Source apportionment of nitrate in the Pearl River Estuary using δ15N and δ18O values and isotope mixing model
Ran Long1, Fei Tian2, Jian-Hua Chen3
1Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Scientific Observing and Experimental Station of South China Sea Fishery Resource and Environment, Ministry of Agriculture and Rural Affairs, Scientific Observation and Research Field Station of Pearl River Estuary Ecosystem, Guangdong Province, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Guangzhou 510300, China; Jiangsu Key Laboratory of Marine Biotechnology, College of Marine Science and Fisheries, Jiangsu Ocean University, Lianyungang 222005, China.
Abstract:
The mitigation of eutrophication in the Pearl River Estuary (PRE) has encountered numerous challenges in regards to source control. Herein, the isotope mixing model (SIAR) was used to quantify the primary nitrate sources in the PRE. The results showed that the nitrate levels were significantly higher in the high-flow season than in the low-flow season. Meanwhile, we found the most important nitrate sources were manure and sewage during the high-flow season, with a contribution ratio of 47 % in the low salt area (LSA) and 29 % in the high salt area (HSA). During the low-flow season, the primary nitrate sources were identified as reduced nitrogen fertilizer in the LSA and manure and sewage in the HSA, which accounted for 52 % and 44 %, respectively. Furthermore, we also suggest that a feasible measure might be to control the pollution caused in the PRE by manure and sewage as well as reduced nitrogen fertilizer.
