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Approach for Ecological Risk Assessment for Jasper Coulffy <f>7 3^,

Prepared by Sally Brown (University of Washington) and Rufus L. Chancy (USDA-AgriculturalResearch Service) in cooperation with Mark Sprenger and Harry Compton(US-EPA-ERT)

February 12, 2001

IntroductionAttempting to determine the best practical approach to restore an active plant and animalcommunity on the mine wastes in Jasper County, MO is a complicated decision. It is desirableto both limit the risks posed by the metal contaminants and to create a functional ecosystem onthe denuded areas in a manner that is both protective and cost effective. Application of biosolidsin combination with limestone has been used on a number of metal contaminated sites to restorea plant cover. These sites include Palmerton, PA (Zn smelter), Katowice, Poland (Zn, Pb slagand waste piles), Bunker Hill, ID (Zn, Pb smelter deposition and tailings materials) andLeadville, CO (alluvial Pb and Zn pyritic tailings). In addition to use on metal contaminatedsites, there is a relatively long history (30 + years) of biosolids use to reclaim lands disturbed bya range of mining activities (Sopper, 1992). For historic reclamation sites, the biosolids oftenhad metal concentrations that would no longer be permitted under 40 CFR Part 503, theregulations concerning the use of biosolids. hi certain cases, these materials were as high inmetals as some of the metal mine tailings that they are now used to revegetate (Pietz et al, 1984).Despite this, application of biosolids has been sufficient to restore a sustainable vegetative coverto these sites.

As part of the development of remediation alternatives for the Jasper County mine wastes andcontaminated soils, in s/rw remediation has been considered. During this consideration, questionswere raised about the potential for harm to wildlife returning to the remediated soils. Thepresent report was prepared to discuss how limits to protect wildlife on biosolids-amended soilswere developed. These may prove a solid technical basis for estimating limits for remediatedsoils to protect wildlife using available data. The combination of biosolids and limestone caninactivate soil Zn, Cd and Pb allowing effective plant growth and potentially reducebioavailability of soil elements to animals that consume soils. Risk assessment using relevantdata should clarify whether in .szYu remediation of the Jasper County soils would be expected toprotect highly exposed organisms or require further demonstration with full wildlife testing onsuch remediated sites.

Development of Risk-Based Regulations for Biosolids UtilizationAs part of the process to determine appropriate metal concentrations for biosolids during thedevelopment of the 40 CFR 503 regulations, scientists working with US-EPA attempted to •define the range of pathways that elements in land-applied biosolids could cause harm to highlyexposed and sensitive species. The species evaluated for this process were the most sensitivepotential receptors for each pathway. Species for the risk assessment included humans, plants,soil organisms and a range of livestock and wildlife species.

40164921

SUPERFUND RECORDS

Biosolids plus Limestone Remediation Risk Assessment for Jasper CountyFor the risk assessment process for remediated soils in Jasper County, we have tried to use asimilar approach to that used in the 503 regulation development. Two potential risk pathwayswere re-evaluated for biosolids-remediated mine wastes. In the instances where information onsimilar sites where biosolids have been used is available, the information from those sites hasbeen the basis for risk estimates. In cases where such directly applicable information is notavailable, the existing literature on ecological effects of Pb, Zn, and Cd from contaminated sitesor from biosolids amended sites has been used to outline potentially acceptable soilconcentrations. These are concentrations that should protect highly exposed and sensitivespecies from adverse effects as a result of exposure to these elements in the remediated minewastes. It should be pointed out that application of biosolids to these sites has consistentlyresulted in a reduction in phyto- and bio-availability of these metals. By evaluating thepotential for adverse effects of the unremediated mine wastes and taking into account theexperience that biosolids and limestone application should reduce this risk, it may be possible todecide if this remedial alternative is acceptable.

Pathways of concernMetals of concern in Jasper County contaminated mine wastes and soils are Zn, Pb, and Cd.Recognizing that the application of biosolids and limestone can restore a vigorous plant cover tothese sites, there are potentially two pathways that these elements might cause damage to anecosystem. Pathway 1 is Soil to Plant to Animal (herbivore exposure). Pathway 2 is RemediatedSoil to Animal. If a vegetative cover is restored to the chat, there is the potential that the metalconcentration in the plants would be sufficient to cause harm to the animals that subsist on thismaterial. For this pathway, there is data available for biosolids remediated sites.

Pathway: Soil to plant to animalZn- In cases where a plant cover has been restored to contaminated sites without priorremediation, Zn levels in plants is generally elevated. In general, restoring a plant cover to siteswithout soil amendment has had limited success. Plant species are often limited to metal tolerantecotypes. The alternative was applying very high rates of clean material over the surface of thecontaminated soils. The problems associated with each of these options were reasons that theapplication of tailor-made biosolids mixtures were developed for these sites.

Zn -PhytotoxicityZinc is phytotoxic in high concentrations. Different plants have different soil- Zn thresholds forZn toxicity. Plant tissue concentrations related to phytotoxicity have been reported as rangingfrom 200 - 1200 mg kg"1 with smaller variation within species (Chancy et al., 2000) As a generalrule, nearly all plant species have very strong yield reduction when foliar Zn exceeds 500 mg kg"l. In most of the studies of metal uptake by mammals in the vicinity of Zn-Pb smelters,vegetation of the heavily contaminated areas is sparse and limited to metal tolerant grasses thatsurvive by excluding Zn from shoot tissue. Despite increased tolerance, these plants generallyhave a similar foliar toxicity threshold to other plants. For Zn to pose a threat to animals throughingestion of high Zn plant materials, higher plant Zn levels would be required than thephytotoxic threshold concentration of 500 mg kg"1. Plant tolerance for excess foliar Zn fromcontaminated soils is lower than animal tolerance of dietary Zn on a chronic exposure basis.

Plants die before the Zn concentrations in them exceeded the tolerance level for animalsconsuming them (Chancy et ai, 1998).

In cases where biosolids have been used to restore Zn-Pb contaminated soils, Zn concentrationsin vegetation has been under the diagnostic threshold phytotoxic concentrations and fell withinthe normal range for healthy crops. This indicates that the potential for Zn contamination ofplants growing on remediated Jasper County contaminated soils is very unlikely to result hi afood chain threat to livestock or wildlife.

Table 1. Elemental concentrations of plant tissue grown on Phase I plots in Bunker Hill, ID for 3years following amendment (biosolids + wood ash) application (± std dev). Soil Zn at the siteranged from 6,000 - 14,700 mg kg'1.

App. Rate Plant Zn

—rag kg'1—1997Normal Plant 20-400

Control 219 ±20

HighN 55 129 ± 1110 114 ±25

1998

HighN 55 47 ±7110 59 ±12

1999

Control 169 ±10

HighN 55 47 ±10110 85 ±4

Figure 1. Rye grass Zn concentration from plants grown in a column study using alluvial tailingsmaterials from Leadville, CO. Biosolids and limestone were each added to the soils at 224 Mtha'1.

Plant Zn Concentration mg kg700

Treatments

m Control B Lime a Ag lime + BSm Lime kiln dust + BS

Table 2. Plant Zn concentration from samples collected from the Joplin City soil Pb inactivationtest site. Values presented are the means of 4 replicates collected in 1999 and 2000. Thebiosolids compost contained 30% CaCOs equivalent. Means followed by the same letter are notsignificantly different (Duncan Waller). Soil Zn concentrations averaged 4550 mg kg'1.

Treatment Plant Znmg kg'1

Control

1% P as TSP

3.2%PasTSP10% Biosolids Compost

191 a

94 b

99 b90 b

Soil or Plant Zn Risk to animalsPlant Zn has been linked to fatality or injury in horses in several cases. In Palmerton, PA, calvesthat grazed on pastures that had elevated Zn concentration (1000 mg kg-1 Zn/kg dry foragelargely the result of smelter deposition on plant tissue) suffered from Zn induced Cu deficiency(Chancy et aL, 1988, Gunson et aL, 1982). In Leadville, Co, horses also suffered Zn induced Cudeficiency as a result of grazing on Zn contaminated pastures (Bernard Smith DVM, personalcommunication). Cu supplementation reversed injury to foals in both locations. Other livestockperformed normally even though their forages were grown on contaminated soils. The NRC(1980) recommended limits for maximum dietary Zn discuss the role of marginal Cu supply inrisk from Zn to ruminant livestock; if dietary Cu is marginal for growth, forage Zn maximumrecommended was 300 mg kg-1, while with adequate Cu higher Zn is readily tolerated. Mostspecies tolerate over 1000 mg Zn kg in diets (NRC, 1980). When forages are grown on biosolidsamended soils, forage Cu will be in the normal rather than marginal level for ruminants, reducing

risk from high dietary Zn. A study of metal absorption by goats fed exclusively corn grown onbiosolids amended soil also noted a depression in Cu adsorption related to the Zn concentrationin the com silage. No adverse effects were observed in this case (Bray et al., 1985).

The potential for this to occur in non ruminants appears to be limited. In non -ruminants, Znaccumulation by the body appears to be regulated by homeostasis mechanisms: (the tendency tomaintain or the maintenance of, normal, internal stability in an organism by coordinatedresponses of the organ systems that automatically compensate for environmental changes).Evidence of this in the literature include: Cooke et al.(1990) and Spurgeon and Hopkin (1996).The first study showed no difference in A. sylvaticus and M. agrestis hi organ Zn betweencontaminated and control sites. The second study also showed a low bioaccumulation factor(BAF) for Zn hi contaminated soils. The study also showed that excess Zn body burden waseliminated after exposure to control soil.

Risk from Cd in Remediated Soils and Mine Wastes-

Pathway 1: Soil-Plant-HumanExcess Cd in diets of subsistance rice farmers has caused renal proximal tubular dysfunction andoccasionally an osteomalacia called itai-itai disease (Kobayashi, 1978). A recent study reportedthat Cd (10 mg kg"1) in willow buds was sufficient to cause negative health effects in ptarmigan(Larison et al., 2000). For this study, Zn concentrations in the buds were not reported. Thissuggests that this pathway may be pertinent for an ecological hazard in Jasper County.There are two factors that need to be considered with these examples.1. In the case of human food-chain Cd health effects from mining and smelting waste

contamination of paddy soils, the staple grain in the diet was rice. Rice is a unique grain asconcentrations of other essential elements in polished rice such as Ca, Fe, and Zn aregenerally present in deficient concentrations for humans. The same amount of Cd thatcaused health effects to subsistence farmers in Japan was not associated with any observedCd accumulation or health effects when other foods carried soil Cd to humans. (Chancy etal., 1999; Reeves and Chancy, 2001)

2. In both rice cultivation and in willow habitat, soils generally alternate between anaerobic andaerobic conditions. Under anaerobic conditions, metals (Zn, Pb, and Cd) will precipitate asmetal sulfides. When aerobic conditions prevail, the sulfides will dissolve. Generally Cdsulfides will dissolve before ZnS. This may lead to excess Cd uptake. It also eliminates theprotection from excess Cd accumulation that is generally seen when Zn is a co-contaminant.In aerobic soil environments, when Zn and Cd are present in ratios > 100:1, uptake andaccumulation of Cd are generally inhibited. The soil chemistry of wetland environmentssuggests that plant uptake of Cd may be pose a greater risk in some wetland systems than inaerobic environments.

There is one example of metal uptake by plants in a wetland environment where biosolidscompost and limestone have been used to restore a vegetative cover. Plant Cd concentrations inthis case are below the level that was associated with negative health effects to ptarmigan.Levels of Zn and Pb are also reduced over the samples collected from the unremediated area.

Table 3. Zinc, Pb and P concentration of cattail (Typha latifolid) collected from the West PageSwamp in Bunker Hill, ID both prior to and post amendment with biosolids compost and woodash. Soils contained 3% Pb and 1.5% Zn.

Plant Zn Plant Pb Plant P Plant Cd

1998Control 1010 125 814 5.5Vegetated area 57 10.1 1547 0.11

2000ControlTreated area 113 5.10 3866 0.44

Aerobic soil environmentsFor aerobic soil environments, plant uptake of Cd is generally inhibited by Zn. In addition,absorption of Cd by animals consuming forages grown on Zn and Cd contaminated soils may berestricted because these forages are rich in Zn which can inhibit Cd absorption (McKenna et al.,1996). A direct test of the potential Cd absorption by livestock consuming forages grown onremediated (biosolids and limestone) mine and smelter wastes was conducted at a smelter wastesite in Poland. Cows were fed forage grown on the remediated site or the same plant speciesgrown on a uncontaminated sit. Those fed forage from the remediated site showed a slightincrease hi organ Cd. This increase of tissue Cdwas not sufficient to suggest a potential for foodchain transfer (Stuczynski et al, 2000). In another study, goats were fed corn silage grown onbiosolids amended soils for 3 years (Bray et aL, 1985). The corn silage contained up to 5 mg kg-1 Cd and total Cd in the diet exceeded recommended limits. Kidney Cd in the highest Cd dietwas 22 mg kg-1 which is more than an order of magnitude lower than the value associated withthe first adverse health effects. Of the total Cd fed to the goats over the three-year feeding test,less than 0.03% of the ingested Cd remained in the carcass at slaughter. There was no increase inliver or heart Zn and no increases in organ Pb as a result of treatment.

Table 4. Cd and Zn in foodstuffs and organs of calves fed hay grown on uncontaminated soil or onbiosolids plus limestone remediated smelter slag in Katowice, Poland. Four treatments were tested,control hay, hay from the remediated site, control hay plus salt-Cd to equal the hay from the remediatedsite, and control hay plus salt-Cd and salt-Zn to equal the hay from the remediated site (Stuczynski et al.,2000).

Treatment

Control HayRemediated HayControl Hay + CdControl Hay +Cd+Zn

Hay LevelsCd Zn

mgkg-'DW0.38 25.36.64 298.

LiverCd Zn

KidneyCd Zn

MuscleCd Zn

0.0340.1340.6480.266

atbcd

41.839.936.138.5

babaab

- mg R.

0.170.532.100.78

6abdc

11 ton rv

28.8 a29.2 a29.5 a27.6 a

0.0010 a0.0012 a0.0016 a0.0014 a

27.5 a29.0 a25.6 a25.3 a

fMeans in a column followed by the same letter are not significantly different according to the Waller-Duncan test (P<0.05)

In other cases where high Zn, Cd, and Pb soils have been remediated using a biosolids limemixture, plant Cd is reduced compared to control soils. Concentrations are sufficiently reducedto suggest that the potential for food chain transfer of this element is limited.

Figure 2. Rye grass Cd concentration from plants grown in a column study using alluvial tailingsmaterials from Leadville, CO. Biosolids and lime were each added to the soils at 224 Mt ha"1.

Plant Cd Concentration mg kg1

Treatments

D Control • Lime Only 0 Ag Lime + Btosottds I Lime Kiln +Btosotld8

Table 5. Elemental concentrations of plant shoot tissue grown on Phase I plots in Bunker Hill, IDfor 3 years following amendment application (± std dev). Soil Pb ranged from 2100- 4900 mgkg"1 and soil Cd ranged from 9-28 mg kg"1.

Treatment Plant Cd Plant PbMg ha"1

(mgkg1)1997

Normal Plant 0.1-1.5 0.1-6

Control 0.4 ±0.1 8.5 ± 2

HighN 55 1.2 ± 0.2 16.2 ±0.5110 0.6 ± 0.3 6.7 ±0.6

1998

HighN 55 0.9 ± 0.1 2.7±1.0110 0.9 ± 0.2 3.0 ±0.7

1999

Control 0.50 ± 0.06 27. ± 9

HighN 55 0.28 ±0.04 3.0 ±0.4110 0.40 ±0.08 4.0 ±1.0

Table 6. Plant Pb and Cd concentrations from samples collected from the Joplin City site.Values presented are the means of 4 replicates collected in 1999 and 2000. Means followed bythe same letter are not significantly different (Duncan Waller) Soil Pb averaged 3225 mg kg'Wdsoil Cd averaged 17.5 mg kg"1.

Treatment

Control

!%PasTSP

3.2%PasTSP

1 0% Biosolids Compost

Plant Pbmg kg "'

6.85 a

3.88 b

3.5 b

4.8 ab

Plant Cdmg kg "'

2.5 a

0.83 b

0.50 b

0.73 b

Food-Chain Transfer of Soil Pb

Plant uptake of Pb is generally limited both by the insolubility of Pb in soils and the precipitationof Pb with phosphates in plant roots. Extensive evaluation of risks from Pb in vegetable gardensoils has shown limited uptake of soil Pb by lettuce and similar plant species which accumulatehigher Pb levels that other garden crops (e.g., Sterrett et al., 1997). Further, application of limedbiosolids compost to high Pb urban garden soils strongly reduced Pb uptake by lettuce. Thus, thehazards associated with excess Pb in soils are generally agreed to be associated with directingestion of soils rather than from plant accumulation of soil Pb. Plant uptake of Pb from minewaste sites remediated with a biosolids-limestone amendment is also reduced over control soils.

Pathway: Soil to animalPathway 40 CFR 503 #10 for Wildlife Consuming Soil Biota Containing Soil

This pathway generally refers to animals that directly consume soil. For the 503 regulations,Pathway 3 was the most limiting pathway for Pb concentrations in biosolids. The animal in thiscase was a child and the IEUBK model was used in developing an appropriate biosolids Pb limit.In the case of ecosystem pathways and consideration of the potential for contaminant transfer,there are two potential approaches involving inadvertent soil ingestion by grazing animals or byanimals which consume soil biota. One can consider earthworms to be highly exposed sensitivespecies as their diet consists exclusively of organic material in soil. Before purging internal soil,earthworms contain a high level of soil, 45% of a dry weight basis or 9% on a wet weight basis(Beyer and Stafford, 1992). It may be more appropriate to consider animals that feed onearthworms as the highly exposed species that must be protected by the remediation technologyused for a contaminated site.

Soil to earthworm to animal.There is a relatively large body of data on concentration of metals in earthworms both frombiosolids amended soils and from Zn, Pb and Cd mine spoils. Some basic patterns are commonfor most reports. Earthworms do not bio-concentrate Zn to levels higher in the earthworm than

present in the soil.. They do bio-concentrate both Pb and Cd. Concentration of Cd in earthwormsis generally greater than soil concentration while Pb concentrations in earthworms are generallysimilar or lower than soil concentrations (Beyer and Stafford, 1992, Pietz et al., 1984). Thesestudies generally report the metal concentrations of worms after they have-been treated toremove internal soil (purged worms). There is no discussion of partitioning of metal intodifferent worm organs, except for Cd that is accumulated in a protein bound form. However,there is little evidence that earthworm consuming animals can avoid ingesting the internal soilalong with the tissues of the earthworms. For the purposes of risk assessment, it may be morepertinent to consider the transfer risk posed by worms that have not been purged.

Earthworm as bag of dirtEarthworms' diet consists of organic debris from plants and soil organisms in soil. At any giventime, the earthworm consists of 20 % earthworm solids, 9% soil solids and 71 % water.Approximately 45% of the dry weight of the unpurged earthworm is soil (Beyer and Stafford,1992). Total soil in the worm on a wet weight basis is 9%. Animals that eat worms generally donot remove the soil from the worm before they eat them. The potential for risk transfer to thevermivore's diet then consists largely of soil in the ingested earthworm. If worms can survive inremediated soil, it is then more pertinent to examine metal risk to animals whose diet consistslargely of earthworms rather than the toxicity to the earthworms themselves.

Earthworm survivability in amended soilsThe first question to address is whether earthworms can survive in biosolids plus limestoneremediated mine tailings. There are two cases where earthworm survivability has been measuredin biosolids remediated Zn, Pb and Cd contaminated soil. Condor, Lonna and Basta (in press)amended tailings with a range of soil amendments and evaluated survival of earthworms exposedto the unamended and amended soils. Lime stabilized biosolids were able to eliminateearthworm mortality while other amendments were not (see figure 3).

Biosolids plus limestone amended soils (alluvial mine tailings deposits) in Leadville, CO alsoreduced earthworm mortality over unamended tailings. Survival in amended tailings wascomparable to control soils (Table 7).

Table 7. Survivability and biomass of earthworms in control and biosolids plus limestoneamended soils from the alluvial tailings deposits hi Leadville, CO (Sprenger et al., unpublished).Sample

CLCOMB/MERA/RBUpstream control

UntreatedSurvival(%)

0000

Biomass (mg)----

TreatedSurvival (%)

10098.9901096.7

Biomass (mg)329323372280196

10

Shrew as most sensitive speciesThese studies suggest that earthworms can survive in biosolids-limestone amended mine wastesoils. If the earthworms can survive in the remediated mine wastes than animals that ingestearthworms can be expected to return to remediated areas. For this case, the common shrew canbe used as the highly exposed species. The shrew has a life-span of approximately 16 months. Ithas a very limited range, suggesting that it would not venture far from the remediated areas. Itsdiet consists of worms and insects. One study analyzed the gut contents of shrews trapped andfound that 70 % of the gut consisted of earthworm chaetae (Read and Martin, 1993).

There have been no studies of shrews from biosolids-lime remediated sites. There are a numberof studies that have examined metal uptake by shrews on contaminated sites. In addition, thereare 2 studies of metal uptake by shrews on biosolids amended soils.

Estimated Zn Risks to Vermivore Wildlife on Remediated Mine WastesFor shrews found on contaminated sites, tissue Zn is generally only mildly increased. As statedearlier in the discussion, homeostasis controls Zn uptake and excretion. For example, in onestudy a 700% increase in dietary Zn resulted in a 48% increase in body Zn. The majority of thisincreased Zn was stored hi bone tissue (Andrews et al., 1989)

Estimated Pb and Cd Risks to Vermivore Wildlife on Remediated Mine WastesBoth Pb and Cd tend to accumulate in shrew tissues. For both metals, the organ that iscommonly used to assess potential harm is the kidney alathough Pb is also accumulated in bonewhere most of the carcas Pb occurs. When supplied in dietary excess , Pb and Cd willaccumulate in the kidney. Negative effects associated with these elements include kidneyinclusion bodies from excessive Pb and renal tubular dysfunction from excessive Cd (Goyer etal., 1970, Roberts and Johnson, 1978). Kidney weight can also increase. When bioavailabledietary Pb is excessive, Pb interferes with heme formation and a heme precursor, delta-amino-levulinic acid (ALAD) levels in blood can also decrease (Beyer et al., 1985). There is also somediscussion in the literature of weight loss or gain as a result of excess Cd and/or Pb. Relativeweights of the kidney to whole body have also been used to assess potential for damage. Resultsfrom these measures have yielded conflicting data. Measures of total kidney Pb and total Cd inkidney cortex appear to be more reliable measures of actual harm from excessive absorption ofPb and Cd by mammals and birds.

Pb calculationOne approach to determining a permissible Pb content in remediated mine wastes that will notinduce chronic kidney damage to shrews is to calculate the uptake slope or translocation slopefor kidney Pb+ soil Pb from the studies that have been published. This uptake slope can then beused with a reference value above which damage may occur. There are two numbers in theliterature for the dry weight of kidney where damage may occur, 25 mg kg"1 (National ResearchCouncil, 1980) and 120 mg kg"1 Pb (Goyer et al., 1970). These numbers are very different.From the literature studied, it may be possible to see which value better approximates fieldobservations (Table 5).

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Table 8. Relationship of kidney Pb concentration to evidence of kidney injury in Pb exposedanimals.

Study

Beyer etal, 1985Beyer etal, 1985CookeetaL, 1990Hegstrom and West, 1989Read and Martin, 1993Read and Martin, 1993Pankakowski et al., 1994Ma, 1989

Kidney Pb DWmg kg"1

1217165, 234

816638.7

380427269

Damage

Yes - inclusions, ALADNoNoNoNo9

mortalityNo

From the reported values, it seems likely that the 120 mg kg"1 Pb kidney dry weight (equivalentto about 25 mg Pb kg"1 fresh weight) is closer to an actual concentration that is associated withadverse health effects than 25 mg kg"1 Pb kidney dry weight. Negative health effects were notobserved in the field for kidney Pb up to 269 mg kg"1 dry weight.

The uptake slopes were calculated for the studies where soil Pb concentrations were provided.The uptake slopes were defined as change in kidney Pb (mg kg) / change in soil Pb (kg Pb ha).These slope values can then be used to determine a maximum loading value of Pb in soil thatwould be protective of the shrew. Here 120 mg kg kidney DW is used as the threshold organconcentration. This is similar to the process used in developing the metal loading limits for theEPA 503 biosolds regulations. The following equation was used substituting the linear responseslope of contaminant in animal organ from consumption of invertebrates for the consumption ofplants:

RPC = TO - ABI

where: RPC =TO =ABI =U0n =

reference cumulative application rate of pollutant (kg/ha)threshold organ concentration (|ig/g DW)background concentration in animal organ (|ag/g DW)linear response slope of contaminant in animal organ from consumption ofplants (ug/g DWXkg/ha)-1

For the uptake slopes generated from field data, the soil Pb limit at which kidney Pb would reach120 mg kg'1 DW range from 166,900 (Johnson et al Minera site) to 375 (Beyer et al., sickanimal).

12

Table 9. Uptake slopes of kidney Pb in relation to total soil Pb for shrews based on valuesreported in specific studies. These values were then extrapolated to determine the soil Pbconcentrations that would be associated with 120 mg Pb kg'1 kidney dry weight for shrews.

StudyHegstrom and West shrewRead and Martin young

matureMaBeyer etal. 1985, healthy

sickJohnson et al., Mouse at Y fan

Mouse at Minera

Uptake slope6/61.2 = 0.09836.5/(1142-33)*2 = 0.014380/(1142-33)*2 = 0.156251/15000*2 = 0.008199.5/1900*2 = 0.05251217/3800 = 0.3220/13900*2 = 7.19x10-434/8330* 2 = 0.002

Safe Soil Pb Concentration1224

8,570770

15,0002286375

167,00060,000

It is likely that animals that experience stress as a result of Pb exposure have different uptakeslopes from healthy animals. For this reason, it is not necessarily relevant to use those uptakeslopes when attempting to determine a soil Pb concentration that will be protective of healthyanimals. The average permissible soil Pb value for shrews with no symptoms of Pb stress is6,700 mg kg Pb.

Further, the biosolids plus limestone treatment has been shown to reduce the bioavailability ofsoil Pb to rats in several tests of treating smelter contaminated soils or urban soils high in Pb.Both the phosphate precipitation of Pb as pyromorphite and increased adsorption of Pb in Fe andMn oxides are effective in reducing bioavailability of soil Pb (Brown et al., 1997; Brown et al.,unpublished data from Joplin plots).

CdUsing a similar approach to the one followed for Pb, one can set an acceptable soil Cdconcentration. There is more information in the literature on Cd concentrations in wildlife.Research in the UK by Johnson and colleagues has actually observed kidney disease fromexcessive Cd exposure to shrews in the field (Hunter et al., 1984). Readers need to understandthe unique aspects on one site where kidney harm to shrews has been repeatedly reported, andother sites where harm was not observed. At the Cu-Cd alloy factory in Prescott, UK, electricalswitchgear is manufactured. Cd is included both to stregthen the metal without reducingelectrical conductivity, and to plate the contact points to prevent corrosion from making itdifficult to open switches. The contamination at this location includes little Zn, so high Cduptake by soil organisms occurs compared to other sites. And food-chain risk transfer is muchgreater than at mine sites where the normal geological Cd:Zn ratio occurs.

Appropriate LOAEL concentration .Shore and Douben (1994) state that Cd concentrations in shrews collected from contaminatedsites have been as high as 140 to 250 mg kg"1 dry weight in kidney without any evidence of illeffect. Kidney cadmium concentrations have been reported as high as 990 - 1200 mg kg"1 dry

13

weight without evidence of adverse effects (Dodds Smith et al, 1992 b). This is in contrast to labstudies where mice sometimes show potential evidence of adverse renal effects at kidney Cdconcentrations as low as 105 mg kg dry weight (much higher dose rates have been used inshort term testing and acute toxic effects on liver were believed to have occurred). Further, miceand voles collected from contaminated sites always had Cd concentrations lower than the 105 mgkg~' level (Shore and Douben, 1994, Beyer, 2000).

Metal Salts in Diets vs Contaminated Soil s in DietsThe discrepancy between results found hi mice in lab studies and actual accumulation patterns ofmice hi the field and the significantly higher concentrations found in shrews may be related tothe nature of the dosing. In lab studies, animals are generally given Cd as salts. In a fieldsituation, uptake of Cd is influenced by the presence of other cations, particularly Zn. Theadsorption of Cd by soil components such as hydrous iron oxides and humic acids also limits itsbioavailability. These affect both the absorption of Cd as well as the concentration required foradverse effects to occur (Beyer, 2000). This is similar to the results observed hi humans whenCd was present as a portion of a balanced diet rather than hi a diet marginal in Fe, Zn, or Casupply (Reeves and Chancy, in press). An example of the difference hi behavior when Cd ispresent in the environment with or without Zn is a study by Chancy et al., 1993. In the casewhere Cd was a co-contaminant with Zn, plant uptake of Cd was reduced by an order ofmagnitude. While this relates to plant uptake, studies of human Cd absorption under similarcircumstances suggest that the findings may be applicable to wildlife as well. Extensive studiesby Fox et al (1984) and others (Jacobs et al., 1983) illustrate that concurrent Zn ingestion inhibitsCd absorption by animals. In the tailings in Jasper County, Zn is always found as a co-contaminant with Cd. This should be taken into account when setting a LOAEL.

Once the LOAEL kidney concentration has been agreed on, the soil concentration necessary toreach this concentration can be determined. The ratio of change in kidney Cd to change in soilCd can be used to set an acceptable soil concentration. While there are no studies of Cd uptakeby shrews on biosolids amended mine sites, there are 3 studies of Cd accumulation in shrewkidneys on biosolids amended sites (Table 7). By determining the uptake slope for the shrews onthese soils, it may be possible to get an approximation of what Cd uptake might be on minewaste sites remediated with biosolids plus limestone.

Table 9. Cadmium accumulation hi kidneys of shrews living in environments where biosolidsraised soil Cd concentration above background.

Study

Hegstrom and West,1989shrewsNickelson and West,1996shrewsAnderson et al, 1982Meadow voles

Uptake slope

24/2.55 = 9.41

25/25.5 = 0.98

5.3/1.18 = 4.49

Safe Soil Cdconcentration

Using kidney concentration of1 05 mg kg "' dry wgt

11

122

23.4

Safe Soil Cd concentrationUsing kidney concentration of

200 mg kg"1 dry wgt

22

244

46.8

14

Alternatively, the concentration of Cd in kidney cortex widely observed to be associated with thefirst evidence of renal tubular dysfunction is 200 mg kg"1 cortex fresh weight. This concentrationmust be converted to whole kidney Cd concentration; using the factor relating Cd in cortex to Cdin whole kidney (1.25) (Svartengren et al., 1986), the whole kidney fresh weight would contain160 mg Cd kg when 200 mg Cd kg"1 kidney cortex fresh weight was reached. Converting thisfigure to dry weight for comparison with wildlife research results is achieved by use of 25.3%dry matter in kidney of shrews (Ma, 1989). The result is 632 mg Cd kg"1 whole kidney dryweight as the threshold for renal tubular dysfunction, which is 3 to 6 tunes higher than used inthis estimate.

It should not be a surprise that soil Cd ingested by shrews that consume unpurged earthworms isof relatively low risk to shrews. The presence of Zn, Fe, and Ca in such diets prevent deficienciesin the animals, and the presence of Cd-adsorbing soil components such as hydrous iron oxidesand humic acids should reduce bioavailability of Cd compared to Cd-salt additions to purifieddiets. In one soil feeding study reported in the literature, Schilderman et al. (1997) found that soilCd bioavailability to rats was 43% that of Cd salts (the test involved feeding CdC^-amendedOECD synthetic soil at 4,400 mg Cd kg"1, and used toxicological methods rather than chronicanimal nutrition testing methods). In other tests in which recommended quality biosolids werefed to test [cattle or sheep], no increase in kidney or liver Cd was observed after 1-4 year feedingperiods with 3-10% biosolids in diets (Decker et al., 1980; Smith et al., 1985).

Conclusions

Existing data indicate that it is possible to restore a persistent vegetative cover to metalcontaminated sites using a biosolids and limestone amendment. Plant concentrations of metals atremediated sites are within acceptable limits for chronic lifetime livestock forages.. Althoughfull scale ecosystem monitoring has not been done at remediated sites, it may be possible topredict ecosystem impact by examining pertinent studies done on unremediated sites. Thesestudies indicate that guidelines can be established as to what sites are suitable for restorationusing biosolids plus limestone amendments. By taking into account existing information, theseguidelines should adequately protect the highly exposed vermivore species attracted to theremediated, revegetated environments.

Acknowledgements

We would like to thank members of the IINERT (In-Place Inactivation and EcosystemRestoration Technology) Action Team (Jim Ryan, Gary Pierzynski and Nick Basta) for their helpin preparing this document.

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