Microbes And Arsenic Contamination Of Groundwater In Maine: Is There A Link?

Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy Volume 11 January 2010 Microbes And Arsenic Contamination Of Groundwater In Maine: Is There A Link? Jean D. MacRae University of Maine Follow this and additional works at: https://scholarworks.umass.edu/soilsproceedings Recommended Citation MacRae, Jean D. (2010) "Microbes And Arsenic Contamination Of Groundwater In Maine: Is There A Link?," Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy: Vol. 11 , Article 8. Available at: https://scholarworks.umass.edu/soilsproceedings/vol11/iss1/8 This Conference Proceeding is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy by an authorized editor of ScholarWorks@UMass Amherst. For more information, please contact . Article 8 MacRae: Microbes And Arsenic Contamination Of Groundwater In Maine Chapter 7 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, ME 04469-5711. Abstract: 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 effects have been well documented in Bangladesh, where millions of people have been exposed to unacceptably high arsenic concentrations since the 1970s and serious health impacts, such as cancer, have emerged. Here in the USA, there are several problem areas, among them, parts of Maine. In 2001, an isolate named NP4, later identified by 16S rRNA sequencing as a member of the genus Sulfurospirillum, 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 presence of NP4 in groundwater, and its ability to reduce arsenate as well as a variety of 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 drinking water standard of 10 ppb. In the Northport area, NP4 accounted for as much as 16% of the total suspended bacterial population. 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. Key words: Arsenic, groundwater, arsenate reduction, iron reduction, Geobacter, Sulfurospirillum Produced by The Berkeley Electronic Press, 2006 Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy, Vol. 11 [2006], Art. 8 114 1. Contaminated Soils- Heavy Metals INTRODUCTION Drinking water is probably the most important source of arsenic in humans who are not occupationally exposed (Matschullat, 2000; Smedley and Kinniburgh, 2002), and a causal link between arsenic exposure in drinking water and cancer has been made (USEPA, 1998). Surface and groundwater may be contaminated with arsenic through human activities such as mining, wood preservation and agricultural use of arsenic compounds among others (Smith et al., 1998; Smedley and Kinniburgh, 2002). Naturally high arsenic levels also occur in waters affected by geothermal activity and in groundwater where aquifer materials contain arsenic (Smedley and Kinniburgh, 2002). Notably, in China, Taiwan, Bangladesh, and India, large populations have been exposed to high arsenic concentrations in drinking water, which has resulted in mass chronic arsenic poisoning with devastating health consequences (e.g. USEPA, 1998; Mukhopadhyay et al., 2002). Many other countries, including the United States, are also affected by high arsenic concentrations. Parts of eastern New England, including regions in Maine, have groundwater with elevated levels of arsenic. The USGS has conducted two major surveys of the area and found that high groundwater arsenic correlates with calcareous metasedimentary bedrock (Ayotte et al., 1999; Ayotte et al., 2003). In Northport, Maine, the arsenic concentration in groundwater from some wells exceeds 1000 µg l-1. Since the bedrock at the site is enriched with arsenic and local surface water is not contaminated, the source of arsenic is thought to be natural (Lipfert et al, 2005). At publicly owned treatment facilities in the United States, the arsenic concentration must be monitored and maintained below the maximum contaminant level (MCL) of 10 µg l-1. Arsenic can be removed from drinking water by a variety of means, including adsorption, ion exchange and reverse osmosis (USEPA, 2000). Water treatment can therefore reduce arsenic to acceptable levels if an uncontaminated source is not available. Where water is self-supplied, however, there is no testing or treatment requirements, and users may be unaware that they are consuming dangerously high levels of arsenic. In Maine, nearly half of the population relies on private wells for drinking water, and up to 13% of these wells contain arsenic above the 10 µg l-1 MCL (Loiselle, et al. 2002). A better understanding of arsenic cycling in the subsurface is needed to develop management tools and direct resources to education and outreach activities in areas that are likely to be affected by high arsenic concentrations. Microorganisms can potentially affect arsenic speciation and mobility in a number of ways. They may act directly on an arsenic species, either oxidizing As(III) or reducing As(V). As(III) oxidation by chemolithotrophs https://scholarworks.umass.edu/soilsproceedings/vol11/iss1/8 MacRae: Microbes And Arsenic Contamination Of Groundwater In Maine MICROBES AND ARSENIC CONTAMINATION OF... 115 has been reported in surface water fed by geothermal sources (e.g. Wilkie and Hering 1998, Langner et al. 2001). As(V) reduction can be mediated by detoxification systems like the ars operon (Rosen 2002), or by arsenaterespiring microorganisms. Arsenate respiring bacteria have been isolated from an array of environments (see Oremland and Stolz, 2005). Since the form of arsenic affects its toxicity and mobility in the environment, these microbial activities could affect both the environmental concentration and effects of arsenic. Microorganisms may also affect arsenic indirec (...truncated)