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ANALYSIS OF LOW-LEVEL PESTICIDES FROM HIGH-ELEVATION LAKE WATERS BY LARGE-VOLUME INJECTION GCMS
Citation:
Rosal, C G., L A. Riddick, E M. Heithmar, G M. Momplaisir, K E. Varner, P. L. Ferguson, D F. Bradford, AND N G. TallentHalsell. ANALYSIS OF LOW-LEVEL PESTICIDES FROM HIGH-ELEVATION LAKE WATERS BY LARGE-VOLUME INJECTION GCMS. Presented at Pittsburgh Confernece on Anlytical Chemistry and Applied Spectroscopy 2003, Orlando, FL, March 9-14, 2003.
Impact/Purpose:
The overall goals of the task are to apply NERL's core capability in advanced chemical science and technology for maximum benefit in estimating exposures of ecosystems and humans to chemical stressors and to identify emerging pollution concerns, in particular long-range airborne transport of contaminants. This task comprises several subtasks, each with individual objectives:
Subtask 1: screen exposures of National Park PRIMENet ecosystems to chemical stressors, identifying indications of exposure requiring further evaluation, and use these samples evaluate new analytical methods as replacements for standard methods in future assessments of ecosystem contaminant exposures.
Subtask 2: evaluate a new mercury analytical approach with superior performance on complex solid matrices such as biological tissues, and apply the approach to estimating exposure of ecosystems and humans to mercury.
Subtask 3: determine distribution patterns of chemical contaminants in the southern Sierra Nevada Range of California, investigate topographic and weather factors that may influence the distributions, and determine if a correlation exists between contaminant distributions and extirpation patterns of the mountain yellow-legged frog.
Subtask 4: provide analytical methods to measure a number of inorganic and organic arsenic species in a variety of environmental matrices, elucidate the environmental transformations undergone by organoarsenic animal-feed additives, and determine if the potential exists for substantially increased exposure of humans and aquatic organisms to arsenic.
Description:
Pesticides are among the factors being proposed as causal agents for amphibian population declines in the Sierra Nevada range of California, USA. We hypothesize that agricultural pesticides applied in the San Joaquin Valley west of the mountains are volatilized or eroded, transported by near-surface winds, and deposited at high-elevation lakes of the Sierra Nevada in the Sequoia and Kings Canyon National Parks. We further hypothesize that the geographic pattern of pesticide deposition depends on the local air flow patterns and correlates with the extirpation of the mountain yellow-legged frog. Such a correlation would support the theory that pesticide exposure may have contributed to the disappearance of this species from some of its historic range. We intend to measure the concentrations of about 40 current-use pesticides in 60 or more lakes, to make the statistical analysis more robust. We anticipate the amounts of pesticides in our study sites to be lower than the detection limits of conventional analytical techniques. Our approach to achieving lower detection limits is to extract analytes from a large volume of water (the subject of a companion paper at this conference) and analyze a substantial fraction of the extract using large-volume injection (LVI) GCMS. This approach should result in a I 00-fold increase in the amount of pesticide reaching the detector, compared with previous studies of pesticides in the Sierra Nevada.' This paper will describe optimal LVI/GCMS conditions, present analytical figures of merit of the method, and compare its performance with that of GCMS with conventional pulsed-splitless sampling.