Advances in Arsenic Research: Introductory Remarks - ACS Publications

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Advances in Arsenic Research: Introductory Remarks 1

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Peggy A . O'Day , Dimitrios Vlassopoulos , Xiaoguang Meng , and Liane Benning Downloaded by 171.25.193.77 on March 31, 2016 | http://pubs.acs.org Publication Date: October 3, 2005 | doi: 10.1021/bk-2005-0915.ch001

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School of Natural Sciences, University of California, Merced, C A 95344 S.S. Papadopulos and Associates, Inc., 815 SW 2 Avenue, Suite 510, Portland, OR 97204 Center for Environmental Engineering, Department of Civil, Environmental, and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 School of Earth Sciences, The University of Leeds, Leeds LS2 9JT, United Kingdom 2

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Water supplies worldwide are impacted by concentrations of dissolved arsenic above acceptable health levels. These health concerns have prompted a reduction in the U.S. drinking water standard for arsenic (from 50 to 10 g 1 ) and focused attention on widespread areas of the Indian-subcontinent, central and southeast Asia, and South America with large populations at risk for adverse health impacts. Although estimates vary, elevated arsenic concentrations in groundwater have the potential to adversely impact on the order of 90 million people (1-3), including 13 million in the U.S. (4, 5). Arsenic in the environment is derived from both natural and anthropogenic sources, including occurrences in sediments, soils, coal, and ore deposits, and releases from mining, coal -burning, and industrial processes. Although arsenic toxicity is not as severe at low levels as that of metals such as lead, mercury, or cadmium, natural occurrences of arsenic above background concentrations are widespread and common. Thus, cumulative effects may impact large populations, particularly in countries where unmonitored groundwater is the primary source of drinking water. -1

Arsenic accumulation and migration is closely tied to its chemical speciation, which is often controlled by a complex combination of abiotic and biotic processes coupled with physical transport. Arsenic is found in the environment in multiple oxidation states, with As(III) and As(V) as the most © 2005 American Chemical Society

O'Day et al.; Advances in Arsenic Research ACS Symposium Series; American Chemical Society: Washington, DC, 2005.

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Downloaded by 171.25.193.77 on March 31, 2016 | http://pubs.acs.org Publication Date: October 3, 2005 | doi: 10.1021/bk-2005-0915.ch001

2 common inorganic forms. Arsenic can form methylated compounds, it occurs in an array of bioorganic substances, and it can be sequestered in a variety of oxide and sulfide minerals (6, 7). Mechanisms for the removal of arsenic from water in natural settings include both adsorption and precipitation, which depend on oxidation state and local geochemical conditions. It is well established that microbial activity strongly influences, and may dominantly control, arsenic oxidation and reduction in many environments. While most microorganisms have mechanisms for detoxifying arsenic, both anaerobic respiration of As(V) and aerobic respiration of As(III) have been identified (8-JO). So although a toxin for most organisms, some microorganisms can take advantage of arsenic as an energy source. The numerous subtleties of arsenic chemistry and its participation in biogeochemical cycling contribute to the challenges associated with predicting the behavior of arsenic in the environment, and with developing and implementing effective and economical treatment and remediation methods. th

This volume is the product of a symposium held at the 226 A C S National Meeting held in September, 2003, in New York (NY), and sponsored jointly by the A C S Divisions of Geochemistry and Environmental Chemistry. The intent of both the symposium and this volume was to foster a more unified understanding of arsenic occurrence, behavior, and mitigation by bringing together researchers from a diversity of areas to exchange new advances and information. A wide cross-section of research and application topics were presented by U.S. and international participants, including studies related to arsenic occurrence, cycling, natural attenuation, biological influences, treatment, and remediation. Although several books discussing arsenic in the environment have been published recently (11, 12), the multitude of ongoing research on arsenic and rapidly developing technologies for treatment and remediation warrants timely publication of new studies. This volume highlights a variety of new research directed at understanding the sources, distribution, and mobilization of arsenic in the environment. It includes recent efforts in the development of cost-effective treatment technologies and in approaches to natural attenuation and accelerated remediation methods. These topics are thematically organized into three sections in the volume, the first focusing on laboratory studies and theoretical modeling, the second on arsenic behavior and cycling in a range of field settings, and the third on studies associated with treatment and remediation technologies and methods. In addition to the presentation of research findings, the symposium in New York included a summary discussion of significant, unresolved issues associated with arsenic-related investigations, and symposium participants identified several key areas for further study. These included: (1) Reduction of arsenic in water supplies worldwide: With increasing world population and the imminent prospect of significant climatic changes, groundwater represents one of the most important stable sources of drinking



3 water. There is an immediate, critical need to supply arsenic-safe drinking water to large populations, and this need will continue to grow. The variability of arsenic concentrations in groundwater and its multifaceted chemical behavior necessitate a transfer of both basic scientific knowledge and optimized technology in order to supply the best available, cost-effective treatments for local populations. This is particularly true for developing nations that rely on groundwater for drinking and agriculture but lack resources for large-scale treatment systems. (2) Improved understanding of arsenic chemistry: Despite the wealth of recent studies, there remain considerable gaps in fundamental aspects of arsenic chemistry that impact prediction of its behavior in natural systems and optimization of treatment and remediation technologies. Thermodynamic databases lack reliable, high quality data for a number of aqueous arsenic species and solid phases, particularly as a function of temperature. Our knowledge of the rates of abiotic and biologically mediated reactions that control arsenic speciation and partitioning is extremely limited, and improvements in theoretical approaches to compilation and synthesis of system kinetics are sorely needed. Research is just beginning to elucidate factors that influence competitive effects associated with arsenic adsorption on different media. More studies using ab initio molecular calculations, particularly coupled to experimental data, would aid in improving fundamental understanding of a range of processes. Advances in these areas would feed directly into the development of optimum treatment strategies and remediation methods that would benefit, for example, from differentiating the chemical behavior of As(III) from that of As(V) or from better quantification of competitive reactions. (3) Improved understanding of arsenic behavior in complex systems, both natural and engineered: A striking feature of arsenic occurrence in numerous groundwater systems is its variability over hydrologically small spatial intervals (i.e., centimeters to meters). This is a reflection of the interplay among chemical, biological, and physical processes that occur at different rates in response to system changes. While studies of arsenic behavior at field sites are increasing, observations need to focus on identifying mechanisms and their relation to rates of abiotic or biologically influenced processes. Examples include cycling between oxidized and reduced conditions, the influence of organic carbon on arsenic cycling and speciation, arsenic uptake by adsorption versus precipitation or release by desorption versus dissolution, and the rates of biogeochemical processes compared to rates of physical transport. These efforts would be aided by closer integration of field studies and analogous measurements in the laboratory. Likewise, a better understanding of subsurface heterogeneity on small scales (centimeters to meters) and short times (minutes to days) and translation to larger spatial (meters to kilometers) and temporal (days to years) scales would improve predictive models. Similar issues pervade research aimed at improving remediation methods, such as the optimization of reactive and bioenhanced barriers, or the use of monitored natural attenuation as an alternative to removal and pump-and-treat approaches. Finally, the development of


4 effective and economical treatment methods would benefit from continued dialogue between basic science and technological application for topics such as optimization of filtration media and scaling from bench and pilot studies to fullscale field or plant implementation.

Acknowledgment We thank Bob Hauserman and Dara Moore in acquisitions and Margaret Brown in editing/production in the A C S Books Department for the opportunity to publish this volume. The 2003 Symposium at 226 A C S National Meeting was supported by funding from the Petroleum Research Fund, the Geochemical Society, S. S. Papadopulos & Associates, Stevens Institute of Technology, and the and the A C S Division of Geochemistry, Inc.


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Kinniburgh, D. G . ; Smedley, P. L . ; Davies, J.; Milne, C. J.; Gaus, I.; Trafford, J.M.;Burden, S.; Ihtishamul Huq, S.M.;Ahmad, N.; Ahmed, K . M . The scale and causes of the groundwater arsenic problem in Bangladesh. In Arsenic in Goundwater; Welch, A . H . ; Stollenwerk, K . G., Eds.; Kluwer Academic Publishers: Boston, 2003; pp 212-257. Smedley, P. L . Arsenic in groundwater -- south and east Asia. In Arsenic in Goundwater; Welch, A . H . ; Stollenwerk, K . G., Eds.; Kluwer Academic Publishers: Boston, 2003; pp 179-209. Smedley, P. L . ; Kinniburgh, D. G. A review of the source, behaviour and distribution of arsenic in natural waters. Applied Geochemistry 2002, 17, 5 17-568. Welch, A . H . ; Westjohn, D. B . ; Helsel, D. R.; Wanty, R. B . Arsenic in the groundwater of the United States: Occurrence and geochemistry. Ground Water 2000, 38, 589-604. Ryker, S. J. Arsenic in Ground Water Used for Drinking Water in the United States. In Arsenic in Goundwater; Welch, A . H.; Stollenwerk, K . G., Eds.; Kluwer Academic Publishers: Boston, 2003; pp 165-178. Cullen, W. R.; Reimer, K . J. Arsenic speciation in the environment. Chemical Reviews 1989, 89, 713-764. Francesconi, K . A.; Kuehnelt, D. Arsenic compounds in the environment. In Environmental Chemistry of Arsenic; Frankenberger, W. T., Jr., Ed.; Marcel Dekker: New York, 2002; pp 51-94. Oremland, R. S.; Hoeft, S. E.; Santini, J. A . ; Bano, N.; Hollibaugh, R. A . ; Hollibaugh, J. T. Anaerobic oxidation of arsenite in Mono Lake water and by facultative, arsenite-oxidizing chemoautotroph, strain M L H E - 1 . Applied and Environmental Microbiology 2002, 68, 4795-4802.


5 Oremland, R. S.; Stolz, J. F. The ecology of arsenic. Science 2003, 300, 939-944. 10. Stolz, J. F.; Oremland, R. S. Bacterial respiration of arsenic and selenium. Fems Microbiology Reviews 1999, 23, 615-627. 11. Arsenic in Groundwater; Welch, A . H.; Stollenwerk, K . G., Eds.; Kluwer Academic Publishers: Boston, 2003; p 475. 12. Environmental Chemistry of Arsenic; Frankenberger, W. T., Jr., Ed.; Marcel Dekker: New York, 2002; p 391.


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Advances in Arsenic Research: Introductory Remarks - ACS Publications

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