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Rancho Murieta, CA, United States

Sample B.E.,Ecological Risk | Lowe J.,CH2M HILL | Seeley P.,Cenibark International | Markin M.,CH2M HILL | And 3 more authors.
Integrated Environmental Assessment and Management | Year: 2015

Soil invertebrates,mammals, and plants penetrate and exploit the surface soil layer (i.e., the biologically active zone) to varying depths. As the US Department of Energy remediates radioactive and hazardous wastes in soil at the Hanford Site, a site-specific definition of the biologically active zone is needed to identify the depth towhich remedial actions should be taken to protect the environment and avoid excessive cleanup expenditures. This definition may then be considered in developing a point of compliance for remediation in accordance with existing regulations. Under the State of Washington Model Toxic Control Act (MTCA), the standard point of compliance for soil cleanup levels with unrestricted land use is 457cm(15ft) belowground surface. When institutional controls are required to control excavations to protect people, MTCA allows a conditional point of compliance to protect biological resources based on the depth of the biologically active zone. This study was undertaken to identify and bound the biologically active zone based on ecological resources present at the Hanford Site. Primary data were identified describing the depths to which ants, mammals, and plants may exploit the surface soil column at the Hanford Site and other comparable locations. Themaximumdepth observed for harvester ants (Pogonomyrmex spp.)was 270cm(8.9ft),with only trivial excavation below 244cm (8ft). Badgers (Taxidea taxus) are the deepest burrowing mammal at the Hanford Site, with maximum burrow depths of 230cm (7.6ft); all other mammals did not burrow below 122cm (4ft). Shrubs are the deepest rooting plants with rooting depths to 300cm (9.8ft) for antelope bitterbrush (Purshia tridentata). The 2 most abundant shrub species did not have roots deeper than 250cm(8.2ft). The deepest rooted forb had amaximumroot depth of 240cm(7.9ft). All other forbs and grasses had rooting depths of 200cm (6.6ft) or less. These data indicate that the biologically active soil zone in the Hanford Central Plateau does not exceed 300cm (9.8ft), themaximumrooting depth for the deepest rooting plant. The maximumdepth at which most other plant and animal species occur is substantially shallower. Spatial distribution and density of burrows and roots over depths were also evaluated. Althoughmaximum excavation by harvester ants is 270cm(8.9ft), trivial volume of soil is excavated below 150cm (~5ft). Maximum rooting depths for all grasses, forbs, and the most abundant and deepest rooting shrubs are 300cm (9.8ft) or less. Most root biomass (>50-80%) is concentrated in the top 100cm (3.3ft), whereas at the maximum depth (9.8ft), only trace root biomass is present. Available data suggest a limited likelihood for significant transport of contaminants to the surface by plants at or below244cm(8ft), and suggest that virtually all plants or animal species occurring on the Central Plateau have a negligible likelihood for transporting soil contaminants to the surface fromdepths at or below305cm (10ft). © 2014 SETAC. Source

van den Brink N.W.,Wageningen University | Arblaster J.A.,Ramboll | Bowman S.R.,Ohio State University | Conder J.M.,Geosyntec Consultants | And 7 more authors.
Integrated Environmental Assessment and Management | Year: 2016

Field-based studies are an essential component of research addressing the behavior of organic chemicals, and a unique line of evidence that can be used to assess bioaccumulation potential in chemical registration programs and aid in development of associated laboratory and modeling efforts. To aid scientific and regulatory discourse on the application of terrestrial field data in this manner, this article provides practical recommendations regarding the generation and interpretation of terrestrial field data. Currently, biota-to-soil-accumulation factors (BSAFs), biomagnification factors (BMFs), and bioaccumulation factors (BAFs) are the most suitable bioaccumulation metrics that are applicable to bioaccumulation assessment evaluations and able to be generated from terrestrial field studies with relatively low uncertainty. Biomagnification factors calculated from field-collected samples of terrestrial carnivores and their prey appear to be particularly robust indicators of bioaccumulation potential. The use of stable isotope ratios for quantification of trophic relationships in terrestrial ecosystems needs to be further developed to resolve uncertainties associated with the calculation of terrestrial trophic magnification factors (TMFs). Sampling efforts for terrestrial field studies should strive for efficiency, and advice on optimization of study sample sizes, practical considerations for obtaining samples, selection of tissues for analysis, and data interpretation is provided. Although there is still much to be learned regarding terrestrial bioaccumulation, these recommendations provide some initial guidance to the present application of terrestrial field data as a line of evidence in the assessment of chemical bioaccumulation potential and a resource to inform laboratory and modeling efforts. © 2015 SETAC. Source

Sample B.E.,Ecological Risk | Fairbrother A.,Exponent, Inc. | Kaiser A.,Exponent, Inc. | Law S.,Exponent, Inc. | Adams B.,Rio Tinto Alcan
Environmental Toxicology and Chemistry | Year: 2014

Ecological soil-screening levels (Eco-SSLs) were developed by the United States Environmental Protection Agency (USEPA) for the purposes of setting conservative soil screening values that can be used to eliminate the need for further ecological assessment for specific analytes at a given site. Ecological soil-screening levels for wildlife represent a simplified dietary exposure model solved in terms of soil concentrations to produce exposure equal to a no-observed-adverse-effect toxicity reference value (TRV). Sensitivity analyses were performed for 6 avian and mammalian model species, and 16 metals/metalloids for which Eco-SSLs have been developed. The relative influence of model parameters was expressed as the absolute value of the range of variation observed in the resulting soil concentration when exposure is equal to the TRV. Rank analysis of variance was used to identify parameters with greatest influence on model output. For both birds and mammals, soil ingestion displayed the broadest overall range (variability), although TRVs consistently had the greatest influence on calculated soil concentrations; bioavailability in food was consistently the least influential parameter, although an important site-specific variable. Relative importance of parameters differed by trophic group. Soil ingestion ranked 2nd for carnivores and herbivores, but was 4th for invertivores. Different patterns were exhibited, depending on which parameter, trophic group, and analyte combination was considered. The approach for TRV selection was also examined in detail, with Cu as the representative analyte. The underlying assumption that generic body-weight-normalized TRVs can be used to derive protective levels for any species is not supported by the data. Whereas the use of site-, species-, and analyte-specific exposure parameters is recommended to reduce variation in exposure estimates (soil protection level), improvement of TRVs is more problematic. Published by Wiley Periodicals, Inc. Source

Sample B.E.,Ecological Risk
Integrated Environmental Assessment and Management | Year: 2011

The accident at the Fukushima Daiichi nuclear power plant, precipitated by the devastating earthquake and subsequent tsunami that struck the northeastern coast of Japan in March 2011, has raised concerns about potential impacts to terrestrial and marine environments from radionuclides released into the environment. A preliminary understanding of the potential ecological impacts from radionuclides can be ascertained from observations and data developed following previous environmental incidents elsewhere in the world. This article briefly summarizes how biota experience exposure to ionizing radiation, what effects may be produced, and how they may differ among taxa and habitats. © 2011 SETAC. Source

Sample B.E.,Ecological Risk | Schlekat C.,Nickel Producers Environmental Research Association Nipera | Spurgeon D.J.,UK Center for Ecology and Hydrology | Rauscher J.,U.S. Environmental Protection Agency | Adams B.,Rio Tinto Alcan
Integrated Environmental Assessment and Management | Year: 2014

An integral component in the development of media-specific values for the ecological risk assessment of chemicals is the derivation of safe levels of exposure for wildlife. Although the derivation and subsequent application of these values can be used for screening purposes, there is a need to identify the threshold for effects when making remedial decisions during site-specific assessments. Methods for evaluation of wildlife exposure are included in the US Environmental Protection Agency (USEPA) ecological soil screening levels (Eco-SSLs), registration, evaluation, authorization, and restriction of chemicals (REACH), and other risk-based soil assessment approaches. The goal of these approaches is to ensure that soil-associated contaminants do not pose a risk to wildlife that directly ingest soil, or to species that may be exposed to contaminants that persist in the food chain. These approaches incorporate broad assumptions in the exposure and effects assessments and in the risk characterization process. Consequently, thresholds for concluding risk are frequently very low with conclusions of risk possible when soil metal concentrations fall in the range of natural background. A workshop held in September, 2012 evaluated existing methods and explored recent science about factors to consider when establishing appropriate remedial goals for concentrations of metals in soils. A Foodweb Exposure Workgroup was organized to evaluate methods for quantifying exposure of wildlife to soil-associated metals through soil and food consumption and to provide recommendations for the development of ecological soil cleanup values (Eco-SCVs) that are both practical and scientifically defensible. The specific goals of this article are to review the current practices for quantifying exposure of wildlife to soil-associated contaminants via bioaccumulation and trophic transfer, to identify potential opportunities for refining and improving these exposure estimates, and finally, to make recommendations for application of these improved models to the development of site-specific remedial goals protective of wildlife. Although the focus is on metals contamination, many of the methods and tools discussed are also applicable to organic contaminants. The conclusion of this workgroup was that existing exposure estimation models are generally appropriate when fully expanded and that methods are generally available to develop more robust site-specific exposure estimates. Improved realism in site-specific wildlife Eco-SCVs could be achieved by obtaining more realistic estimates for diet composition, bioaccumulation, bioavailability and/or bioaccessibility, soil ingestion, spatial aspects of exposure, and target organ exposure. These components of wildlife exposure estimation should be developed on a site-, species-, and analyte-specific basis to the extent that the expense for their derivation is justified by the value they add to Eco-SCV development. © 2013 SETAC. Source

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