Spatial and Temporal Trends of Metal and Organic Contaminants in the Huron-Erie Corridor: 1999–2014

Spatial and temporal patterns of sediment contamination were examined in the Huron-Erie Corridor (HEC) of the Laurentian Great Lakes. Both the St. Clair and Detroit Rivers are designated Great Lakes Areas of Concern (AOCs) and are subject to past and prospective future sediment remediation efforts. Data generated using a system-wide probabilistic sampling design were compiled and contrasted between an early year period (1999–2004) and late period (2008–2014). Contaminants considered included trace metals, organochlorines, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The general ranking of sediment contamination across waterbodies was Detroit River > St. Clair River = St. Clair Delta > Lake St. Clair. Canadian and US nearshore areas remained distinct in their pollution signatures as a result of hydraulic barriers formed by shipping channels that longitudinally bisect the system. Canadian segments of the St. Clair River were enriched with hexachlorobenzene (HCB), octachlorostyrene (OCS), and mercury (Hg) and demonstrated a dilution gradient across subsequent downstream Canadian segments. US segments of the Detroit River were enriched with PCBs, PAHs, chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Temporal trends differed between waterbodies and associated chemicals and explained less overall variation in contaminant concentrations compared to spatial patterns. Most chemicals with concentrations exceeding sediment quality guidelines at the probable effect concentration (PEC) showed little or no difference in sediment contamination between early and late year periods. This study provides support for planned forthcoming sediment cleanup actions in the two AOCs and can serve as a baseline for evaluating future recovery of the system.