Key Laboratory of Marine Chemistry Theory and Technology, Ocean University of China, Ministry of Education, Qingdao 266100, China; Institute of Marine Chemistry, Ocean University of China, Qingdao 266100, China.
Key Laboratory of Marine Chemistry Theory and Technology, Ocean University of China, Ministry of Education, Qingdao 266100, China; School of Oceanography, Shanghai Jiaotong University, Shanghai 200030, China.
Mar Pollut Bull. 2020 Dec;161(Pt A):111699. doi: 10.1016/j.marpolbul.2020.111699. Epub 2020 Oct 3.
Nitrate is the major chemical form of N-nutrient to sustain primary production in Changjiang Estuary and adjacent seawaters. We employed δN-NO and δO-NO to constrain the source, cycling, and sink of nitrate in early spring. Both δN-NO and δO-NO 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.
硝酸盐是长江口及邻近海域初级生产力的主要氮营养化学形式。本研究利用 δN-NO 和 δO-NO 约束了早春硝酸盐的来源、循环和汇。δN-NO 和 δO-NO 在长江冲淡水（CDW）、黄海沿岸流（YSCC）和台湾暖流（TWC）之间有显著差异。在沿海地区，硝酸盐的分布及其同位素主要受长江输入的影响。化肥和污水/粪便来源的硝酸盐共同贡献了 CDW 中最多的硝酸盐。在近海地区，硝化作用分别贡献了 YSCC 中硝酸盐的 44 ± 21%和 TWC 中硝酸盐的 17 ± 16%；在 TWC 中，硝酸盐的主要去除过程是同化作用（35 ± 16%）。总的来说，硝化作用和同化作用是早春硝酸盐循环的关键过程，共同塑造了硝酸盐及其双同位素的近海分布模式。
