Identification of the nitrate pollution in surface water of Dongshan Bay based on stable isotope technology
Identifying and quantifying water nitrate pollution is crucial for managing aquatic environment of a bay.Dongshan Bay,a significant semi-enclosed bay in the southeastern coastal area of Fujian Province,features man-grove and coral reef ecosystems at its estuary and bay mouth,respectively.Dongshan Bay is impacted by human ac-tivities such as mariculture.We quantified and analyzed nitrate pollution status in the surface waters of Dongshan Bay by measuring physicochemical parameters,stable isotopes(δ15N-NO3-,δ18O-NO3-and δ15N-NH4+)of the surface waters,and using statistical methods including the MixSIAR isotope mixing model.The results showed that the concentrations of chlorophyll a and dissolved inorganic nitrogen in the surface waters exhibited a noticeable gra-dient change,decreasing from the estuary of the Zhangjiang River to the mouth of Dongshan Bay.The maximum concentrations of chlorophyll a,NH4+,NO3-and NO2-were 45.2 µg·L-1,52.67 μmol·L-1,379.2 μmnol·L-1 and 3.93 μmol·L-1,respectively.The nitrogen and oxygen isotope values of NH4+and NO3-in the surface waters showed significant spatial variations.According to the MixSIAR model results,nitrogen sources in the surface waters of Dongshan Bay were mainly freshwater inputs of the Zhangjiang River estuary,aquaculture wastewater,and groundwater.The freshwater input from the Zhangjiang River estuary contributed the most(25.2％ ),while aquacul-ture wastewater,groundwater and urban sewage accounted for 24.6％ ,19.0％ ,and 15.1％ ,respectively.It is evi-dent that freshwater input from the Zhangjiang River estuary is the primary source of nitrate in the surface waters of Dongshan Bay.
stable isotopenitrateisotope mixing modelDongshan Bay
万方数据
维普
