Delta Regional Monitoring Program: Current-use Pesticides Active

The Sacramento-San Joaquin Delta is an area of critical habitat for numerous species of concern, including chinook salmon and the threatened Delta Smelt. In recent years multiple pelagic species within the Delta have been in sharp decline. Previous studies have shown that current-use pesticides associated with agricultural and urban runoff are present in the Delta throughout the year. While studies have suggested that contaminants (including current-use pesticides) may play a role in the decline of pelagic fish species in the Delta, less than half of all pesticides applied in the Delta watershed are analyzed for during routine monitoring. The concentrations and potential ecological effects of these unmonitored pesticides in the Delta ecosystem are unknown.

This study will utilize the unique analytical capabilities of the USGS Pesticide Fate Research Group (PFRG), Organic Chemistry Research Laboratory (OCRL) to assess the occurrence of a large suite of understudied, current-use pesticides and pesticide degradates in surface waters entering the Sacramento/San Joaquin Delta. Water and suspended sediment samples will be collected and analyzed for these pesticide compounds from sites undergoing concurrent toxicity monitoring by the U.C. Davis Aquatic Health Program (AHP) Laboratory. Analyses conducted by the USGS will greatly aid in evaluating these toxicity testing data. The results of this study will be used by the cooperator to evaluate whether pesticides are present in surface water inflows to the Delta at levels determined to be above toxicity values, to prioritize which pesticides, if any, warrant further investigation, and provide valuable information regarding the health of the Delta ecosystem.

The proposed study will be a an ongoing effort to better understand the occurrence of current-use pesticides and pesticide degradates in surface waters and suspended sediment entering the Sacramento/San Joaquin Delta and the possible effects of exposure to these waters on laboratory-cultured test organisms. Samples will be collected monthly from five baseline sites and five times per year at an additional four sites during specified storm-related and seasonal events. Water samples will be analyzed at the USGS PFRG laboratory by two analytical methods (GC/MS and LC/MS/MS) for a suite over 150 pesticides and degradates. Suspended sediments associated with these water samples will be analyzed for 128 pesticides and degradates by GC/MS. This study will consist of four tasks: (1) project oversight and reporting; (2) sample collection; (3) analyses of environmental and QA/QC samples; (4) preparation of a USGS Data-Series Report.

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