PARENT SESSION
TP1 - Arid Ecosystems: Unique Considerations
Chair: Gensemer, Bob1, 1 ENSR Corporation, Fort Collins, CO
Co-chair: Meyerhoff, Richard2, 2
2:10 PM to 5:30 PM - Tuesday, 19 November 2002
Room Ballroom G-I
(418) Relevance and Applicability of Ambient Water Quality Criteria for Selenium in Arid West Streams.
DeForest, David*,1, Brix, Kevin2, Adams, William3, Gensemer, Robert4, Curley, Ed5, Sierra, Karen5, 1 Parametrix, Inc., Kirkland, WA, USA2 EcoTox, Newport, OR, USA3 Kennecott Utah Copper, Magna, UT, USA4 ENSR International, Fort Collins, CO, USA5 Pima County Wastewater Management, Tuscon, AZ, USA
ABSTRACT- The USEPA′s draft chronic ambient water quality criterion (AWQC) for selenium in freshwater systems is based on a whole-body fish tissue residue. A tissue residue-based AWQC was proposed to reflect the principle exposure route by sensitive fish species (i.e., diet) and the extreme between site variability in selenium bioaccumulation potential. Selenium speciation and bioaccumulation in aquatic systems depends on a variety of factors (e.g., redox, biological productivity, food web characteristics), generally resulting in much greater bioaccumulation in lentic (non-flowing) systems than lotic (flowing) systems. Accordingly, the water selenium concentration resulting in a given whole body fish tissue concentration can vary widely between sites. Application of a tissue residue-based criterion to Arid West streams provides unique challenges because many streams are ephemeral or effluent-dominated and the aquatic community structure is much different than the typical mesic systems on which AWQC are generally based. The potential influence of selenium bioaccumulation kinetics and Arid West biological characteristics in such streams are discussed in terms of their relevance to the default exposure duration and exceedance frequency components of the chronic AWQC.
Key words: selenium, arid west streams, ambient water quality criteria