Monday, May 26, 2008 - 10:15 AM
21

Nutrient criteria development to protect aquatic life uses in the Pennsylvania Piedmont: Multiple lines of evidence

Michael J. Paul and Lei Zheng. Tetra Tech, Inc, 400 Red Brook Boulevard, Owings Mills, MD 21117

Nutrient criteria are being developed nationwide to protect a variety of designated uses. A variety of different approaches have been used, all with different advantages and disadvantages as well as linkages to use protection. We developed nutrient criteria using multiple lines of evidence to protect aquatic life uses for the Piedmont in Southeastern Pennsylvania.  The first candidate criteria were developed using the standard frequency distribution approach, the second using a modeled reference expectation, the third using a variety of stressor-response analysis with different endpoints, the fourth were based on mechanistic water quality models, and the last candidate criteria were derived from existing literature.  Candidate total phosphorus criteria ranged from 2 to 100 ug/L.  We weighed the stressor-response analyses more than the other lines of evidence because of the strength of their linkage to actual use protection.  The final recommended criterion concentration was 40 ug/L. There were difficulties developing the criteria for total nitrogen, including linkages to use protection.  Using multiple lines of evidence provided a reasonable alternative to single approaches.  The approach can fit into a variety of criterion frameworks, including a new two-tiered model.


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