Improved water quality in response to pollution control measures at Masan Bay, Korea

The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005–2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p < 0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p < 0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ∼1 month. Land-based nutrient loads were also significantly reduced for TN (p < 0.01) and TP (p < 0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.