Distribution and Toxicity of Sediment-Associated Pesticides in the Sacramento River Watershed
Project Contractor
Dr. Donald Weston, UC Berkeley/Integrative Biology Department
dweston@berkeley.edu
SRWP Project Lead
Kathy Russick, SRWP Program Coordinator
krussick@comcast.net
Project Budget
$189,870
Funding Source
Prop 13 Pesticide Research and Identification of Source and Mitigation (PRISM)
Grant Program
Project Schedule
August 1, 2005 – March 31, 2007
Project Background
Due to increasing regulatory restrictions on organophosphate pesticides, pyrethroid pesticides have replaced organophosphates for many residential uses, and many sectors of the California agriculture industry are also increasingly relying upon them. The major difficulty at this time is that most stakeholders are aware of emerging pyrethroid use and potential for environmental impacts, but lack data by which to assess these risks. This study will provide data to all stakeholders, and by doing so, will alleviate the current uncertainties and promote environmentally protective selection of methods for pest control.
Project Description
The purpose of this study was to: 1) determine environmentally realistic levels of pyrethroids in aquatic sediments of agriculture- and urban-dominated waterbodies; 2) determine if these levels approach toxic thresholds; 3) promote awareness of sediment-associated pesticides and demonstrate the analytical feasibility of studying this group of chemicals; and 4) provide data needed to direct mitigation efforts should any be deemed necessary. Following are the three main tasks in this project:
- Field Sediment Monitoring—Monitor urban and agricultural drainages in the Sacramento River Watershed to determine levels of pyrethroid and other sediment-associated pesticides and determine if these sediments are toxic to Hyalella azteca, a standard sediment toxicity testing organism. Twenty-six agricultural samples were collected at 22 sites over a six-month period spanning late summer to early spring. In areas around Sacramento receiving urban drainage, 11 sites were sampled up to five times over the course of one year.
- Lab Tests to Establish Toxicity Thresholds—Clean sediment samples were spiked with known levels of pyrethroids. H. azteca were exposed to the samples and toxic responses were measured. From the known pesticide concentrations and responses, toxicity threshold concentrations for the pyrethroids were developed.
- Pyrethroid Persistence Studies—Two farm soils on which pyrethroids were applied were monitored to determine how long pyrethroids persist in agricultural field soils. Pyrethroid concentrations in the soil and toxicity to H. azteca were monitored immediately after application, and at various time points following application (two days, one month, three months) to determine if they persist long enough through the growing season to pose a toxic threat if they are transported to surface waters in irrigation flow during summer or in runoff during winter rains.
Project Findings
The findings from this project have been written up in several peer-reviewed professional journal articles. Reference information for these articles is provided below. The data generated from this grant project has been merged with projects funded by several other sources to generate the journal articles and the findings presented here..
