Background versus Risk-Based Cleanup Goals - An Examination of Arsenic Background Concentrations in Seven States
Kelly A.S. Vosnakis, M.S., ENSR, Westford , MA
Karen Madsen, M.A., M.S., ENSR, Westford , MA  
Lisa J.N. Bradley, Ph.D., DABT, ENSR, Westford , MA   

Arsenic in Historic Fill Soils, Consideration of the Occurrence and Impact of the Natural and Anthropogenic Components.
William R. Swanson, CDM Inc., Cambridge , MA

Variation of Total Arsenic in Playground Soil as a Function of Distance from CCA-Treated Wooden Structures
Cielito DeRamos King, PhD Bridgewater State College, Bridgewater , MA

Microorganisms Associated with Private Wells with High Levels of Arsenic Located in Northport , Maine
Student Presenter
Jennifer M Weldon, University of Maine, 5711 Boardman Hall Room 101, Orono, ME 04469-5711, USA, Tel:  207-581-3401, Fax:  207-581-3888, Email:  Jennifer.Stowe@umit.maine.edu
Dr. Jean D. MacRae, University of Maine, 5711 Boardman Hall Room 101, Orono, ME 04469-5711, USA, Tel:  207-581-2137, Fax:  207-581-3888, Email:  Jean.MacRae@umit.maine.edu

Consumption of arsenic laden drinking water can cause a variety of health effects. In Maine , approximately 40% of residents obtain their drinking water from private wells, many of which contain arsenic in excess of the 10ppb EPA limit. As a result thousands of residents may unknowingly consume arsenic laden water.

For arsenic to occur in groundwater it must be present in aquifer materials and conditions must be favorable for its release. Many microorganisms accelerate natural weathering processes or alter arsenic speciation. Some microorganisms can reduce arsenate, As (V), to the more toxic and mobile form arsenite, As (III).  Others can alter the iron oxyhydroxides that bind arsenic to surfaces, causing the arsenic to be released. As the redox potential of the groundwater decreases, microbial activities that can increase total arsenic and arsenite concentrations are favored. 

The microbial populations in groundwater samples from four wells of varying arsenic concentrations from a single aquifer in Northport , ME were identified using molecular biology techniques.  Based on Ribosomal Intergenetic Spacer Analysis (RISA) it appears that the microbial populations in the recharge region of the aquifer are similar to one another and different from the discharge wells.  Also, populations from the two wells in the discharge region of the aquifer appear to be quite different from each other. 

Organisms from the samples were identified using cloning and it appears that wells in the recharge region contain a greater proportion of bacteria from Gamma Proteobacteria and Eubacteria divisions.  Only the discharge region wells contained organisms from the Delta Proteobacteria division.  The populations from the wells in the discharge region differed in that one contained a greater proportion of organisms from the Beta Proteobacteria division and the other from the Alpha Proteobacteria division.  Additional studies are being conducted to analyze for temporal variations in the microbial communities. 

Background versus Risk-Based Cleanup Goals - An Examination of Arsenic Background Concentrations in Seven States
Kelly A.S. Vosnakis, M.S., ENSR, 11 Phelp's Way, P.O. BOX 506 , Willington , CT , 06279-0506 ,  USA , Tel: 860-429-5323 x 226, Fax: 860-429-5378, Email: kvosnakis@ensr.aecom.com
Elizabeth Perry, M.S., PG, ENSR, 2 Technology Park Drive, Westford , MA   01886 , USA , Tel: 978-589-3167, Fax: 978-589-3100, Email: eperry@ensr.aecom.com
Karen Madsen, M.A., M.S., ENSR, 2 Technology Park Drive, Westford , MA   01886 , USA , Tel: 978-589-3427, Fax: 978-589-3100, Email: kmadsen@ensr.aecom.com
Lisa J.N. Bradley, Ph.D., DABT, ENSR, 2 Technology Park Drive, Westford , MA   01886 , USA , Tel: 978-589-3059, Fax: 978-589-3100, Email: lbradley@ensr.aecom.com

Arsenic is often present in soils naturally or from historical anthropogenic activities.  Arsenic is commonly a constituent of potential concern at environmental remediation sites, even where there is no reason to suspect a release. Site risks are frequently driven by arsenic, and risk-based cleanup goals below background are not uncommon.  However, determining whether arsenic concentrations are consistent with background requires an extensive background data set.  Consequently, many sites undergo characterization and potentially remediation for arsenic concentrations in soil that may in reality be representative of background (natural or anthropogenic).  This study examines a large soil arsenic background data set to provide insight on typical concentrations of arsenic that are naturally occurring or represent anthropogenic background.

Between 1995 and 2001, over 1600 background soil samples were collected from 189 sites in Kentucky, Maryland, New York, Ohio, Pennsylvania, Virginia, and West Virginia.  Samples were collected using strict Quality Assurance/Quality Control procedures under a USEPA Superfund Administrative Order on Consent (AOC) and were analyzed by USEPA-approved laboratories.  All data were verified and 10% underwent detailed data validation.  Arsenic concentrations ranged from 1.1 mg/kg to 89 mg/kg.  Data are considered by state and geologic province and are compared to USEPA and state risk-based cleanup goals. Some standard Background Threshold Values (BTVs) are derived for each state and distinct geologic province.  The BTVs are greater than risk-based cleanup goals.  This extensive, regional data set should be considered by all stakeholders involved in relevant risk-based decisions related to arsenic in soils.  The consideration of this data set and the BTVs may aid in the appropriate identification of arsenic in soils above typical background concentrations, and in turn, aid in identifying where risks are truly elevated relative to background, and thus where remediation may or may not be appropriate. 

Arsenic in Historic Fill Soils, Consideration of the Occurrence and Impact of the Natural and Anthropogenic Components.
William R. Swanson, CDM Inc., 50 Hampshire Street , Cambridge , MA 02139 , Tel: 617-452-6274, Email: swansonwr@cdm.com

Arsenic in concentrations normal to urban fill soil or historic fill may present a potential significant risk to persons who live proximate to as well as may grow vegetables for consumption. This is because there is a key component of arsenic in some natural soils and this may be further added to by human activity over decades or centuries. Finally, arsenic, along with lead and benzo(a)pyrene, dominate the human health risk associated with urban fill soil generally contributing in excess of 85% of the risk.

The objective of this paper is to critically examine arsenic data for natural soil and historic fill soils in Massachusetts , based largely on major urban construction projects, for the concentrations of arsenic present. To that end a data base of over 5,000 Central Artery/Tunnel soil samples was well as data bases consisting of hundreds of other soil samples will be considered leading to practical answers as follows:

Determine if the detected arsenic of natural origin by understanding the occurrence of arsenic in natural soils and how to recognize if the distribution of concentrations is evident of natural conditions.

Provide statistics for concentrations of anthropogenic arsenic in historic fill and detail how to recognize background levels versus distinct sites of release.

 What is the human health risk significance/ what levels constitute potential significant risk for a variety of scenarios.

How significant is the impact of arsenic in urban fill/ historic fill relative to the other key constituents, lead and benzo(a)pyrene?

The presentation will provide persons with a succinct, yet comprehensive overview of the topic as well as a handy tool box for use on sites in which they may have an interest.

The Rainbow’s End playground in Bridgewater , Massachusetts was built in the early 1990s with wooden play structures treated with chromated copper arsenate (CCA). The EPA banned the use of pressure-treated wood containing CCA for residential applications on December 31, 2003. However, studies showed that existing CCA structures pose a risk of arsenic exposure especially to small children from hand-to-mouth contact with CCA structures and accidental ingestion of contaminated soil. Our earlier investigation of the study site showed that 33 % of more than 100 subsurface soil samples collected at random have arsenic levels above the Massachusetts DEP’s action level of 30 mg/kg. The goal of this study is to extend our earlier investigation and determine the extent of arsenic contamination as a function of distance from the base of CCA-treated wooden structures. A total of 105 test and 13 control soil samples were collected in early fall of 2007.  The test samples were collected approximately 5, 15 and 30 cm from the base of a wooden fence and two picnic tables, with additional samples taken underneath the picnic tables.  After sieving and oven-drying at 40 ⁰C, the soil samples were analyzed for total arsenic using a Perkin-Elmer AAnalyst600 graphite furnace atomic absorption spectrometer following EPA method 3050B.  For the 24 x 75 ft² wooden fence, mean total arsenic in mg/kg dry mass were 99.3 ± 47.0, 52.9 ± 36.0 and 23.3 ± 24.5 within 5, 15 and 30 cm, respectively, from the base of the fence. For the picnic tables, all but one sample collected underneath the structure showed more than twice the action level for arsenic, while levels drop significantly even within 5 cm from the base of the structure. In comparison, the mean arsenic concentration of control samples was 4.61 ± 2.60 mg/kg.

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