2012年夏季长江口颗粒有机碳、氮分布特征及其来源

Distribution and Source of Particulate Organic Carbon and Particulate Nitrogen in the Yangtze River Estuary in Summer 2012

基于2012年8月对长江口及其邻近海区的调查资料,分析了长江口夏季颗粒有机碳（particulate organic carbon,POC）、颗粒氮（particulate nitrogen,PN）的空间分布特征及其与环境因子的关系,并结合C/N摩尔比值和叶绿素a（chlorophyll a,Chl a）探讨了POC的主要来源及浮游植物的贡献.结果表明,2012年夏季长江口POC的质量浓度范围在0.68-34.80mg·L^-1之间,均值为3.74 mg·L^-1;PN的质量浓度范围为0.03-9.13 mg·L^-1,均值0.57 mg·L^-1,二者浓度均表现为底层高于表层.POC和PN平面分布相似,高值区均出现在口门附近和调查海区西南部,并向外海浓度迅速降低,整体呈现近岸高、远岸低的趋势,与总悬浮物（total suspended matter,TSM）的平面分布规律基本相同;POC与PN间呈极显著正相关,表明二者具有高度的同源性.POC、PN与TSM、化学需氧量（chemical oxygen demand,COD）间均呈现极显著线性正相关,而与盐度（salinity,S）和Chl a的相关关系较弱,表明POC和PN的分布受陆源输入的影响较大,浮游植物生产不是该水域颗粒有机碳、氮的主要来源.C/N摩尔比和POC/Chl a法分析表明夏季长江口POC主要为陆源,有机碎屑是POC的主要存在形式.定量估算结果表明,浮游植物生物量对夏季长江口表层POC的平均贡献率仅为2.54%,非生命POC占绝对优势地位.

Based on the data from the cruise carried out in August 2012 in the Yangtze River Estuary and its adjacent waters,spatial distributions of particulate organic carbon（ POC）,particulate nitrogen（ PN） and their relationships with environmental factors were studied,and the source of POC and the contribution of phytoplankton to POC were analyzed combined with n（ C） /n（ N） ratio and chlorophyll a（ Chl a） in the Yangtze River Estuary in summer 2012. The results showed that the concentrations of POC in the Yangtze River Estuary ranged from 0. 68 mg·L^- 1to 34. 80 mg·L^- 1in summer and the average content was 3. 74 mg·L^- 1,and PN contents varied between 0. 03 mg·L^- 1and 9. 13 mg·L^- 1with an average value of 0. 57 mg·L^- 1. Both of them presented that the concentrations in bottom layers were higher than those in the surface. POC and PN as well as total suspended matter（ TSM） showed a extremely similar horizontal distribution trend that the highest values appeared in the near of the mouth and southwest of the survey waters,and decreased rapidly as toward the open seas,both of them showed higher contents in coastal zones and lower in outer sea. There was a fairly good positive linear relationship between POC and PN,which indicated that they had the same source. POC and PN expressed significantly positive correlations with TSM and chemical oxygen demand（ COD）,but showed relatively weak correlations with salinity and chlorophyll a,which demonstrated that terrestrial inputs had a strong influence on the distribution of POC and PN,and phytoplankton production was not the major source of organic matters in the Yangtze River Estuary. Both the n（ C） /n（ N） ratio and POC /Chl a analysis showed that the main source of POC was terrestrial inputs,and organic debris was the main existence form of POC.Quantitative analysis showed the biomass of phytoplankton only made an average of 2. 54% contribution to POC in the Yangtze River Estuary in summer and non-living POC occupied the overwhelming advantage.