of hazardous
waste, EPA will be proposing a revised test (Friedman, 1985) that would
expand the list of organic compounds tested to 44 and modify the procedure
itself to the Toxicity Characteristic Leaching Procedure (TCLP). If the
extractant concentration from the TCLP 1s above the maximum threshold limit
for any of the 8 inorganic or 44 organic chemicals, the waste is defined as
hazardous. Each municipality that produces sewage sludge must make the
determination whether or not their sludge 1s hazardous. This determination
can be based upon their knowledge of their sludge or they may choose to use
the TCLP to help them make it. The EPA believes that the way to determine
1f a municipal sludge 1s hazardous 1s to determine whether or not its
112
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extract concentrations exceed the maximum threshold limits. However, many
have argued that a testing procedure based on the worst-case scenario in
which large quantities of sludge are disposed of in a landfill has little
relevance to assessing any potential hazard from recycling low rates of
sludge to land.
The U.S. EPA is currently having eight sewage sludges tested with the
new TCLP procedure. The sludges were selected to include purely domestic
sewage sludge as well as sludges expected to have high concentrations of
contaminants from industrial sources. While none of the sludges appear to
have TCLP extract concentrations that exceed the threshold limits, results
are too preliminary to know for sure. Therefore, the impact of changing
from the EPTC to the TCLP on sludge application programs is too early to
ascertain.
MUTAGENICITY TESTING OF SLUDGES
A number of studies have recently reported results of mutagenicUy
tests on extracts of sludge (Babish et al., 1983; Boyd et al., 1982; Hang
et al., 1983; Hopke and Plewa, 1984; Hopke et al., 1982). While most
sludge extracts tested by Babish et al.(1983) were mutagenic by the Ames
test (Ames et al., 1975) many foods, drinking water, and other substances
in our environment also test positive for mutagenic activity (Loper, 1980;
Mast et al., 1984; Nagao et al., 1979; and Salmeen et al., 1985). Ames
(1983) has also indicated that "the human diet contains a great variety of
natural mutagens and carcinogens, as well as many natural antimutagens and
anticarcinogens". Thus, one must use extreme care in interpreting mutage-
nic tests of sludge extracts to keep them in perspective with the presence
of mutagenic constituents in all parts of our environment.
In addition to the Ames Salmonella assay, plant test systems have
been used to investigate the mutagenic activity of sewage sludges (Hopke
and Plewa, 1984; Hopke et al., 1982). Mutagens present in sludge-amended
soil can be transported into a crop plant and induce genetic damage in germ
cells; however, no mutagenicity occurred in the kernels from corn grown on
sludge-amended soil nor were mutagens transferred from the sludge to soil
or surface waters.
These studies imply that tha chemicals causing mutagenicity are trace
organics, but the specific chemicals responsible for the mutagenic affects
have not been identified. Another difficulty is interpreting these
bioassay results, since agricultural soils can exhibit mutagenic response
without sewage sludge amendments (Boyd et al., 1982; Brown et al., 1985;
and Hopke et al., 1982). Therefore, results of these mutagenicity tests
are not easy to put into perspective (Davis et al., 1984; Dean and Suess,
1985), and the data cited suggest that mutagen activity is greater for
sludges generated by more industrialized municipalities.
While mutagens present 1n sludges were shown to degrade relatively
rapidly (e.g., within 2-3 weeks) in one sludge-amended soil (Angle and
113
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Baudler, 1984), recent work at Pennsylvania State University indicates that
the loss of mutagenic activity may take as long as one growing season for
other sewage sludge/soil mixtures (Baker et al., 1985). How well results
from these laboratory incubations will duplicate under field conditions is
untested and still unknown.
Due to the large number of organic chemicals which can be present in
sewage sludge, a short-term bioassay offers the advantage of testing for
potential biological toxicity inherent in a sludge (or other waste) con-
taining a complex mixture of chemicals (Brown et al., 1982). For example,
Psters (1985) useci the Ames test to screen 38 Pennsylvania sewage sludges
containing potentially harmful trace organics, and Brown et al. (198i!) used
the Ames test plus two other bioassays to examine the acute toxicity of ten
hazardous wastes.
Using a bioassay test for identifying a sludge contaminated with an
organic chemical(s) could provide an additional degree of safety in
managing sewage sludge applications to agricultural/forest soils. To
be useful, however, bioassay test results for sludges must be correlated to
mutagenic activity or biological toxicity of soil/sludge mixtures in the
field. Based on the generally low concentrations of trace organics in
sludges and the low rates of sludge (e.g., agronomic) typically applied,
the probability of any transfer of mutagenic activity to animals or humans
as a result of sludge application to land is very low.
FATE OF TRACE ORGNICS ADDED TO SOIL-PLANT SYSTEMS
Potential health hazards associated with organic chemical residues
in sludge applied to land have been discussed in several review articles
(Chaney, 1984; Dacre, 1980; Davis et al., 1984; Kowal, 1983; Kowal, 1985;
Majeti and Clark, 1981; and Pahren et al., 1979).
Principal pathways by which organics could be transferred to humans
from sludge-amended soils were listed by Dean and Suess (1985):
1. Uptake by plant roots in sludge-treated soil, transfer to edible
portions of plants, consumption by humans;
2. Direct application to edible parts of plants as sludge, or as dust
or mud after sludge 1s mixed with the soil, consumption by humans;
3. Uptake via plants used as feed or fodder for animals, transfer to
animal food products, consumption by humans;
4. Direct Ingestion of soil and sludge by grazing animals and
transfer to animal food products, consumption by humans;
5. Direct ingestlon of sludge contaminated soil by children; an
abnormal behavior called "pica".
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Two other possibilities might be included with this list:
6. Surface runoff/erosion to streams or rivers used as a source of
drinking water downstream, and
7. Leaching to a groundwater aquifer used as a source of drinking
water.
These pathways have all been demonstrated but are not equally
important. Indeed, Pathway 4, which does not go through plants, is the
only one by which organic pollutants have been traced from sludge to animal
products (Chaney, 1984).
While plant contamination can occur (as discussed later), soil residue
levels necessary for this to happen are usually higher than would be anti-
cipated from low application rates of non-industrialized sewage sludges.
In addition, soil incorporation of organics, like PCBs for example, can
greatly reduce plant "uptake" of the chemical (Harms and Sauerbeck, 1983).
Lindsay (1983) also reported that several recalcitrant organics are so
strongly bound to soil and sludge as to be almost totally unavailable for
plant uptake.
Trace organics may biomagnify. For example, detritus eating insects
were found to contain 1.3 x the soil concentration of PCB, which could lead
to further bioconcentration in insect-eating birds (Davis et al., 1984).
As with metals, trace organics may accumulate in animal food products
following direct sludge ingestion during grazing. The problem is par-
ticularly important for dairy cows since milk is the animal product most
likely to be influenced by organic contaminants in sludge applied to land
(Dean and Suess, 1985), although management practices can significantly
reduce this possibility.
The potential exists for direct ingestion of organics, especially by
children through the phenomenon of pica (Pathway 5] if sludge was used to
fertilize home gardens. Dean and Sufc=>s (1985) concluded, however, that
this is likely to be a minor or Insignificant route of exposure, as is
inhalation of dust or vapors. As with Pathway 1, significant human con-
sumption of sludge organics by human management (e.g., culinary procedures
like cleaning and peeling of root crops that tend to accumulate lipophilic
substances) would seem most unlikely (Naylor and Loehr, 1982b).
Bioaccumulation factors (i.e., ratio of an organic in plant or animal
tissue to concentrations in soil) are available for very few compounds.
For plants, the factor (when known) is almost always <1 and usually <0.1
(Overcash, 1985) and for animal products (e.g., milk) estimates of 0.7 for
PCB (Fries, 1982) and 0.5 for dieldrin (Lindsay, 1983) have been made.
Field data are largely non-existent, but Baxter et al. (1983) reported no
plant uptake of 22 persistent organics from land amended with Denver Metro
sludge. Also, no increases 1n persistent trace organics content of
the fat tissue content of cattle grazing a sludge application site were
observed.
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If ingested, organics present in sludge or soil can be bioavailable
(Chaney, 1984; McConnell et al., 1984). Jelinek and Braude (19/7) found
an increased content of PCBs in the milk fat of cattle fed green forages
and roughages grown on sludge-treated land. This prompted the U.S. FDA to
recommend a maximum permissible content of not more than 10 mg/kg PCBs in
sludges used on agricultural lands (Braude et al., 1975). Therefore,
apparently absorption of ingested sludge organics can only be prevented by
limiting their concentration in sludges or avoiding direct ingestion until
compounds have been degraded or dissipated.
Assimilative Pathways Within the Soil-Plant System
Organic compounds may undergo a variety of chemical and biological
processes when applied to a soil or soil -vegetation system. The various
assimilative pathways have been discussed by several authors (Davis et al.,
1984; Kaufman, 1983; Lue-Hing et al., 1985; Overcash, 1983). The pathways
include:
1. adsorption onto soil and its constituents;
2. volatilization;
3. degradation (microbial, chemical, photolysis);
4. leaching to groundwaters and runoff/erosion to surface waters:
5. plant retention (contamination vs. uptake and translocation); and
6. macro- and micro-fauna uptake (bioaccumulation by insects, grazing
animals).
While research on the fate of sludge organics in soils is limited,
the behavior of organics in soil, has been extensively studied, particu-
larly agricultural pesticides, (e.g., Guenzi, 1974; Goring and Hamaker,
1972) and with non-agricuKural chemicals in the petroleum industry (API,
1983). In general, trace organics are strongly adsorbed to soils and its
constituents, especially soil organic matter. Thus, leaching and plant
uptake are usually very limited. Some runoff/erosion may occur for orga-
nics firmly bound to soil particles or debris, but this can be minimized
by using good soil and water conservation practices at sludge application
sites.
Some trace organics (notably, PCBs, lindane, dieldrin) are known to
volatilize readily when surface applied, although soils and slurine itself
can drastically reduce these volatizilation losses. Some organics are
recalcitrant to microbial degradation, but most are expected to degrade.
Of concern are the persistent organics and some of the readily degraded
components that can break down to toxic metabolites. Pathways of most
Interest are plant uptake/contamination, degradation, volatilization,
and leaching.
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Plant Uptake/Contamination
Chaney (1984) provided a good discussion about the uptake of organics
by plants. Because this summary seemed more appropriate than others (Davis
et al., 1984; Harms and Sauerbeck, 1983; Kaufman, 1983; Lue-Hing et al.,
1985; and Overcash, 1983) and is not readily available, much of his dis-
cussion was used for this section, sometimes verbatim. Readers are en-
couraged to review these other references, however, for a more complete
understanding of plant uptake/contamination.
Trace organics can enter edible parts of plants by two processes:
1) uptake from the soil solution, with trv.nslocation from roots to shoots,
or 2) absorption by roots and shoots of volatile organics from the soil.
Systemic pesticides are applied to the soil, then absorbed and translocated
to the plant leaves. These kinds of compounds are quite water soluble and
would probably not appear in wastewater treatment sludges at appreciable
levels.
Lipophilic halogenated, organics represent the case for water inso-
luble compounds which are largely sorbed by plants from the soil air or the
organic-enriched air near the soil surface. Beall and Nash (1971) deve-
loped a method to discriminate between movement of an organic through the
plant vascular system (uptake-translocation) vs. vapor phase movement.
They found soybean shoots were contaminated by soil-applied dieldrin,
endrin, and neptachlor largely by uptake-translocation, while vapor
transport predominated for DDT and was equal to uptake-translocation of
endrin. Using this method, Fries and Marrow (1981) found PCBs reached
shoots via vapor transport, while the less volatile PBBs did not con-
taminate plant shoots by either process (Chou et al., 1978; Jacobs et al.,
1976).
Root crops are especially susceptible to contamination by the vapor-
transport route. Carrots have a lipid-rich epidermal layer (the "peel")
which serves as a sink for volatile lipophilic organics. Depending on the
water solubility and vapor pressure of the individual compound, it may
reside near'y exclusively in the peel layer of carrots, or penetrate
several millimeters into the storage root (lichtenstein et al., 1964, 1965;
Jacobs et al., 1976; Lichtenstein and Schulz, 1965; Iwata and Gunther,
1976; Iwata et al., 1974; Fox et al., 1964; Landrigan et al., 1978).
Carrot cultivars, however, were found to differ in uptake &nd in peel
vs. pulp distribution of the chlorinated hydrocarbon pesticides endrin and
heptachlor (Lichtenstein et al., 1965; H«»rmanson et al., 1970). Other root
crops (sugar beet, onion, turnip, rutabaga) are much less effective in
accumulating lipophilic organics in their edible roots, possibly because
the surface of the peel is lower in lipids (Moza et al., 1979, 1976; Fox et
al., 1964; Chou et al., 1978; Lichtenstein and Schulz, 1965).
Based on carrot accumulation of volatile chlorinated hydrocarbon
pesticides, Iwata et al. (1974) evaluated PCB uptake by carrots from a low
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organic matter (0.6%) sandy soil, which represents a worst-case surface
soil, in the field (it should be recognized that 100 mg/kg is a very high
concentration of PCBs in soil. For the environmentally persistent 5 and 6
chlorine isomers, unpeeled fresh carrots contained PCB at about 4.9% of the
soil level. Peeling removed 14i of the carrot fresh weight and 97% of the
PCB residue, so peeled fresh carrots container PCB at only 0.16% cf the
soil PCB level.
The level of chlorinated hydrocarbon in carrots is also sharply
reduced by increased organic matter in soi",. The increased organic matter
adsorbs lipophilic compounds and keeps them from being released to the soil
solution or soil air (Filonow et al., 1976; Weber and Mrozek, 1979; Chou et
al., 1978; Strek et al., 1981). Since added sewage sludge can increase the
aDility of soils to adsorb PCBs (Fairbanks and O'Connor, 1984), the in-
creased sorption capacity may fully counteract the PCBs in sludge at low
levels.
The residue of PCBs in waste materials such as municipal sludge can
be depleted of the more volatile and more easily biodegraded lower rhlori-
nated compounds. Because plant contamination (uptake via volatilization)
by the higher chlorinated compounds is much less than for the more volatile
lower chlorinated compour.ds at equal soil levels (Iwata and Gunther, 1976;
Suzuki et al., 1977; Moza et al., 1976, 1979; and Fries and Marrow, 1981),
the lack of plant contamination from sludge-applied PCBs is not unexpected.
For example, in a study by Lee et al. (1980), a sludge containing 0.93
mg/kg PCBs was applied at a rate of 112 dry mt/ha, yet "no PCBs were
detected in the sludge grown carrots". Since other root crops are not
nearly as good PCB accumulators as carrot (Moza et al., 1979), remarkably
low potential human PCB exposure would be predicted for recommended sludge
utilization practices.
Other research efforts have centered on assessing risk from polycyclic
aromatic hydrocarbons (PAHs), some of which are carcinogenic (e.g.,
benzo(a)pyrene). Researchers found that carrot roots (but not mushrooms)
accumulated many PAHs from compost-amended soils (Milller, 1976; Linne and
Martens, 1978; Wagner and Siddiqi, 1971; Siegfried, 1975; Siegfried and
Muller, 1978; Ellwardt, 1977; Borneff et al., 1973). The level of
3,4-benzypyrene in carrot roots declined with successive cropping of com-
post amended soils. Harirs and Sauerbeck (1983) also found PAH contamina-
tion of potato tubers, radish and carrots where direct contact with the
soil allowed transfer of these organics. Concentrations in the above-
ground parts of plants were, however, low.
Nitrosamines are another group of organics which have been found in
sewage wastes (Yoneyama, 1981; Green et al., 1981). Although accumulated
from nutrient solution ana soil by plants (Brewer et al., 1980;
Dean-Raymond and Alexander, 1976), nitrosamines appear to be rapidly
degraded 1n soils and plants. Research on N-nitrosodimethylamine and N-
m'trosodiethyl amine found rapid degradation in soil; plant uptake co<'ld
occur initially but these compounds were rapidly degraded (Dresse'l, 1976a,
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1976b). While traces of nitrosamines are found in nitroanaline based her-
bicides, these compounds are rapidly degraded and no detectable nitrosamine
was found in soybean shoots (Kearney et al ., 1980b). An International
Union for Physics and Chemistry (IUPAC) committee assessed the environmen-
tal consequences of these trace nitrosamines, and found no risk to the fjod
chain (Kearney et al., 1980a).
Many other carcinogenic or toxic compounds could be present in sludges
and contaminate the food chain through plant uptake or volatile con-
tamination of crop roots or shoots. While information on these other orga-
nics is limited, two data bases are available which consider plant uptake
of organic molecules. PHYTOTOX deals with the direct effect of exogenously
supplied organic chemicals on the growth and development of terrestrial
plants (Royce et al., 1984). As of July 1985, 9,800 papers had been
included with data on 3,500 chemicals and 700 species (Rygiewicz, 19^6,
Personal communication). This data base is now available through a private
service (Fein-Marquart Associates, 7215 York Rd., Baltimore, MD 2121?).
The second data base (UTAB) contains information pertaining to the _U_ptake,
Transport, Accumulation and Biotransformation of organic compounds by
vascular plants. This database includes 3,900 papers, with information
about 700 chemica1s and 250 species and is available through the University
of Oklahoma (John Fletcher, Dept. of Botany, Univ. of Oklahoma, Norman, OK
73019). These data bases offer the opportunity to evaluate basic research
on the uptake of organics by plants which may help to understand the
effects of sludge applied organics.
Degradation
Degradation of organic chemicals in soil may occur by chemical, pho-
tochemical, or biological processes. Degradability of a compound depends
on its chemical structure, some being rapidly decomposed while others are
relatively recalcitrant to degradation. Biodegradation can occur in micro-
bial cells, in the soil solution by chemical mechanisms, or by extracellu-
lar enzymes sorbed to soil particles (Kaufman, 1983).
Often, soil microbes capable of degrading a compound proliferate in
soil, and the effective population may remain several years after the last
treatment. Maintaining a supply of biodegradable organic matter in soils
receiving wastes would likely provide a higher population of diverse micro-
bes capable of degrading more kinds of trace organics. Microbes may uti-
lize a particular organic as an energy source, or may cometabolize it with
other norma' metabolic processes. Although the kinds of organisms and even
types of enzymes involved in biodegradation are known for some pesticides
and other organics, little is known about most of the organics found in
wastes like sewage sludges (Kaufman, 1983).
Microbiological as well as chemical reactions are usually acting
simultaneously. Chemical reactions (abiotic routes) are a part of the
overall measure of organic compound decomposition. Two typical reactions
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are hydrolysis and neutralization of the parent organic species, but such
reactions typically leave the bulk of the parent structure still intact
(Over-cash, 1983). Soil factors known to affect chemical degradation of
organics include temperature, aeration, microbial populations, pH, organic
matter, clay, cation exchange capacity, and moisture (Kaufman, 1983).
The action of sunlight may chemically alter and degrade organic chemi-
cals in the environment. The importance of photochemical reactions to the
degradation of waste organics applied to land will depend largely upon the
mode of application and soil incorporation. Sludge organics can be sub-
jected to some photolytic action during the time they are on exposed soil
surfaces following a surface application (Kaufman, 1983). Under these con-
ditions an organic compound may be degraded via photolytic mechanisms.
Phenolics and polynuclear aromatics are two groups that readily undergo
such reactions (Overcash, 1983). Photolytic degradation will be
nonexistent, however, when sludges are incorporated into the soil since
sunlight does not penetrate the soil surface (Kaufman, 1983).
Following an extensive literature search concerning the decomposition
of specific organics in the terrestrial environment, Overcash (1983)
concluded that very few organic compounds can be said to be non-degradable.
Considering the long time periods typical in soil systems, only two classes
of compounds were regarded as nondegradable based on available ttrrestrial
research information: (1) synthetic polymers manufactured for stability,
and (2) very insoluble large molecules, e.g., 5-10 chlorinated biphenyls
(Overcash, 1983).
Other organics will have varying decomposition half-lives or per-
sistence in soils. Overcash (1983) provided examples of half-life ranges
for several organic chemicals (Table 44) and Kaufman (1983) listed the
relative persistence for several organic chemical classes (Table 45).
Tabak et al. (1981) compared the relative biodegradation of organic
priority pollutants with a static culture flask procedure. While their
decomposition re<="lts may not be directly extrapolated to degradation of
organics in the soil, the relative degree of biodegradation may prove to be
similar in soils. Significant biodegradation was found for phenolic com-
pounds, phthalate esters, napthalenes, and nitrogenous organics; variable
results were found for monocyclic aromatics, polycyclic aromatics, polych-
lorinated biphenyls, halogenated ethers, and halogenated aliphatics; and no
significant biodegradation was found for organochlorine pesticides.
Volatilization
Vapor movement of organics (i.e., diffusion and volatilization) are
important factors affecting the distribution and persistence of some orga-
nic chemicals in soil. An estimate of potential volatility can be obtained
from the ratio of water solubility to vapor pressure, which indicates the
proportion of an organic in the vapor phase. This ratio is only a guide,
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however, since adsorption of the organic in the soil will decrease the
amount present in the vapor phase (Kaufman, 1983).
An organic spread on the surface of or injected into a soil with
sludge will partition between the gas and liquid phases to exert a vapor
pressure. The conditions of the soil and the application technique used,
as well as the inherent organic compound volatility, are important factors
in quantifying how an organic compound might be lost through volatiliza-
tion. The level of vapor pressure at which volatile losses are known to be
significant is usually taken at 5 x 10~6 mm Hg at 25°C. However, vapor
pressure alone may be misleading because highly volatile organics like
toluene are prevalent in municipal sludges, even after opportunities have
occurred for volatile loss during wastewater treatment (Overcash, 1983).
Volatilization losses were considered as significant processes of
organic chemical removal when wastewaters are applied to land (Chang and
Page, 1984; Jenkins et al., 1983). Jenkins et al. (1983) stated "as a rule
the higher the vapor pressure the lower the water solubility, the higher
the Henry's law constant and the higher the removal rate by volatiliza-
tion." Once the organic reaches the soil, the actual volatilization loss
of trace organics from the soil will depend on factors affecting the move-
ment of the organics to the soil surface and its dispersion into the air
(Chang and Page, 1984).
For soil-applied pesticides, the vapor density was found to be the
main factor controlling volatilization (Farmer et al., 1972). Other fac-
tors which affect volatilization include soil pesticide concentration,
temperature, rate of air movement over the soil surface, and soil water
content (Farmer et al., 1972; Igue et al., 1972). More recently Jury et
al. (1983, 1984a,b,c) have used benchmark properties of vapor density and
solubility in water in a mathematical model to determine the relative vola-
tility of a specific soil-applied organic.
As with earlier work done with pesticides, how well research results
will predict volatilization losses for the same organics applied to soils
as part of a sludge matrix is unknown. Research reported by Fairbanks and
O'Connor (1984) indicate that sludge additions to soil can decrease volati-
lization losses of PCBs, so the sludge matrix could be expected to have
some effect. Nevertheless, models and research data which apply to soil-
applied pesticides provide a good "point of departure" for understanding
potential volatilization losses of pesticides and other organics added by
sludge applications.
Leaching
The downward movement of an organic chemical is largely governed by
sorption and biodegradation. At least two steps are involved in the
Teachability of an organic chemical in soil: (1) entrance of the compound
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into solution, and (2) adsorption of the compound to soil surfaces (Kauf-
man, 1983). Partitioning between the adsorbed and soil solution phases
may occur immediately upon application to the soil or may be delayed
until the organic separates from the waste medium. At the same time,
decomposition reactions can vary the actual amount of a particular organic
compound that resides on the soil/waste phase or in the soil-water solution
(Over-cash, 1983).
Therefore, the inherent persistence of each chemical in soil will
affect whether any mobile chemical might pollute groundwater. The half-
life of many organic chemicals in soil is sufficiently short to make it
highly unlikely that the chemical would ever reach the water table under
ordinary field leaching conditions (Kaufman, 1983). Overcash (1983) also
concluded that for most sludge application sites where normal application
rates and management techniques are used, leaching of organics is probably
negligible.
Effects of_ Sludge Properties
Few studies have considered the effect of sludge on the assimilative
pathways of adsorption, volatilization, and degradation. Since organics
typically associate with the organic fraction of soils, one might expect
even greater retention of trace organics in amended vs. unamended soils as
was shown by Fairbanks and O'Connor (1984) for di-3-(ethylhexyl)phthalate
(DEHP), PCBs, and two herbicides. The greater adsorption in sludge-amended
soils should reduce contaminant mobility and plant availability, and data
did show that volatilization of PCBs from sludge-amended soils was signifi-
cantly reduced (Fairbanks and O'Connor, 1984).
Sludge additions may also affect organic contaminant degradation.
The increased microbial activity found in sludge-amended soils suggests
that previous sludge applications cause a preconditioning with respect to
microbes and/or enzymes which may increase organic degradation by cometa-
bolism (Fairbanks and O'Connor, 1984). The degree and duration of sludge
effects on trace organic behavior are influenced by type and concentration
of compound, incubation time, sludge rate, and soil type.
Most experiments designed to determine the effects of sludge or or-
ganic behavior have used "spiked" systems in which the target organic is
added as reagent grade chemical to soil or soil-sludge systems. Pre-
equilibrium of the target organic with sludge has been minimal. Thus,
most data generated to date are tainted by limitations similar to the
early "mineral salt" work with metals. Organics indigenous to sludge may
have drastically different properties with respect to their fate in soils
compared to these same trace organics added to the soil alone or in com-
bination with sludge. Research is needed with selected sludges to study
the assimilative pathways of specific organics (indigenous to these
sludges) compared to results for comparable amounts of the same organic
added to the same soil in the absence of the sludge matrix. Correlations
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between controls and sludge-treated soils could then be used to predict
the fate of other sludge-applied organics when actual field data are
unavailable.
Utilizing Physical/Chemical Properties and Models
Due to the thousands of organics which can potentially be present in
society's wastes such as sewage sludge, the task of researching each orga-
nic to determine its fate in the environment is impossible. A more
realistic approach would be to utilize basic physical/chemical properties
of organics and soils to compare the research results assessing the
environmental fate of selected organics, representative of larger groups,
with the fate predicted by mathematical models.
The more important physical/chemical characteristics for assessing the
potential transport, persistence, and fate of substances in sludge land
applications are: (a) water solubility, (b) soil adsorption-partitioning,
(c) half-life in soil, and (d) vapor pressure. Laboratory measurements can
be used to obtain values for all these characteristics except soil half-
life, or they may be estimated by methods such as those discussed by Lyman
et al. (1982).
The fates of greatest interest for sludge organics incorporated into
the soil are volatilization, degradation, plant uptake, and leaching. The
persistence, or ease of degradation, and volatilization of an organic are
major characteristics which will affect the time during which an organic
may be "available" for plant uptake or loss by leaching to groundwater.
Adsorption to soil colloids (organic and inorganic) and water solubility
of an organic are also important factors which help determine this avail-
ability. When plant uptake and leaching are not significant for ar, orga-
nic, potential for transfer back to man is reduced. Likewise, when an
organic is completely degraded in soils, additional pathways (discussed
earlier in this section) for transferring a sludge organic to humans are
eliminated.
Examples of using benchmark properties in mathematical models or for
estimating the behavior of organics applied to soils include Chang and Page
(1984), Jury et al. (1983, 1984a,b,c), and Wilson et al. (1981). Based on
calculations using the soil adsorption coefficient, water-air partition
coefficient, and octanol-water partition coefficient, Chang and Page (1984)
compared the environmental fate and transport in soils of several pestici-
des with several trace organics. Their conclusion regarding the addition
of wastewater organics to soils was that their environmental impact was not
expected to be very significant.
Using a simple mathematical model based on water solubility of an
organic chemical and the organic carbon content of the soil, Wilson et al.
(1981) were able to predict t!ie retardation factors for 13 organic pollu-
tants within a factor of three. They found retardation by soil with
respect to water movement generally increased with decreasing water
solubility.
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Jury et al. (1983) developed a more complicated mathematical model for
describing transport and loss of soil-applied organic chemicals. This
screening model uses benchmark properties (organic C partition coefficient,
vapor pressure, solubility, half-life) to determine the relative convective
mobility, diffusive mobility, volatility, and persistence (Jury et al.,
1984a,b). When this model was tested on published experimental data for
volatilization, leaching, and persistence, experimental results and those
predicted by the model agreed reasonably well (Jury et al., 1984c).
Although experiments under field conditions are the only reliable way
to determine the fate of an organic applied to soils with sewage sludge,
the expense and time required to test the large number of organic chemicals
used in society and found in sewage sludges are prohibitive. Therefore,
models like those mentioned above can and should play a significant role in
assessing the environmental risk of applying sludge organics to soils.
COMPARISON OF MUNICIPAL SLUDGE EXPOSURE/RISK ASSESSMENTS
Several independent evaluations have recently been published to assess
the relative risk from specific organic compounds present in municipal
sludge when applied to land (Metro, 1983; Munger, 1984; Connor, 1984;
Naylor and Loehr, 1982a,b; EPA, 1985). All of the risk assessments cited
above are published in non-peer reviewed journals. No in-depth scientific
evaluation or analysis was performed on these individual exposures/risk
assessments. Therefore, their results and conclusions should be viewed
with this in mind. As far as the authors are aware, no risk assessments
for sludge have appeared to date in a peer-reviewed journal.
Risk could be defined as a measurement of the probability of harm
occurring to human health as a result of an organic chemical being present
in land-applied sludge (Munger, 1984). To the extent possible a common
concept was used to assess "acceptable risk", i.e., the ratio of daily
intake required to stay below a risk level of 10~6. If this ratio is
greater than 1.0, the resulting risk level is (numerically) greater than
ID"6 and when less than 1.0, the risk level is less than 10'°. This ratio
is actually the inverse of the "hazard index" used in EPA environmental
profiles (EPA, 1985) but was the method chosen to express risk levels in
the other risk analyses.
A risk assessment concerning the health effects of land applying
sludge was prepared by S. Munger for the Municipality of Metropolitan
Seattle (Metro, 1983). This assessment was updated and expanded specifi-
cally for the "Municipal Wastewater Sludge Health Effects Research Planning
Workshop" held in Cincinnati by EPA in January 1984 (Munger, 1984). That
estimate of risk was based on the quantities of soil, water, or food
obtained from a sludgt application site which could be consumed without
exceeding a risk level of 10"5.
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The assumptions and values used by Munger (1984) for assessing the
risk of two organics, polychlorinated biphenyls (PCBs) and benzo(a)pyrene
[B(a)P], are shown in Table 46. The concentrations of PCBs and B(a)P
which would occur in the various environmental compartments (i.e., soil,
water, plant and animal tissues) were estimated. Using these concentra-
tions (Munger, 1984) and the organic chemical consumption equivalent to
10"6 risk level, the quantities of various materials that could be con-
sumed without exceeding this risk were calculated (Tables 47 and 48). The
quantities for materials from sludge-amended areas could then be compared
to similar materials from control (untreated) areas to evaluate any in-
creased risk due to sludge application to forest land. The author (Munger,
1984) concluded that for these two organics, PC8s and B(a)P, any increased
risk would be minimal and could be controlled by proper site management.
The Naylor and Loehr efforts (1982a,b) considered several perspec-
tives on risk, deluding the human intake routes by comparing the addition
of sludge organics to soils with the application of agricultural chemicals
to soil. Naylor and Loehr (1982a) begin by defining relative toxicity
categories (Table 49) and then comparing the +.oxicities of common chemicals
(Table 50), common pesticides (Table 51) and selected priority pollutant
organics in 13 sludges (Table 52). In general, the agricultural chemicals
are more toxic than the sludge organics. When <"omparing normal pesticide
rates, the projected application rates for sludge organics are usually
10 fold less than for pesticides. In this perspective municipal sludge
practices were judged to have no greater risk than using agricultural
chemicals.
A second form of comparison was more similar to that used in the £PA
Profiles for direct consumption of sludge against acute (LD^o dose) and
chronic (acceptable daily dose, or Dj) concerns. From the group of 24
sludge organics listed, Naylor and Loehr (1982b) selected three for further
evaluation: (1) hexachlorobutadiene (HCBO), a highly toxic chemical; (2)
bis(2-ethyl-hexyl)phthalate, a chemical having a relatively low toxicity
but present in high concentrations; and (3) 1,1,2-trichloroethane, a
chemical of moderate concentration and moderate toxicity.
Based on the maximum sludge concentrations, the rat or a cow would
have to eat an amount of sludge equivalent to more than 10 times it body
weight to ingest a LD50 dose of the most t^xic HCBD (Table 53). When
considering a chronic exposure occurring by daily intake of sludge alone
or soil treated with sludge (Table 54), a "pica" child would have to con-
sume sludge for 41 years to consume a LD50 dose of HCBD, the most toxic
sludge organic Naylor and Loehr (1982b) considered. When considering the
irore logical case of a "pica" child consuming sludge treated soil rather
than pure sludge, a safety factor of 45 to 450 was obtained (Table 54).
Therefore, from a different perspective, 24 organics in sludge were judged
to be a relatively low health hazard when sludges are land applied at
agronomic rates.
Connor (1984) used the same sludge characteristics as Naylor and Loehr
(1982a,b) but an independent risk/exposure assessment (Table 55). Assuming
125
-------
a low (15 g) and high (139 g) amount of contaminated soil per day is
ingested, safety factors were calculated based on soil concentrations
expected from pesticide or sludge application. The safety margins were (1)
greater for sludge organics than for common agricultural chemicals applied
to soils and (2) greater than 1 for a1.! chemicals except the polycyclic
aromatic hydrocarbon (PAH) group which had a margin of safety of about
0.3 to 0.03.
While Naylor and Loehr (1982b) did not develop u dietary scenario for
PAH chemicals, they cited references which indicated that soils may contain
.natural PAH concentrations of 0.05-0.14 mg/kg and manure can contain 0.15
to 1.21 mg PAH/kg. The addition of PAH assumed by Connor (1984) in his
risk assessment (Table 55), i.e., 15 mt/ha of sludge containing 13 mg/kg
of PAH, would be equivalent to a soil concentration of 0.08 mg PAH/kg soil
Therefore, Connor's analysis for PAH would suggest that any soil contain-
ing the background levels given above would have a low safety factor.
The fourth risk assessment reviewed for sludge organics is the envi-
ronmental profiles and hazard indices conducted on several sludge consti-
tuents (EPA, 1985). The methodology used to assess the risk of a
particular organic included the use of 12 indices to evaluate different
pathways by which the sludge-applied organic could be exposed to plants,
animals, or humans. The index which most lends itself to a comparison of
the Naylor and Loehr (1982a,b) and Connor (1984) assessments is index 12,
the index of human cancer risk from soil ingestion by a "pica" child.
Only two organics included in Naylor and Loehr's or Connor's list of
organics had an index 12 value calculated: Hexachlorobutadiene (HCBD) and
B(a)P. By inverting the EPA hazard index value, essentially a safety fac-
tor value can be obtained. The safety factor for HCBO was calculated as
238 by EPA (1985) and 45 by Naylor and Loehr (1982b), and for B(a)P was
0.018 by EPA (1985) and 0.27 for total PAH by Connor (1984). While these
results vary, there was agreement in terms of whether risk was greater than
or less than 10"6.
Following a similar calculation as Naylor and Loehr (1982b) used for
bis(2-ethylhaxyl)phthalate and HCBD, a safety factor was also calcul'.ced
for methylene chloride (MeCl) and phenanthrene. Comparing the safety fac-
tors of Connor's and Naylor and Loefr's results for 15 g/day soil ingestion
show:
Loehr Connor
BEHP 415 4,700
MeCl 4.6 150,000
PAH 35 (phenanthrene) 0.27 (total PAH)
Results tended to be in the same direction from 1.0 except for PAHs, al-
though the magnitude of differences were substantial.
126
-------
Differences between the three risk assessments can be attributed to
differences in acceptable daily intake values used, sludge concentrations
assumed, sludge rates assumed, quantities of soil assumed to be ingested,
etc. The large differences obtained by these authors and cited above indi-
cate how important it is to have correct assumptions and realistic data for
calculating safety factors. When tne accepted daily intake values vary by
103 or more betweer, assessments, large differences can be expected for the
safety factors obtained.
Answers obtained using risk assessment methodology must provide
realistic values to be useful. If nothing else, the methodology will indi-
cate weaknesses in the assumptions or data used when unrealistic values are
obtained with these models and help identify where further research data
are needed. Overall, the general consensus of these risk assessments seems
to indicate that organics applied to soil from sludge will not increase the
health risk to animals and humans. However, the data base on which the
previous statement is made is limited, and better risk assessment method-
ologies for land application of organics from sludge are urgently needed.
CONCLUSIONS
1. Because sewage sludges can theoretically contain thousands of orga-
nic compounds, wastewater treatment plants should identify the orga-
nics being discharged by users, particularly industry. This
information should guide the testing of sludges for appropriate
organics to determine concentration levels.
2. Available surveys measuring trace organic concentrations in sludges
indicate that sewage sludges can have unusually high concentrations
(i.e., a few percent, dry weight). Most organics are present at con-
centrations less than 10 mg/kg and about 30% of the organics tested
were below detection limits. Based on their prevalence and potential
loading to soils using agronomic or low sludge rates, sludge organics
appear to have minimal risk.
3. Mutagenicity tests have been used to evaluate the safety of sewage
sludges from land application. While the test might provide an addi-
tional means of checking sewage sludges prior to land application,
they are difficult to interpret and have not been correlated to muta-
genic activity of soil/sludge mixtures in the field. Therefore, their
value for helping manage land application fograms is uncertain at
this time.
4. Major assimilative pathways for organic chemii.:'!., applied to the soil-
plant system include adsorption, volatilization, degradation,
leaching, and plant uptake. Many organics are strongly adsorbed to
soil organic matter and/or undergo degradation, reducing the potential
for plant uptake or leaching.
127
-------
5. Due to the thousands of organics which can potentially be present in
sewage sludges, a realistic approach may be to utilize basic physical/
chemical properties of an organic and mathematical models to predict
the likely fate of that sludge organic in the soil. However, limited
field research with selected sludge organics, which are representative
of organic chemical groups, is needed to validate these models.
6. In general, risk assessments appear to suggest ihat most sludge orga-
nics will not increase the health risk to animals and humans, based on
their relative toxicities and anticipated loadings to soil from agro-
nomic or low sludge application rates.
128
-------
TABLE 40. SUMMARY OF ORGANIC CHEMICALS FOUND IN SEWAGE SLUDGES.
ro
o
Chetni cal
NO. or
sludges
tested
I
Occur-
rence'
Concentrations for Samples Testing^
Positive. I.e. , > Detection Limits
mQ/kg (dry wt. )§
Range
Median
Phthalate Esters
Bi s(2-ethylhexyl )phthaUte
Bu ty 1 ben* ylphtha late
Diethylphthalate
Dime thylphth'late
Oi-ri-butyl phthalate
Oi -n-cctyl phthalate
234
437
234
437
234
437
236
437
237
437
237
437
84
95
60
43
63
9
23
5
45
45
40
10
0.415 -58,300
0.0469-12.800
0.0987-3.780
0.106-941
0.0776-3,210
0.0222-2,610
168
59.1
50.0
11.7
17.3
4.9
Mg/L
Range
2-47.000
2-45.000
1-786
3-650
1-6.900
4-1.024
- Ref.ft
1
2
1
2
1
2
I
2
1
2
1
2
Monocycllc Aroma tics
Benzene
Chlorobenzene
l-chloro-2,4-di nitrobenzene
1-ch) oro-2 ,6-
-------
TABLE 40 (continued)
UJ
o
Chemical
No. of
sludges
tested
1
Occur-
rence
Concentrations for Samples Testing
Positive, i.e., > Detection Limits
n^/kg (dry wt.) (1<)/L
TUnge Median Rim ye
Ref.
Honocyclic Aromatlcs (cont'd.)
1 , 2-di chl orobenzene
1 , 3-di chl orobenzene
1 ,4-dichl orobenzene
l-chloro-2.4-di nitrobenzene
2.4-dinitrotoluene
2.6-di ni trotoluene
Ethyl benzene
Hexachlorobcnzene
Ni trobenzene
pentach) oroni trobenzene
Styrene
Toluene
1 , 2, 3-tri chl orobenzene
101/215
71/437
117/215
40/437
141/216
74/437
0/238
238
431
238
431
220
436
102/237
7/437
0/238
0/431
233
219
437
434
215
47
16
54
9
66
17
0
0
0
0
0
6
63
43
2
0
0
0
10
13
94
37
0.0229-809 0.645
3-1.319
0.0245-1.650 1.76
14-1,900
C. 0402-633 2.02
2-12,000
All samples < detection limit
All samples < detection limit
All samples < detection limit
All samples < detection limit
All samples < detection limit
1.22-65.5 19.8
1-4.200
0.000188-26.2 0.018
28-780
All samples < detection limit'
All samples < detection limit
All samples < detection Unit
1.53-5.850 26.6
2-8.300
1-42/.OOC
0.00<:78-152 0.0667
1
2
1
2
1
2
1
1
2
1
2
1
2
1
2
1
2
1
1
2
2
1
-------
TABLE 41) (continued)
Chemical
1 ,2,4-tri chl orobenzene
1 ,3,5-t nchlorobenzene
1.2, 3, 4-tetrich! orobenzene
1 ,2.3,5-tetrachlorobenzene
1 ,2,4. 5-teCrichl orobenzene
No. of
sludges
tested
217
217
23B
738
238
1
Occur-
rence
Concentrations for Samples Testing
Positive, i.e.. > Detection Limits
mg/kg
kange
Honocycllc Aroma tics
57 o.oKTnm
33
0
0
0
0.00502-39.7
All samples <
All samples <
All samples <
Polynuclear Aromatlcs
2-chl oronaphthalene
Naphthalene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluorantiiene
Pyrene
Chrysene
2.3-o-phenylenepyrene
437
2J6
437
437
437
437
437
437
12
437
436
t37
1 ?
0.2
50
34
S
6
53
48
44
100
53
31
2
100
0.0554-6.610
0.34-11.*
0.06-6.86
{dry wt.) jjQ/L
Median Range
(cont'd.)
0.274
0.0632
detection limit
detection limit
detection limit
(PAH)
1.600
30.3
1-5.200
6-4,600
1-1.300
1-10.100
1-10.100
1-9.930
2.06T
1-1.700
1-1.500
17-102
0.88
Ref.
1
1
1
1
1
2
1
2
2
2
2
2
2
10
2
2
2
10
8cnzo(a)anthracene
437
27
1-1.500
-------
TABLE 40 (continued)
UJ
ro
Chenical
No. of
sludges
tested
%
Occur-
rence
Concentrations for Samples Testing
Positive, i.e., > Detection Limits
mg/kg (dry wtj
Range Hedij
v-g/L
»n HRange Ref.
Polynuclear Arnmatics (PAH) (cont'd.)
Oenzo (a)pyrene
3,4-b.nzofluoranthene
11,12-benzofluoranthene
Acenaphthylene
1.12-benzoperylene
1,2.5 . 6 -di be nz anthracene
Isophorone
437
12
437
12
438
12
437
437
12
437
431
5
100
11
100
8
100
1
2
100
0.4
0
0.12-0.14 0.
0.06-9.14 1.
0.06-4.57 0.
0.06-9.14 0
t 1-490 2
88T 10
+ 1-2,400 2
47T 10
t 1-379 2
49T 10
24-320 2
12-133 2
65T 10
12-50 2
All samples < detection limit 2
Halogenated Biphenyls
PCBs (Arochlor 124Q)
(Arochlor 1254)
(Arochlor 1260)
(decachlorobiphenyl s)
(ruf . std.unspeci fled)
(Arochlor 1016, 1221.
1232, 1242)
PBB (polybromi nated
bipaenyl )
431
107
431
111
431
74
9
431 ea.
210
0
39
0
58
0
100
100
0
0
All samples < detection limit 2
0.0667-1,960 5.35 1
All samples < detection limit 2
0.0468-433 4.18 1
AH samples < detection Unit 2
0.11-2.9 0.99 7
0.36-7.60 1.20 8
All samples < detection limit 2
All samples < detection limit 1
-------
TABLE 40 (continued)
OJ
CO
Chenical
Chlorinated
Tetra-COOs
Penta-CDOs
Hexa-COOs
Hepta-COOs
Octa-CODs
Tetra-COFs
Penta-COFs
Hexa-COFs
Hepta-CDFs
2,3,7,8-TCOO
Acrolein
Acrylonitrile
No. of J
sludges Occur-
tested rence
Concentrations for Samples Testing
Positive, i.e., > Detection Limits
nig /*9 (dry wt.) uq/L
Mange tfTcfian nimii
Ref.
Dibenzo-p-dioxins (CDDs^ and Chlorinated Dlbennfurans (COFs)§
2
2
1
2
2
2
2
2
2
1
2
2
2
431
431
155
436
(1)
(2)
(0)
(2)
(2)
(2)
(2)
(2)
(2)
(0)
(0)
(0)
(0)
0
Halogenated
0
61
1
7.2 pg/kg
0.138 and 0.222 yg/lig
Sample < detection limit
0.3 and 2.1 wgAg
1.41 and 1.43 yg/kg
0.9 and 6.J yg/kg
9.4 and 7.6 pg/kg
7.6 and 60 ug/kg
SO and 60 pg/kg
Sample < detection limit
Sample < detection limit
Sample < detection liml t
Sample < detection limit
All samples < detection limit
Aliphatics (Short Chain)
All samples < detection limit
0.0363-82.3 1.04
5-290
g
11
g
9
n
9
11
9
11
9
9
9
9
2
2
1
2
bis(2-chlorotthoxy)methane 431
All samples < detection limit
-------
TABLE 40 (continued)
Chuni cal
bis(chl oromethyl )ether
bis(2-chloronethyl)ether
bis(2-chloroisopropyl) ether
Carbon tetrachloride
Chi orodibrQTioma thane
Chloroethane
2-chl oroethyl vinyl ether
Chlorofonn
Oi chl orotiroiiomethane
Oichlorodi fluorcxne thane
1.1-di chloroethane
1,2-dichloroethane
1 . 1-di chl oroeihylene
1.2-dichloropropane
1,3-dichl oropropane
1 . 3- Detection Limits
mgAg (dry wt.) ,,g/L
Range Median Range
(Short Chain) (cont'd.)
All samples < detection limit
H
All samples < detection limit
5-3.030
10-75
5-71,000
u
1-366
3-260
2-4.300
' 1-2.880
1-10.000
1-14.000
0.00243-66.0 0.464
1-103
0.209-309 3.08
0.00203-1.230 3.42
Ref.
2
2
2
2
2
2
2
2
2
2
2
2
2
1
2
1
1
-------
TABLE 40 (continued)
CO
en
Chemical
Hexachloro-l,3-butadiene
Hexachl oroethane
Methyl bromide
Methyl chloride
Methyl ene chl oride
Pentachl oroethane
1, 1, 2,2-tetrachl oroethane
Tetrachl oroethylene
Tribrcmomethane
1,1,1-trichloroethane
1,1,2-trichl oroethane
1 ,2-trans-di chl oroethyl ene
1,2,3-trichl oropropane
1,2,3-trichlcropropene
Trichl oroethy1. ene
Trichl orofluoromethane
vinyl chloride
No. of
sludqes
tested
Halogenated
217
437
216
431
431
436
436
199
434
128
436
436
436
434
436
141-
137
. 432
436
435
%
Occur-
rence
Ali phatics
47
0.2
61
0
0
6
0.4
28
15
73
40
0.2
19
4
60
48
48 ''
54
5
8
Concentrations for Samples Testing
> Detection Limits
mg/kg (dry wt. ) yg/L
Range Median Range
(Short Chain) (cont'd. )
<10-"-3.74 0.0355
2,700
0.00036-61.5 0.0199
All samples < defection limit
33-30,000
12-6,100
5-19
0.00025-9.22 0.030
1-3,040
<10"5-0.122 0.00052
1-2,800
5
•1-10,900
1-2,100
1-96,000
0.00459-19.5 0.352
<10-4-167 1.14
1-32,700
2-113
8-6.2,000
t
Ref.
1
2
1
1
2
2
2
2
1
2
1
2
2
2
2
2
1
1
2
2
1
-------
TABLE 40 (continued)
Chemical
Cresyl diphenyl phosphate.
Tricresyl phosphate
Trixylyl phosphate
Eenzidine
u» 3,4-dichloroanili ne
3,3'-dichlorobenzidine
p-nitroanil ine
N-nitrosodimethylami ne
N-nitrosodi ethyl amine
N-ni trosodi bu tyl ami ne
N-nitrosppiperidi ne
N-nitrosopyrrolidine
No. of
sludges
tested
238
235
236
238
431
238
238
431
238
431
15
11
15
11
15
11
15
11
15
11
Occur-
rence
Triaryl
3
69
68
Aromatic
0.4
0
0
0
0
0
0
93
82
27
54
0
0
0
9
13
18
Concentrations for Samples
> Detection Limi ts
mg/kg (dry wt. } M
-------
TABLE 40 (continued)
Chanical N,°'°f4
sludges
tested
N-nitrosomorpholine
N-ni trosodi phenylami ne
N-nitrosodi -n-propylaraine
p-chl oro-ra-cresol
o-chl orophenol
m-chl orophenol
p-chl orophenol
o-cresol
2,4-dichl orophenol
2,4-dimethylphenol
4 ,6-dinitro-o-cresol
2,4-dini trophenol
Hydroquinone
15
11
431
431
438
231
438
231
231
231
230
438
231
431
228
431
220
431
229
%
Occur-
rence
Aromatic
20
54
0
0
1
9
2
7
9
6
7
2
18
0
9
.0
30
0
27
Concentrations for Samples Testing
> Detection Limits
mg/kg [dry wt.) pg/L
Ran ge
Median Range
Ref.
and Alkyl Amines (cont'd.)
2.0-9.2 pg/kg
1.3-2.9 pg/kg
All samples <
All samples <
Phenols
0.0766-90.0
0.123-93.3
0.0277-90.0
0.177-183
0.209-203
0.0899-86.7
Al 1 s amp 1 e s <
0.202-187
• All samples <
0.153-500
All samples <
0.138-223
2.9 pg/kg
1.8 pg/kg
detection limit
detection limit
12-35
3.6
11-72
0.891
3.28
2.05
4.75
14-298
2.19
detection limit
2.34
detection limit
4.62
detection limit
2.55
3
4
2
2
2
1
2
1
1
1
1
2
1
2
1
2
1
2
1
-------
TABLE 40 (continued)
Chemical
2-nitrophenol
4-nitrophenol
Penlachlorophenol
Phenol
2.4,6-trichlorophenol
No. of
sludges
tested
431
431
223
4^8
229
438
223
438
Occur-
rence
0
0
70
14
78
50
30
0.4
Chlorinated Pes
Aldrin
Chi ordane'
Dieldrin
Endrin
223
431
74
431
74
221
431
40
14
74
223
431
74
0
0
100
0
100
28
0
7
93
100
0
0
100
Concentrations for Samples Testing
> Detection Limits
mg/kg (dry
Range
Phenols (conf
All samples
All samples
0.172-8.490
0.0166-288
0.195-1.330
wl.) ,,9/L
Median Range
d).
< detection limit
< detection limit
5.00
10-10.500
2.00
5-17.000
4.81
11-16
Ref.
2
2
1
2
1
2
1
2
tlcides and Hydrocarbons
All samples
All samples
0.05-0.64
All samples
0.46-12
0.000377-64.
All samples
<0. 01-1. 26
0.04-2.2
0.05-0.81
All samples
0.11-0.17
< detection limit
< detection limit
0.08
< detection limit
2.75
7 1.06
< detection limit
0.26
0.16
0.11
< detection limit
u
0.14
1
2
7
2
7
1
2
5
6
7
1
2
7
-------
TABLE 40 (continued)
Chemical
No. of
sludges
tested
I
Occ
ren
Chi ori nated
Endrin aldehyde
p.p'-DDD
p.p'-ODE
_ p.p'-DDT
oo
vo
Heptachlor
Iteptachl or epoxide
Linda ne(Y-OHC)
Hethoxychlor
2,4-D
Hexachlorocyclopentadi ane
Toxaphene
431
221
431
219
443
40
74
219
431
74
431
74
431
221
431
40
74
223
223
431
431
0
4B
0
92
0
100
0
95
0
100
0
100
0
17
0
?
100
0
25
0
0
Concentrations for Samples Testing
> Detection Limits
ur- mg/kg (dry wt. ) ,,9/L
ce Range Median Range
Pesticides and Itydcocarbons (cont'd.)
All samples < detection lira! I
0.00114-84.1 0.363
All samples < detection limit
0.00118-564 1.14
.2 10.000
0.01-0.49 0.02
All samples < 0.05
<10"4-135 0.211
All samples < detection limit
0.06-0.14 0.03
All samples < detection limit
0.05-0.55 0.13
All samples < detection limit
0.00059-12.5 0.0746
All samples < detection limit
<0. 01-0. 93 0.18
0.05-0.22 0.11
All samples < detection limit
0.000554-7.34 0.122
All samples < detection limit
All samples < detection limit
Ref.
2
1
2
1
2
5
7
1
2
7
2
7
2
1
2
5
7
1
1
2
2
-------
TABLE 40 (continued)
-£»
o
Chemical
No. of
sludges
tested
t
Occur-
rence
Concentrations for Samples
> Detection Limits
mg/kg {dry wt. ) 1,9/1
Range Median Range
Testing
Ref.
Chlorinated Pesticides and hydrocarbons (cont'd.)
a-endosulf an
8-endosulf an
Cnaosulfan sulfate
o-BKC
B-BHC
6-BHC
1.2-Uiphenylhydranne
4-chl orophenyl phenyl ether
4-branophenyl phenyl Jther
Mercaptobenzothiazole
Bi phenyl
431
431
431
431
431
431
431
431
431
238
236
0
0
0
0
0
0
Hi scellaneous
0
0
0
0
33
All samples < detection limit
All samples < detection limit
All samples < detection limit
All samples < detection limit
All samples < detection limit
All samples < detection limit
Compounds
All samples < detection Unit
All samples < detection limit
All samples < detection limit
All samples < detection limit
0.0437-1,730 8.61
2
2
2
2
2
2
2
2
2
1
1
-------
Table 40. FOOTNOTES
'A concentration range was given in Reference 10 for each of the 12 sludges tested.
The concentration for each PAH organic was obtained by taking the average of the
high and low values to get an average concentration for each of the 12 sludges.
These 12 averages were then used to report the range'and median value in Table 40.
*"% occurrence" times the total "no. of sludges tested" equals the number of
samples testing positive, i.e., having a concentration greater than the detection
limit.
*Under "% occurrence", Values given in parentheses are the number of samples which
had a detectable concentration rather than a "percent" value.
§Note: Concentrations (on dry weight basis) for dioxins and furans and several
i- alkyl amines are in gg/kg rather than mg/kg as for all other organics.
»—•
ttReferences:
1. Jacobs and Zabik, 1983. (Various sludges from 204 Michigan WWTPs)
2. Burns and Roe, 1982. (Primary, secondary, and combined sludges from 40 POTWs)
3. Mumma et al., 1934. (Various sludges from 31 American cities)
4. Mumma et al., 1983. (Various sludges from 24 New York communities)
5. Mclntyre and Lester, 1982. (Various sludges from 40 WWTPs in England)
6. Furr et al., 1976. (Various sludges from 14 American cities)
7. Clevenger et al., 1983. (Various sludges from 74 Missouri WWTPs)
8. Diercxsens and Tarradellas, 1983. (Various sludges from 9 Switzerland WWTPs)
9. Weerasinghe et al., 1985. (Two sludges from Syracuse, NY and Sodus, NY)
10. Mclntyre et al ., 1981. (Various sludges from 12 United Kingdom WWTPs)
11. Lamparski et al., 1984. (Two samples of Milorganite, one each produced in
1981 and 1982)
-------
TABLE 41. SUMMARY COMPARING THE NUMBER OF ORGANIC CHEMICALS TESTED TO THE NUMBER OF
ORGANICS NOT DETECTED IN SEWAGE SLUDGES OR FOUND IN 10, 50 OR 90% OF THE SLUDGES.
Reference*
1 (204 WWTPs)
2 (40 POTWs)
1 (204 WWTPs)
2 (40 POTWs)
1 (204 WWTPs)
2 (40 POTWs)
10 (12 WWTPs)
1 (204 WWTPS)
2 (40 POTWs)
3 (31 WWTPs)
4 (24 WWTPs)
5 (40 WWTPs)
6 (M WWTPs)
7 (74 WWTPs)
8 (9 WWTPs)
2 (40 POTWs)
q (2 WWTPs}
11 (2 samples of
Milorganite)
No. of Ho. of
organic undete
chemicals all s
tested tes
6
6
23
12
1
18
6
3
3
1
1
1
1
1
1
1
0
0
12
3
0
1
0
1
3
0
0
0
0
0
0
1
(Not enough
. (Mot enough
1 organics
:cted in No. of organic chemicals with
samples ' occurrence:
ltCd MOt >50X >90*
Phthalate Esters
6
4
Monocyclic Aroma tics
8
7
Polynuclear A-omatics
1
9
6
Halogenated Biphenyls
2
0
1
1
I
1
1
1
Dioxins and Furans
0
samples tested to suggest t c
3
1
3
3
(PAH)
1
2
6
1
0
1
1
1
1
1
1
0
ccurrence.'
0
1
0
1
0
0
6
0
0
1
.1
' 1
1
1
1
0
samples tested to suggest X occurrence.)
-------
TABLE 41 (continued)
Reference*
No. of No. o
organic undet
chemicals all
tested te
f organ! cs .. . • ,_ , , -n.
ected in ^0- ° Ol"9an1c chemicals with
5?nTie5 occurrence:
StCd >10X >SOX >9(tt
Halogenated Aliphatics
1 (204 WWTPs)
2 (40 POTWs)
1 (204 WWTPs)
1 (204 WWTPs)
2 (40 POTWs)
3 (15 WWTPs)
4 (11 WWTPs)
1 (204 WWTPs)
2 (40 POTWs)
1 (204 WWTPs)
2 (40 POTWs)
5 (40 UWTPs)
6 (14 WWrPs)
7 (74 WWTPs)
10
32
3
4
5
6
6
12
11
9
19
3
1
8
0
7
0
3
5
2
1
0
5
3
18
0
0
1
ft
9
Triaryl Phosphate
2
Aromatic and Alkyl
0
0
4
4
Phenols
6
2
Chlorinated Pesticides and
6
0
1
1
7
5
3
Esters
2
Ami nes
0
0
1
3
2
0
Hydrocarbons
2
0
1
i
7
0
0
0
0
0
1
0
0
0
2
0
1
1
7
Miscellaneous Compounds
1 (204 WWTPs)
2 (40 POTVs)
TOTALS:
2
3
219
1
3
70
1
0
102
0
0
53
0
0
26
^Reference number used refers to the same references as used in Table 40. Number
of wastewater treatment plants tested are given in parentheses.
-------
TABLE 42. SUMMARY SHOWING THE DISTRIBUTION OF MEDIAN DRY MATTER CONCENTRATIONS
FOR DATA REPORTED IN TABLE 40.*
Chanical group
Phthalate esters
Monocyclic aroma tics
Polynuclear aromatic* (PAH)
Halogenated blphenyls
Dioxins and furans
Halogenated aliphatic*
Triaryl phosphate esters
Aromatic { alkyl amines
Phenols
Chlorinated pesticides
and hydrocarbons
Hi seel laneous
TOTALS:
No. of
organic
chunicals
tested
6
23
7
9
(Inadequate
Table V-l
10
3
' 16
12
21
2
no
No. of organic chemicals tested
having median concentrations in
sludges (mg/kg, dry wt. basis):
NDf
0
12
0
1
ddta
were
0
0
6
0
4
1
24
<1
0
5
4
3
1-10
1
2
2
5
10-100
4
4
1
0
; all concentrations reported
significantly <1 mg/kg or 1000
6
0
9
1
14
0
42
4
2
0
11
3
1
31
0
1
1
0
0
0
11
>100
1
0
0
0
in
yg/kg.)
0
0
0
0
0
0
~T
^Summary does not include data from Burns and Roe (1982) which was reported on a wet
basis without median values provided. Also note that median values used are only
for thosf. samples having detectable concentrations and are not true median values,
which would be lower if all "NO" samples were included as zeroes. Waste Water
Treatment Plant (WWTP);Publicly Owned Treatment Plant (POTW).
^NO = organic was "not detected" in any sludge samples tested
-------
TABLE 43. GUIDELINES USED BY ONE FOOD PROCESSING COMPANY FOR INTERPRETING
THE SIGNIFICANCE OF RESIDUES IN SOILS BEING CONSIDERED FOR
GROWING ROOT CROPS.
Si gni ficance
Aldrin/DeiIdri n
Range of soil residues (mg/kg)
DDT
Diuron1
Suitable for
plantingt
May be planted,
but crop must be
analyzed before
acceptance
Do not plant
0-0.1
0.1-0.2
over 0.2
0.75
0.75-1.5
over 1.5
0.3
0.3-0.5
over 0.5
*Regardless of residues present, beets and carrots must not be planted
in soil which has received (a) an improper application of diuron or
(b) an application of diuron for which the minimum treatment-to-
planting interval has not expired.
tPlant carrots in least-contaminated soil.
145
-------
TABLE 44, ILLUSTRATIVE RANGE OF DECOMPOSITION HALF-LIFE FOR OF3ANIC
COMPOUNDS.*
Compound
Approximate half-life
Aminoanthroquinone dyes
Anthracene
Benzo(a)pyrene
Di-n-butylphthalate ester
Nonionic surfactants
2,4-methyaniline
n-Ni t rosodi etfiy 1 ami ne
Phenol
Pyrocatechin
Cellulose
Acetic acid
Hydroquinone
100-2,200 dsys
110-180 days
60-420 days
80-180 days
300-600 days
1.5 days
40 days
1.3 days
12 hours
35 days
5-8 days
12 hours
*From Over-cash (1983), p. 211.
146
-------
TA3LE 45. RELATIVE PERSISTENCE AND INITIAL DEGRADATIVE REACTIONS OF
NINE MAJOR ORGANIC CHEMICAL CLASSES.*
Chemical class
Carbamates
Aliphatic acids
Nitriles
Phenoxyalkanoates
Toluidine
Amides
Benzoic acids
Ureas
Triazines
Persistence
2-8 weeks
3-10 weeks
4 months
1-5 months
6 months
2-10 ironths
3-12 months
4-10 months
3-18 months
Initial degradative process
Ester hydrolysis
Dehalogenation
Reduction
Dealkylation, ring hydroxy lation
or oxidation
Dealkylation (aerobic) or
reduction (anaerobic)
Dealkylation
Dehalogenation or decarboxylation
Dealkylation
Dealkylation or dehalogenation
*From Kaufman (1983), p. 119.
147
-------
Table 46. ASSUMPTIONS/VALUES USED FOR METRO ANALYSIS (MUNGER, 1984).
Sludge contains: 1.1 mg/kg CW RGBs (Metro sludge)
2.6 mg/kg DW B(a)P (Metro fludge)
Application rate: 45 mt/ha for silviculture
Estimated soi1
concentration: Calculated assuming even mixing in top 15 cm
Risk level used
as benchmark: 10"5 (Values from Munger, 1984 were divided by
10 to give a 10"6 risk level for values in
Tables 45 and 46.)
Normal daily dietary intake: 8,/QO ng PCBs/day
160 - 1,600 ng B(a)P/day
Consumption equivalent to a
lifetime cancer risk of 10'5: ?04 ng PCBs/day
61 ng B(a)P/day
148
-------
TABLE 47. METRO ASSESSMENT OF LIFETIME CANCER RISK FOR PCB.*
Estimated quantities of enviromnental compartments
which can be consumed on a daily basis without
exceeding a lifetime cancer risk of 10"6 based
on PCB concentrations
Months after application
Envi ronmental
compartment 0 3 6 12 24
Sludge-soil (g/day) 0.8 0.8 0.9 1.0 1.0
Control soil (g/day) £2.0 -
Surface water (liters/day) <2.Q
Control water (liters/day) _<2.0
Edible plants (g/day) 20-100
Control plants (g/day) £200
Deer fat (g/day) 2
Control deer fat (g/day) unknown
Groundwater (liters/day) <2
*Munger (1985). See Table 46 for assumptions used.
149
-------
TABLE 48. METRO ASSESSMENT OF LIFETIME CANCER RISK FOR B(a)P.*
Estimated quantities of environmental compartments
which can be consumed on a daily basis without
exceeding a lifetime cancer risk of 10~6 based
on B(a)P concentrations
Envi ronmental
compartment
Months after application
0
12
24
Sludge-soil (g/day)
Control soil (g/day)
Edible plants (g/day)
Control plants (g/day)
Animal tissue
Groundwater and control
groundwater (liters/day)
0.1 0.2 0.6 0.6-6 0.6-6
.6-6
1-10 2-20 30-300 30-300 30-300
30-300 -
unknown
*Munger (1985). See Table 46 for assumptions usad.
150
-------
TABLE 49. DEFINITIONS FOR "RELATIVE TCXICITY" CATEGORIES AS USED
BY NAYLOR AND LOEHR (1982a).
Ratings
Acute oral Relative
LDrr, mg/kg toxicity
Probable lethal oral
dose of the pure chemical
for a 70-kg human adult
Supertoxic
Extremely toxic
Very toxic
Moderately toxic
Slightly toxic
Practically non-toxic
<5 6 a taste to 7 drops
5-50 5 7 drops to a teaspoon
50-500 4 1 teaspoon to 1 ounce
500-5,000 3 1 ounce to 1 pint (1 pound)
5,000-15,000 2 1 point to 1 quart (2 pounds)
>15,000 1 more than 1 quart
151
-------
TABLE 50. EXAMPLES OF CHEMICALS COMMONLY CONSUMED OR USED AND
THEIR TOXICITY RATINGS (NAYLOR AND LOEHR, 1982a).
Acute oral LD5Q *
Chemical for rats, mg/kg Toxicity rating"1'
Sodium chloride 3,000 3
Sugar 25,800 1
Aspirin 1,000 3
Nicotine 4
Oxalic acid (present in
chard, spinach,
rhubarb leaves, etc.) 375 4
Caffeine 192 4
Ethyl alcohol 14,000 2
Safrole (80%) of oil
of sassafras) - 5
Gasoline, kerosene - 3
Antifreeze - 3
Strychnine - 6
Cayenne pepper - 3
Laundry bleaches - 3-4
Aftershave lotions - 3
Vanilla and lemon extract - 1
Bouncing putty - 3
*Lewis and Tatkin (1979)
interpretation, see Table 49
152
-------
TABLE 5]. TOXICITIES AND APPLICATION RATES FOR SEVERAL PESTICIDES
(NAYLOR AND LOEHR, 1982a).
Pesticide
Methyl parathion
Parathion
Malathion
Diazinon
Dilox
2,4-0
Methoxychlor
+ Malathion
Di azinon
Sevin
Disyston
Das i nit
Oyfonate
Lorsban
Phosdrin
Maneb 80
Sencor
Systox
Acute oral
LU50
for rats*
mg/kg
6
2
885
76
945
375
5,000
76
250
5
2
3
145
4
6,750
2,200
1,700
Recommended appli-
cation rate of
Relative active ingredient
toxicity1' Use* to soil,* Ibs/acre
5
6
3
4
3
4
2
4
4
6
6
6
4
6
2
3
3
Oat and
wheat
insect
control
Forages,
alfalfa
Corn borer
Corn borer
Corn root
worm
worm
worm
Corn leaf
aphid
Herbicide:
tomato, potato
Herbicide:
soybeans,
Systemic
insecticide
0.25
0.25 to
1.0
1.0
0.5 to
1.0
1.5 + 1
1.0 to
1.0 to
1.0
0.75 to
0.75 to
0.75 to
0.125
up to 2
0.38
0.38
1.0
.5
2.0
2.0
1.0
1.0
1.0
.0
*Lewis and Tatkin (1979)
^See Table 49 for explanation
*New York State Coll. of Agric. & Life Sci. (1982a,b)
153
-------
TABLE 52. TOXICITIES, SLUDGE CONCENTRATIONS, AND PROJECTED APPLICATION LOADINGS FOR SELECTED
PRIORITY POLLUTANT ORGANICS (NAYLOR AND LOEIIR. 1982a).
Ul
-fa.
Chemical
bis-2-ethylexyl pht*\alate
chlor oethane
1.2-trans-dichloroethylene
toluene
butylbenzyl phthalate
2-chloronaphthalene
hexachlorobutadiene
phenanthrene
carbon tetrachloride
vinyl chloride
dibenzo (a,h) anthracene
1.1,2-trichloroethane
anthracene
naphthalene
ethylbenzene
d1 -n-butylphthalate
phenol
methylene chloride
pyrene
chrysene
f luoranthene
benzene
tetrachloroethylene
trichloroethylene
Acute oral
LOso
rating
nig/kg*
31000
volatile
volatile
5000
3160
2078
90
700
2800
500
-
1140
-
1780
3500
1200
414
167
-
-
2000
1400
8100
4920
Toxicty
ratingt
1
.
-
2
3
3
4
3
3
3
-
3
.
3
3
3
4
4
-
-
3
3
2
3
No. times
detected
in
combined
sludge
13
2
11
12
11
1
2
12
1
3
1
2
13
9
12
12
11
10
12
9
10
11
11
10
Concentration 1n combined sludges
pg/1, wet
median
3806
1259
744
722
577
400
338
278
270
250
250
222
272
238
248
184
123
89
125
85
90
16
14
57
range
157-11257
517- 2000
42-54993
64-26857
1-17725
400
10- 675
34- 1565
270
145- 3292
25
3- 441
34- 1565
23- 3100
45- 2100
10- 1045
27- 4310
5- 10b5
10- 734
15- 750
10- 600
2- 401
1- 1601
2- 1927
mg/lcg, dry
median
109
19
21
15
15
4.7
4.3
7.4
4.2
5.7
13
3.5
7.6
7.5
5.5
3.5
4.2
2.5
2.5
2.0
1.8
0.32
0.38
0.98
range
4.1-273
14.5- 24
0.72-865
1.4-705
0.52-210
4.7
0.52-8
0.89-44
4.2
3-11(1
13
0.036-6.9
0.89-44
.9-70
1.0-51
0.32-17
0.9-113
0.06-30
0.33-18
0.25-13
0.35-7.1
0.063-11.3
0.021-42
0.048-44
Projected
application rate§
lc(j/!ia, dry
medi an
1.2
0.17
0.24
0.16
0.11
0.03
0.03
0.05
0.041
0.064
0.16
0.034
0.0'jO
0.070
0.063
0.01?
0.032
0.022
0.024
0.022
0.016
0.1)027
0.0035
0.0125
raruje
0.053-2.1
0.16-0.17
0.009-8.4
0.018-1.3
0.001)3-1.4
0.03
0.0063-0.054
0.009-0.53
0.041
0.02-1.3
0.16
0.0002-0.068
0.009-0.53
0.01-0.59
0.013-0.38
0.003-0.21
0.0011-1.5
0.0004-0.97
0.04-0.1'?
0.0024-0.16
O.OU24-O.Ob
0.0007-0.13
0.0002-0.54
O.OOU36-0.52
'National Academy of Sciences (1972)
tSee Table 49 for Interpretation
§Feiler (1980)
-------
en
en
TABLE 53. TIMES AND AMOUNTS OF SLUDGE WHICH MUST BE INGESTED BY THE RAT OR COU TO REACH LD50 DOSES OF
THREE SLUDGE ORGANICS (NAYLOR AND LOEHR, 1982a).
Priority
pollutant
hexachloro-
butadiene
dis-2-
ethylhexyl
phthalate
1,1,2-tri-
chloroethane
Max.concn.
in sludges
mg/kg*
8
273
6.9
LD50
dose,
mg/kg*
90
31000
1140
Toxicity
rating*
4
1
3
Example
animal
rat
cow
rat
cow
rat
cow
Typical
animal
wt, kg
0.5
500
0.5
500
0.5
500
L05Q
dose
45 mg
45 g
15.5 g
15.5 kg
570 mg
570 g
Amount of
sludge equal
to LD5Q dose
of chemical ,
kg
5.6
5600
57
57000
83
83000
Time to
consume ir>$Q
dose of
chemical ,
yrs
7.7 (2800 days)
6.2
78
62
113
91
*From Table 50.
Daily food intake: rat = 20 g/day (6); cow = kg/day, with sewage sludge (dry basis) intake
equivalent to 10 percent by weight of total diet
Because of the length of exposure period to consume an LDso dose of chemical, health effects
observed are not necessarily equivalent to those observed where the dosage is ingested
within more conventional LD5Q test exposure periods of several days or less.
Life expectancy of rat
5 to 10 years
700 to 800 days (2 to 2.5 years) and of a lact.tting cow =
-------
TABLE 54. EQUATION OF POTENTIAL INTAKE OF THREE SLUDGE ORGANICS DUE TO SLUDGE OR
SOIL WITH SLUDGE INGESTED BY A "PICA" CHILD OR A COW.
Maximum
Weight, LD50
kg dose
Child
Cow
20 1.8
500 45
9
9
Maximum
Child
Cow
20 0.62
500 15.5
kg
kg
Hexachlorobutadiene LD5Q = 90 mg/kg
concentration of chemical in soil* = 0.027 mg/kg, in sludget = 8 mg/l
Soil
con-
sump-
tion
g/d
15
1500
Time to consume LD5Q
dose of priority
pollutant, yrst
Soil
w/sludge
1
1
X
X
10§
10*
Sludge
only
41
10
Bis-2-ethylhexyl phthalate
concentration of chemical in
15
1500
1
1
X
X
105
104
415
104
1,1,2-trichloroethane LDso =
Maximum concentration of chemical in soil
Child
Cow
20 22.8
500 570
kg
kg
15
1500
1
1
X
X
105
10 •*
604
151
(D2) (DT)
Daily intake Acceptable
.from soil , dai ly
g dose, g§
4 x 10-7 !.8 x 10-5
4 x 10-5
LD5Q ^ 31000 mg/kg
soil = 1.0 mg/kg, in sludge
1.5 x 10-5 6.2 x 10-3
1.5 x ID'3
1140 mg/kg
= 0.034 mg/kg, in sludge = 6
5.1 x 10-7 2.3 x 10-"
5.1 x lO-5
Safety
factor5
DT/D2
45
= 273 mg/kg
415
.9 mg/kg
450
*Adapted from Naylor and Loehr (1982a)
tFrom Table 53
^Estimated LD5Q dose = LD5Q mg/kg x body wt. kg
§For humans, acceptable daily dose of toxic pollutants
10-5
(safety factor of 105),
-------
TABLE 55. SAFETY FACTORS FOR INGESTING SOIL CONTAINING PESTICIDE AND SLUDGE
ORGANICS (CONNOR, 1984).
Appl ication
rate
(kg/ha)
Soil
concn.
(ug/g)
ADI
(pg/day)
Safety factor
Low diet High di^t
Pesticide
2,4-D
Diazinon
Malathion
Methoxychlor
Parathion
Methyl parathion
SIudge
Bis-2-ethyl-
hexyphthalate
Toluene
Ethyl benzene
Oi-n-butylphthalate
Phenol
Methylene chloride
Total PAH*
1.1
1.1
1.1
1.7
.29-.44
.29
Concn.
(ppm dry)
109
15
5.5
3.5
4.2
2.5
13
0.5
0.5
0.5
0.9
.15-.22
.14
0.6
0.08
0.032
0.024
0.016
0.011
0.10
21,000
140
1,400
7,000
350
70
42,000
29,500
1,600
88,000
100
25,000
0.4
Potency
(kg day/rng)
2,800
19
190
420
110
33
4,700
25,000
3,300
240,000
420
150,000
0.27
300
2
20
56
14
4
500
2,700
360
26,000
45
16,000
0.03
10"6 risk 10"6 risk
Hexachlorobutadiene
Carbon tetrachloride
Vinyl chloride
1,1,2-trichloroethane
Benzene
Tetrachloroethylene
Trichloroethylene
Total PAH
4.3
4.2
5.7
3.5
0.32
0.38
0.98
13
0.015
0.020
0.032
0.017
0.0014
0.0018
0.006
0.10
0.495
0.083
0.017
0.057
0.052
0.040
0.012
11.5
0.16
0.36
0.12
0.21
0.016
0.015
0.015
250
1.5
3.3
1.9
1.9
0.14
0.14
0.14
2300
Safety factors (AOI divided by daily consumption) and 106 risk calculated
assuming 70 kg person ingesting equivalent of is g (low diet) or 139 g
(high diet) ot contaminated soil per day. See text for further explanation
PAH includes acenaphthene, fluoranthene, benzanthracene/chrysene,
anthracene/phenanthrene, and pyrene. ADI calculated from WHO drinking water
standard of 0.2 gg/liter and assuming consumption of 2 liters of water per
day.
Soil concentration calculated assuming an average sludge application rate of
15 tons/ha.
157
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SECTION 7
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