Research Areas > Contaminants > Sediment Quality Assessment > Direct Effects in Estuaries > Delta Direct Effects Assessment

Project: Assessing the Direct Effects of Sediment Contamination in the Sacramento and San Joaquin River Delta

Background and Objectives

Studies of the biological resources of the Delta have focused primarily on the water quality and fishery resources. There is very little information on sediment contamination and toxicity that can be matched with biological community data to support the development of assessment tools. The objective of this project is to obtain synoptic data on sediment quality in the Delta that can be used for the development of chemical indicators and benthic indices.

Status

This is an ongoing study with anticipated completion in 2012.

Methods

Sediment quality surveys of the Delta were conducted in fall 2007 and spring 2008 in collaboration with the California Department of Water Resources, which used a stratified random sampling design. A total of 144 stations were analyzed for acute toxicity to amphipods (Hyalella azteca); of these, a subset of 75 samples were selected for additional analyses of toxicity and sediment chemistry.

Findings

Toxicity of Delta sediments to H. azteca was low overall. Toxicity was detected only in the 2007 survey, with three percent of the stations causing a significant reduction in amphipod survival. A subset of 75 stations from both surveys were selected for the full suite of sediment quality triad analyses, including a second toxicity test (using Chironomus dilutus), benthic community analysis, and chemistry analysis.
 

The sediment chemistry results indicate contamination by legacy contaminants and current use pesticides is widespread in the lower Delta. DDTs, PAHs, diuron, and piperonyl butoxide were detected at more than 90% of stations. Pyrethroids (primarily bifenthrin and permethrin) were detected in about 30% of the samples. Analysis of the toxicity, chemistry, and benthic community data is in progress. The results will be used to develop sediment quality assessment tools for this region.

Partners

This project is being conducted in collaboration with State Water Resources Control Board, San Francisco Estuary Institute, and California Department of Water Resources.