M6 AM Suspended and Bedded Sediments and Nutrients: Exposure-response Relationships
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 324-326

(PAR-1119-046572) EPA National Water Quality Criteria Programs: Nutrients and Suspended and Bedded Sediments.

Parker, A¹, Cantilli, R¹, ¹ US EPA Headquarters, Office of Water, Office of Science and Technology, Health and Ecological Criteria Division, Washington, DC, USA

ABSTRACT- Nutrients and sediments are consistently cited in the top five stressors that lead to water quality impairment as reported to EPA by states, tribes, and territories. EPA has created two water quality criteria and standards programs to help address these impairments. The National Nutrient Program and the Suspended and Bedded Sediments Program. Both nutrient and sediment criteria development are somewhat different from that of chemical criteria, because nutrients are necessary for aquatic life, and sediments are part of the aquatic system, but both are problematic in excess. This truism makes a single criterion for the nation for these pollutants unfeasible. Instead EPA has recommended a reference system approach for nutrient and sediment criteria development. This approach involves identifying the set of conditions that represent a system that is minimally affected by anthropogenic effects, and developing criteria using those conditions as a starting point. The reference approach has more scientific rigor when specific stressor effects can be identified in the biotic community, hence these Programs recommend monitoring of both causal and response variables. Indeed, most states developing numeric criteria for these stressors have adopted a stressor-response approach that includes identifying response thresholds that lead to water quality degradation. These National programs are looking for innovative methods for identifying stressor-response relationships to better define regionally and locally appropriate criteria. In addition, nutrients and sediments are frequently transported together in flowing waters due to the anion binding capacities of many sediments. These two stressors are also often closely associated in lakes and reservoirs as well, due to anion and cation associations and the reducing conditions in many lake and reservoir sediments that provide autochthonous nutrient regeneration. EPA is beginning to look at integrating criteria for stressors that are strongly related, and sediments and nutrients seem well poised for this integration.

Key words: nutrients, sediments, stressor-response