A PRELIMINARY EVALUATION OF SEDIMENT QUALITY ASSESSMENT VALUES FOR FRESH-WATER ECOSYSTEMS

Sediment quality assessment values were developed using a weight of ev idence approach in which matching biological and chemical data from nu merous modelling, laboratory, and field studies performed on freshwate r sediments were compiled and analyzed. Two assessment values (a thres hold effect level (TEL) anal a probable effect level(PEL)) were derive d for 23 substances, including eight trace metals, six individual poly cyclic aromatic hydrocarbons (PAHs), total polychlorinated biphenyls ( PCBs), and eight pesticides. The two values defined three ranges of ch emical concentrations; those that were (1) rarely, (2) occasionally, a nd (3) frequently associated with adverse biological effects. An evalu ation of the percent incidence of adverse biological effects within th e three concentration ranges indicated that the reliability of the TEL s (i.e., the degree to which the TELs represent concentrations within the data set below which adverse effects rarely occur) was consistentl y good. However, this preliminary evaluation indicated that most of th e PELs were less reliable (i.e., they did not adequately represent con centrations within the data set above which adverse effects frequently occur), Nonetheless, these values were often comparable to other biol ogical effects-based assessment values (which were themselves reliable ), which increased the level of confidence that could be placed in our values. This method is being used as a basis for developing national sediment quality guidelines for freshwater systems in Canada and sedim ent effect concentrations as part of the Assessment and Remediation of Contaminated Sediments (ARCS) program in the Great Lakes.