ESTIMATION OF EFFECT THRESHOLDS FOR THE DEVELOPMENT OF WATER QUALITY CRITERIA

摘要

Biological and ecological effect thresholds can be used for determining safe levels of nontraditional stressors. The U.S. EPA Framework for Developing Suspended and Bedded Sediments (SABS) Water Quality Criteria (WQC) [36] uses a risk assessment approach to estimate effect thresholds for unacceptable levels of SABS in water bodies. Sources of SABS include: 1. Erosion from agricultural, construction, forestry practices, and stream banks 2. Resuspension of deposited sediment 3. Direct discharge from municipal, industrial, and agricultural sources Excessive levels of SABS can destroy habitat for plants and animals, reduce the quality of drinking water, impair the quality and safety of recreational waters, increase the costs associated with irrigation and navigation, and decrease aesthetics. The SABS Framework is intended as a guide to the development of water quality criteria (WQC) and restoration targets. The SABS Framework uses an eco-epidemiological perspective to incorporate information from field observations with data from controlled laboratory experiments. The combined information is used to develop relationships that estimate the levels of SABS that will impair aquatic life or pollute sources intended for drinking water. The SABS Framework uses several statistical procedures to compare the estimated effects levels derived from field and laboratory data. Protective levels and restoration goals are recommended based on scientific precedent, logical argument, and statistical resolution. The risk estimates that result from using this approach are readily applicable for use in future emergency situations.