Natural and Anrthropogenic "Background" Levels of Arsenic in Florida's Soils
Ming Chen, University of Florida, Belle Glade, FL
Lena Q. Ma, Ph.D., University of Florida, Gainesville, FL
Samira H. Daroub, Ph.D., University of Florida, Belle Glade, FL
Tait Chirenje, University of Florida, Gainesville, FL
Willie G.Harris, University of Florida, Gainesville, FL

Naturally Occurring Arsenic in Overburden in Central Massachusetts
Kevin A. Doherty, Knoll Environmental, Inc., Needham, MA
Rudolph Hon, Boston College, Chestnut Hill, MA 

Bench-scale Evaluation of Sorbents for In-Situ Treatment of Groundwater Arsenic
Richard W. Arnseth, Tetra Tech NUS, Inc., Oak Ridge, TN
Raju Dantuluri, Tetra Tech NUS, Inc., Oak Ridge, TN
Steve McCoy, Tetra Tech NUS, Inc., Oak Ridge, TN
Barbara Nwokike, Southern Division Naval Facilities Engineering Command, North Charleston, SC 

Elevated Arsenic and Iron in Groundwater at a Gravel Pit Reclamation Project using Manufactured Topsoil
Richard S. Behr, Maine Dept of Environmental Protection, Augusta, ME

Arsenic in Landfill Environments, Massachusetts, USA
Rudolph Hon, Boston College, Chestnut Hill, MA
William C. Brandon, USEPA Region I: New England Region, Boston, MA
Carol L. Stein, Gannett Fleming, Inc., New Ipswich, NH
David F. McTigue, Gannett Fleming, Inc., New Ipswich, NH
Thomas Davidson, Boston College, Chestnut Hill, MA

Arsenic Geochemistry:  Ponding, Slime, Iron and Elevated Arsenic in Groundwater
Eric Butler, Gradient Corporation, Cambridge, MA
Chris Slagle, Martin & Slagle,Black Mountain, NC 
Robert Martin, Martin & Slagle,Black Mountain, NC 
Damian Shea, Ph.D., North Carolina State University Raleigh, NC 

Ming Chen, Ph.D., University of Florida, Everglades Research and Education Center, 3200 E. Palm Beach Road, Belle Glade, FL, 33430, Tel: 561-993-1527, Fax: 561-993-1528, Email: mchen@mail.ifas.ufl.edu
Lena Q. Ma, Ph.D., Soil and Water Science Department, University of Florida, Gainesville, FL32611-0290, Tel: 352-392-9063, Fax: 352-392-3902
Samira H. Daroub, Ph.D., University of Florida, Everglades Research and Education Center, 3200 E. Palm Beach Road, Belle Glade, FL, 33430, Tel: 561-993-1593, Fax: 561-993-1528
Tait Chirenje, Soil and Water Science Department, University of Florida, 2169 McCarty Hall, Gainesville, FL, 32611-0290, Tel: 352 392-1951, Fax: 352-392-3902, Email: tchir@gnv.ifas.ufl.edu
Willie, G. Harris, Soil and Water Science Department, University of Florida, 2169 McCarty Hall, Gainesville, FL , 32611-0290, Tel: 352 392-1951, Fax: 352-392-3902, Email: wghs@gnv.ifas.ufl.edu

Arsenic is a Class A human carcinogen and is a public concern due to its widespread usage in both agriculture and industry.  Background concentrations of arsenic in soils are essential for establishing soil cleanup goals. The current Florida Department of Environmental Protection regulatory standards for arsenic contamination in soils, regardless of the taxonomic, geographical differences and land uses, cannot provide an adequate assessment in soil arsenic contamination.  This presentation addresses issues related to the determination (sample collection, analyses and data analyses) and interpretation (geometric mean, upper confidence limit of the mean, nth percentile of the data) of natural and arthropogenic sources of arsenic and the definition of arsenic “background” levels in soils.  Standardization of soil collection, sample digestion, laboratory and data analytical procedures, and a good quality assurance plan will reduce variability in arsenic determination. Our study indicates concentrations of total Fe and P are two most important soil properties that influence arsenic background levels in near pristine soils.  Wet soil suborders in south Florida have naturally high arsenic background concentrations.  This was also reflected in the athrogenic background levels of arsenic in urban soils. Arsenic release from bedrock and arsenic bioaccumulation by aquatic organisms are possible explanations for relatively high arsenic in those wet soils. Baseline soil concentration, which is defined as 95% of the expected range of the background arsenic concentrations in different soil categories, is necessary for properly assessing potential arsenic contamination.

Naturally Occurring Arsenic in Overburden in Central Massachusetts

Kevin A. Doherty, Knoll Environmental, Inc., 69 Wexford Street, Needham, MA  02494, Tel: 781-449-1566, Fax: 781-449-1623
Rudolph Hon, Geology & Geophysics, Boston College, 140 commonwealth Avenue, Chestnut Hill, MA  02467, Tel: 617-552-3656, Fax: 617-552-2462

The Presence of elevated levels of arsenic in a zone that traverses N-S across Central Massachusetts had been periodically noted and reported, however, without a specific reference to neither the origin of arsenic nor the arsenic sources.  Suspected sources included past applications of lead arsenate in orchards as a control for coddling moth, industrial applications in metal and leather processing facilities, and/or from natural sources.  An accumulated set of data in the archives of state environmental agencies provides a confirmation of the widespread reports of arsenic levels that are well above the regulatory “background” levels (17 ppm) in overburden.  We report arsenic data that (1) were compiled from selected sites listed with the Massachusetts Bureau of Hazardous Waste within this region; and (2) data obtained by this study on samples of overburden obtained from drilled profiles at randomly selected sites.  The compiled data are for sites within a corridor along the NNE-SSW trending tract that passes through the geographic center of the state.  Both data sets have similar arsenic frequency distribution curves (histograms) with identifiable two frequency subsets: 20 to 50 ppm and 50 to 800 ppm.  Comparison with distribution curves for lead proves that there is no connection between lead and arsenic therefore suggesting that lead arsenate is not the arsenic source.  Microprobe analysis of sulfides from bedrock samples confirms the presence of pyrites (FeS2) and cobaltites (CoAsS) in the underlying bedrock formations.  Elevated arsenic occurrences within the overburden of Central Massachusetts is best explained by the derivation of the overburden from local bedrock formations and by the occasional incorporation of sulfides into the overburden which may account for the observed arsenic “hot” spots.  The Central Massachusetts “arsenic province” is part of a larger lithotectonic zone as previously reported by Ayotte and others (1999-WRIR 99-4162). 

Bench-scale Evaluation of Sorbents for In-Situ Treatment of Groundwater Arsenic 

Richard W. Arnseth, Tetra Tech NUS, Inc., 800 Oak Ridge Turnpike, Oak Ridge, TN  37830, Tel: 865-220-4721, Fax: 865-483-2014
Raju Dantuluri, Tetra Tech NUS, Inc., 800 Oak Ridge Turnpike, Oak Ridge, TN  37830, Tel: 865-220-4766, Fax: 865-483-2014
Steve McCoy, Tetra Tech NUS, Inc., 800 Oak Ridge Turnpike, Oak Ridge, TN  37830, Tel: 865-220-4730, Fax: 865-483-2014
Barbara Nwokike, Southern Division Naval Facilities Engineering Command, P.O. Box 190010, 2155 Eagle Drive, North Charleston, SC  29419, Tel: 843-820-5566, Fax: 843-820-5563

Elevated arsenic concentrations in groundwater, whether the result of natural or anthropogenic influences, represent a human health risk.  Over the last decade, with activities ranging from documenting health effects in Bangladesh to revision of international drinking water guidelines, there has been an increased focus on the effects of exposure to high arsenic concentrations in groundwater.  In the United States this focus culminated in the recent adoption of a more stringent drinking water standard, lowering the arsenic Maximum Contaminant Level (MCL) from 50 ppb to 10 ppb.   Research on innovative treatment technologies to meet the new standards has been conducted in parallel with the health investigations.  The Navy has identified arsenic contaminated groundwater In its environmental studies which are conducted prior to the transfer of surplus facilities to local communities.  The Navy has a vested interest in identifying treatment technologies that can be shown to operate properly and successfully (OPS) in-situ and in a passive mode.  Tetra Tech NUS identified three sorptive media that promised to meet the Navy’s requirements.  The ability of the three media, an iron-modified zeolite, a surfactant-modified zeolite and activated alumina, to sorb dissolved arsenic from site groundwater was evaluated in batch tests.  Two of the sorbents, iron-modified zeolite and activated alumina, were tested further in column tests with synthetic groundwater and influent arsenic concentrations (350 – 450 mg As/L) similar to those observed at the site.  Column breakthrough was defined when the effluent arsenic concentration was ³ 5 mg/L.  The results of the tests indicated that activated alumina was capable of extracting dissolved arsenic under simulated in-situ conditions.  Based on the column test results, the activated alumina treated >3900 bed volumes prior to breakthrough.  The sorption capacity of the activated alumina was >2500 mg arsenic/g of sorbent.  Based on these results, the Navy is proceeding with a pilot scale field implementation of activated alumina in a permeable reactive barrier.

Richard S. Behr, Maine Department of Environmental Protection, 17 State House Station, Augusta, Maine 04333-0017 Tel: 207-287-6828, Fax: 207-287-7826

State regulations require gravel pit owners to minimize the area open for aggregate mining.  To reclaim gravel pits, soil suitable to establish a vegetative cover is occasionally obtained from nearby agricultural land.  Thus, reclamation activities may inadvertently create additional erosion and sediment control problems.  In an effort to reduce topsoil mining, some reclamation projects use treated sewage sludge in-lieu of natural topsoil.  In this investigation, six acres of an active gravel pit was reclaimed using a mixture of short paper fiber derived from a newsprint pulp and paper mill and commercial fertilizer.  To reduce nitrogen leaching to groundwater the manufactured topsoil was blended to achieve a carbon to nitrogen ratio (C:N) equal to 30:1.  The established groundwater monitoring well network consists of four monitoring wells: one upgradient and three downgradient of the reclamation area.  The database consists of one round collected before reclamation and six rounds post reclamation. 

Groundwater data from the downgradient monitoring wells revealed significant impacts from reclamation activities relative to the upgradient well.  Organic carbon leached from the manufactured topsoil quickly depleted dissolved oxygen concentrations in groundwater beneath and downgradient of the reclaimed area.  There has also been a steady increase in calcium, magnesium, and alkalinity in downgradient wells.  Since the rapid depletion of oxygen, two redox sensitive parameters: iron and arsenic, have increased significantly.  The reduced forms of iron and arsenic are generally more soluble than the oxidized forms.  Therefore, the development of anaerobic conditions will increase the solubility of both iron and arsenic and may have released these parameters from the aquifer matrix.  Neither the short paper fiber nor the fertilizer contained much arsenic; therefore, it’s likely the iron and arsenic are released from the aquifer matrix.

Arsenic in Landfill Environments, Massachusetts, USA

Rudolph Hon, Department of Geology & Geophysics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA  02467, Tel: 617-552-3656, Fax: 617-552-2462
William C. Brandon, Office of Site Remediation and Restoration, USEPA Region I: New England Region, 1 Congress St, Boston, MA 02114, Tel: 617-918-1391, Fax: 617-918-1394
Carol L. Stein and David F. McTigue, Gannett Fleming, Inc., 15 Willard Road, New Ipswich, NH 03071, Tel: 603-878-4056, Fax: 603-878-4056
Thomas Davidson, Department of Geology & Geophysics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA  02467, Tel: 617-797-9595, Fax: 617-552-2462

Solid-waste landfills can modify the oxidation-reduction potential (ORP) of underlying groundwater, thereby influencing solubilities of redox-sensitive species.  Elevated aqueous concentrations of Fe, Mn, and As have been observed at many landfill sites, but sources are a subject of conjecture.  Arsenic may be associated with landfill waste; alternatively, its presence may be from natural sources.  Reductive dissolution of hydrous ferric oxide (HFO) coatings on aquifer materials is a common mechanism by which sorbed constituents, particularly arsenic, are released to groundwater.

Overburden, bedrock, and groundwater samples were collected upgradient and downgradient of four landfills in central Massachusetts.  The overburden at these sites consists primarily of glaciolacustrine sediments.  Bedrock lithology comprises metasedimentary rocks of the mid-Paleozoic Merrimack belt.  Groundwater downgradient of the landfills is characterized by low ORP and relatively high levels of arsenic, typically 0.05 to 0.5 mg/L.  Elevated arsenic is associated with high Fe and Mn.  Fe and As concentrations are broadly correlated, suggesting that both are mobilized by the same process.  In contrast, at two landfill sites in southeastern Massachusetts, downgradient groundwater is characterized by low ORP, but concentrations of iron and arsenic are low.  Bedrock is distinctly different, consisting of Precambrian granites, and overlying glacial deposits are characteristically lower in iron and arsenic as compared to overburden in the central Massachusetts region. 

Landfill leachates high in dissolved arsenic appear to be the unfavorable result of a combination of factors: location within or proximal to bedrock containing arsenic-bearing mineralogies; glacial transport of bedrock minerals; post-glacial chemical alteration and redistribution of iron and arsenic; sorption of arsenic by HFO surfaces; landfill-induced lowering of groundwater ORP; and dissolution of HFO and re-mobilization of arsenic.

Arsenic Geochemistry:  Ponding, Slime, Iron, and Elevated Arsenic In Groundwater

Eric L. Butler, Ph.D., Principal Scientist, Gradient Corporation, 238 Main Street, Cambridge, MA 02142, Tel:  617-395-5000, Fax:  617-395-5001
Chris Slagle and Robert Martin, Martin & Slagle, PO Box 1023, 208 Sutton Avenue, Black Mountain, NC  28711, Tel: 828-669-3929, Fax: 828-669-5289
Damian Shea, Ph.D., North Carolina State University, Dept. of Environmental & Molecular Toxicology, 850 Main Campus Drive, Raleigh, NC  27606, Tel: 919-513-3899

This presentation will use a case study to discuss and illustrate the biological mediation of arsenic concentrations in groundwater.

A company had satisfied its RCRA permitting obligations for a closed Hazardous Waste Management Unit - assessing the unit following cleanup, characterizing the hydrogeology of the site, and monitoring the groundwater for many years.  When it came time to end the monitoring, having observed non-detectable levels of chemicals listed on it RCRA permit for three years in succession, the State balked, pointing to elevated arsenic levels in several of the wells.  Although arsenic was never a notable or significant constituent in the manufacturing process, was not elevated in wastes associated with the site, nor listed in the permit, the State, approximately 18 years after closure of the unit, sought to re-write the permit to include arsenic and retain the closed unit in its program, thus requiring many more years of monitoring and associated costs.

A coherent, thorough evaluation of site characteristics, including, aerial photography, waste testing, numerous groundwater measurements, field notes, soil metals, background metals, and agriculture activity in surrounding properties was performed.  The elevated arsenic concentrations (100-200 mg/L) were shown to be unrelated to the manufacturing facility or its wastes.  The high arsenic levels resulted from the biogeochemistry of iron which controlled the arsenic concentrations in the wells.  Although many on-site wells exhibited reducing conditions, only wells in areas which periodically endured surface water ponding were noted to foul sampling bailers with slimy bacteria and exhibit high iron concentrations.  Only these wells with high iron concentrations exhibited elevated arsenic concentrations.

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