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Adapted with permission from: Böhlke, J.K.; Hatzinger, P.B.; Sturchio, N.C.; Gu, B.; Abbene, I.; Mroczkowski, S.J. 2009. Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York. Environmental Science & Technology. 43: 5619-5625. Copyright 2009 American Chemical Society.
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Contacts
Dr. JK Böhlke
United States Geological Survey
(703) 648-6325
Dr. Paul Hatzinger
Shaw Environmental, Inc.
(609) 895-5356
Perchlorate (ClO4-) has been detected in groundwater at a number of different locations on Long Island, NY, and various sources may contribute to this contamination (Pokorny, 2003; Abbene, 2006; Munster, 2008; Bohlke et al. 2009). Possible sources, among others, include fireworks production and use, agricultural fertilizer application (historical and current), road flares, military facilities including missile launch sites, disinfection with bleach, and use of perchloric acid in manufacturing. Conventional methods for detection of perchlorate in groundwater include ion chromatography with conductivity detection (USEPA Method 314) and more recent methods using conventional mass spectrometry such as USEPA Method 331.0 (ion chromatography with electrospray ionization/mass spectrometry). These methods provide accurate concentration data, but do not yield relevant information on perchlorate sources (see USEPA 2009 for a summary of analytical methods).
CSIA was used to quantify ratios of the stable isotopesForms of an element that do not undergo radioactive decay at a measureable rate. of chlorine (37Cl/35Cl) and oxygen (18O/16O and 17O/16O) in ClO4- using isotopeTwo atoms with the same number of protons but a different number of neutrons.-ratio mass-spectrometry (IRMS; Böhlke et al. 2005; Sturchio et al. 2006, 2011a; Böhlke et al. 2009). This technique can be used to distinguish natural ClO4- (derived from past application of natural fertilizers or from atmospheric formation) from synthetic ClO4- sources and to evaluate the extent of ClO4- biodegradationA process by which microorganisms transform or alter (through metabolic or enzymatic action) the structure of chemicals introduced into the environment (USEPA 2011). in the environment.
The objective of this study was to determine sources of ClO4- in groundwater at multiple locations within Suffolk County on Long Island, NY. The full details of this work are presented in Böhlke et al. (2009).
Groundwater samples were collected from three distinct areas in Suffolk County with ClO4- in groundwater (Figure A.1-1). However, historical land use and potential sources of ClO4- were distinctly different.
Figure A.1-1. Location map of groundwater wells sampled for perchlorate isotopes on Long Island, NY (North Fork, Northport, and Westhampton).
Source: Adapted with permission from Böhlke, J.K.; Hatzinger, P.B.; Sturchio, N.C.; Gu, B.; Abbene, I.; Mroczkowski, S.J. 2009. Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York. Environmental Science & Technology 43: 5619-5625. Copyright 2009 American Chemical Society.
The wells are located in the following areas:
CSIA analysis of Cl and O isotopes in ClO4- was used to forensically identify the source of ClO4- in the wells from each area. Samples also were analyzed for various geochemical parameters, dissolved gases, and atmospheric environmental tracers (3H and 3He isotopes, SF6, and CFCs) to determine the likely timing of the ClO4- infiltration to the aquifers.
Perchlorate was present in all three areas, and a number of the wells had concentrations in excess of the New York State Department of Environmental Conservation guidance level of 5 micrograms per liter (μg/l), as follows:
Stable isotope analyses of Cl (δ37Cl) and O (δ18O, Δ17O) were obtained from groundwater samples in each region as well as data for supporting geochemical and groundwater dating parameters. The δ37Cl, δ18O, and Δ17O values of the ClO4- collected from the BM wells (n=2) were consistent with values typical of synthetic ClO4-, while samples from the NP production wells (n=2) and the DL series agricultural wells (n=3) were consistent with natural ClO4- from Chilean fertilizers, including the elevated values of Δ17O that have been reported for this source (Figure A.1-2; Böhlke et al. 2005; Bao and Gu, 2004). There was no indication of isotopic fractionationSome processes (for example, those which involve breaking chemical bonds) have slightly different rates for different isotopes, leading to a more rapid consumption of one isotope over the other. This characteristic is manifested in a change in the isotopic ratio of the residual compound. of ClO4- consistent with partial biodegradation in the site groundwater (Hatzinger et al. 2009). In Figure A.1-2, the data from the Long Island wells are plotted as black diamonds, the data from synthetic sources as open red circles, and those from Chilean samples as open blue squares.
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Figure A.1-2. Comparison of δ37Cl vs. δ18O (left) and Δ17O vs δ18O (right) in ClO4- from wells on Long Island with those of synthetic and Chilean source materials.
Source: Adapted with permission from Böhlke, J.K.; Hatzinger, P.B.; Sturchio, N.C.; Gu, B.; Abbene, I.; Mroczkowski, S.J. 2009. Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York. Environmental Science & Technology 43: 5619-5625. Copyright 2009 American Chemical Society.
The two BM wells, which contained unusually high concentrations of ClO4-, were near a fireworks disposal pit used by the Suffolk County Police Department. The groundwater in these wells also had anomalously high concentrations of K, Sr, and Sb, which are present in fireworks to provide various colors (Conklin, 1985). Although a number of local sources of synthetic ClO4- may be present at this site, leaching of unexploded fireworks as the cause of groundwater contamination is supported by presence of a fireworks disposal pit in the area, the extremely high ClO4- levels in each of the wells, the anomalously high concentrations of trace elements common to many fireworks, and the young ages of the groundwater (1-2 years, based on environmental tracer data).
In contrast to the BM wells, the isotopic characteristics of ClO4- from the DL and the NP production wells were consistent with those of the ClO4- found in Chilean nitrate deposits and fertilizers. Groundwater in these wells also had relatively high concentrations of NO3- and other constituents that are typical of recharge beneath fertilized agricultural land in this region, such as Ca, Mg, and SO42-. No other ClO4- sources, including the US indigenous sources, are currently known to have the distinctive combination of low δ37Cl, low d18O, and high Δ17O that characterize the Chilean ClO4-. Thus, the data indicate that the ClO4- in these wells was derived from the historical use of Chilean nitrate fertilizers on Long Island. Age dating of groundwater supports this hypothesis, as much of this water was determined to have recharged decades ago.
The ClO4- stable isotope results (δ37Cl, δ18O, and Δ17O) and key supporting chemical and environmental tracer data collected from several wells on Long Island provide strong evidence for the presence of ClO4- derived from Chilean nitrate fertilizer as well as that from a synthetic source, presumably fireworks disposal. The groundwater at all locations was aerobic and un-denitrified, and ClO4- apparently was not affected isotopically by biodegradation or exchange processes in the subsurface. Stable isotope analysis of ClO4- indicates that imported Chilean nitrate fertilizer use on Long Island has led to contamination of some aquifer units, even though this fertilizer may have been applied in relatively small quantities as long as 40 or more years ago. In the absence of CSIA analysis, and key supporting parameters, perchlorate in groundwater could not be attributed to a particular source, making this technique invaluable for forensic investigations. Further information on this study can be found in Böhlke et al. (2009) and Hatzinger et al. (2011).
The CSIA technique described in this case study provided critical information concerning the sources of ClO4- in several monitoring and municipal wells on Long Island, NY. The isotope and supporting data clearly showed that multiple sources, including fireworks and imported natural Chilean fertilizers, contribute to ClO4- contamination in this region. A recent CSIA study from a site in southern California showed a similar result. In this case, two distinct ClO4- plumes were defined, one derived from a synthetic source and the other from past application of natural Chilean fertilizer (Sturchio et al. 2012). In the absence of the CSIA technique used at each site, source discrimination would be difficult, if not impossible.
The CSIA technique described in this case study is currently available on a commercial basis from the Environmental Isotope Geochemistry Laboratory at the University of Illinois at Chicago. The current cost for the analysis can be obtained from this facility.
Compared to many other environmental sampling and analysis techniques, CSIA is relatively new and ClO4- stable isotope analysis has only been performed during the past several years. There are currently no USEPA-certified methods for CSIA of organic or inorganic compounds of any type. However, a recent document from the USEPA acknowledges the utility of CSIA for forensics and monitored natural attenuation and provides guidance concerning method application and relevant QA/QC during sampling and analysis (USEPA 2008a). While the USEPA document is primarily focused on (1) carbon isotope analysis in organic compounds and (2) using CSIA to document biodegradation, some of the general principals also apply to ClO4- isotope analysis. In addition, a new guidance document specifically focused on perchlorate isotope analysis is now available (Hatzinger et al. 2011).
CSIA for ClO4- is a relatively new technique, and methodological development and improvement is ongoing. Some of the current challenges include: (1) the quantity of ClO4- required for analysis (~5 μg is recommended during field collection) which requires sample collection with specialized ion exchange columns (Bohlke et al. 2009; Sturchio et al. 2011; Hatzinger et al. 2011); (2) the requirement for extensive purification of ClO4- from other anions and organic compounds prior to analysis; (3) the few laboratories that perform the analysis; and (4) an inability to distinguish different sources of synthetic ClO4- from each other due the general similarity between δ37Cl and Δ17O among synthetic forms, (although some consistent variability in δ18O has been reported; Sturchio et al. 2006).
Abbene, I. 2006. Identifying sources of perchlorate in groundwater, Suffolk County, New York project plans and some preliminary results. Abstract from the Thirteenth Conference on Geology of Long Island and Metropolitan New York, State University of New York at Stony Brook, April 22, 2006. http:/pbisotopes.ess.sunysb.edu/lig/Conferences/abstracts06/abbene.pdf.
Bao H. and B. Gu. 2004. "Natural perchlorate has a unique isotopic signature." Environmental Science & Technology 38: 5073-5077.
Böhlke, J.K., P.B. Hatzinger, N.C. Sturchio, B. Gu, I. Abbene, S.J. Mroczkowski. 2009. "Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York." Environmental Science & Technology 43: 5619-5625.
Böhlke, J.K. N.C. Sturchio, B. Gu, J. Horita, G.M. Brown, W.A. Jackson, J.R. Batista, P.B. Hatzinger. 2005. "Perchlorate isotope forensics" Analytical Chemistry 77: 7838 -7842.
Conklin, J.A. 1985. Chemistry of Pyrotechnics. Basic Principles and Theory. New York:Marcel Dekker.
Hatzinger, P.B., J.K. Böhlke, N.C. Sturchio, B. Gu, L.J. Heraty, R.C. Borden. 2009. "Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer." Environmental Chemistry 6: 44-52.
Hatzinger, P.B., J.K. Böhlke, N.C. Sturchio, and B. Gu. 2011. Guidance Document: Validation of Chlorine and Oxygen Isotope Ratio Analysis to Differentiate Perchlorate Sources and to Document Perchlorate Biodegradation. ER-200509. Environmental Security Technology Certification Program, Arlington, VA. 107 pp. www.SERDP.org.
Munster J., G.N. Hanson, W.A. Jackson, and S. Rajagopalan. 2008. "The fallout from fireworks: perchlorate in total deposition." Water, Air, and Soil Pollution. 198: 149-153.
Pokorny, J.M. The Challenge of perchlorate. 2003. Long Island Ground Water Symposium, June 6, 2003. Brookhaven National Laboratory: Upton, NY; pp. 13-15.
Sturchio, N.C., J.K. Böhlke, B. Gu, J. Horita, G.M. Brown, A. Beloso, Jr., L.J. Patterson, P.B. Hatzinger, W.A. Jackson, J.R. Batista. 2006. "Stable isotopic composition of chlorine and oxygen in synthetic and natural perchlorate." In Perchlorate Environmental Occurrences, Interactions, and Treatment. B. Gu and J.D. Coates, (Eds). New York:Springer, pp. 93-109.
Sturchio, N.C., Böhlke, J.K.; Gu, B.; Hatzinger, P.B.; Jackson, W.A. 2011. "Isotopic tracing of perchlorate in the environment." In Handbook of Environmental Isotope Geochemistry, M. Baskaran (Ed), Springer-Verlag, New York, pp. 437-452.
Sturchio N.C., J.R. Hoaglund III, R.J. Marroquin, A.D. Beloso, Jr., L.J. Heraty, S.E. Bortz, and T.L. Patterson. 2012. "Isotopic Mapping of Groundwater Perchlorate Plumes." Ground Water 50 (1): 94-102.
USEPA. 2008a. A Guide for Assessing Biodegradation and Source Identification of Organic Groundwater Contaminants using Compound Specific Isotope Analysis (CSIA). US EPA Office of Research and Development, National Risk Management Research Laboratory, ADA, OK EPA 600/R-08/148. 67 pp.
USEPA 2009. Emerging Contaminant - Perchlorate. Fact Sheet. Office of Solid Waste and Emergency Response. EPA 505-F-09-005. 4 pp.