Nitrate in the Changjiang diluted water:an isotopic evaluation on sources and reaction pathways  

作　　者：Shan JIANG Jie JIN Guosen ZHANG Yan CHANG Zhaoru ZHANG Meng ZHOU Xiaolu WANG Jing ZHANG Ying WU 

机构地区：[1]State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai 200062,China [2]School of Oceanography,Shanghai Jiao Tong University,Shanghai 200240,China

出　　处：《Journal of Oceanology and Limnology》2021年第3期830-845,共16页海洋湖沼学报（英文）

基　　金：Supported by the National Natural Science Foundation of China(Nos.41530960,41706081);the Scientifi c Research Foundation of SKLEC(No.2017RCDW04)。

摘　　要：A cruise covering two transects in the Changjiang(Yangtze)estuary in July 2017 was conducted,aiming to explore the sources for riverine NOˉ3 and identify reactions involved in the NO_(3)^(-)transformations along the transport of the Changjiang diluted water(CDW).In the river water,NO_(3)^(-)was fundamentally contributed by chemical fertilizer leakage in the watershed according to isotope signals.Sewage discharge may also be significant on riverine NO_(3)^(-)inventory,while the isotope signal was masked by nitrification.Together with the transport of the CDW,NO_(3)^(-)production was observed in waters with low salinities(<20)and high turbidities.Nitrification resulted from the mineralization of riverine organic nitrogen;therefore,the high turbidity was linked to active production.In the outer plume,coupled with stratification,a significant decrease in NO_(3)^(-)concentration was observed in the surface water.In parallel,enrichment inδ^(15)N-NO_(3)^(-)andδ^(18)O-NO_(3)^(-)was found,indicating biological consumption by phytoplankton.The difference in the stratification intensity between two transects led to variations in NO_(3)^(-)concentrations and isotope compositions.In the benthic water,denitrification(sediment-water interface)and nitrification(bottom water)coexisted.Furthermore,accumulations of NH4+and dissolved organic nitrogen in the bottom water were observed,indicating that nitrification was constrained by oxidant(mainly dissolved oxygen)supplies.

关 键 词：Changjiang diluted water(CDW) denitrification and nitrification ESTUARY production and removal stable isotope 

分 类 号：P342[天文地球—水文科学] X143[天文地球—地球物理学]