United States       Office of Water &
            Environmental Protection    Waste Management      SW718
            Agency         Washington D.C. 20460     September 1978

            Solid Waste
vvEPA    Cadmium Additions
           to Agricultural Lands
           Via Commercial
           Phosphate Fertilizers

           A Preliminary Assessment

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                       CADMIUM ADDITIONS

TO AGRICULTURAL LANDS VIA COMMERCIAL PHOSPHATE FERTILIZERS

                  A  Preliminary Assessment
             finpoit  (SW-718) de-icixfae-s wotik  peirfcorned
    the.  O^lde, o£ Sol-id Watte. u.nde.n c.on&LO.c.t  no.  6S-01-4625
    and  xc.4  fi Jie.c.&
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     This report was prepared by SCS Engineers, Inc., Long
Beach, California, under contract no. 68-01-4625.

     Publication does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of commercial products
constitute endorsement by the U.S. Government.

     An environmental protection publication  (SW-718) in the
solid waste management series.

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                           ABSTRACT


     Current literature was reviewed to determine cadmium (Cd)
concentrations in phosphate rock and commercial  phosphate
fertilizers.  The data were utilized to estimate annual  Cd
loading rates and 100-yr Cd accumulations in soil attributable
to the use of phosphate fertilizers.  The annual quantity of
cadmium contributed to the environment in the form of phosphate
fertilizers was estimated and compared to other  Cd emission
sources.   In addition, the probable impacts of Cd loading and
accumulation via phosphate fertilizers and municipal  sewage
sludge were compared.

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                          CONTENTS
                                                       Page

Abstract                                               iii
List of Figures                                           vi
List of Tables                                            vi
Acknowledgements                                       viii
Introduction                                             1

Sources, Production, and Trends in the                   3
Phosphate Fertilizer Industry

     Sources of Ore                                      3

     Production and Trends                               3

Cadmium in Phosphate Fertilizers                         8

     Cadmium Concentrations  in  Phosphate Ores            8

     Cadmium Concentrations  in  Phosphate                 8
     Ferti1i zers

     Distribution of Phosphate  Fertilizers               8

     Distribution of Cadmium to Agricultural           12
     Land

     Assessment                                        16

     Comparison of Cd Loadings  from Sewage             28
     Sludge and Phosphate Fertilizers

Bibliography                                           31
                              v

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                           FIGURES

Figure                      Title                           Page

   1         Types and Locations of Phosphate Deposits         4

   2         Phosphate Ore Production                          6

   3         Partitioning of States as to Source of           13
            Phosphate Fertilizers


                           TABUS

Number                      Title

   1         Phosphate Ore Production - United States          5

   2         U.S.  Phosphate Fertilizer Consumption             7

   3         Cadmium Concentrations in Phosphate Ores          9

   4         Concentrations of Cadmium in Phosphate           10
            Fertilizers (Western and Southeastern Sources)

   5         Concentrations of Cadmium in Phosphate           11
            Fertilizers

   6         Annual  Cd Loading Rates Attributable to          14
            Phosphate Fertilizers in the Western
            Region - 1974

   7         Annual  Cd Loading Rates Attributable to          15
            Phosphate Fertilizers in the Eastern
            Region - 1974

   8         Estimated Totaled Contribution to the           17
            Environment from the Use of Domestic
            Phosphate Fertilizers - 1976

   9         Estimated Cd Contribution to the Environment     19
            From All Sources, 1974-75

  10         Cadmium Concentrations in Selected               21
            U.S.  Soils

  11         100 Year Accumulation of Cadmium in Soil         22
            from the Annual Application of Phosphate
            Fertilizers from Western and Southeastern
            Sources
                               VI

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TABLES (Continued)

Number                     Title                         Page

 12        Projected Years of Allowable Phosphate         24
           Fertilizer Applications Based on Cd
           Loading Limits Recommended By The NC-118
           Study Group

 13        Concentrations of Cadmium in the Edible        26
           Tissue of Various Crops Grown in Soils
           Containing 20 ppm Cd

 14        Annual Cd Loading Rates at Nine                29
           U.S. Sewage Sludge Spreading Sites
                                vil

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                        ACKNOWLEDGEMENTS
     We wish to thank Mr. Alessi Otte and Dr. Albert Page for
their guidance and assistance in the preparation of this docu-
ment.
                            viii

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                        INTRODUCTION
     Cadmium has been found to be a potentially toxic heavy
metal.   Chronic human exposure and animal studies on cadmium
indicate a positive correlation between the quantities of
cadmium (Cd) intake or accumulation and kidney damage do,  19,
28, 36, 48).

     One source of cadmium entering our environment is phosphate
ore used in the production of phosphate fertilizer.  Cadmium
is also present in sludge from treatment plants.   When these
fertilizers or sludges are applied to agricultural lands, the
potential  exists for cadmium to enter the food chain through
plant uptake or grazing animals.

     In the latest market basket studies for Cd,  the U.S. Food
and Drug Administration (FDA) determined that teenage male  Cd
intake is  approaching the recommended maximum (72 ug/gm/day).
In deriving this finding, FDA used maximum weekly Cd intakes
suggested  by the World Health Organization.  Accordingly, several
states have taken steps to regulate the amount of cadmium applied
to agricultural lands from municipal  wastewater treatment plant
siudge.

     The requirements and the proposed Cd levels  are being
challenged.  Accordingly, the U.S. Environmental  Protection
Agency (EPA) sponsored this research  effort to identify the
following:

     •  The range of Cd concentrations present in commercial
        phosphate fertilizers,

     •  Annual Cd loading rates to agricultural  land via
        phosphate fertilizer application,

     •  Short and long-term Cd additions to agricultural
        lands through phosphate fertilizer applications,

     •  Potential effects of cadmium  in phosphate fertilizers
        on groundwater and plants, and

     t  Comparative assessment of potential Cd additions
        to agricultural lands from phosphate fertilizers and
        sewage sludge.

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     To perform the research, a review of the literature was
conducted,  and.data supplied by knowledgeable individuals were
assessed.   Where data necessary to the project were lacking,
assumptions were made and are noted.

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                SOURCES, PRODUCTION, AND TRENDS
              IN THE PHOSPHATE FERTILIZER INDUSTRY
SOURCES OF ORE

     All of the principal  types of phosphate ore deposits are
found in the United States.  McKelvey (23)  noted that one or
more types of phosphate deposits are found  in 30 of the con-
tinental states (Figure 1).  The reserves in the U.S.A. are
located in two major geographic locations:   the western region,
comprised of mines in Idaho, Montana, Wyoming, and Utah; and
the southeastern region, comprised of mines in Florida, North
Carolina, and Tennessee.  The Western states contain the
largest reserves, but most of the mining activity is presently
centered in Florida (30).

PRODUCTION AND TRENDS

     Phosphate ore production in the United States for the 1960-
1975 period is tabulated in Table 1  and illustrated graphically
in Figure 2.  Major products derived from the ore are phosphate
fertilizers, elemental  phosphorus, and phosphoric acid; the
latter is used as a feed stock in the manufacture of phosphate
fertilizer.

     Consumption figures for phosphate fertilizers for the years
1960-1975 are presented in Table 2.   While  total phosphate fer-
tilizer consumption (expressed as P20§)* has increased, led
by concentrated superphosphates and  diammonium phosphates, the
production of normal  superphosphates has decreased.
*In phosphate fertilizers, p£05 is more often used than P.   To
 convert P to P?OK, multiply by 2.29.

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             TABLE 1.   PHOSPHATE ORE  PRODUCTION—UNITED STATES*
Year

1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
Western
Amount
(103 t)f
5,276
4,845
5,519
5,347
5,945
7,182
8,360
7,066
7,462
7,070
6,767
6,109
6,086
6,993
7,896
7,362
Sources
Produced
(% of Total)
29.7
25.7
28.0
26.5
25.5
26.5
23.6
19.6
19.5
20.6
19.3
17.3
16.4
18.3
19.1
16.6
Southeastern
Sources
Amount Produced
(103 t) (*
12,517
14,008
14,170
14,823
17,379
19,558
27,053
28,942
29,952
27,147
28,369
29,161
30,948
31,225
33,541
36,914
of Total )
70.3
74.3
72.0
73.5
74.5
73.1
76.4
80.4
80.1
79.4
80.7
82.7
83.6
81.7
80.9
83.4
*  Fertilizer  Trends  (11).



 t t denotes metric ton;  to  convert metric ton to ton, multiply by 1.12.

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                                                   SOUTHEASTERN

                                                   SOURCES
                                                  WESTERN SOURCES
               1960
              1965
1970
                                                1975
Figure
Phosphate  ore production  (data from  Table 1)

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               CADMIUM IN PHOSPHATE FERTILIZERS


CADMIUM CONCENTRATIONS IN PHOSPHATE ORES

     Several available reports indicate that Cd concentrations
in phosphate ores are highly variable.  Table 3 presents data
and appropriate references relating Cd content in phosphate
ore to geographical location.  In general, Cd concentrations
in phosphate deposits in the southeastern United States are
low (approximately 10 ppm*); concentrations in western U.S.
phosphate deposits are considerably higher (approximately
150 ppm).

CADMIUM CONCENTRATIONS IN PHOSPHATE FERTILIZERS

     Virtually all phosphate-derived fertilizers contain cadmium.
Schroeder and Balassa (36)  recognized that phosphate fertili-
zers were a contributing source of cadmium to agricultural
lands.  Lee and Keeney  (210  estimated that the amount of
cadmium contained in fertilizers added annually to farmland  in
Wisconsin was equivalent to that contained in all sewage sludge
from Wisconsin wastewater treatment plants.

     The literature, however, contained little substantive data
on Cd concentrations in domestic fertilizers.  Fifty-nine
commercially available phosphate fertilizer samples from western
sources were collected and analyzed by EPA Region X (46).
These data  (Table 4) compare with the phosphate ore Cd values
noted above and affirm the difference in Cd concentrations
reported for the western and southeastern region ores.  Results
of work by  Mortvedt and Giordano (24), presented in Table 5, also
substantiate the previous findings.

     Considerably more data would be required to determine how
the Cd content  in phosphate ores differs with the phosphate  ore
source, method of processing, or fertilizer formulation.

DISTRIBUTION OF PHOSPHATE FERTILIZERS

     The proceedings of the 1977 Tennessee Valley Authority
(TVA) Fertilizer Conference (33)  provided national  and regional
phosphate fertilizer consumption data for 1974.  Reported were:


*For the purposes of this report, the terms ppm, yg/g, and mg/kg
 are identified by one term - ppm.

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      TABLE 4.  CONCENTRATIONS OF CADMIUM IN PHOSPHATE FERTILIZERS
                    (WESTERN AND SOUTHEASTERN SOURCES)
                               Range of Cd Concentration
                                   (ppm  Fertilizer)
Fertilizer Type

Triple superphosphate

     (0-45-0)

Diammonium phosphate

     (11-46-0)

Monoammonium phosphate

     (11-48-0)

Superphosphate
Western Region
 Fertilizers*
   40-175
   50-160
   40-90
(various percent mixture)   25-40
Southeastern Region
   Fertilizers
      12-14
       6-14
       6-7
                          5-7
*  Unpublished data - EPA, Region X .{46.).
                                    10

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         TABLE 5.  CONCENTRATIONS OF CADMIUM IN PHOSPHATE
                            FERTILIZERS*
                                    Cd Concentration
Fertilizer Type	(ppm  Fertilizer!

Diammonium phosphate
  (Reagent)                                0.9

Diammonium phosphate
  (Idaho phosphate rock)                  50.0

Diammonium phosphate
  (North Carolina phosphate
   rock)                                  30.0

10-15-0
  (Idaho phosphate rock)                  44.0

10-15-0
  (North Carolina phosphate
   rock)                                  17.0
*  Mortvedt and Giordano (24).
                                  11

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     •  Jons of phosphate fertilizers (as  P2C>5)  consumed,  and

     •  Harvested acreage for major crops  (feed grains,  wheat,
        soybeans, cotton, and tobacco), for which fertilizers
        were used.

     For this assessment, the various regions denoted in the
TVA Conference proceedings have been classified as
belonging to either the  western or  eastern regions (Figure 3).  The
following assumptions were made to  simplify the distribution
analysis:

     t  Phosphate fertilizers consumed in  the western region
        were manufactured using western phosphate rock.

     t  Similarly, phosphate fertilizer consumed in the  eastern
        region were manufactured with southeastern phosphate
        rock.

     •  All  acreage planted to agricultural crops utilized
        phosphate fertilizers.
     In 1974, a total of 3,098,550 t*of phosphate fertilizer
(expressed as ?2^^) was distributed nationally to a total  of
94,015,000 ha under cultivation to the above-noted crops.   On
a regional basis, the western region (Figure 3) distributed an
average of 19.6 kg of P205/ha; in the remainder of the United
States, P20c was distributed at an average rate of 37.9 kg/ha
for 1974.

DISTRIBUTION OF CADMIUM TO AGRICULTURAL LAND

     Tables 6 and 7 present estimated low, intermediate, and
high Cd loading rates for acreage utilized for the cultivation
of the five crops.  The following assumptions were made in
performing the calculations:

     •  All land identified with a specified crop received equal
        application rates of fertilizer.
     •  No losses of cadmium occurred as a
        floods, or natural causes.
re suit of erosion
     •  The low-intermediate-high Cd values of western fertili-
        zers were assumed at 25, 100, and 175 ppm, respectively;
        corresponding values for southeastern fertilizers were
        5, 15, and 30 ppm.

     •  Phosphate fertilizers were assumed to have an average
             content of 50 percent.
*Denotes metric tons.
                               12

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     From the  tabulations, the maximum annual average Cd
contribution  in  the  western region would be 0.0162 kg/ha on feed
grain fields.   In  the  eastern region, tobacco fields would receive
the maximum  average  contribution of 0.0214 kg/ha of cadmium.

 ASSESSMENT

      A preliminary assessment of the above estimated Cd contri-
 butions from phosphate fertilizers follows.  Four topic areas
 are addressed:

      •  Total Cd contributions from phosphate fertilizers,
      •  Cd effects on soils,
      •  Cd effects on groundwater, and
      t  Cd effects on plants.

      For comparison, potential  Cd loadings from sewage sludge
 applications are also discussed.

 Total Cd Contributions  from Phosphate Fertilizers

      The utilization of phosphate fertilizers results in quanti-
 fiable additions of cadmium to the environment, as shown above.
 Table 8 presents a breakdown of estimated quantities on a
 regional and national basis.  Quantities were calculated based
 on the following assumptions:

      •  Intermediate Cd concentrations were 100 ppm (western
         sources) and 15 ppm (southeastern sources) in the
         phosphate fertilizers consumed.

      0  83 percent of the fertilizer consumed was obtained from
         southeastern manufacturing sources (derived from 1975
         TVA  statistics).

 In 1976, Cd  addition from the use of phosphate fertilizers on a
 national basis was approximately 280 t.

      To place these quantities in perspective invites further
 comparisons  between (43) cadmium contributed to the environment
 from the utilization of sewage sludges, and (1) total Cd emis-
 sions to the environment from all sources.

 Estimated Cd Loadings from Sewage Sludge--

       An  estimated  73 t of elemental cadmium  was  distributed
  to cropland  from municipal  sewage  sludge  sources  during
  1976,  based  on  the  following  assumptions:

      •  1976 national generation of municipal sewage sludge
         was  4.5  million dry t  (l ).
                               16

-------
                 TABLE 8.   ESTIMATED TOTAL Cd CONTRIBUTION TO
                        THE ENVIRONMENT  FROM THE  USE OF
                      DOMESTIC  PHOSPHATE  FERTILIZERS -  1976
  Phosphate Fertilizer Production (1976)*
       Western Sources                     1,614,000 t
       Southeastern Sources                7,878,000 t

  Intermediate Cd Concentrations
       Western Sources                           100 ppm
       Southeastern Sources                       15 pom

  Annual  (1976) Contribution of Cd
       Western Sources                           162 t
       Southeastern Sources                	118 t
                        Total                     280 t
* Unpublished data - EPA, Region X (46).
                                    17

-------
     •  Average Cd concentration in dry sludge  was  81  ppm
        (12) •

     •  20 percent of all  municipal sludge generated was
        utilized on agricultural lands (44).

     Cadmium distribution  from fertilizer sources was  slightly
more than four times greater than distribution  from municipal
sewage sludge.

     The phosphate application rate normally  depends on the
soil type, crop to be grown, and method and frequency  of
application.   Typically, fertilizers are applied prior to
planting and,  for some crops, during various  stages of crop
growth.  Based on which particular fertilizer formulations are
used, application rates may range from 50 to  250 kg P/ha.

     Sewage sludge, on the other hand, offers a source of
phosphorus but in a greatly diluted form.  Usually, the sludge
is utilized on an available N basis (5) with  application  rates
ranging from 2 to 50 t/ha  (40).   If all available sludge  were
used as a soil amendment,  distribution would  approach  2 percent
of available agricultural  land  (5).

     Phosphate fertilizers, on the other hand,  are utilized
at much lower application  rates  - 25 to 250 kg/ha - and are
liberally distributed to a high  percentage of the nation's
croplands.

Estimated Cd Loadings from All Sources--

     Under contract to the EPA Office of Toxic  Substances,
Versar  (33,)  had revised Cd emission estimates  based upon data
originally calculated by Fulkerson and Goeller  (n ) for all
contributing sources (Table 9).   Cadmium from phosphate
fertilizers constitutes approximately 5.5 percent of the  total.
If the total  estimated 1976 quantity (280 t)  shown in Table 8
were substituted, this percentage would increase to approxi-
mately 14 percent.  The difference in Cd contributions from
sewage sludge shown in Table 9  and the sewage  sludge contri-
butions presented earlier (73 t)  is attributed to the follow-
ing:

     •  The Versar study (Table 9) cites all  land disposal of
        sludge, e.g., landfill,  lagooning, and  agricultural
        utilization.

     •  The 73 t estimate reflects the loading of cadmium from
        only  those sludges employed for agricultural utiliza-
        tion  - approximately 40 percent of the total sludge
        destined to land (44).
                              18

-------
         TABLE  9.   ESTIMATED  Cd CONTRIBUTIONS TO
         THE ENVIRONMENT FROM ALL SOURCES,  1974-75*
Source
Zinc Ore Minir»j &
Bene f icia tion
Primary Zinc Industry
Total: Extraction,
Pe fining & Prcduction
Electroplating Shops
Pigment Manufacture
Stabilizer Manufacture
Alloy f-anufacture
Battery I-ianufacture
Ibtal: Industrial Conversion
Secondary Non-Ferrous Metals
Iron ard Steel Injustry
Galvanized Prod-jets
Rubber Tire \.'ear
Incineration
Total: Consumption 4
Disposal of
Cd -containing products
Phosphatfl Fertilizers
Phosphate Detergents
Coal Cdttustion
Diesel t Fuel Oil
Carbustion
Lubricating Oils
Sewage Sludge
Total: Inadvertent Sources
GraM Totals
A.irlximc
Daissioiis
0.2t
102
102
-1
9.5t
2.7 t
2.3f
0.7 +
15
2.2
10.5
-0
5.2t
16
34
-0
-0
80(1974)
50 t
o.at
20
151
300
Watcrbome
Effluents
-0
2.0(1977)
-7(1974-75)
4.0(1977)
0.75
-0
• -o
0.3
-8(1974-75)
-0
-0
-0
-0
-0
-0
-0
10.2
-0
-0
-0
-0
-0
10
25(1074-75)
Land -Destined
Waste's
250
-0
250
80(1977)
16.5
-0
-o
11.4(1977)
-102(1974-75)
- 75(1980)
20
330
40
-0
70
460
100(1975)
130(1900)
-0
370(1974)
680(1980)
-0
-0
250
720(1974-75)
1,500(197-1-75)
Total
Baissions


359(1974-75)





125(1974-75)
93(1980)





494






831(1974-75)
1.800(1974-75:
 Metric tons per year as elemental cadmium,
"^Estimates unchanged from Fulkerson-Goeller estimates (IX)
                          19

-------
     t  Calculations within theVersar study  are based on an
        annual  sludge generation of 10.9 million dry t.   In our
        study a more conservative figure of 4.5 million  dry t
        (1) was used.

Cadmium Effects on Soils

     To assess the soil  effects of cadmium from the use  of
phosphate fertilizers, naturally occurring Cd levels in  soils
must be considered.

     Page and Bingham (28) suggested that soils derived  from
igneous rock contain 0.1 to 0.3 ppm Cd and that soils of sedi-
mentary origin contain 0.1 to 1.0 ppm Cd.  Page (27) reported
that typical soil Cd concentrations range from 0.03 to approxi-
mately 1.4 ppm, and that a median level  for U.S. soils is
approximately 0.3 ppm.  Stearns, Lofy, and LaConde (40)  reported
naturally occurring Cd levels ranging from 0.24 ppm for  a
Morley clay loam to 3.77 ppm for a Salinas silty clay loam
(Table 10).

     A preceding section presented estimated annual mass Cd
emissions to the environment.  To examine the potential  effects
of Cd loading, however,  fertilizer application rates must be
examined over longer time frames to determine both net addition
and cumulative effects.   Table 11 presents such an approach
showing the hypothetical cumulative Cd loadings for 100  con-
tinuous years of phosphate fertilizer addition.  The data in
this table were based on the following assumptions:

     •  Fertilizer was applied annually  for 100 yr at the two
        rates indicated.

     •  The intermediate values of Cd concentration (western-
        100 ppm, southeastern-!5 ppm) represented the phosphate
        fertilizer used.

     t  The natural Cd concentration of the soil was
        0.3 ppm.

     •  Application rates of 100 and 250 kg P/ha represented
        the range of typical phosphate fertilizer applicatio
        rates.
on
     •  Phosphate fertilizers contained 50 percent P205-

     The Cd loading data in Table 11 are presented in two
forms.  The first shows the 100-yr cumulative Cd addition in
kg/ha for two different application rates; the second presents
a factored Cd addition in terms of 1,000 kg/ha fertilizers
added.
                              20

-------
       TABLE  10.   CADMIUM CONCENTRATIONS  IN SELECTED U.S. SOILS*
                                    Average Cd Concentrationt
Soil Type                           	(ppm )	
Congaree sandy loam                          0.76
Salinas silty clay loam                      3.77
Xenia silty clay loam                        0.87
Britwater silt loam                          0.73
Burkhardt sandy loam                         0.46
Pembroke silt loam                           0.83
Morley clay loam                             0.24
Ross silty clay                              0.78
*  From Stearns, Lofy, and LaConde (40).
t  HN03-HC104, oven-dry (11QOC) basis.
                                   21

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     It is recognized that farming practices may preclude the
continuous addition of phosphate fertilizers.  When such addi-
tion is assumed, the above calculations indicate that the annual
amount of cadmium added to soils via phosphate fertilizers is
quite small.   However, the long-term (100 years) accumulation
of cadmium from the western fertilizer source could be signifi-
cant.  Total  Cd additions of 4.6 and 11.5 kg/ha, respectively.


     Williams and David (49) performed a similar analysis on
Australian phosphate fertilizers.  Soils that had received
regular top-dressing of superphosphate for 30 to 45 yr and
total cumulative dressings of 2,500 to 4,5.00 kg fertilizer/ha
were analyzed for cadmium.  The results were expressed in
terms of Cd increase per 1,000 kg fertilizer/ha and ranged
from 0.023 to 0.053 kg Cd per 1,000 kg fertilizer/ha (0.12 to
0.26 kg Cd per 1,000 kg P/ha).  The data presented in Table 11,
0.07 to 0.46  kg Cd per 1,000 kg P/ha, are in general agreement
with the Australian findings.

     Some state regulatory agencies have proposed restricting
annual Cd additions to 0.5 kg/ha after 1985.  Data from Table 11
when expressed on an annual basis, indicate that the greatest
possible incremental net increases in cadmium from the use of
phosphate fertilizers are quite small - 0.12 kg/ha for western
and 0.02 kg/ha for southeastern sources, both at fertilizer
application rates of 250 k P/ha.  As a result, the use of
typical amounts of phosphate fertilizers, regardless of source,
will not result in annual Cd concentrations greater than those
indicated.

     In regard to heavy-metal loading from sewage sludge, it
has been recommended that soils with a cation exchange capacity
(CEC) value less than 5 meq/100 g soil be restricted to a total
cumulative Cd addition of 5 kg/ha; those with CEC's between
5 and 10, to  a maximum of 10 kg/ha; and those with CEC's greater
than 15, 20 kg/ha (18).  Table 12 extends that data in Table 11
and shows the number of consecutive years that phosphate ferti-
lizer can be  applied before the first two limits are exceeded.

     The following assumptions were made in calculating these
data:

     •  Cadmium concentration of western phosphate fertilizer
        was 100 ppm; of southeastern phosphate fertilizer,
        15 ppm.

     t  Five  percent of the cadmium applied in the form of
        phosphate fertilizer was removed with the harvested
        plant tissues.  (Williams and David (49) showed that
        plant uptake ranged from 0.4 to 7 percent.
                              23

-------





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     •  Phosphate fertilizers  contained 50 percent

     0  Annual  applications of phosphate fertilizers were spread
        at the  suggested rate.

     The loading period encompassing the shortest time span
for western phosphate fertilizers would occur at the heavier
application rate of 250 kg P/ha.   Even at this rate, an esti-
mated 46 yr would be required to  reach a cumulative total of
5.0 kg Cd/ha.   Using southeastern fertilizer, more than
1,532 yr would  be required to exceed 10.0 kg Cd/ha at the lower
loading rate.

Cadmium Effects on Groundwater

     Williams  and David (49,  50)  examined soils (10 percent
or greater clay) that had received cumulative additions of
superphosphate  of up to 4,000 kg/ha over 20 or more years.
They indicated  that more than 80  percent of the fertilizer
cadmium was retained in the surface 10 cm of soil.  In one
soil containing siliceous sand (2 percent clay), 50 percent
of the cadmium  had been retained  over a time span encompassing
a 900 kg/ha cumulative loading of phosphate fertilizer.

     These data suggest that available cadmium applied to soils
by the use of  phosphate fertilizers is chemically precipitated
or retained by  the soil matrix (e.g., cation exchange).  Thus,
its mobility is greatly reduced.

Cadmium Effects on Plants

     The use of phosphate fertilizers on vegetable
crops presents  one of the greatest potential hazards of
Cd addition to  the food chain.   The CAST Report (5) indicated
that crops may  contain undesirable Cd concentrations in their
tissues without showing visible symptoms of phytotoxicity.
Further, Bingham et al . (3),  CAST (5), Dowdy and Larsen (8),
and others have shown that leafy  vegetables take up more
cadmium than other vegetable or grain crops.  Table 13 presents
relative Cd uptake by selected vegetables and grains.  The
ultimate Cd concentration in plant tissues is dependent upon
many factors,  such as application rates, form of applied cadmium,
crop species and variety,  CEC, soil pH, texture, organic matter
content, and concentrations of other heavy metals present in the
soil .

     Williams  and David (49)  reported that cadmium in superphos-
phate was soluble in water.  The  cadmium was associated with both
the phosphate  and sulfate compounds of the fertilizer, and
appeared to be  as readily available to plants as CdCl2-  However,
they found low  Cd concentrations  (0.012 to 0.036 ppm) in grain
and breakfast-cereal foods made from Australian wheat grown
                              25

-------
      TABLE 13.  CONCENTRATIONS OF CADMIUM IN THE EDIBLE TISSUE
  OF  VARIOUS  CROPS GROWN IN  SOILS  CONTAINING 20  ppm Cd*
Crop species

Rice grain
Zucchini squash
Field bean
Corn grain
Cabbage
Tomato fruit
Radish

Cd
Concentration
ppm t
0.6
1.0
1.0
2.4
3.4
3.6
6.3

Crop species
Red beet
Wheat grain
Turnip
Soybean grain
Carrot
Lettuce
Curlycress
Spinach
Cd
Concentration
ppm t
7.4
8.7
11
17
19
135
154
188
*  Derived from Bingham et al.  (3); to produce a  concentration of
   20 ppm Cd in soil, 1% sewage sludge which had  been spiked with
   CdS04 was mixed with the soil.

t  Oven dry weight (70°C) basis.
                                 26

-------
in fields with a  long history of superphosphate  usage  (contain-
ing 44 ppm of Cd).   Plant uptake of cadmium from these  fields
ranged from 0.4 to  7 percent of total  cadmium,  and  the  uptake
was greatly influenced by soil  type.

     Assuming that  only a small percentage of the cadmium from
fertilizer sources  is available for plant uptake, the  effects
of incremental vs.  cumulative Cd loadings will  be examined.

     The CAST Report (5), commenting on Cd concentrations in
corn leaves, stated:

     "...data on  repeated annual applications of sludge
     to soil cropped to corn show that the amounts
     applied in a given year influenced the cadmium
     content in the leaves to a greater extent than did
     the total cumulative amounts of cadmium applied.
     The implication of these results  is that, at the
     rates used,  most of the applied cadmium was being
     converted to forms of relatively  low availability
     to plants."

     Recent studies on ryegrass (2) and snap beans  ( 9 ) also
suggest that cadmium in plant tissues  is more a  function of
periodic incremental Cd additions than the cumulative  Cd total.

     Reuss, Dooley  and Griffis (3l) recently reported  a linear
relationship between Cd additions to soils in the form  of
phosphate fertilizers and resultant plant (various  species)
uptake.  These data, while suggesting  a relationship  between
total soil and plant Cd concentrations, are seemingly  in con-
tradiction with the above referenced studies.  Several  limita-
tions of the study, however, are noted:

     •  The study entailed greenhouse  potting studies  conducted
        over a one-year period.

     •  The test conditions may not have been typical  of field
        conditions.

     t  Extrapolation of one year's data may not be valid,
        especially  in light of the previously presented
        references .

     •  The fertilizers were "spiked"  with cadmium.

     The calculations in this study show a range of annual Cd
loading from 0.007  to 0.12 kg/ha, depending on the  fertilizer
sources (Table 11).  Williams and David (49) presented  data
showing that up to  7 percent of cadmium in Australian  phosphate
fertilizer was available for uptake by plants.  Using  this
                              27

-------
availability as a maximum,  the above-cited range would diminish
to 0.00049 to 0.0084 kg Cd/ha/yr.

     If cumulative loadings play an important role in plant
uptake, a specific but unknown amount of cadmium in phosphate
fertilizers applied to soil will increase the latter range
somewhat.  It should be considered, however, that of the
available 100-yr Cd total,  some cadmium will be precipitated or
fixed in the soil matrix.   Therefore, it would seem unlikely
that reasonable application rates  of phosphate fertilizer con-
taining an average of 100  ppm cadmium would increase the Cd
levels of plant species to  any significant degree.

     There are not sufficient data which can be used to compare
the plant availability of  cadmium in phosphate fertilizers with
that in sewage sludge.  Cunningham et al. (7) presented data
which showed that the treatments involving inorganic salts of
heavy metals (Cr, Cu, Zn,  and Ni)  resulted in lower corn
yields, and in general, higher metal concentrations than the
equivalent sludge treatments.  Chemical speciation affects rates
of precipitation and dissolution of metals in soil, thereby
influencing their availability to plants (22).  These data
seem to indicate that cadmium in phosphate fertilizers would be
more available for plant uptake than that in sewage sludge,
assuming Cd loadings were  the same from both sources.  However,
more research is needed to  substantiate this speculation.


COMPARISON OF Cd LOADINGS  FROM SEWAGE SLUDGE AND PHOSPHATE
FERTILIZERS

     A recent study by Stearns, Lofy, and LaConde (40) provided
Cd loading data at nine agricultural locations where sewage
sludge had been utilized for 5 to 17 yrs (Table 14).  With the
exception of Site 7, the Cd loading rates ranged from 0.08 to
1.0 kg/ha/yr.  It is worthy of note that the Cd concentration
of sludges used at Sites 1, 2, 3,  5, 6, and 9 were of the same
magnitude as Cd concentrations of southeastern phosphate ferti-
lizers.  Sites 4 and 8 approximated Cd values of western phos-
phate fertilizers.

     Site 8 received an annual Cd application rate of 1.0 kg/ha
when amended with Cd-containing sewage sludge.  If this site
were to be treated with an  additional western source phosphate
fertilizer (100 ppm Cd) at  an annual fertilizer application
rate of 250 kg P/ha (equivalent to 55 kg P/ha), the Cd loading
rate attributable to the fertilizer would be 0.025 kg/ha.  By
comparison, therefore, the  annual Cd addition from sewage sludge
at Site 8 would be 40 times greater than that from phosphate
ferti1izer.
                              28

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     Similarly, Lee and Keeney (21)  indicated that sludge
additions, compared to phosphate fertilizer additions,  had a
greater potential  of significantly increasing the  soil  concen-
tration of cadmium because of the  much  higher application rates
used.   They estimated that 186 yr  of continuous  (once  per year)
phosphate ferti1izer application at 50 kg/ha/yr would be required
to equal  one application  of sewage sludge at a rate of 9 dry
t/ha (assuming a  sludge Cd concentration of 18 ppm).

     The  largest  contributing difference in the  above  cited
example stems from the application rates of the  sewage  sludge
compared  to those  of the  fertilizer.  On a short-term  basis,
therefore, the net addition of cadmium  to soil by  the  use of
phosphate fertilizers is  probably  not significant.  The long-
term cumulative additions are, however, of potential signi-
ficance .
                              30

-------
                                    SCS BIBLIOGRAPHY FOR

             Preliminary Assessment of Cadmium Additions to Agricultural Lands
                            Via Commercial Phosphate Fertilizers


1.      Bastian, R. K.  Municipal sludge management: EPA construction grants
             program.  In R. C. Loehr, ed.  Land as a Waste Management Alterna-
             tive; Proceedings; 1976 Cornell Agricultural Waste Management
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                                            31

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12.     Hannah,  S. A.,  D. F. Bishop, M. K. Stinson,  C. E. Frank, and T. E.
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                                            32

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28.     Page, A. L. and F. T. Bingham.  Cadmium residues in the environment.
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                                            33

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31-      Reuss, J., H. L. Dooley, and W. Griffis.   Plant uptake of cadmium from
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32.      Roher, M. S. Goldman Sachs & Co.  Fertilizer industry outlook.   Invest-
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                                            34

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 44.     U.S.  Environmental Protection Agency,  Office of Water Program Operations.
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 45-     U.S.  Environmental Protection Agency,  Effluent  Guidelines  Division.
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4 Q
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                                           35

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