Local and landscape influences on PAH contamination in urban stormwater

Polycyclic aromatic hydrocarbons (PAHs) are toxic organic pollutants produced from combustion. Associated with urban runoff, they have been detected worldwide in urban wetlands. Because PAHs and their associated metabolites are often carcinogenic, mutagenic, and teratogenic, they can pose significant risks to wetland-dependent organisms. We investigated the occurrence of 16 PAHs within water samples and tissues of damselflies (Odonata: Enallagma civile, a flagship group of predatory wetland insects) from seven urban wetlands (known regionally as playas) along a constructed stormwater gradient in Lubbock, Texas. PAH detections from water samples were highly variable across sites and dates, with naphthalene and pyrene occurring most often. PAH detections in adult damselflies were also variable but significantly different from corresponding water samples (suggesting bioaccumulation rather than passive chemical exposure), with naphthalene and fluoranthene occurring most often. The number of specific PAH detections was significantly associated with percent impervious surface within 300 m of a playa, but not with position along the stormwater gradient or number of drainage inflows. Therefore, for the urban playas and odonates of Lubbock, local factors were more important in determining PAH contamination than were landscape-level factors. PAH contamination can be reduced in future urban landscape planning and design by minimizing the amount of impervious surface around stormwater retention ponds, even if they are linked along a hydrologic gradient.