Arsenic Cleanup Criteria for Soils in the US and Abroad: Comparing Guidelines and Understanding Inconsistencies
Christopher M. Teaf, Florida State University, Tallahassee, FL
Douglas J. Covert, Hazardous Substance & Waste Management Research, Inc., Tallahassee, FL
Patrick A. Teaf, Hazardous Substance & Waste Management Research, Inc., Tallahassee, FL
Michael J. Starks, Environmental Resources Management, Tampa, FL

An Investigation of the Natural and Anthropogenic Contributions of Arsenic to Urban Fill Soil

William R. Swanson, LSP, P.E., CDM Inc., 50 Hampshire Street, Cambridge, MA 02139, Tel/Fax: 617-452-6274, Email: swansonwr@cdm.com
John A. Monacelli, CDM Inc., Coop Student, 50 Hampshire Street, Cambridge, MA 02139, Tel: 617-452-6274, Email: monacellija@cdm.com

Arsenic in urban/historic fill soil, originating from both natural and anthropogenic sources, is a continuing concern from a human health risk point of view. This concern is heightened at locations where the soil is to be used for growing vegetables for consumption in urban gardens.

The presentation will explore the origin of arsenic present in urban/historic fill soil in New England and will derive an understanding of the relative contribution of the natural and anthropogenic components using available data sets. These data sets include over 5,000 urban soil samples from the Central Artery/Tunnel Project in Boston statistically analyzed using ProUCL 4.0, over 2,700 samples of a natural/rural background data set from a comprehensive study of rock and stream sediment arsenic in New England analyzed by USGS, supported by other available data sets resulting in a broad base of up to approximately 10,000 individual sample results. These multiple data sets will be reviewed and summarized such that there are a mean/median and upper values presented for natural soils and rocks and a mean/median and upper values presented for anthropogenic impacted soils, with and without outliers. From this compilation will be derived an understanding of the numerical differential between them. Finally, we will apply standard human health risk calculations provided by MassDEP to illustrate the magnitude of potential impacts of the natural soil and the anthropogenic impacted soil. The derived mean, median and upper percentage values will be considered in the context of the human health risk assessment calculations. In conclusion, the exercise will identify the risk significance of the anthropogenic contribution relative to the natural soil and provide an understanding of the overall impact associated with background in the urban environment.

Field Trials of Enhanced Bioremediation of Arsenic for Remediation of Contaminated Sediments 

Robert Stanforth, RMT, Inc. 744 Heartland Trail, Madison, WI 53717, Tel: 608 662-5310, Fax: 608 831-3334, Email: robert.stanforth@rmtinc.com
Kent McCord, RMT, Inc. 744 Heartland Trail, Madison, WI 53717, Tel: 608 662-5382, Fax: 608 831-3334, Email: kent.mccord@rmtinc.com

A marsh in northern Wisconsin is contaminated with arsenic from a railroad spill in the 1940s. The top foot of marsh sediment still contains arsenic concentrations in the 250 to 1000 mg/kg range, sufficiently high to require remediation. A variety of remediation methods were evaluated in bench-scale laboratory studies, with the most cost-effective and least-intrusive method being enhanced bioreduction of the arsenic. Under highly reducing (methane forming) conditions arsenic can be converted to and volatilized as arsine gas. The process can be enhanced by the addition of food sources for the bacteria doing the arsenic conversion. The bench-scale testing demonstrated that the concept works in the laboratory. Field trials are being conducted in the marsh to evaluate full-scale application of the approach. The field trials were started during the summer of 2008, with mixed results during the first year, and are being continued in 2009. The paper presents the results of both the bench-scale and field trial studies.

Modeling and Design of Wetland Microcosms to Use in Arsenic Remediation

Student Presenter

Matthew W. Gorr, Department of Environmental Sciences, University of Toledo, 2801 W. Bancroft, Toledo, OH 43606, Tel: 419-530-5053, Email: Matthew.Gorr@utoledo.edu
Dr. Daryl Dwyer, Department of Environmental Sciences and Lake Erie Center, University of Toledo, 2801 W. Bancroft, Toledo, OH 43606, Tel: 419-530-2661, Email: Daryl.Dwyer@utoledo.edu

Arsenic is both the number one contaminant of concern in the United States and the cause of global health concerns when present in irrigation and potable water.  Current methods of arsenic remediation produce toxic transformation by-products and are expensive, which preclude their use in many parts of the world.  Treatment wetlands offer a potentially more cost-effective approach that removes arsenic from contaminated water, and ideally eliminates the production of by-products.  This report discusses the processes and environmental conditions that are involved in arsenic removal including plant uptake, microbial transformations, and soil adsorption.  Rates for each process are being measured to optimize the design of effective treatment wetlands.  Microcosms (6.1 m x 1.2 m x 1.5 m) were created and filled with a sandy-loam soil at a field bulk density of 1.5 g/cm³.  Soil pore water samplers were placed throughout the entire microcosm in order to obtain flow-data.  A conservative tracer (NaBr, 190 mg/l) was introduced continuously at the head of each microcosm by gravity flow, and water samples from each location in the array were obtained and used to measure the concentration of bromide.  Initial data were used to access the reproducibility of flow in each microcosm.  Experiments using plants and arsenic will begin in spring 2009 to access the affect of plant uptake on arsenic transport.

Microbial Transformation of Arsenic Compounds 

Dominik Freikowski, University of Karlsruhe, Institut für Ingenieurbiologie und Biotechnologie des Abwassers, Am Fasanengarten, D-76128 Karlsruhe, Germany, Tel. 0049-721-608-3841, Fax 0049-721-608-7704, Email: dominik.freikowski@iba.uka.de
Claudia Gallert, University of Karlsruhe, Institut für Ingenieurbiologie und Biotechnologie des Abwassers, Am Fasanengarten, D-76128 Karlsruhe, Germany, Tel. 0049-721-608-3274, Fax 0049-721-608-7704, Email: claudia.gallert@iba.uka.de
Josef Winter, University of Karlsruhe, Institut für Ingenieurbiologie und Biotechnologie des Abwassers, Am Fasanengarten, D-76128 Karlsruhe, Germany, Tel. 0049-721-608-2297, Fax 0049-721-608-7704, Email: josef.winter@iba.uka.de

Arsenic contaminated groundwater is a serious worldwide problem. Arsenic concentrations above 50 µg l^-1 could be found in Asian countries as well as in the United States and South America. In India in the West Bengal Delta plain, the arsenic concentration in the groundwater reaches more than 400 µ l^-1 and in the sediments 2 – 8 mg kg^-1. This high arsenic concentrations influences the health of several million people.

Despite progresses in understanding the geochemical processes behind this calamity, the cause of the high Arsenic concentrations in groundwater is still unclear, impeding the implementation of efficient mitigation measures. There is an educated guess that bacteria and related biogeochemical processes may play a key role in the mobilization of Arsenic from aquifer sediments, but the validity of this hypothesis remaines largely unexplored until now.

After an extensive hydrogeological and microbiological screening of groundwater from different wells in Kalyani, West Bengal, with a focus on Fe, As, DOC/TOC determination as well as microbiological  characterization, an area for drilling at a “high” and “low” As contaminated underground was selected. A drilling under non-contaminating conditions to a depth of 12 m (well into water saturated soil) was undertaken in order to get sediment samples for laboratory experiments. Also piezometers for hydrogeochemical and microbiological monitoring were installed for delivering water samples at regular intervals to monitor seasonal variations which strongly determine the groundwater level.

The role of microorganisms in the mobilisation of arsenate by reduction of As(V) to the mobile As (III) and the role of Fe (III) reducing microorganisms in the sediment and groundwater of the West Bengal Delta plain are elucidated by population analysis and activity tests of sediment and groundwater samples. Isolation of microbes under oxic and anaerobic conditions as well as PCR experiments with specific primers for As(III) oxidizers and As(V) reducing bacteria were performed. Pure culture isolates were characterised by classical microbial test systems as well as by analyses of 16 S rRNA genes or other specific genes (arsA, arsC). Isolation of several pure cultures that reduce arsenate to arsenite was achieve. Their role in Arsenic mobilisation and detoxification is still in work. 

Column experiments with high and low contaminated sediment samples ± addition of different carbon sources ± sulfate or Fe, as well as microorganisms for bioaugmentation were established in the laboratory. The influence on arsenic mobilisation and change of As species was monitored for all conditions. A sterile control column was installed to monitor possible abiotic arsenic transformations. The laboratory experiments will be compared with field examinations at the experimental site by analysing arsenic concentrations and dissolved organic carbon concentrations (DOC) in water samples derived from the wells.

Arsenic Cleanup Criteria for Soils in the US and Abroad: Comparing Guidelines and Understanding Inconsistencies

Christopher M. Teaf, Center for Biomedical & Toxicological Research, Florida State University, 2035 E. Dirac Dr., Tallahassee, FL, 32310, Tel: 850-644-5524, Fax: 850-574-6704, Email: cteaf@fsu.edu
Douglas J. Covert, Hazardous Substance & Waste Management Research, Inc., 2976 Wellington Circle West, Tallahassee, FL, 32309, Tel: 850-681-6894, Fax: 850-906-9777, Email: dcovert@hswmr.com
Patrick A. Teaf, Hazardous Substance & Waste Management Research, Inc., 2976 Wellington Circle West, Tallahassee, FL, 32309, Tel: 850-681-6894, Fax: 850-906-9777, Email: steaf@knights.ucf.edu
Michael J. Starks, Environmental Resources Management, 5090 Hampton Oaks Parkway, Suite D, Tampa, FL, 33610, Tel: 813-622-8727, Fax: 850-230-1939, Email: mike.starks@erm.com

Widely divergent cleanup targets, guidelines and standards for arsenic in soils have been established by many regulatory, scientific and advisory organizations in the past 25 years, both in the United States and in other countries.  In contrast to many other substances, for which guidelines and standards are similar or identical among agencies, arsenic has provided a powerful study in just how many different ways a single issue can be viewed.  This paper provides a detailed survey concerning the breadth of arsenic soil criteria that have been proposed and applied, and explores the basic differences in their derivation, which can be based upon toxicological properties, geological background levels, anthropogenic background contributions, and practical site-specific considerations.  A broad comparison of extant values in common use for USEPA, individual states, and non-US entities will be presented, coupled with a discussion regarding common examples of the technical bases for arsenic soil cleanup guideline development.  Arsenic target levels in many cases can dominate remedial considerations at sites where the applicable criteria are very stringent.  Several case studies will be presented to illustrate the problems that are inherent in such variable criteria for this ubiquitous and extraordinarily common substance. 

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