Compound Impacts of Fluvial Flooding and Sea-Level Rise on Benzo[]pyrene Transport in the Lower Darby Creek Area Superfund Site, Pennsylvania, USA.

The compound effects of fluvial flooding, tidal dynamics, and sea-level rise (SLR) have the potential to mobilize pollutants at contaminated sites, which are often situated in flood-prone areas. We assessed the compound effects of these flood drivers on benzo-[]-pyrene (B-[]-P)-contaminated sediments in the Lower Darby Creek Area (LDCA) Superfund Site in Pennsylvania, USA. B-[]-P, ubiquitous in the sediments of LDCA, is a known human carcinogen and is an indicator of polycyclic aromatic hydrocarbons in the environment. The LDCA is tidally influenced via the Delaware Bay, is projected to experience sea-level rise, and is situated within an active river floodplain. These conditions lead to potential B-[]P transport within and out of the LDCA. Using a one-way coupling of the Hydrologic Engineering Center-River Analysis System (HEC-RAS) model and the Water Quality Analysis Simulation Program (WASP), we demonstrate that by 2050 fluvial flooding will continue to be the major driver of contaminant transport in the LDCA system. Fluvial-driven sediment transport defines B-[]P deposition, which is largely influenced by tributary inputs and the distribution of B-[]P in floodplain sediments. The complex patterns of B-[]P redistribution at the LDCA, influenced by multiple drivers of flooding, demonstrate the utility of a coupled modeling approach to inform remediation and community resilience.