Nitrate processing traced by nitrate dual isotopic composition in the early spring in the Changjiang (Yangtze River) Estuary and adjacent shelf areas. (December 2020)

• Record Type: Journal Article
• Authors: Zhong, Xiaosong; Yan, Maojun; Ning, Xiaoyan; Yan, Zhenwei; Xin, Yu
• Is Part Of: Marine pollution bulletin. Volume 161:Part A(2020)
• Publication Date: 2020-12
• Subjects: Nitrate -- Dual isotopes -- Changjiang Estuary -- SIAR -- Nitrification; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2020.111699
• Languages: English
• ISSNs: 0025-326X

Abstract

Abstract: Nitrate is the major chemical form of N-nutrient to sustain primary production in Changjiang Estuary and adjacent seawaters. We employed δ 15 N-NO3 − and δ 18 O-NO3 − to constrain the source, cycling, and sink of nitrate in early spring. Both δ 15 N-NO3 − and δ 18 O-NO3 − differentiate significantly among Changjiang Diluted Water (CDW), Yellow Sea Coastal Current (YSCC), and Taiwan Warm Current (TWC). In coastal areas, nitrate distribution and its isotopes are mainly affected by Changjiang inputs. Chemical fertilizers and sewage & manure originated nitrate jointly contribute the most nitrate in CDW. In offshore areas, nitrification contributes 44 ± 21% of the nitrate in YSCC and 17 ± 16% in TWC; assimilation is the dominant process to remove nitrate in TWC (35 ± 16%). Overall, nitrification and assimilation are the key nitrate cycling processes in early spring and co-shape the offshore distribution pattern of nitrate and its dual isotopes. Highlights: Chemical fertilizers and manure&sewage originated nitrate jointly contribute the most exogenous nitrate to Changjiang Diluted Water. Nitrate regenerated by nitrification is an important NO3 - source replenishing the consumed NO3 - by assimilation. Nitrification and assimilation are essential processes of NO3 - cycling in early spring ECS and co-shape the dual isotopes distribution pattern.