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Arsenic species distribution in drinking water wells in the USA with high arsenic concentrations


Arsenic is a common, naturally occurring element in ground water in many countries and its concentration varies widely and regionally. Moreover, ground water is a major source of drinking water and the occurrence of arsenic in drinking water has been associated with adverse heath effects in humans. While municipal water suppliers in the US are required to meet the E.P.A.’s safety standard of 10 p.p.b. for arsenic in drinking water, no such regulation exists for private wells. Researcher estimate, that nationwide about 13 million people get drinking water from private wells with arsenic levels above the federal standard.

The variability of the arsenic concentration in ground waters is attributed to the arsenic content of the aquifer materials and the varying desorption/dissolution processes that release the arsenic from the solid phase into the liquid phase. As a result of such processes, arsenic exists in ground water as oxyanions having two oxidation states, As(III) and As(V). Because of the difference in toxicity and removability of As(III) and As(V), arsenic speciation is important in the selection and design of an arsenic treatment system. Identifying the arsenic species is also helpful in explaining and understanding the origin, behavior and characteristics of arsenic in the environment.
However, arsenic speciation analysis is more complex than just arsenic trace element determination and requires either an appropriate preservation method that stabilizes both As(III) and As(V) or make use of field separation methods that are somewhat complex and costly.  Thus, very few studies have incorporated arsenic speciation.

The new study:
A U.S. Environmental protection Agency (EPA) arsenic treatment research program provided a unique opportunity to determine the concentration of  the naturally occurring arsenic species in 65 well waters scattered across the USA with many of them being speciated monthly for up to three years. Because of the lack of a univerase preservation method for arsenic species in ground waters containing different amounts of iron and manganese, the researchers used an on-site procedure to separate  As(V) and As(III). This well established method makes use of an anion exchange resin whereby the uncharged As(III) passes through the resin while the charged As(V) is retained on the resin.

Graph showing the percent arsenic III in well waters by regions of the USA
Percent arsenic III in well waters by regions of the USA.

Speciation test data obtained by this method showed that 31 wells had predominantly As(V), 29 had predominantly As(III) and five had a mixture of both. A general pattern was found where As(III) was the dominant species in midwest ground waters where anoxic conditions and elevated iron concentrations prevailed and the well waters in the east, west and farwest had either As(III) or As(V) as the dominant species. The monthly (12–36) speciation tests results at many of these sites also found no major changes in the ratio of arsenic species over time even for those few well waters that showed significant variability in total arsenic concentration.

The original study:

Thomas J. Sorg, Abraham S.C. Chen, Lili Wang, Arsenic species in drinking water wells in the USA with high arsenic concentrations, Water Research, 48 (2014) 156–169. doi: 10.1016/j.watres.2013.09.016

Related studies (newest first)

L.A. Munk, B. Hagedorn, D. Sjostrom, Seasonal fluctuations and mobility of arsenic in groundwater resources, Anchorage, Alaska, Appl. Geochem., 26/6 (2011) 1811–1817. doi: 10.1016/j.apgeochem.2011.06.005

Q. Yang, H.B. Jung, C.W. Culbertson, R.G. Marvinney, M.C. Loiselle, D.B. Locke, H. Cheek, H. Thibodeau, Y. Zheng, Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in Greater Augusta, Maine, Environ. Sci. Technol., 43/8 (2009) 2714–2719. doi: 10.1021/es803141m

T. Möller, S. Sylvester, D. Shapard, E. Morassi, Arsenic in groundwater in New England – point-of-entry and point-of-use treatment in private wells, Desalination, 243/1–3 (2009) 283–304. doi: 10.1016/j.desal.2008.05.016

S.C. Peters, Arsenic in groundwaters in Northern Appalachian mountain belt: a review of patterns and process, J. Contam. Hydrol., 99/6 (2008) 8–21. doi: 10.1016/j.jconhyd.2008.04.001

S. Haque, J. Junfeng, K.H. Johannesson, Evaluating mobilization and transport of arsenic in sediments and groundwaters of Aquia, aquifer, Maryland, USA, J. Contam. Hydrol., 99/3 (2008) 68–84. doi: 10.1016/j.jconhyd.2008.03.003

M.A. Thomas, The Association of Arsenic with Redox Conditions, Depth and Ground-water Age in the Glacial Aquifer System of the Northern United States,  U.S. Geological Survey (2007), Scientific Investigations Report 2007-5036

J.G. Thundiyil, Y. Yaun, A.H. Smith, C. Steinmaus, Seasonal variation of arsenic concentration in wells in Nevada, Environ. Res., 104/4 (2007) 367–373. doi: 10.1016/j.envres.2007.02.007

S.E. Haque, K.H. Johannesson, Concentrations and speciation along a groundwater flow path in the upper Floridan aquifer, Florida, USA, Environ. Geol., 50/3 (2006) 219–228. doi: 10.1007/s00254-006-0202-8

S. Haque, K.H. Johannesson, Arsenic concentrations and speciation along a groundwater flow path: the Carrizo sand aquifer, Texas, USA, Chem. Geol., 228/1–3 (2006) 57–71. doi: 10.1016/j.chemgeo.2005.11.019

S.C. Peters, J.D. Blum, M.R. Karagas, C.P. Chamberlain, D.J. Sjostrom, Sources and exposure of the New Hampshire population to arsenic in public and private drinking water supplies, Chem. Geol., 228/1–3 (2006) 72–84. doi: 10.1016/j.chemgeo.2005.11.020

M.L. Erickson, R.J. Barnes, Arsenic concentration variability in public water systems wells in Minnesota, USA, Appl. Geochem., 21/2 (2006) 305–317. doi: 10.1016/j.apgeochem.2005.12.005

M.J. Slotnick, J.R. Meloker, J. Nriagu, Effects of time and point-of-use devices on arsenic levels in Southeastern Michigan drinking water, USA, Sci. Total. Environ., 369/1–3 (2006) 42–50. doi: 10.1016/j.scitotenv.2006.04.021

M.L. Erickson, R.J. Barnes, Glacial sediment causing regional-scale elevated arsenic in drinking water, Ground Water, 43/6 (2005) 796–805.  doi: 10.1111/j.1745-6584.2005.00053.x

C.M. Steinmaus, Y. Yuan, A.H. Smith, The temporal stability of arsenic concentrations in well water in western Nevada, Environ. Res., 99/2 (2005) 164–168. doi: 10.1016/j.envres.2004.10.003

M.L. Erickson, R.J. Barnes, Well characteristics influencing arsenic concentrations in ground water, Water Res., 39/8 (2005) 4029–4039. doi: 10.1016/j.watres.2005.07.026

D.B. Kent, P.M. Fox, The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz and gravel aquifer, Geochem. Transact., 5/1 (2004) 1–12. doi: 10.1186/1467-4866-5-1

J.D. Ayotte, D.L. Montgomery, S.M. Flanagan, K.W. Robinson, Arsenic in groundwater in eastern New England: occurrence, controls, and human health implications, Environ. Sci. Technol., 37/10 (2003) 2075–2083. doi: 10.1021/es026211g

S.C. Peters, J.D. Blum, The source and transport of arsenic in a bedrock aquifer, New Hampshire, USA, Appl. Geochem., 18/11 (2003) 1773–1787. doi: 10.1016/S0883-2927(03)00109-4

K.L. Warner, A. Martin Jr., T.L. Arnold, Arsenic in Illinois Ground Water-community and Private Supplies, USGS (2003) Water-resources Investigations Report 03–4103.

M.J. Kim, J. Nriagu, S. Haack, Arsenic species and chemistry in groundwater of Southeast Michigan, Environ. Pollut., 120/2 (2002) 379–390. doi: 10.1016/s0269-7491(02)00114-8

K.L. Warner, Arsenic in glacial drift aquifers and the implication for drinking water-lower Illinois River basin, Ground Water, 39/3 (2001)  433–442. doi: 10.1111/j.1745-6584.2001.tb02327.x

A.H. Welch, D.B. Westjohn, D.R. Heisel, R.B. Wanty, Arsenic in ground water of the United States: occurrence and geochemistry, Ground Water, 38/4 (2000) 589–604. doi: 10.1111/j.1745-6584.2000.tb00251.x

S.C. Peters, J.D. Blum, B. Klaue, M.R. Karagas, Arsenic occurrence in New Hampshire drinking water, Environ. Sci. Technol., 33/9 (1999) 1328–1333. doi: 10.1021/es980999e

M.M. Fry, M.A. Edwards, Surveying arsenic occurrence, J. Am. Water. Works. Assoc., 89/3 (1997) 105–117.

N.E. Korte, Naturally occurring arsenic in groundwaters of the Midwestern United States, Environ. Geol. Water Sci., 18/2 (1991)  137–141. doi: 10.1007/BF01704667

A.H. Welch, M.S. Lico, J.L. Hughes, Arsenic in ground water of the Western United States, Ground Water, 26/3 (1988) 333–347. doi: 10.1111/j.1745-6584.1988.tb00397.x

Related information

British geological survey: Arsenic contamination of groundwater
National Resources Defense Council: Arsenic in drinking water
USEPA: Arsenic in drinking water
USGS: Arsenic in groundwater of the United States
Water Management Association of Ohio: Arsenic in Ohio groundwater
WHO: Arsenic in drinking water

Related EVISA Resources

Link database: Toxicity of arsenic species
Link database: Environmental arsenic pollution
Brief summary: Speciation and Toxicity

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last time modified: December 9, 2013


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