United States
                     Environmental Protection
                     Agency
 Hazardous Waste Engineering
 Research Laboratory
 Cincinnati OH 45268
                     Research and Development
 EPA/600/S2-86/108 Apr. 1987     '/I
&EPA          Project Summary
                     Retention  of Zinc,  Cadmium,
                     Copper,  and  Lead  by  Geologic
                     Materials
                     J. P. Gibb and K. Cartwright
                       The vertical and horizontal migration
                     patterns of zinc, cadmium, copper, and
                     lead through the soil and shallow aquifer
                     systems at  a secondary zinc smelter
                     were studied by the use of soil coring
                     and monitoring-well  techniques. The
                     migration of metals that occurred was
                     limited to relatively shallow depths into
                     the soil profile by attenuation processes.
                     Cation exchange and precipitation  of
                     insoluble metal compounds, as a result
                     of pH changes in the infiltrating solu-
                     tion, were determined to be the principal
                     mechanisms controlling the movement
                     of the metals through the soil. Increased
                     metals content in the shallow ground-
                     water systems was confined to the
                     immediate plant site.
                       Soil coring was an effective investi-
                     gation tool, but not suitable by itself for
                     routine  monitoring of waste disposal
                     activities. However,  it should  be used
                     to gather preliminary information to aid
                     in  determining the  proper horizontal
                     and vertical locations for monitoring-
                     well  design. The analysis of water
                     samples collected in this project gen-
                     erally did not provide an understandable
                     pattern of results. A brief experiment
                     on monitoring-well sampling indicated
                     the need to develop reproducible sam-
                     pling  techniques to obtain representa-
                     tive water samples. The failure of some
                     well seals in a highly polluted environ-
                     ment also indicates the need for addi-
                     tional research  in  monitoring well
                     construction.
                       This Project Summary was developed
                     by EPA't Hazardous Watte Engineering
                     Research Laboratory, Cincinnati, OH, to
                     announce key findings of the research
                     project that  Is  fully documented In a
 separate report of the same title (see
 Project Report ordering Information at
 back).

 Introduction
  The primary purpose of this study was
 to verify in the field the effectiveness of
 glaciated region soils and associated sur-
 face deposits  in retaining  specific haz-
 ardous chemicals. The study  also was
 designed to develop effective investigative
 and monitoring techniques for detecting
 and quantitatively evaluating the extent
 of groundwater pollution from surface
 waste disposal activities.
  Special emphasis was placed on defin-
 ing: 1) the vertical and horizontal migra-
 tion  patterns  of  chemical pollutants
 through the soil and shallow aquifer sys-
 tems; and 2) the residual chemical buildup
 in soils in the vicinity of pollution sources.
  Four industrial complexes were select-
 ed for study of the effects of their waste
 disposal practices on the soils and shal-
 low groundwater systems. Site Ar where
 most of the time, money, and effort was
 spent will be discussed.
  Site A  is a secondary  zinc smelter
 located in south-central Illinois. The plant
 started operations between 1885 and
 1890, initially  processed zinc  ore, and
was converted to a secondary zinc smelt-
 ing facility about 1915. Waste from the
smelting operations during the first 85
years principally were  heavy metals-rich
cinders and ashes. During the early years
 large quantities of cinders were used as
road fill or surfacing in the plant area. As
a result of these disposal practices, there
now  is a 1- to 10-foot thick layer of
metals-rich cinders covering about  12
acres of the plant property.

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  In compliance with air pollution control
regulations, a scrubber was installed on
the plant stack in 1970. Prior to that time,
wind-blown ash, rich  in zinc and other
heavy metals, was deposited on the plant
site and on the surrounding farmland.
This source of pollution has now been
minimized, but  wastewater from the
scrubber is disposed of in a seepage pit
constructed on the cinder materials that
form  the present-day  land surfaces.
Several hundred tons  of high zinc con-
tent sludge have accumulated from the
frequent cleaning of this pit and are being
reprocessed for  zinc recovery. Most  of
the water from the pit  infiltrates into the
ground underlying the  plant property.
  The collection of continuous vertical
core samples for geologic  study and
chemical analyses, and the construction
of piezometers  or  monitoring wells for
water  level measurements  and water
sampling were the principal field techni-
ques used in this study.
  Water level measurements were made
and water samples were collected from
each well once a month. Water samples
were  analysed for heavy metals at the
Environmental Research Analytical Labo-
ratory with zinc as the  target element.
Two electrochemical  methods,  anodic
stripping voltammetry  and pulse polaro-
graphy, proved  to  be  most effective for
making zinc determinations and screen-
ing for the presence of  other metals of
interest. Total mineral analyses were also
conducted.

Results
  Altogether, 49 wells at  36 locations
were completed at Site A. Core samples
were taken at each of these locations and
at an  additional 23 sites. Total well and
core sampling footages are about 1309
and 1454 feet respectively.
  The glacial  materials at the site range
in thickness from  about 55 feet on the
east to  about 75 feet  on the west. The
stratigraphic  units recognized  are es-
sentially uniform in character and thick-
ness and generally flat lying across the
site. The elevation of the bedrock surface
dips from 449 feet above sea  level on the
east to 432 feet on the west.
  The expandable clay minerals, generally
referred to as montmorillonite, make up
more than 80 percent of the clay minerals
within the Peoria Loess, Roxana Silt, and
Berry Clay Member, thereby suggesting a
high base exchange potential in the upper
13 feet of the materials encountered. The
thin, continuous silty  sand zone at the
top of the Vandalia Till would appear to
be the  only  permeable  unit to  allow
groundwater  to  travel laterally at any
moderate  rate away from the site. Al-
though there is probably some downward
movement of groundwater through the
remainder of the Glasford Formation, it
would be expected to be extremely low.
  On the basis of the geologic description
of this site,  it is quite obvious  that no
significant aquifer exists in the immediate
vicinity of the plant site. The Hagarstown
Member, a thin  (1  to 2 feet thick) con-
tinuous  silty sandy zone, appears to be
the only permeable zone that could allow
for significant lateral groundwater move-
ment away from the site. To develop even
a domestic water supply from this sand
unit probably would require the construc-
tion of two or more large-diameter bored
wells.
  Water table contour maps show a water
table mound beneath the plant complex.
The relatively high permeability of the fill
materials at the plant site, its topographic
setting, and the liquid disposal activity at
the plant  all contribute to the develop-
ment of this recharge mound.
  No stabilized  water levels were ob-
served in some of the deep wells for the
period of record. In general, water levels
in the deep wells are higher than those in
the shallow wells, indicating a probable
upward  movement of water within the
glacial drift sequence. In  the immediate
plant area, where the shallow water levels
are mounded, the movement of water in
the shallow deposits probably is down-
ward and horizontal. The average rates of
groundwater  movement  from the
mounded  area were, for example, 0.17
ft/day in March 1976 and 0.19 ft/day in
November 1975.
  Chemical analysis of the core samples
were conducted to define: 1) the vertical
and  horizontal  migration  patterns of
chemical pollutants through the soil; and
2) the residual chemical buildup in soils
in the  vicinity of the pollution source.
Preliminary analysis of core samples dur-
ing the early stages of the study indicated
that four elements (zinc, cadmium,
copper, and lead) were most likely to be
carried  into the soils and groundwater
system beneath  the plant property. As a
result these elements were  selected for
routine analyses.
   Results of chemical analysis of core
samples from the Site A control hole
located approximately 3 miles south-
southwest of the plant, and samples from
unaffected soil horizons beneath the plant
property suggest that background con-
centrations for the four elements  tested
should be about 20 to 50 ppm for zinc,
0.04 to 1.5 ppm for cadmium, 10 to 30
ppm for copper, and  10 to 40 ppm for
lead. There appears to be  no significant
chemical variation with depth or between
geologic unit boundaries. Some zinc levels
in isolated Pleistocene soils were higher.
  A  series of cross  sections for  zinc,
cadmium, copper,  and  lead concentra-
tions of the soil were prepared to outline
the limits of  migration of these  metals
beneath the plant and give an indication
of the effectiveness of the soils in retain-
ing these metals. Small quantities of zinc
were found in the upper 3 to 5 feet of the
soil profile outside of the plant property.
Most of the zinc introduced into this area
probably was wind  blown dust and ashes
from the plant stack. The area of greatest
accumulation and deepest concentration
of zinc in the soil occurred immediately
beneath the plant property.
  The general shapes of the cross sec-
tions for cadmium, copper,  and lead were
similar to those for zinc.  The depth of
penetration of cadmium is slightly less
than that of zinc but considerably greater
than that of copper and lead.
  The very shallow depths  of penetration
of these elements indicate the relative
immobility of these metals.  In general,
the areas of greatest penetration of the
four elements occurred  beneath  the
scrubber wastewater pit.  Here  waste-
water is a significant source of the metals
and the recharge into the  soil system is
greatest. In  other  areas removed  from
the pit, the presence of the  cinders be-
came the dominant source  of metals, and
lowland areas where  ponded water ac-
cumulates was the secondary source.
  In addition to the direct  percolation of
metals-rich waste at the plant  site, a
significant amount  of metals-rich surface
water  runs  off the plant  property and
percolates into the stream  beds draining
the plant to the southwest and southeast.
An  accumulation of metals-rich  cinder-
type sediments in  the stream bed was
noted.  The concentration  of metal re-
tained and depth of penetration decreases
as the  distance away from the plant site
increases.
  The mechanisms retaining the metals
in the soil  profile at  Site A are  pre-
dominantly cation exchange and precipi-
tation of insoluble metal compounds as a
result  of pH  change. Cation Exchange
Capacity data generated  indicate  little
variation in the retention capabilities of
the upper geologic units, the silts, clays,
and tills. Therefore, as metals-rich water
percolates  downward  through the soil

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profile, the metals are exchanged pre-
ferentially in reverse order  of their
mobility.
  Cation  Exchange  Capacities (CEC) of
soils  measured  at  Site A range from
about 4 to 10 me/100 grams with the
larger values occurring in the shallower
soils.  If zinc  were transferred onto the
available exchange sites of the soil, cation
exchange could account for soil zinc con-
centrations up to about 3500 ppm. This
value could be higher, according to some
soil specialists,  because  the measured
CEC may be lower than  the original
capacity of the soil. Some researchers
maintain that the  soil  becomes "poi-
soned" in the presence of pollutants and
true CEC values cannot be measured.
  Aside from that possibility, three other
factors may  explain the  difference be-
tween the very high soil zinc concentra-
tions shown in the upper part of the soil
profiles and  the values attributable to
cation exchange:
1) Some of the very high values obtained
   for the surface  and near surface
   samples actually are chemical analy-
   ses of cinder fill samples.
2) Immediately beneath the cinder fill,
   fine-grained  sediments  from  the
   cinders have  been illuviated (washed
   down)  into the underlying  soil, also
   resulting in high zinc values of those
   samples.
3) Soluble and insoluble salts of zinc and
   the other  metals may  be temporarily
   stored in the aerated zone waiting for
   eventual  migration  downward  with
   later recharge events. This also results
   in  higher  zinc concentrations in  soil
   samples from this horizon.
  As the Cation Exchange Capacity of the
soil is exhausted and sufficient depth is
reached to eliminate the three  factors
just noted, the metals buildup in the soil
slowly continues to advance deeper  into
the soil profile. As the exchange process
occurs, calcium and magnesium  are re-
leased into the water from the soil and
the pH of the infiltrating fluid is lowered.
As  the pH increases, the formation of
zinc precipitates results, and a sharp break
or decrease in soil zinc content is noted.
Samples of water collected after perco-
lating through the cinder fill materials
forming the sides of the disposal pit  had
measured pH values near  5. It can be
assumed that the same pH was experi-
enced by  water  filtering  downward
through the cinder fill covering the plant
surface. It is  suspected that sulfur con-
tained in the cinders was dissolved to
form a weak sulfuric acid, thus creating
 the low pH and increasing the mobility of
 the zinc.
   Conclusions pertaining to the mecha-
 nism of zinc  and other metals fixation
 drawn from this field study indicated that
 increased removal of metals from solution
 occurs  with increasing pH  values and
 with  increasing  concentrations of the
 heavy metal in solution.
   Chemical analysis of water collected
 from  deep wells  at Site A showed less
 than  0.5 mg/l zinc. The zinc contents of
 water collected from the shallow  wells
 tapping the Hagarstown sand unit  were
 10,000 mg/l  near the scrubber sludge
 pit and decreased  to  1  mg/l at the
 boundary of the plant property.  Because
 the sampling procedure was  not satisfac-
 tory and the attempt to detect well seal
 failures was unsuccessful, further analy-
 sis of the water  quality data generated
 probably is not worthwhile. The sampling
 procedure used in this study could ac-
 count for as much as 40 to 80 percent of
 the fluctuations noted between sampling
 periods.
   To better define the quality of water in
 an affected and unaffected  area, water
 samples were collected from  wells in
 each  area for total mineral analysis. The
 results of the analysis of a water sample
 from  the shallow control hole  well in-
 dicated general agreement  for the un-
 affected area  well. In the affected area
 well,  increases in mineral constituents
 were observed. Also, the zinc concentra-
 tion (750 mg/l)  and pH (6.5)  were in
 excellent agreement with the solubility of
 zinc (800 mg/l at  6.5pH). Evidence of ion
 exchange was shown by the high  con-
 centrations  of calcium (2400 mg/l) and
 magnesium (893  mg/l). The cation ex-
 change positions in soils in this region of
 Illinois are principally filled with calcium
 and lesser amounts of magnesium. Zinc
 is higher in the montmorillonite exchange
 series than Ca and Mg and thus will
 replace these ions on the clay structure.
 This  process  releases calcium   and
 magnesium to the environment,  even
 when these are not part of  the original
 waste stream.
   Because of  these phenomena,  it is
 recommended that total mineral  analysis
 be conducted  on  water  samples  from
 monitoring wells where cation exchange
 is likely  to  occur. Increases in one or
 more  of these constituents could be an
 early warning of the eventual  appearance
 of more toxic  metals.  However, to in-
terpret a series of samples properly, the
problem associated with collecting com-
parative samples must be solved.
   In attempting to evaluate the relative
 merits of soil sampling versus well instal-
 lation and water samplings, the costs of
 analytical work and the results obtained
 should be considered. Depending on the
 type of waste to be disposed of or moni-
 tored,  soil sampling  may prove to  be
 more effective even though  more costly.
 If a research project is being conducted,
 coring would prove to  be most useful.
 The coring  and analyses of  the core
 samples give a  better understanding of
 the phenomena taking place in the soil.
 However, due to the  costs, coring may
 not be practical as a  routine monitoring
 technique.


 Recommendations
  On the basis of the results of this study
we recommend the following:
 1) Coring and  soil  analysis should  be
   used in waste disposal research pro-
   jects or in waste disposal operations
   when the toxicity of a waste product
   warrants the additional expenditure.
 2) A limited number of core samples, soil
   analyses, and geologic interpretations
   are advisable for evaluating alternative
   disposal sites. Soil  analyses provide a
   better understanding of soil interaction
   with the waste product than is other-
   wise  possible,  and  geologic  inter-
   pretation of the core samples provides
   better  information for design and
   location of monitoring wells.
 3) Routine monitoring of most disposal
   sites should  be accomplished with
   wells  located and  designed on the
   basis of preliminary  coring analysis.
   Periodic coring and soil analysis may
   be worthwhile to substantiate original
   soil effectiveness assumptions.
  The full report was submitted in partial
fulfillment of Grant No. R803216 by the
Illinois State Geological Survey and the
Illinois State Water  Survey under the
sponsorship of the U.S. Environmental
Protection Agency. The report, entitled
"Retention of Zinc, Cadmium, Copper,
and Lead by Geologic Materials," was
published as Cooperative Groundwater
Report 9 by the Illinois State Water Survey
and the Illinois State Geological Survey.

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    J. P. Gibb is with Illinois State Water Survey, Champaign, IL 61820; and K.
      Cartwright is with Illinois State Geological Survey, Champaign, IL 61820.
    Mike H. Roulier is the EPA Project Officer (see below).
    The complete report, entitled "Retention of Zinc, Cadmium, Copper, and Lead
      by Geologic Materials," (Order No. PB 83-232 819; Cost: $18.95, subject
      to change) will be available only from:
            National Technical Information Service
            5285 Port Royal Road
            Springfield, VA 22161
            Telephone: 703-487-4650
    The EPA Project Officer can be contacted at:
            Hazardous Waste Engineering Research Laboratory
            U.S. Environmental Protection Agency
            Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 452G3
                                                                                     hi\ rV.' ,
Official Business
Penalty for Private Use $300
EPA/600/S2-86/108
                0000329

                U  S  ENVIR

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