Chapter 3
Characterization of a Carbofuran-Contaminated Site in the Hawaiian Islands National Wildlife Refuge 1,3
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Michael D . David , Sonia Campbell , LeeAnn Woodward , and Qing X . L i Downloaded by COLUMBIA UNIV on September 17, 2012 | http://pubs.acs.org Publication Date: November 1, 2000 | doi: 10.1021/bk-2001-0771.ch003
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Department of Environmental Biochemistry, University of Hawaii, Honolulu, HI 96822 U.S. Fish and Wildlife Service, Hawaiian Islands NWR, Honolulu, HI 96850 2
An area of shore on Laysan Island in the Hawaiian Islands National Wildlife Refuge has been observed over the last 10 years to cause mortality to several species of birds, crabs, and insects which come into contact with the sand. Previous analysis of two composite samples from 1993 and 1997 indicated contamination of carbofuran in the sand at levels in the low μg/g range. In November of 1997, and July and October of 1998, 129 additional samples were collected in order to define the extent of the carbofuran contamination. Sand samples were extracted with acetone in a pressurized fluid extractor and analyzed by GC-MS. Localized contamination was present at 1,639 μg/g of carbofuran and over 8,832 μg/g of its primary breakdown product, carbofuran-7-phenol. In addition to carbofuran -7-phenol,four other known transformation products were observed in sample extracts, including 3-hydroxy carbofuran, 3-keto carbofuran, 3-keto carbofuran phenol, and carbofuran diol. Two additional compounds which have not been previously reported as carbofuran breakdown products were also found. Spectra are presented and structures are proposed for these two compounds. The structure of one compound, carbofuran acetate, was confirmed by synthesis and GC/MS. To assess relative toxicity, Microtox bioassays were conducted for standards of carbofuran, 3-hydroxy carbofuran, and carbofuran-7-phenol, as well as for water extracts of native contaminated and clean sand. These assays supported the conclusion that the toxicity at the site can be explained by the presence of carbofuran and its products. 3
Current address: American Cyanamid, P.O. Box 400, Princeton, NJ 08534.
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© 2001 American Chemical Society In Pesticides and Wildlife; Johnston, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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Downloaded by COLUMBIA UNIV on September 17, 2012 | http://pubs.acs.org Publication Date: November 1, 2000 | doi: 10.1021/bk-2001-0771.ch003
Introduction The Hawaiian Islands National Wildlife Refuge extends about 800 miles from the main Hawaiian Islands toward Midway island (Figure 1). Because of its remote location and near isolation from anthroprogenic activities, this area is an important breeding area for many marine species, including the endangered Hawaiian Monk seal, the threatened Hawaiian Green turtle, and four species of endangered seabirds (1,2). The largest island in the refuge is Laysan Island, encompassing approximately 1700 acres. In May of 1988, researchers stationed on Laysan Island observed an area near the northern shore which contained an unusually large number of dead seabirds. Dead scavengers such as ghost crabs and insects were also observed within close proximity of the bird carcasses within this area. The area was marked and referred to as the "dead zone" (DZ). The first samples analyzed to determine the cause of the observed mortality were taken in August of 1993. The site was initially partitioned in a 30 χ 30 ft grid for reference of sampling locations. Site investigations included observations of background radiation, an electromagnetic survey, metals analysis, and sampling of air and sand. Two sand samples were analyzed for presence of organic contaminants and tested positive for carbofuran at 11 and 22 μg/g. These two samples were composites consisting of small samples taken at several locations over the surface of the site, and therefore did not pinpoint the exact location of the contamination. A second investigation was done in June of 1997 in which the original sampling grid was extended to 60 χ 60 ft. Sampling included carbofuran immunoassays of 22 samples, which revealed contamination in the 10-20 ng/g range, and five samples analyzed for carbofuran by commercial analytical laboratories, which were reported at similar contamination levels (1 ). The initial reports of carbofuran contamination at this site led to speculation that there may have been an underground source of carbofuran, such as a buried drum. The analytical results from thefirsttwo site surveys failed to definitively establish carbofuran as the source of the observed toxicity, and led directly to the samples collected, analyzed, and reported in this chapter. The insecticide carbofuran is a potent acetylcholinesterase inhibitor (3,4). It has been demonstrated to be toxic to non-target species such as fish and mammals (5) and has been shown to alter avian neurochemical function (6). Physical transport of carbofuran in the environment is dictated by its water solubility: 0,32 g/L (25°C), vapor pressure: 2.7 mPa (33°C) (4), and other physical and chemical properties. Carbofuran has been estimated to be leachable through soil to groundwater (7), and has been observed in agricultural field runoff (8). The primary degradation pathways of carbofuran are hydrolysis, photolysis, and biodégradation (3,9-12). Hydrolysis has been demonstrated to be the dominant breakdown mechanism under environmental conditions (11). Half-life values of carbofuran degradation have been reported in the range of 107 days (13), 46-117 days (14), 14-73 days at three depths in soil (15), and 20-40 days for biodégradation (12). The primaiy breakdown product observed in degradation studies was carbofuran7-phenol, which is produced by the of hydrolysis of the carbamate (5,12,16). Other degradation and oxidation products which have been reported include 3-keto
In Pesticides and Wildlife; Johnston, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
In Pesticides and Wildlife; Johnston, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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