Tracing Pb Isotopic Compositions of Common Arsenical Pesticides in a Coastal Maine Watershed Containing Arsenic-enriched Groundwater
Robert A. Ayuso, US Geological Survey, Reston, VA  

Factors Influencing Arsenite Removal by Zero-Valent Iron
Xueyuan Yu, University of California, Riverside, CA   

Negotiating Achievable Arsenic Soil Cleanup Standards in the Context of High Natural Arsenic Background
Matt Stinchfield, Zenitech Environmental, LLC, Bolder City, NV

Copper, Chromium and Arsenic in Soil and Plants Near Coated and Uncoated CCA Wood
David E. Stilwell, The Connecticut Agricultural Experimental Station, New Haven, CT

In Vitro Gastrointestinal Bioavailability of Arsenic in Soils Collected Near CCA-Treated Utility Poles
Gerald J. Zagury, Ecole Polytechnique de Montreal, Montreal, QC, Canada 

Microbes and Arsenic Contamination of Groundwater in Maine: is there a Link?
Jean D. MacRae, University of Maine, Orono, ME

Arsenic-Rich Iron Floc Deposits in Seeps Downgradient of Solid Waste Landfills

Steven Parisio, NY State Dept of Environmental Conservation, 21 South Putt Corners Rd, New Paltz, NY 12561, Tel: 845-256-3153, Fax: 845-255-3144
Alison R. Keimowitz, Department of Earth & Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, Tel: 845-365-8793, Fax: 845-365-8155
Andrew Lent, Earth Tech, Inc., Bloomfield, NJ, Tel: 973-338-6680
H. James Simpson, Department of Earth & Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, Tel: 845-365-8570, Fax: 845-365-8155

Iron flocculate or “floc” deposits are commonly observed in groundwater discharge zones such as seeps, springs or stream margins downgradient of unlined solid waste landfills.  Typically, these deposits are bright orange and may manifest as a surface coating on soil or sediment particles or as suspended particles loosely adhering to submerged rocks, plant stems or vegetative debris. Composed predominantly of amorphous iron oxy-hydroxides, these deposits generally have been regarded as aesthetically unpleasant, but environmentally benign.  In recent years, there has been increased awareness of the widespread occurrence of elevated arsenic in sediments and groundwater.  Research carried out at a municipal landfill in Maine indicates that naturally occurring arsenic exhibits redox-sensitive mobility and may be associated with iron as a dissolved constituent in leachate impacted (reduced) groundwater.   If iron precipitates in discharge zones where reduced groundwaters are exposed to atmospheric oxygen, it follows that arsenic may co-precipitate with iron in these areas.  To assess the prevalence of this problem within the lower Hudson Valley of southeastern NY, staff from the regional office of the New York State Department of Environmental Conservation (NYSDEC) and researchers from Columbia University’s Lamont-Doherty Earth Observatory sampled iron floc deposits at seven inactive solid waste landfills, and at one control site where iron floc deposition is derived from a natural spring.  At six of seven landfill sites, arsenic concentrations exceeded the NYSDEC sediment guidance value of 30 mg/kg (severe effects level for aquatic life) at one or more sampling points.   These results indicate that arsenic contamination is a potential concern downgradient of landfills wherever iron-stained leachate discharges are observed.  Sampling and analysis of iron flocs associated with such leachates could provide a means of identifying landfills which may present risks to downgradient water supply wells, especially in cases where groundwater monitoring wells are not available for sampling. 

Tracing Pb Isotopic Compositions of Common Arsenical Pesticides in a Coastal Maine Watershed Containing Arsenic-enriched Groundwater

Robert A. Ayuso, M.S. 954 12201 Sunrise Valley Drive, National Center, U.S. Geological Survey, Reston, Virginia, 20192, Tel: 703-648-6347, Fax: 703-648-6383, Email: rayuso@usgs.gov
Gilpin R. Robinson, M.S. 954 12201 Sunrise Valley Drive, National Center, U.S. Geological Survey, Reston, Virginia, 20192, Tel: 703-648-6113, Fax: 703-648-6383, Email: grobinso@usgs.gov

Arsenical pesticides and herbicides were extensively used on apple, blueberry, and potato crops in New England.  Lead arsenate was the most heavily used arsenical pesticide until it was officially banned (USEPA, 1988).  Arsenic and lead concentrations in stream sediments are higher in agricultural areas that used arsenical pesticides than in other areas; arsenic and lead concentrations are positively correlated (r = 0.68).  Historical pesticide residues remain in soils and stream sediments when agricultural land previously contaminated with arsenical pesticides becomes residential.  The common arsenical pesticides have similar Pb isotope compositions: ²⁰⁸Pb/²⁰⁷Pb = 2.3839-2.4721, and ²⁰⁶Pb/²⁰⁷Pb = 1.1035-1.2010.  For other arsenical pesticides such as copper acetoarsenite (or Paris green), methyl arsonic acid and methane arsonic acid, as well as for arsanilic acid (used as feed additives to promote swine and poultry growth) range widely.  The pesticides partially overlap the composition of the stream sediments from areas with the most extensive agricultural use.  Soil profiles from a watershed containing arsenic-enriched groundwater contain labile Pb showing a moderate range in ²⁰⁶Pb/²⁰⁷Pb = 1.1870-1.2069, and ²⁰⁸Pb/²⁰⁷Pb = 2.4519-2.4876. The isotope values vary as a function of depth: the lowest Pb isotope ratios (e.g., ²⁰⁸Pb/²⁰⁶Pb) representing labile lead (acid leach) are in the uppermost soil horizons.  Lead contents decrease with depth in the soil profiles.  Arsenic contents show no clear trend with depth.  Labile lead in the profiles represents lead that is held in soluble minerals (Fe- and Mn-hydroxides, carbonate, etc.).  Lead isotope compositions of stream sediments and soils from areas with heavy use of pesticides include contributions from rock, silicates, sulfides, and their weathering products, in addition to industrial lead (mostly from atmospheric deposition).  In agricultural regions, the extensive use of arsenical pesticides and herbicides can also be a significant anthropogenic source of arsenic and lead to soils and sediments.   

Factors Influencing Arsenite Removal by Zero-Valent Iron

Xueyuan Yu, Dept. of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, Tel: 951-827-2956, Fax: 951-827-5969, Email: xyu@engr.ucr.edu
Christopher Amrhein, Dept. of Environmental Sciences, University of California, Riverside, Riverside, CA 92521, Tel: 951-827-5196, Fax: 951-827-3993, Email: christopher.amrhein@ucr.edu
Yiqiang, Zhang, Dept. of Environmental Sciences, University of California, Riverside, Riverside, CA 92521, Tel: 951-827-5218, Fax: 951-827-3993, Email: yiqiang.zhang@ucr.edu
Mark R. Matsumoto, Dept. of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, Tel: 951-827-5318, Fax: 951-827-5696, Email: matsumot@engr.ucr.edu

Arsenic (As) contamination of ground water is a world wide problem. Recently, laboratory and field scale experiments have shown that zero-valent iron (ZVI), a reactive material commonly used in permeable reactive barriers (PRBs) for ground water treatment, can remove arsenic from ground water.

The adsorption of As to iron (hydr)oxides, or iron corrosion products (ICPs), formed as a result of ZVI corrosion is the primary As removal mechanism by ZVI.  While a Langmuir isotherm is generally accepted as the model to describe the adsorption capacity of As to ZVI, there is no consensus regarding the sorption kinetics and the water quality factors that affect them. 

In this study, laboratory-scale experiments were conducted to investigate the effects of pH, alkalinity, and mass transfer efficiency on the removal of arsenite [As(III)] by ZVI.  The optimum pH range for As(III) removal was found to be between 7 and 8.  Within this pH range, both iron corrosion and iron oxide formation rates are favored.  The effect of alkalinity was found to be dependent on salinity, pH, and the concentrations of bicarbonate/carbonate and As(III).  Inhibition of As(III) removal was observed only under conditions of high alkalinity and arsenic concentrations (alkalinity>10 g CaCO3 / L and 2.9 mg/L As(III)).  Adverse alkalinity effects were not observed when As(III) concentration was low, 100 µg/L.  The strong correlation between As(III) removal and increasing Reynolds number suggests that mass transfer efficiency plays a key role in the removal of As(III) by ZVI.  A combined diffusion-adsorption model was developed to describe the removal of As(III) upon contact with ZVI as the result of adsorption to precipitated iron oxides.  After an initial period of As(III) rapid adsorption to surface rusts formed during manufacturing and exposure to air, As(III) removal rate is most likely controlled by diffusion to adsorption sites in ZVI/iron oxides.

Negotiating Achievable Arsenic Soil Cleanup Standards in the Context of High Natural Arsenic Background

Matt Stinchfield, Zenitech Environmental, LLC, 764 Fairway Dr., Boulder City, NV 89005, Tel: 702-293-1330, Fax: 702-293-0141, Email: matt@zenenv.com
Todd Croft, Nevada Division of Environmental Protection, 1771 E. Flamingo Rd., Las Vegas, NV 89119, Tel: 702-486-2871, Fax: 702-486-2863, Email: tcroft@ndep.nv.gov
C. Michael Moffitt, Consultant, 300 Colonial Affair, Austin, TX 78737, Tel. 512-517-0277, Email: mmoffitt@austin.rr.com
Scott Foster, Bureau of Reclamation, Department of the Interior, PO Box 61470, Boulder City, NV 89006, Tel. 702-293-8144, Fax: 702-293-8766, Email: sfoster@lc.usbr.gov

Highly mineralized desert regions pose exceptional challenges in remediation due to naturally occurring toxic metals in the soil background. Such can be the case in mine restoration, mill site and foundry remediation, or facilities with cooling water surface impoundments in arid climates. When background concentrations of metals exceed safe levels predicted by risk models or legislated action levels, cleanup stakeholders can find themselves at an impasse. In order to establish site-specific cleanup levels that maximize human health protection while fostering an achievable cleanup, owners, consultants, and regulators must negotiate cleanup levels in an economic, scientific, and political milieu. In the small residential community of Boulder City, Nevada naturally occurring arsenic in area soils range from about 3 to 9 mg/kg, yet current health-based cleanup goals recommend arsenic be controlled to below 0.39 mg/kg in a residential, one in a million, cancer endpoint model. The former US Bureau of Mines Metallurgical Research Laboratory site operated for half a century in the center of this community and resulted in uncontrolled soils and tailings with elevated levels of arsenic, lead, and chromium. By involving specialists in regulatory decisionmaking, risk assessment, dynamic site assessment, remediation and site engineering, an eighteen year stalemate was ended and a successful remediation and site closure was obtained.

Copper, Chromium and Arsenic in Soil and Plants Near Coated and Uncoated CCA Wood

David E. Stilwell, The Connecticut Agricultural Experiment Station, PO Box 1106 New Haven CT 0504 USA, Tel: 203-974-8457, Fax: 203-974-8502, Email: David.Stilwell@po.state.ct.us
Craig L. Musante, The Connecticut Agricultural Experiment Station, PO Box 1106 New Haven CT 0504 USA, Tel: 203-974-8454, Fax: 203-974-8502, Email: Craig.Musante@po.state.ct.us
Brij L.Sawhney, The Connecticut Agricultural Experiment Station, PO Box 1106 New Haven CT 0504 USA, Tel: 203-974-8520, Fax: 203-974-8502, Email: Brij.Sawhney@po.state.ct.us

Chromated Copper Arsenate (CCA) was a widely used wood preservative, whose use was phased out partly due to concerns about CCA leaching into soil. In this study we determined the effects that coating CCA wood has on reducing leaching. Ten boxes were constructed, 6 of which were coated with film forming (FF) or penetrating finishes (PF), filled with soil, and weathered for 2 years. The soil was periodically sampled up to 2 years, and then romaine lettuce, arugula, basil and chives were grown under greenhouse conditions in these boxes. After 2 years, the average amount of As in the in soil 2 cm from the CCA wood was 29 (mg/kg, dry weight), 27 from wood coated with PF finishes and 6 in those coated with FF finishes.   Soil As in samples 6 cm from the wood were near the background value of 3.4. Only the opaque, film-forming finishes were effective.  The average amount of As in arugula grown 2 cm from the CCA wood was 60 (mg/kg, dry weight), 61 from wood coated with PF finishes and 24 in those coated with FF finishes. Similarly, the amounts in chives were,75 (CCA), 75 (PF), 12 (FF); lettuce 5 (CCA), 5 (PF), 1.4 (FF); basil 6 (CCA), 10 (PF), 3 (FF). The amounts of As in plants grown in the control boxes were all <1. There was no reduction in plant As when grown next to the non-opaque finished wood, while the reduction in plant As ranged from 50-84% in plants grown next to the opaque finished wood. The reduction in arsenic in samples grown 6 cm from the wood compared to 2 cm from the wood ranged from 55-84%. The amounts of arsenic in the arugula and chives exceeded the British limit for plant As of 1 mg/kg (fresh weight).

In Vitro Gastrointestinal Bioavailability of Arsenic in Soils Collected Near CCA-Treated Utility Poles

Gerald J. Zagury, Eng., Ph.D., Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-Ville, Montreal, QC, Canada H3C 3A7, Tel: 514-340-4711 ext: 4980, Fax: 514-340-4477, Email: gerald.zagury@polymtl.ca 
Priscilla Pouschat, M.A.Sc. Student, Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-Ville, Montreal, QC, Canada H3C 3A7, Tel: 514-737-2548, Email: Priscilla.pouschat@polymtl.ca

Chromated copper arsenate (CCA) has been widely used in North America to treat outdoor play structures and wood utility poles. However, there’s a growing scientific concern about children exposure to the arsenic that leaches from these structures. Previous studies have shown that arsenic concentrations in soils beneath outdoor play structures or immediately adjacent to CCA-treated utility poles often exceed background levels.

Soil ingestion by children is an important pathway in assessing health risks associated with exposure to As-contaminated soils. In order to estimate the bioavailable arsenic from soil ingestion, in vitro gastro-intestinal methods that are based upon human gastrophysiology have been developed in last decade. The fraction of soil arsenic dissolved in the gastrointestinal system and potentially available for absorption can be defined as the bioaccessible As.

The purpose of this study was: (1) to evaluate the bioaccessible arsenic in soils collected immediately near CCA-treated utility poles and (2): to assess the influence of various contaminated soil properties (particle-size distribution, pH, organic carbon, and arsenic fractionation) on bioaccessibility.

In November 2002, twelve CCA-treated utility poles were installed in four different locations (clayey, organic, and sandy environments) in the Montreal area (QC, Canada). After 18 months, soil samples immediately adjacent to each pole were collected and characterized. Bioaccessibility (in triplicates) was determined according to the in vitro gastrointestinal (IVG) method. This chemical extraction method is performed at 37°C with a gastric phase (1h, pH = 1,8, with pepsin) followed by an intestinal phase (1h, pH = 5,5, with bile and pancreatin). Bioaccessibility of arsenic in the certified reference material NIST SRM 2710 was also determined.

Bioaccessibility of arsenic ranged from 20.7 ± 2.9 % to 63.6 ± 1.2 % for the gastric phase and from 25.0 ± 2.7 % to 66.3 ± 2.3 % for the intestinal phase. Bioaccessible As was strongly influenced by soil organic carbon content and was independent of total arsenic content. Correlations between arsenic fractionation and bioaccessible arsenic in soils were determined.

Microbes and Arsenic Contamination of Groundwater in Maine: is there a Link?

Jean D. MacRae, University of Maine Department of Civil and Environmental Engineering, 5711 Boardman Hall, Orono Maine 04469-5711. Tel: 207-581-2137, Fax: 207-581-3888, Email: jean.macrae@umit.maine.edu  

High arsenic concentrations occur naturally in groundwater in some locations and can result in serious health effects when the groundwater is used as a drinking water supply. The most infamous example in Bangladesh, where millions of people have been exposed to unacceptably high arsenic concentrations since the 1970s and serious health impacts, such as cancer, are beginning to emerge. Here in the USA, there are several problem areas, among them, parts of Maine. In 2001, an isolate named NP4 was obtained from a contaminated well in Northport Maine. The well is among a cluster of wells with very high arsenic concentrations, and with no known anthropogenic sources of arsenic. At the time of sampling, the total arsenic concentration in the water was 1400 ppb. The isolate was identified by sequencing the 16S rRNA gene and found to be closely related to two other arsenate reducing bacteria, Sulfurospirillum barnesii, and S. arsenophilum, both of which were isolated from surface water sources. Its presence in groundwater, and its ability to reduce arsenic as well as a variety to other electron acceptors, including Fe(III) and Mn(IV), prompted a fluorescence in situ hybridization (FISH) study to determine its prevalence in the environment. Well water was taken from wells in the Northport area and in the Branch Lake area of Ellsworth, Maine, where the groundwater has much lower concentrations of arsenic, but with some readings still higher than the proposed drinking water standard of 10 ppb. While NP4 as a percentage of total bacterial numbers does not correlate with total As concentrations in groundwater, it does correlate with As(III). A positive correlation was also found between Geobacter, a genus that includes many iron-reducing bacteria, and total arsenic. These results indicate that microorganisms may be important in arsenic mobilization and speciation in groundwater.

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