Polycyclic aromatic hydrocarbons in surface waters, sediments, and unionid mussels: relation to road crossings and implications for chronic mussel exposure

Transportation infrastructure is a prominent feature across all landscape types, and road crossings over streams are a source of pollutant influx, especially polycyclic aromatic hydrocarbons (PAH) associated with vehicle oils and fuel combustion. Freshwater mussels (Unionoida) are vulnerable to pollutants entering streams because of their sessile benthic lifestyle and their filter- and deposit-feeding exposure routes. We assessed the effect of road crossings on PAH concentrations in mussels, sediment, and water via passive sampling devices (PSDs) at 20 sites in the upper Neuse River basin of North Carolina, and investigated the utility of PSDs for estimating PAH concentrations in mussels. Road crossings significantly increased Total PAH in downstream reaches compared to upstream for all compartments sampled (P < 0.01). Total PAH in mussels were correlated with those in PSDs both upstream and downstream of road crossings (P ≤ 0.01), and PSDs provided a reliable prediction equation for mussel tissue concentrations of Total PAH (r 2 = 0.90). Overall, PAH contributions from crossings to streams in a single, relatively rural watershed are substantial and statistically significant, suggesting that the cumulative PAH influx within an entire river basin may be considerable and exert adverse effects over a chronic lifetime exposure for mussels, especially as their contributions may amplify downstream.