The assessment and characterization of emerging and legacy contaminants occurrence and distribution in coastal freshwater systems is often complex and challenging. As these compounds are detected in various coastal environmental matrices, their persistence and toxicological endpoints creates growing concern and their potential risks warrant added assessment of their likely drivers and sources. In this study, a suite of legacy (historical) and emerging contaminants were assessed and characterized at select Great Lakes National Centers for Coastal Ocean Science (NCCOS) Mussel Watch Program (MWP) sites based on a multi-matrix approach, in an attempt to identify and examine the likely drivers behind the occurrence and distribution of these contaminants and their relationship to land-use gradients at both site and watershed scales, and their proximity to point sources (e.g., WWTPs and STPs).

Pharmaceuticals and personal care products (PPCPs) were detected at all Great Lakes mussel study sites and their concentrations varied significantly among sampling locations, site land-use categories, and sites sampled upstream, sites in proximate location to point sources and sites downstream and along gradients of wastewater discharges. Elevated PPCP concentrations were detected in mussels sampled at designated low-developed sites, followed by urban and open-water sites, with concentrations detected 1 to 2 orders of magnitude higher at some low-developed, urban and open-water sites. Proximity to point source discharges played an integral role in controlling PPCP composition and concentration (magnitude), with elevated concentration detected in agricultural influenced watershed riverine systems impacted by complex wastewater and combined sewer overflow (CSO) systems. Equally important, both legacy and current-use pesticides (CUPs) were ubiquitously detected as complex mixtures in mussels, clams and POCIS devices, at all sampled nested sites in the lower Maumee and Ottawa riverine systems. Residual pesticide frequency, magnitude and composition varied significantly by matrix type, compound group, site types and site and sub-watershed land-use categories.

The results from this study indicate that PPCPs and residual pesticides detected at sampling locations within Great Lakes Basin coastal zone watersheds and associated riverine systems are occurring as complex mixtures and their effects on non-targeted organisms and biota is unknown. The results presented will serve as an initial assessment to characterize various suites of legacy and emerging contaminants that had the highest probability of being detected in tissue as well as POCIS devices, and identify what methods could be used in the future to support the validity of ongoing contaminant assessment and classification at select Great Lakes MWP sites.