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Pesticide occurrence and transport mechanisms and bioassessment in the Central Valley, California
Project Summary Information:
The objective of the summer synoptics is to quantify pesticide loads and major sources in 2001 and compare them to 1994. Although diazinon is primarily transported during winter storms, other pesticides have their main transport during summer.
The wet/dry deposition study will provide a better determination of the contribution of atmospheric deposition, both wet – precipitation, and dry – gaseous and particle, of airborne organophosphorous insecticides and other pesticides to the overall pesticide loading in the San Joaquin and Sacramento basins during an 18-month period for wet deposition (12-month period for dry deposition).
The objective of the bioassessment sampling is to assess macroinvertebrate and algae communities, using NAWQA protocols, in selected water bodies of the San Joaquin River drainage of interest to the RWQCB. Habitat assessments will also be conducted in support of the bioassessments. The results will be used to establish existing conditions in the selected water bodies. Also, to the extent possible, the relative importance of habitat quality and water quality will be
The objective of the Sacramento River basin storm sampling is to quantify pesticide loads and identify major sources of dormant spray pesticides. The work will be similar to that done by the USGS during winter storms in 2000 and 2001. However, the 2002 and 2003 sampling will not be evaluated in an interpretive report – the flow and pesticide concentration data will published in on-line, non-interpretive USGS Open-File Reports.
Revelance and Impact:
The overall project will relate to goals 4 and 6 outlined in the WRD Memorandum 95.44:
Goal 4 -- "Providing data or results useful to multiple parties in potentially contentious interjurisdictional conflicts over water resources." This project will provide data necessary for establishing TMDLs for organophosphate pesticides in the Central Valley.
Goal 6 -- "Providing water-resources information that will be used by multiple parties for planning and operational purposes." The data and interpretations will be used in the process of establishing TMDLs. The data and interpretations
will also assist growers by indicating where and how pesticide loads might be reduced.
The TMDL approach to regulating water quality in support of the Clean Water Act is now being widely applied in California and throughout the United States. The underlying purpose of TMDLs is the protection and support of the beneficial uses of water bodies. Bioassessments are a direct measure of the ability of a water body to support aquatic life. Although this effort is a modest beginning, it will be locally important in establishing bioassessments as valuable measures of water quality. The results of this study are relevant to Topics 2 (Water Quality) and 4 (Ecosystems) of the California District Science Plan. The water bodies to be sampled are also of interest to the San Joaquin-Tulare NAWQA
study unit and will provide valuable additional information for that study.
Strategy and Approach:
A. Summer Synoptics: Sampling will occur in June and August 2001 at 22 sites in the San Joaquin basin for OP pesticides (schedule 2001). Pesticide occurrence and distribution in the 2001 synoptics will be compared to a 1994 synoptic. Instantaneous loads will be calculated and compared between synoptics. Loads and pesticide use will be compared to application data by basin. Univariate and multivariate statistical methods will be used to relate occurrence, land use, loads, and application data.
B. Wet/Dry Deposition: The deposition of airborne pesticides will be collected at six locations in the SJB -- on both sides of the SJR in five ag and one urban setting; and two locations in the Sacramento basin – one ag and one in the
foothills downwind from ag areas. The primary collection surface will be Teflon-lined metal funnels that will collect precipitation on an event basis, and dry particulate and gaseous deposition for extended dry periods. Three sites (one urban and two ag) will also collect atmospheric deposition in separate stainless steel buckets using automated wet/dry samplers. In addition, soil boxes will be co-located at these three sites that also will collect both dry and wet deposition.
The soil boxes are being deployed to simulate a more natural interception surface. They will be used to investigate the amount of pesticide deposited to a representative, natural surface. Subsamples of the soil will be analyzed on a regular basis to monitor for changes in concentration and chemical state of the sorbed pesticides over extended dry periods.
During the rainy season, the soil boxes will also intercept rainfall. The resulting runoff will be collected and filtered to separate the water from the suspended sediments. The results will be compared to the rain only sample to determine the pesticide contribution to runoff from direct rainfall verses that mobilized from dry deposition. All samples will be analyzed for NWQL schedule 2003. Wet and dry deposition data will be related to ancillary data where possible. Types of ancillary data include pesticide application, land use, and meteorological data.
C. Bioassessments: Assessments of macroinvertebrate communities, algae communities, and habitat will be conducted at each of five sites during Spring 2001 (April-May) and Summer 2001 (August-September). Results from the five sites
will be compared to previous results for those sites and others sampled during Cycle 1 of the San Joaquin NAWQA.
Combining the new data with the existing data allows for comparisons between sampling periods for previously sampled sites and provides a larger background data set for evaluation of the new data. Comparison of the seasonal samples will
indicate if season is an important factor to consider in the design of subsequent sampling programs in the study area. Data analysis will consist of a variety of univariate and multivariate statistics including correlation, cluster analysis, principal components analysis, and correspondence analysis.
D. Sacramento River Basin Storms: Sampling in 2002 will include completely sampling three storms at eight sites (over five days) in January and February after the main application of diazinon. Monitoring will consist of one sample/day collected for 5 consecutive days during each of 3 dormant season storm events (in January and February). All samples will be analyzed at the NWQL for schedule 2001.
The USGS involvement in storm sampling in January and February 2003 will include flow measurements and water quality sampling at three sites. This storm sampling will include completely sampling three storms at the three sites (over
five days) in January and February after the main application of diazinon. The flow and water quality data collected and analyzed by USGS will be published in on-line USGS Open-File Reports.
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