Pesticide Studies in the Sacramento/San Joaquin Delta and San Francisco Bay Estuary

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The objectives of this specific study are to characterize the mixtures of current-use pesticides and pesticide degradates entering the Sacramento/San Joaquin Delta from its two main river sources over a period of 12 consecutive months. 

map showing pesticide study area

Map of study area.

The occurrence and potential effects of current-use pesticides are a point of concern in the Sacramento/Joaquin Delta (Delta) and San Francisco Estuary. Less than half of all pesticides applied in the Delta watershed are routinely analyzed in monitoring studies and new pesticides are continually being registered for use. The concentrations and potential effects of these pesticides in the Delta ecosystem are unknown.

The objectives of this specific study are to characterize the mixtures of current-use pesticides and pesticide degradates entering the Sacramento/San Joaquin Delta from its two main river sources over a period of 12 consecutive months. The data produced during this project will contribute greatly to the current knowledge of the occurrence of pesticides in the Delta ecosystem and provide essential data to the cooperator. By providing a robust dataset on pesticides entering the Delta this study will serve as a basis for additional targeted studies.

The proposed study will be a year-long monitoring of over 90 current-use pesticides and pesticide degradates in surface-water samples collected from two sites (Sacramento River at Freeport and San Joaquin River near Vernalis). These sites were chosen because they represent the two major inputs to the Delta with watersheds of approximately 23,000 and 13,500 square miles for Freeport and Vernalis respectively. Samples will be collected at these sites twice per month for a period of one year beginning in April of 2012. Additional samples will be collected for five consecutive days following one major storm event in each basin. Samples will be collected in cooperation with the USGS National Water Quality Assessment (NAWQA) Program. All samples will be collected using depth-integrating, discharge-weighted techniques, following established USGS protocols. Water samples will be analyzed at the USGS PFRG laboratory by two analytical methods (GC/MS and LC/MS/MS). This study will consist of four tasks: (1) project oversight and reporting; (2) collection of water samples twice per month at two sites for one year, and over 5 consecutive days following a major storm in each watershed; (3) analysis of environmental and QA/QC samples for pesticides using two analytical methods; (4) preparation of a USGS Data-Series Report and a USGS interpretive report.

By providing data on the occurrence of current-use pesticides in the Delta this project addresses a key science direction of the USGS: "Understanding Ecosystems and Predicting Ecosystem Change". This project also addresses two priority issues of the USGS Cooperative Water Program (Ecosystem Change and Human Health). The project involves utilization of new analytical methods for current-use pesticides and will "provide standardized, quality-assured data to national databases available to the public that will be used to advance the understanding of regional and temporal variations in hydrologic conditions" which are two broad goals listed in WRD Policy Memorandum No. 04.01. This project specifically addresses the issues of "Urban Runoff" (section 2.5) and "Agricultural Nonpoint Source Pollution" (section 2.7) of the California Water Science Center (CAWSC) Science Plan. This project also addresses the issues of "Endangered Species" (section 4.1), and "Fish and Wildlife Habitat" (section 4.2) of the CAWSC Science Plan.

Project Add-On: Pesticide Occurrence in the Sacramento/San Joaquin Delta and San Francisco Bay Estuary (Project 2015-16)

The initial focus of this project (CA12L) was a year-long monitoring of a large suite of current-use pesticides entering the Sacramento/San Joaquin Delta from the two main tributaries to the Delta (Sacramento and San Joaquin rivers). Environmental samples were collected by USGS Pesticide Fate Research Group (PFRG) personnel and analyses of all samples were conducted at the PFRG Organic Chemistry Research Laboratory (OCRL) in Sacramento, California. This research project was successfully completed in 2014 with the publication of a USGS Data Series report (Orlando, and others, 2014). All data associated with this project are publicly available through the USGS National Water Information System (NWIS) database. Data and results of this project were also presented to the scientific community and public on multiple occasions, (Bay Delta Science Conference, 2014, Delta Science Council meeting, 2014, State and Federal Contractor Water Agency conference, 2014, Interagency Ecological Program Science Conference, 2013).

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 or during specified storm-related and seasonal events at five baseline input sites to the Delta. 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.

Additional work to be conducted in 2015-2017 will consist of analysis of current-use pesticides in water and sediment for both environmental water samples collected from the Sacramento/San Joaquin Delta region and laboratory mesocosm samples. Mesocosm studies are being conducted by researchers and graduate students at the University of California Davis and involve exposing native invertebrates to mixtures of multiple current-use pesticides and assessing their toxicity. PFRG will be analyzing water and sediment samples collected from the mesocosms at various time points and determining the concentrations of the pesticides applied as well as their degradates. When coupled with the invertebrate toxicity data this will provide valuable information on the toxicity of mixtures of a suite of current-use pesticides and degradates at environmentally relevant concentrations.

References

Orlando, J.L., McWayne, Megan, Sanders, Corey, and Hladik, Michelle, 2014, Dissolved pesticide concentrations entering the Sacramento–San Joaquin Delta from the Sacramento and San Joaquin Rivers, California, 2012–13: U.S. Geological Survey Data Series 876, 28 p., http://dx.doi.org/10.3133/ds876.