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Kuperman R.G.,U.S. Army | Siciliano S.D.,University of Saskatchewan | Rombke J.,ECT Oekotoxikologie GmbH | Oorts K.,Arche Assessing Risks of Chemicals
Integrated Environmental Assessment and Management | Year: 2014

Although it is widely recognized that microorganisms are essential for sustaining soil fertility, structure, nutrient cycling, groundwater purification, and other soil functions, soil microbial toxicity data were excluded from the derivation of Ecological Soil Screening Levels (Eco-SSL) in the United States. Among the reasons for such exclusion were claims that microbial toxicity tests were too difficult to interpret because of the high variability of microbial responses, uncertainty regarding the relevance of the various endpoints, and functional redundancy. Since the release of the first draft of the Eco-SSL Guidance document by the US Environmental Protection Agency in 2003, soil microbial toxicity testing and its use in ecological risk assessments have substantially improved. A wide range of standardized and nonstandardized methods became available for testing chemical toxicity to microbial functions in soil. Regulatory frameworks in the European Union and Australia have successfully incorporated microbial toxicity data into the derivation of soil threshold concentrations for ecological risk assessments. This article provides the 3-part rationale for including soil microbial processes in the development of soil clean-up values (SCVs): 1) presenting a brief overview of relevant test methods for assessing microbial functions in soil, 2) examining data sets for Cu, Ni, Zn, and Mo that incorporated soil microbial toxicity data into regulatory frameworks, and 3) offering recommendations on how to integrate the best available science into the method development for deriving site-specific SCVs that account for bioavailability of metals and metalloids in soil. Although the primary focus of this article is on the development of the approach for deriving SCVs for metals and metalloids in the United States, the recommendations provided in this article may also be applicable in other jurisdictions that aim at developing ecological soil threshold values for protection of microbial processes in contaminated soils. © 2014 The Authors.

Heijerick D.G.,Arche Assessing Risks of Chemicals | Regoli L.,International Molybdenum Association | Carey S.,International Molybdenum Association
Science of the Total Environment | Year: 2012

The REACH Molybdenum Consortium initiated an extensive research program in order to generate robust PNECs, based on the SSD approach, for both the freshwater and marine environments. This activity was part of the REACH dossier preparation and to form the basis for scientific dialogues with other national and international regulatory authorities. Chronic ecotoxicity data sets for the freshwater and marine environments served as starting point for the derivation of PNECs for both compartments, in accordance with the recommended derivation procedures established by the European Chemicals Agency (ECHA). The HC5,50%s that were derived from the generated Species Sensitivity Distributions were 38.2mgMo/L and 5.75mgMo/L for the freshwater and marine water compartment, respectively. Uncertainty analysis on both data sets and available data on bioaccumulation at high exposure levels justified an assessment factor of 3 on both HC5,50% leading to a PNECfreshwater of 12.7mgMo/L and a PNECmarine of 1.92mgMo/L. As there are currently insufficient ecotoxicological data available for the derivation of PNECs in the sediment compartment, the equilibrium partitioning method was applied; typical KD-values for both the freshwater and marine compartments were identified and combined with the respective PNEC, leading to a PNECsediment of 22,600mg/kg dry weight and 1980mg/kg dry weight for freshwater and marine sediments, respectively. The chronic data sets were also used for the derivation of final chronic values using the procedures that are outlined by the US Environmental Protection Agency for deriving such water benchmarks. Comparing PNECs with FCVs showed that both methodologies result in comparable protective concentration levels for molybdenum in the environment. © 2012 Elsevier B.V.

Smolders E.,Catholic University of Leuven | Oorts K.,Arche Assessing Risks of Chemicals | Lombi E.,University of Adelaide | Lombi E.,University of South Australia | And 5 more authors.
Journal of Environmental Quality | Year: 2012

Metals in soils amended with sewage sludge are typically less available compared with those in soils spiked with soluble metal salts. However, it is unclear if this difference remains in the long term. A survey of copper (Cu) availability was made in soils amended with sewage sludge, manure, and compost, collectively named organic amendments. Paired sets of amended and control soils were collected from 22 field trials where the organic amendments had aged up to 112 yr. Amended soils had higher total Cu concentrations (range, 2-220 mg Cu kg -1; median, 15 mg Cu kg -1) and organic C (range, 1-16 g kg -1; median, 4 g kg -1) than control soils. All samples were freshly spiked with CuCl 2, and the toxicity of added Cu to barley was compared between amended and control soils. The toxicity of added Cu was significantly lower in amended soils than in control soil in 15 sets by, on average, a factor of 1.4, suggesting that aged amendments do not largely increase Cu binding sites. The fraction of added Cu that is isotopic exchangeable Cu (labile Cu) was compared between control soils freshly spiked with CuCl 2 and amended soils with both soils at identical total Cu concentrations. Copper derived from amendments was significantly less labile (on average 5.9-fold) than freshly added Cu in 18 sets of soils. This study shows that Cu availability after long-term applications of organic amendments is lower than that of freshly added Cu 2+ salts, mainly because of its lower availability in the original matrix and ageing reactions than because of increased metal binding sites in soil. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Ma Y.,Chinese Academy of Agricultural Sciences | Ma Y.,CSIRO | Lombi E.,CSIRO | Lombi E.,University of South Australia | And 7 more authors.
Chemosphere | Year: 2013

Although aging processes are important in risk assessment for metals in soils, the aging of Ni added to soils has not been studied in detail. In this study, after addition of water soluble Ni to soils, the changes over time in isotopic exchangeability, total concentrations and free Ni2+ activity in soil pore water, were investigated in 16 European soils incubated outdoors for 18months. The results showed that after Ni addition, concentrations of Ni in soil pore water and isotopic exchangeability of Ni in soils initially decreased rapidly. This phase was followed by further decreases in the parameters measured but these occurred at slower rates. Increasing soil pH increased the rate and extent of aging reactions. Semi-mechanistic models, based on Ni precipitation/nucleation on soil surfaces and micropore diffusion, were developed and calibrated. The initial fast processes, which were attributed to precipitation/nucleation, occurred over a short time (e.g. 1h), afterwards the slow processes were most likely controlled by micropore diffusion processes. The models were validated by comparing predicted and measured Ni aging in three additional, widely differing soils aged outdoors for periods up to 15months in different conditions. These models could be used to scale ecotoxicological data generated in short-term studies to longer aging times. © 2013 Elsevier Ltd.

Van Gestel C.A.M.,VU University Amsterdam | McGrath S.P.,Rothamsted Research | Smolders E.,Catholic University of Leuven | Ortiz M.D.,VU University Amsterdam | And 4 more authors.
Environmental Pollution | Year: 2012

To determine if long-term equilibration may alleviate molybdenum toxicity, earthworms, enchytraeids, collembolans and four plant species were exposed to three soils freshly spiked with Na 2MoO 4.2H 2O and equilibrated for 6 or 11 months in the field with free drainage. Total Mo concentrations in soil decreased by leaching, most (up to 98%) in sandy soil and less (54-62%) in silty and clayey soils. Changes in residual Mo toxicity with time were inconclusive in sandy soil. In the other two soils, toxicity of residual total Mo was significantly reduced after 11 months equilibration with a median 5.5-fold increase in ED50s. Mo fixation in soil, i.e. the decrease of soil solution Mo concentrations at equivalent residual total soil Mo, was maximally a factor of 2.1 only. This experiment shows natural attenuation of molybdate ecotoxicity under field conditions is related to leaching of excess Mo and other ions as well as to slow ageing reactions. © 2011 Elsevier Ltd. All rights reserved.

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