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Project Component: Development of Chemical Indicators

Background and Objectives

Chemical concentrations are often the first line of evidence in determining sediment quality, yet they tell only part of the story. Chemical values enumerate the entire amount of a constituent within a sample, but do not elicit what portion of the contaminant is available for uptake by organisms (bioavailable) and may be capable of causing adverse effects. In sediment quality assessment, a number of methods have been developed to relate measured chemical concentrations to observed biological effects. None of the approaches alone consistently provides a highly reliable and accurate measure of chemical exposure; therefore, chemistry data is usually integrated with toxicity and benthic community information to assess sediment quality. This multiple lines of evidence (or MLOE) approach provides greater confidence in the assessment of sediment quality.

The objectives of this project were to evaluate the accuracy of chemical indicators as part of sediment quality guidelines (SQGs) for predicting biological effects in California bays, and to calibrate a suite of SQGs for use in sediment quality assessment.

Chemically measured values of most sediment contaminants, including copper, are somewhat predictive of sediment toxicity (amphipod mortality), though the values are not closely correlated.
Typical measures of sediment chemical contamination, such as copper, explain only some of the variability that is observed in benthic macrofauna community condition (Benthic Response Index).


This study was completed in 2008.


To support SQG evaluation, a large database of California sediment samples, matching chemistry, toxicity, and benthic community data, was compiled from numerous monitoring and research studies. SCCWRP researchers then developed and calibrated a number of approaches for incorporating chemical indicators into SQGs, and evaluated their accuracy for relating measurement of chemical concentrations to sediment toxicity and benthic community condition.


Indices of overall sediment condition based on sediment quality guidelines (SQGs) were found to have a better relationship to biological effects than existing regulatory guidelines for individual chemicals. Two chemistry indices were selected for future use in evaluating sediment quality: CA LRM (the maximum probability of toxicity predicted from logistic regression models) and the CSI (Chemical Score Index based on the mean predicted benthic community response).


National Oceanic and Atmospheric Association (NOAA)


Development of Sediment Quality Guidelines Based on Benthic Macrofauna Response - January 2007 presentation at the Remediation of Contaminated Sediments Conference. Describes the development and application of the Chemical Score Index, a sediment quality guideline based on the response of benthic macrofauna to sediment contamination.


Chemical List - List of the chemicals required for application of the CA LRM and CSI sediment quality guidelines.

Direct Effects Assessment Sample Calculation - Document describing the calculations needed to interpret chemistry, toxicity, and benthic infauna data for sediment quality assessment. Calculations are illustrated using a sample data set.

For more information on Development of Chemical Indicators, contact Steve Bay at (714) 755-3204.
This page was last updated on: 6/24/2014