Use of Chemical Analysis and Assays of SPMD Extracts to Assess the Response of Hydrophobic Organics Contaminants in Streams to Urbanization in Six Metropolitan Areas of the U.S.
As part of an integrated assessment of stream responses to urbanization, semi-permeable membrane devices (SPMDs) were deployed in streams along a gradient of urban land-use in and around Atlanta, Georgia; Raleigh, North Carolina; Denver, Colorado; Dallas, Texas; Milwaukee, Wisconsin; and Portland, Oregon. The goals of this study were: (1) to assess the occurrence and distribution of selected hydrophobic organic contaminants (HOCs) in streams across a range of urban land use conditions and not having the influence of large point source discharges; (2) to determine if the concentrations of HOCs and their potential toxicity to aquatic biota responded in some way along a gradient of urbanization within each metropolitan area; and (3) to compare these responses among the six metropolitan areas studied. Petite SPMDs (6") were deployed in 30 streams in each metropolitan area for 30-45 days during base flow conditions; Denver, Raleigh and Atlanta in 2003, and Milwaukee, Dallas and Portland in 2004. Despite some losses, a total of 167 SPMDs were retrieved successfully. Of the 74 compounds detected and three assays utilized, 29 were strongly related to increases in urban intensity in at least one of the six metropolitan areas investigated. These 29 endpoints included: 16 polycyclic aromatic hydrocarbons (PAHs), a wood preservative (pentachloranisole), 2 insecticides (chlorpyrifos and chlordane), 3 herbicides (benfluralin, trifluralin, and dacthal), a synthetic musk (AHTN), 2 furans (methyl-dibenzofuran and benzo(b)naphtho [2,3-d]furan), and a flame retardant (BDE 47). In addition, the number of compounds detected and results of the Fluoroscan, Microtox ®, and P450RGS assays were strongly related to urban intensity. Petrogenic PAHs and dibenzofurans increased with increasing urban intensity in Atlanta, Raleigh, Milwaukee, and Denver while pentachloroanisole, pyrogenic PAHs, and P450RGS increased with increasing urban intensity in all six metropolitan areas. The number of endpoints related to urban intensity ranged from three in Portland to 21 in Raleigh and Denver. In addition to the numbers and types of endpoints related to urban intensity, graphical methods and analysis of covariance were used to investigate differences in the response patterns in the six metropolitan areas. Analytical chemistry and in-vitro assays of petite SPMDs extracts proved to be a powerful tool to assess response of HOCs in streams to urbanization.