Progress 03/01/03 to 02/28/09
Outputs
OUTPUTS: Since 2002 when this project was initiated, we obtained over $175,000 in grants and contracts from U.S. Environmental Protection Agency (EPA), USGS, and the Nebraska Health and Human Services and System (NHSS). Our primary goal was to understand the behavior of arsenic and uranium in public water supply wells across Nebraska. We worked with nearly 40 public water systems plus personnel from NHHSS and consultants for at least five towns in an effort to evaluate and assess options for mitigating arsenic (As) and uranium (U) concentrations that exceed the maximum contaminant levels (MCL) for these metals. Our work included: field sampling of public water supplies using a variety of methods, designing experiments to assess the variability of As and U over varying intervals that ranged from minutes to years, extracting As and U from mineral accumulations in the well and on the well screen using various leaching techniques, identifying and characterizing microbiological organisms, extracting DNA from organisms, characterizing mineral accumulations using x-ray diffraction and scanning electron microscopy, developing surveys to learn about the attitudes about people related to public water supplies, evaluating vertical variations in As and U in various aquifer systems, maintaining data bases for all project water samples, initiating a website to access project data, analyzing data, writing reports for state and federal agencies, consulting with municipal water supply managers and/or consultants, mentoring graduate students, supervising field and laboratory technicians, and writing proposals to obtain support for ongoing water investigations. Information was disseminated using a variety of mechanisms. They included: over 30 oral and poster presentations to local and national audiences that included the governor's state water committee and various advisory committees to NHHSS; annual and final reports to state and federal agencies, a journal article, and a four chapter Ph.D. dissertation which should result in at least three journal articles. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our work documented that the behavior of arsenic and uranium in public water supplies can be quite variable and dynamic. Our data support the conclusion that the installation and operation of public water supply wells in a groundwater system substantially influences the biogeochemical environment, which, in turn, influences the behavior of arsenic and uranium. We have observed the relatively rapid accumulation of red to black, fibrous materials (aka, slime) on casing walls and well screens. It is likely that these types of materials are accumulating in the adjacent gravel pack and aquifer material. The long-term accumulation of this material leads to the biofouling of wells and pumps. These fibrous materials are likely forms of iron oxides and/or hydroxides that accumulate and release As and U depending on the conditions. Our sequential leaching and extraction experiments clearly document the accumulation of both arsenic and uranium in materials in and around the well. These accumulations provide an in-situ source for these metals, which can be remobilized during changes related to pumping. Evidence of abundant iron-reducing microorganisms was observed during culturing and phylogenetic analyses, which may indicate stronger links to iron metabolism in the sampled PWS well environments. Phylogenetic techniques indicated unique microbial communities at each well sampled, with several species of iron-reducing bacteria such as Geobacter metallireducens and iron oxidizing bacteria such as Leptothix sp. which were common in multiple well systems. Our observations strongly suggest that the physical, chemical and microbial environment in and around the well are continually modified during the drilling of the well, construction of the well, and pumping of the groundwater into the well. These modifications, some of which are reversible and some of which are not, continue inside and outside the well from the time of construction and throughout its operation. There is a strong likelihood that these modifications. Our work funded by EPA, the United States Geological Survey, and NHHSS strongly suggests that a variety of processes influence the concentration of uranium and arsenic in public water supplies. These processes and the combined effects and synergistic interactions within and adjacent to a drinking water production well before, during and after well installation need to be understood to mitigate the impact of As and U on public water supplies. Microbial species can strongly influence the accumulation of "slime" and the behavior of these metals; therefore, if we understand their behavior in these systems, we may be able to remediate drinking water supplies as well as mitigate the biofouling of wells.
Publications
- Dissertation: McVey, K.J. 2009 Biogeochemical behavior of dissolved arsenic and uranium concentrations in public water supply wells. University of Nebraska-Lincoln.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Activities: During the last year we have worked with Nebraska Department of Health and Human Services to assess the extent to which the mineralogy of well encrustations and microbial presence in water and biofilms affect the concentrations of uranium and arsenic in individual public water supply wells. Our work has focused on eight communities that have problems with uranium and/or arsenic. The first goal was to better understand the mineral phases and other materials present within biofilm/encrustation samples. The six communities chosen for mineralogical analyses are: Bellwood, Clarks, Haigler, Stromsburg, Wauneta, and York, Nebraska. At all the communities, the following activities were conducted: 1. Collection of well sediments/encrusted materials prior to well cleaning; 2. Mineralogical analyses using electron dispersive and wavelength dispersive spectroscopy of samples to determine association of arsenic and uranium with metals; and 3. Imagery of samples using scanning electron microscopy to document visible mineral phases and organics present in biofilm samples. The second goal was to better understand the microbiological factors affecting arsenic and uranium concentration and mobilization in water supply wells. The six communities chosen for microbial analyses are: Bellwood, Cambridge, Clarks, McCook, Stromsburg, and York, Nebraska. At all the communities, the following activities were conducted: 1. Perform thirty minute sampling for field parameters, arsenic, uranium, cations, anions, total organic carbon; 2. Collect water samples for microbial analyses and inoculate selective enrichment cultures targeting redox bacteria with well samples; 3. Growth and examination of enrichment cultures for microbial growth; 4. Extraction of DNA from well water samples and use of phylogenetic techniques to verify presence of redox bacteria known to affect arsenic and uranium; and 5. Document presence of bacteria in each well sample and determine what affects they may have on metals, arsenic, and uranium within a public water supply system. Products: We improved our operational understanding of the microbiology affecting geochemistry in wells and the extent to which arsenic and uranium are associated with various mineralogical phases in the sediments and materials collected from wells. We prepared four manuscripts for publication. We created interactive educational opportunities related to water quality field testing for high school students involved with Upward Bound. Biological investigations of water and biofilm samples were performed by Kevin McVey, Barbara Clement, and Lynne Klawer at Doane College Department of Biology. Mineralogical investigations of well materials were performed by Mike Spilde and Kevin McVey at the University of New Mexico Institute of Meteorics. These results were presented as a powepoint presentation at the 2007 Geological Society of America Annual Meeting and Exposition in Denver Colorado and the 2008 Nebraska Academy of Sciences 108th Annual Meeting in Lincoln, Nebraska. PARTICIPANTS: David C. Gosselin, PhD, Principal Investigator/Project Director. The following individuals from the University of Nebraska at Lincoln, School of Natural Resources were on staff over the project life: Lynne M. Klawer, Project Manager; and Kevin J. McVey, Graduate student. Partner organizations included: Doane College Department of Biology, and the University of New Mexico Institute of Meteorics. Collaborators were: Barbara J. Clement, Doane College, Crete NE; Mike N. Spilde, University of New Mexico, Albuquerque, NM; Jens Walter, University of Nebraska, Food Science and Technology, Matt Marxson and Jeremy Poell, University of Nebraska at Lincoln School of Natural Resources. TARGET AUDIENCES: Target audiences include communities involved with the project (Bellwood, Cambridge, Clarks, Haigler, McCook, Stromsburg, Wauneta, and York), as well as Nebraska and United States public water supplies with arsenic and uranium concentrations above the federal mandated MCLs. Efforts to deliver research experiments as an interactive laboratory experience for high school students were presented to Upward Bound at the University of Nebraska-Lincoln. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The U.S. Environmental Protection Agency limits the amount of arsenic and uranium in drinking water. The maximum contaminant levels (MCL) for arsenic and uranium are 10 and 30 parts per billion, respectively. Change of Action: Our work has provided data and information on mineralogy and microbiology of water and biofilm encrustations affecting dissolved contaminants from six community water supplies. Our work has provided a framework for water quality sampling strategies which may reduce the accumulation rates of biofilm encrustations and trace metal concentration in water supply wells. Change in Knowledge: Our reports have provided information and data to state and local officials including water supply operators that have improved their knowledge and understanding. Our work demonstrated examples of diverse microbial communities present within and surrounding both water supply and monitoring wells. These communities are present within biofilms as well as within the water itself, and influence the redox state of arsenic, uranium, and other metals. Accumulation and concentration of organics and metals in biofilms can influence the concentrations of the uranium and arsenic. Examination of these biofilms indicated various iron and iron sulfide minerals were concentrated with organic materials, which sorb mobile arsenic and uranium. These encrusted materials accumulate within and around a well as a result of the pumping environment. Changes in pumping protocols may change the chemistry of the pumping environment, and reduce the rates at which these biofilms accumulate.
Publications
- McVey, K.J., Gosselin, D.C., Klawer, L.M., and Clement, B.J. 2008. Microbial mediation of uranium and arsenic concentrations in Nebraska public water supply wells. Nebraska Academy of Sciences 108th Annual Meeting.
- McVey, K.J., Gosselin, D.C., Clement, B.J., Klawer, L.M. 2007. High uranium and arsenic concentration affects microbial diversity in Nebraska public water supply wells. 2007 Earth Sciences for Society, Annual Meeting and Exposition, Geological Society of America Abstracts, 39(6).
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Activities: During the last year we have worked with Nebraska Department of Health and Human surfaces to continue assessing the extent to which well rehabilitation, hydrogeologic avoidance and well management can be used to reduce the concentration of uranium and arsenic in individual public water supply wells. Our work has focused on six communities that have problems with uranium and/or arsenic. The six communities are: Bellwood, Clarks, Haigler, Stromsburg, Wauneta, and York, Nebraska. At all the communities except York, the following activities were conducted: 1. Perform four hour sampling for field parameters, arsenic, uranium, cations, anions, total organic carbon; 2. Characterized the PWS well using down-hole cameras and geophysical logging; 3. Vertically profiled the well using flow and/or high flow water quality sampling utilizing packers above and below desired screened interval; and 4. Recommended and implemented potential mitigation strategies followed by water
quality monitoring. The goal at York was to improve our understanding of the behavior of uranium under the influence of pumping rate and time, and make recommendations for mitigation of high uranium concentrations. Two activities were completed: 1. Evaluated the influence of pumping rates on uranium concentrations; and 2. Characterized well bottom materials obtained during cleaning/bailing of the well using sequential leaching of arsenic and uranium from the materials. Sequential leaching experiments for arsenic and uranium were conducted on sediment collected from the bottom of wells during bailing and from scrapings of the well column from Bellwood, Haigler, Stromsburg, Wauneta, and York. Products: We improved our operational understanding of the factors that influence the behavior of arsenic and uranium in public water supply wells and the extent to which arsenic and uranium are associated with various geochemical phases in the sediments and materials collected from wells. We
collaborated with state and local agencies. We created interactive educational opportunities related to water quality field testing for high school students involved with Upward Bound; and the University of Nebraska Lincoln Center for Science, Mathematics and Computer Education, and Nebraska EPSCoR Women in Science Conference. Sequential leaching experiments of arsenic and uranium were performed by an undergraduate student as part of the University of Nebraska-Lincoln's Undergraduate Creative and Research Experience (UCARE). These results were presented as a poster at the UNL Undergraduate Research Conference. Additional presentations were given at the University of Nebraska at Lincoln School of Natural Resources Colloquium, the Nebraska Health and Human Services (NHHS) Informational Workshop, and the 2007 Geological Society of America Annual Meeting and Exposition in Denver Colorado.
PARTICIPANTS: David C. Gosselin, PhD, Principal Investigator/Project Director. Dr. Gosselin received $63K in project support from the Nebraska Health and Human Services. The following individuals from the University of Nebraska at Lincoln, School of Natural Resources were on staff over the project life: Lynne M. Klawer, Project Manager; Kevin J. McVey, Graduate student; and Mark D. Christenson, Undergraduate student. Partner organizations included: Nebraska Health and Human Services; and the University of Nebraska-Lincoln Water Center. Collaborators were: cities of Bellwood, Clarks, Haigler, Stromsburg, Wauneta and York; Barbara J. Clement, Doane College, Crete NE; Matt Marxson and Jeremy Poell, University of Nebraska at Lincoln School of Natural Resources; Tagge Engineering, Holdrege NE; Miller and Associates, McCook NE; Snyder Engineering, Columbus NE; Sargent Drilling, Broken Bow NE; and Layne-Western, Valley NE.
TARGET AUDIENCES: Target audiences include communities involved with the project (Bellwood, Clarks, Haigler, Stromsburg, Wauneta, and York), as well as Nebraska and United States public water supplies with arsenic and uranium concentrations above the federal mandated MCLs. Efforts to deliver research experiments as an interactive laboratory experience for high school students were presented to Upward Bound; and the University of Nebraska Lincoln Center for Science, Mathematics and Computer Education, and Nebraska EPSCoR Women in Science Conference. Sequential leaching experiments of arsenic and uranium were performed by an undergraduate student as part of the University of Nebraska-Lincoln UCARE Undergraduate Research Experience. The results were presented as a poster at the University of Nebraska-Lincoln Undergraduate Research Conference. Additionally, presentations were given at the University of Nebraska at Lincoln School of Natural Resources Colloquium, the Nebraska Health and
Human Services (NHHS) Informational Workshop, and the 2007 Geological Society of America Annual Meeting and Exposition in Denver Colorado.
Impacts
The U.S. Environmental Protection Agency limits the amount of arsenic and uranium in drinking water. The maximum contaminant levels (MCL) for arsenic and uranium are 10 and 30 parts per billion, respectively. Change of Action: Our work has provided data and information has been used by the Nebraska Department of Health and Human Services to revise sampling protocol. The six communities involved this year are employing new sampling strategies to determine the extent to which new approaches can be used to manage the water quality in their wells. Our work has provided a framework for water quality sampling strategies that is being used by a local consulting company in a study of water supply options for a small community in Wyoming. Our work may also provide the foundation for a new approach for the installation of water supply wells. Change in Knowledge: Our reports have provided information and data to state and local officials including water supply operators and city
engineers that have improved their knowledge and understanding. The water supply operators have also been exposed to better sampling methods and approached for their water supply evaluation. Our work indicates that well design and capacity can influence the concentration of the uranium. In addition, the behavior of uranium can be influenced by the management of pumping and reducing the stress on the aquifer system. Uranium concentrations can be stratified whereby distinct zones of higher and lower concentrations of uranium can be found. This stratification provides the opportunity for zones with high uranium concentrations to be packed off, which would lead to lower uranium concentrations. In contrast to uranium, the results for arsenic are not as conclusive. Limited data suggests that in some cases arsenic concentrations can be lowered below the MCL using well design modifications. Our results also indicate that there is a potentially significant amount of arsenic and/or uranium
available from the materials and sediments accumulating in and around the well.
Publications
- McVey, K.J., Gosselin, D.C., Clement, B.J., Klawer, L.M. 2007. High uranium and arsenic concentration affects microbial diversity in Nebraska public water supply wells. 2007 Earth Sciences for Society, Annual Meeting and Exposition, Geological Society of America Abstracts, 39(6).
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Progress 10/01/05 to 09/30/06
Outputs
Our work with a third EPA Grant ($56) awarded in October 2004 ended in September 2006. The goal of this third grant was to provide technical assistance to PWS to help lesson the economic impact of the new maximum contaminant level (MCL) of 10 ug/L. We are currently reviewing data for a report due in December 2006. In April 2004 the Arsenic Information System partnered with the University of Nebraska Public Policy Center in a Community Water and Development Project to address arsenic in PWS and economic development within small rural communities. Stromsburg (population 1,232) and Shelby (population 690) identified three primary objectives they would address over the next coming months: 1. Identify options to comply with the new MCL; 2. Consider the costs and benefits of joining in a regional system; and 3. Increase community members knowledge of drinking water standards, and costs and benefits of compliance. This project was completed in May 2005. Several important
outcomes came from this collaboration: 1. Created new partnerships with neighboring community Osceola. 2. Discussion on possible regional solutions for their water economic challenges. The collaborative project that began in June 2005 with the Nebraska Health and Human Services System (NHHSS) and the Nebraska Water Quality Information System (NWQIS) was renewed through another grant in May 2006. The intent of the project was to determine if geologic rehabilitation of a PWS well in Benkelman, Bridgeport, and York was feasible was also extended to several other communities: Bellwood, Clarks, Haigler, Stromsburg and Wauneta. Arsenic (Haigler, Stromsburg, Wauneta) and uranium (Bellwood, Clarks, York) were collected to characterize their concentrations over a four hour period. In addition other water quality tests were performed including: field parameters (pH, temperature, specific conductance, dissolved oxygen, alkalinity), major anions (chloride, sulfate, nitrate, phosphate) and cations
(Ca, Mg, Na, K) plus manganese, iron, total organic carbon, and silica. The pumps were then removed and the wells were characterized using a down-hole camera, geophysical logging and water quality profiling through low-flow sampling. Project (NHHSS) testing in 2005 and again in 2006 indicated that most of the variation in arsenic and uranium concentrations occurred generally within the first 30 to 60 minutes of the pumping cycle therefore sampling should be performed at the 30 minute interval or for a more realistic assessment a water sample would be taken at the midpoint and at the end of the average time that the pump typically runs. Interval sampling was performed with packers to isolate flows in the casing and gravel pack. The results indicated a possible reduced arsenic concentration therefore in Haigler and Wauneta packers were installed and pumping rates reduced to approximately 100 gpm. Clarks uranium interval sampling results were below the 30 ug/L MCL at several depths. A
packer is scheduled to be installed at Clarks to determine if that will have an impact on meeting the MCL.
Impacts
Web site continues to go through development to include an image mapper of Nebraska test holes, monitoring wells and PWS wells with a link to water quality data from AIS, USGS and the National Uranium Resource Evaluation databases. Additional work with NHHSS has produced three communities with a possibility of decreasing their arsenic and uranium through lower pumping rates and the use of packers to isolate parts of the well casing and gravel pack. Other communities have cleaned the casing and bore hole, and are developing well field best management practices through monitoring their water quality.
Publications
- Gosselin, D.C., L.M. Klawer, R.M. Joeckel, F.E. Harvey, A.R. Reade, and K. McVey. 2006. Arsenic in groundwater and rural public water supplies in Nebraska, U.S.A. Great Plains Research 16:137-148.
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Progress 10/01/04 to 09/30/05
Outputs
In October 2002 we were awarded two EPA Grants ($75K) and one $15K grant from the United States Geological Survey (USGS) 104b Program to document the spatial and temporal variations in arsenic (As) concentrations in Nebraska public water supplies as well as the chemical form in which the As occurs in the groundwater. Our work has continued and expanded with a third EPA Grant ($56) awarded in October 2004 to include one well within 13 public water supplies (PWS) with a total of 23 Nebraska communities impacted. The goal of this third grant is to provide technical assistance to PWS to help lesson the economic impact of the new maximum contaminant level (MCL) of 10 ug/L beginning in January 2006. Participating public water supplies include: Cairo, Cedar Bluffs, Colon, Culbertson, Elgin, Humphrey, Lyman, Morrill, Osceola, Palisade, Shelby, Stratton, and Wauneta. In April 2004 the Arsenic Information System partnered with the University of Nebraska Public Policy Center in
a Community Water and Development Project to address arsenic in PWS and economic development within small rural communities. Stromsburg (population 1,232) and Shelby (population 690) joined this project along with numerous other university educators/researchers and government and private agencies. The two communities identified three primary objectives they would address over the next coming months: 1. Identify options to comply with the new MCL; 2. Consider the costs and benefits of joining in a regional system; and 3. Increase community members knowledge of drinking water standards, and costs and benefits of compliance. Nebraska NPR? A collaborative project between the Nebraska Health and Human Services System (NHHSS) and the Arsenic Information System (AIS) began in June 2005 to address not only high arsenic within PWS but also uranium. The project's main intent was to determine if geologic rehabilitation of a PWS well in Benkelman, Bridgeport, and York was feasible. Arsenic,
uranium, selenium, and nitrate were collected in all three wells to characterize their concentrations over a four hour period. With one exception, a monitoring well was drilled 25 feet away from the PWS well in Benkelman where equivalent water quality tests and sampling protocols were used. In addition other water quality tests were performed including: field parameters ( pH, temperature, specific conductance, dissolved oxygen, alkalinity), major anions (chloride, sulfate, nitrate, phosphate) and cations (Ca, Mg, Na, K) plus manganese, iron, total organic carbon, and silica. The pumps were then removed and the wells were characterized using a down-hole camera, geophysical logging and water quality profiling through low-flow sampling. The results of the four-hour sampling experiments for all three wells indicate that most of the variation in arsenic and uranium concentrations occurred generally within the first 30 to 60 minutes of the pumping cycle therefore sampling should be
performed at the 30 minute interval or for a more realistic assessment a water sample would be taken at the midpoint and at the end of the average time that the pump typically runs.
Impacts
Web site development will expand to include an image mapper of Nebraska test holes, monitoring wells and PWS wells with a link to water quality data from AIS, USGS and the National Uranium Resource Evaluation databases. Due to our previous EPA and USGS grant work, the NHHSS concluded that communities facing an uncertain future in finding good quality water should assess each well individually to determine if the well can be rehabilitated. Potential future work for Benkelman and York will be to rehabilitate their wells through bore hole cleaning, well relining (Benkelman), new well screen placement, and developing well field best management practices through monitoring water quality and pumping schematics over a three to six month period.
Publications
- Gosselin, D.C., L.M. Klawer, R.M. Joeckel, F.E. Harvey, A.R. Noe, and K.J Warren. 2004. (Submitted). Arsenic in Rural Nebraska Public Water Supplies, Nebraska, U.S.A. Awwa Journal.
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Progress 10/01/03 to 09/30/04
Outputs
Since October 2002, we have been awarded three EPA Grants ($131K) and one $15K grant from the United States Geological Survey (USGS) 104b Program to document the spatial and temporal variations in arsenic (As) concentrations in Nebraska public water supplies as well as the chemical form in which the As occurs in the groundwater. Our work plan has been guided by an Arsenic Task Force that consists of representatives from 10 public water supplies, 3 representatives from the Nebraska Department of Health and Human Services System; and 1 representative each from the Nebraska Department of Environmental Quality, Nebraska Association of Resource Districts, and the League of Municipalities. Two wells from ten public water supplies have been monitored to assess the spatial and temporal distribution of As plus field parameters, pH, dissolved oxygen, specific conductance, temperature, and alkalinity. Participating public water supplies include: Benkelman, Cambridge, McCook,
Stromsburg, Shelton, Elwood, Lodgepole, Broadwater, Oshkosh, and Anselmo. The data from 20 PWS wells in Nebraska indicate that As concentrations were essentially constant over the one-year study. The general absence of temporal variability in As concentrations suggests that the collection of one sample per year from most of these wells in this study will adequately characterize the As concentration to which the population drinking this water will be exposed. The results of this study were actually unexpected because previously conducted studies in other parts of the U.S.A. had documented the occurrence of significant variability in As concentrations in high-capacity wells over similar time scales. The fact that some wells show significant variability while others do not, precludes the use of one sample per year, therefore it is recommended that a minimum of four quarterly samples be used to characterize the potential annual variations in As concentrations. The 24-hour sampling
experiments indicate that variations in As concentrations can occur early in the pumping cycle. It is recommended that a well be allowed to pump for at least 30 minutes prior to sampling. If the primary purpose of the chemical monitoring of PWS is to assess the As concentration to which the drinking water public is exposed, then the sampling scheme for a given system should be designed around the typical operational history of the wells within a system. A water manager would sample the well at the midpoint and at the end of the average time that the pump typically runs to provide a more realistic assessment of the arsenic concentration to which PWS consumers are exposed. The USGS and NURE data document a complex spatial distribution of As in groundwater throughout Nebraska. The non-uniform occurrence of As reflects differences in the geology, groundwater flow systems, and associated geochemical environments throughout the state. The geologic, hydrogeological and geochemical factors
make the prediction of As concentrations very difficult. However, assessing historical quality controlled information can improve the likelihood of finding a new source of water that has lower arsenic concentrations.
Impacts
The primary contribution of this project to date is that we have improved our understanding of As behavior in Nebraska's small public water supplies (PWS). This knowledge is being used by the Nebraska Department of Health and Human Services to establish new guidelines for well sampling. Our project has also provided the foundation for a collaborative project involving Stromsburg, NE, the Arsenic Information System and the University of Nebraska Public Policy Center.
Publications
- Gosselin, D., Klawer, L. and Noe, A. 2004. Arsenic in Nebraska's groundwater public water supplies. Univ. NE-Lincoln. Cons. Sur. Div. ESN 7:1-8.
- Gosselin, D.C., Klawer, L.M., Harvey, F.E. and Warren K.J. 2004. Arsenic in Nebraska's groundwater and public water supplies. Geoscience in a Changing World 2004 Annual Meeting and Exposition, Geological Society of America Abstracts, 36(5).
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Progress 10/01/02 to 09/30/03
Outputs
Since October 2002, we have been awarded two EPA Grants ($75K) to document the spatial and temporal variations in arsenic concentrations in Nebraska public water supplies. Our work plan has been guided by an Arsenic Task Force that consists of representatives from 4 public water supplies, 3 representatives from the Nebraska Department of Health and Human Services System; and 1 representative each from the Nebraska Department of Environmental Quality, Nebraska Association of Resource Districts, and the League of Municipalities. Two wells from ten public water supplies (20 wells total) are currently monitored to assess the spatial and temporal distribution of arsenic plus field parameters, pH, dissolved oxygen, specific conductance, temperature, and alkalinity. Participating public water supplies include: Benkelmen, Cambridge, McCook, Stromsburg, Shelton, Elwood, Lodgepole, Broadwater, Oshkosh, and Anselmo. To complement the EPA awards, we also obtained $15K from the
United States Geological Survey (USGS)104b Program. This project will provide information about: (1) the chemical form in which the arsenic occurs in the groundwater; and (2) the geological distribution and occurrence of arsenic. Currently, there are two strategies for As remediation: 1) find a new source of drinking water; or 2) employ a treatment technology to remove the As from the groundwater. Both alternatives are expensive, especially for small PWS. Our data documents distinct spatial variability on regional scale that makes the prediction of arsenic concentrations very difficult. This, in turn, makes finding a new source of water at best a trial and error process. A third alternative that we are still investigating is to use well hydraulics and pumping strategies to control As concentrations in PWS wells. Our data indicates that arsenic concentrations are variable in individual wells on several different time scales. In some cases, the monthly variability is great enough to
bring the arsenic concentrations in compliance with the MCL. For two wells that we have sampled at regular intervals over 24 hours, we have found that the arsenic concentrations can change significantly over short time intervals, especially after the pump has been turned on. These results have potentially interesting implications for how water supply operators obtain their water samples. In addition, the procedures that operators use to quality assure the data being provided to them by the laboratory need to be further investigated. A fourth alternative that has potential, but has not been thoroughly investigated is the in-situ removal of arsenic within the groundwater system. This process involves the reduction of arsenic concentrations by adsorption of arsenic onto iron oxides that form by injecting water that has higher oxygen levels into the aquifer. A prototype of our Arsenic Information System website is available at http://nesen.unl.edu/arsenic_test/proto/. This site includes
project background, powerpoint presentations, and maps, photos, pictures and information for participating public water supplies.
Impacts
The primary contribution of this project to date is that we have improved our understanding of As behavior in the small public water supplies of Nebraska. This knowledge is required to reduce the economic impact of arsenic regulations on small public water supply systems and protect their users from the carcinogenic effects of arsenic.
Publications
- No publications reported this period
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