Quantifying land-based pollutant loads in coastal area with sparse data: Methodology and application in China

A systematic approach was developed to quantify land-based pollutant loads in selected bays in China where there is sparse or limited relevant data. The approach was applied to Luoyuan Bay and Xiamen Bay. Despite the data limitations in the two study areas, the approach was able to show that in Luoyuan Bay, the chemical oxygen demand (CODMn) load was mainly from soil losses, which accounted for 63 percent of the total pollutant load, whereas point sources only contributed 4 percent. Soil losses constituted the main pollution source for total nitrogen (TN) and total phosphorus (TP). Similarly, spatial variability of the source portion of land-based pollution was detected in Xiamen Bay. Non-point sources were the main source of CODMn load in all Xiamen Bay sub-sea areas, accounting for over 60 percent of the total pollutant loads. Non-point sources contributed largely to the TN and TP loads for most Xiamen Bay sub-seas. However, river discharges and point sources of pollution were also responsible for considerable TN and TP loads in some sub-seas. The application of the approach at the two bays resulted in a clear identification of the source apportionment and spatial distribution of land-based pollutant loads.