Source apportionment of nitrate in the Pearl River Estuary using δ15N and δ18O values and isotope mixing model

• Published in: Marine pollution bulletin 2023-06, Vol.191, p.114962-114962, Article 114962
• Main Authors: Long, Ran, Tian, Fei, Chen, Jian-hua, Zhou, Yan-bo, Li, Xue-fei, Li, Yi-tong, Tang, Hai-wei, Chen, Hai-gang
• Format: Article
• Language: English
• Subjects: Nitrate source; Pearl River Estuary; SIAR model; Stable isotopes
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2023.114962

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. [Display omitted] •The nitrate levels in the PRE exist two different areas, with a salinity value of 32 being the distinguishing factor.•The main nitrate sources are manure and sewage during the high-flow season, and which is higher in the LSA than in the HSA.•Reduced nitrogen fertilizer, manure, and sewage are the primary sources of nitrate in the low-flow season.•Runoff, rainfall, and human activity result in significant seasonal variation in nitrate sources in PRE.