Sink (Pollutant)

A pollutant sink is the environmental compartment where a contaminant accumulates and is removed from active circulation, the counterpart to its source in a mass balance. Marine sediment is the dominant sink for hydrophobic, persistent pollutants: PCBs, PAHs, heavy metals, and microplastics partition out of the water column and settle, governed by the contaminant’s partition coefficient and particle flux. Sinks can re-release their load if disturbed, so a buried drill-cuttings pile or contaminated harbor sediment acts as a secondary source when dredged or resuspended. Identifying sinks closes the source inventory and shows where long-term contaminant burden resides.