夏季洪水对长江口及邻近海域颗粒有机碳分布与来源的影响

Impacts of summer floods on the distribution and source of particulate organic carbon in the Changjiang(Yangtze River)Estuary and its adjacent sea area

基于2020年7月洪水期间采集的长江口及邻近海域的温度、盐度、总悬浮物(Total Suspended Matter,TSM)质量浓度、颗粒有机碳(Particulate Organic Carbon,POC)质量浓度和颗粒有机碳稳定同位素(δ^(13)C_(POC))等数据,分析了洪水事件对该区域POC分布与来源的影响。结果显示,研究区域内POC和盐度呈显著负相关(r^(2)=0.41,p<0.01),与TSM呈显著正相关(r^(2)=0.92,p<0.01),表明咸淡水的混合是影响POC分布的重要因素。研究区域东北部表层海水POC质量浓度局部升高,并且δ^(13)C_(POC)值显示为海源信号,表明浮游植物生产是影响该海域POC分布的另一重要因素。此外,由于高径流量形成的稀释效应,洪水事件会降低陆源输入的POC质量浓度,研究区域东南侧偏轻的δ^(13)C_(POC)也表明,洪水事件会扩大陆源POC在东海的影响范围。

The impact of the flood event on the distribution and source of particulate organic carbon(POC)in Changjiang(Yangtze River)Estuary and adjacent waters was analyzed based on the data of temperature,salinity,total suspended matter(TSM),POC andδ^(13)C_(POC),which were collected during the July 2020 flood.The results show that POC is negatively correlated with salinity(r^(2)=0.41,p<0.01),and positively correlated with TSM(r^(2)=0.92,p<0.01).The mixing of salt and fresh water is an important factor affecting the distribution of POC.The distribution ofδ^(13)C_(POC) values in the surface water indicates that the phytoplankton production is another important factor affecting the distribution of POC in the northeastern part of the study area.Flood events reduce the concentration of terrigenous POC due to the dilution of high runoff,meanwhile,lightδ^(13)C_(POC) values in the southeastern part of the study area indicate that flood events could expand the influence range of terrigenous POC in the East China Sea.