乌梁素海悬浮颗粒物和沉积物有机碳同位素特征及来源

Isotopic characteristics and sources of organic carbon in suspended particulates and sediments in Lake Wuliangsuhai

悬浮颗粒物和沉积物是湖泊有机污染物的主要承载物质,其稳定同位素研究对有效识别有机质污染导致的湖泊富营养化具有重要意义.本研究选取乌梁素海为研究区,于2019年4月(融冰期)、7月(夏灌期)和10月(秋灌期)对湖区及入湖渠道的表层沉积物和悬浮颗粒物中有机碳的δ13 C、C/N比及总有机碳(TOC、POC)和总氮(TON、PON)含量进行测定分析,联合采用δ13 C、C/N及同位素多元混合模型研究湖泊有机碳来源及其贡献率.结果表明,乌梁素海悬浮颗粒物有机碳δ13 C POC的变化范围为-23.29‰~-29.75‰,呈现10月>4月>7月、入湖渠道>湖区的趋势,悬浮颗粒物POC/PON比变化范围为4.10~21.35,呈现出4月<7月<10月的时间变化,悬浮颗粒有机质主要来源于浮游植物(51.59%)、入湖渠道泥沙(34.60%)和大型水生植物(13.76%).沉积物有机碳δ13 C TOC变化范围为-27.58‰~-22.68‰,呈现4月<10月<7月的变化,沉积物TOC/TON比变化范围为3.06~23.77,时空变化明显,沉积物有机质则主要源于入湖渠道挟带的泥沙,贡献达72.79%以上,而浮游植物与大型水生植物的贡献率相差较小,分别为11.85%和15.36%.本研究可以初步判定受入湖渠道影响的富营养化湖泊中悬浮颗粒物和沉积物有机碳来源,为改善湖泊有机污染和研究有机碳来源提供更多理解.

Suspended particulates and sediments are the main substances of lake organic pollutants and organic carbon,and their stable isotope research is of great significance for effectively identifying lake eutrophication.We select Lake Wuliangsuhai as our research site to measure and analyze the index,such asδ13 C,C/N,total organic carbon(TOC,POC)and total nitrogen(TON,PON)content of organic matter in surface sediments and suspended particulates of the lake area and the inflow canal in April(melting period),July(summer irrigation period)and October(autumn irrigation period)in 2019.We usedδ13 C and C/N in combination with isotope multivariate mixed model to investigate the sources and contributions of the lake organic carbon.The results indicate that the variations ofδ13 C POC in the suspended particulates organic carbon range from-23.29‰to-29.75‰,with a trend of October>April>July and inflow canal>lake area.POC/PON ratio of the suspended particulates changes from 4.10 to 21.35,with a trend of October>July>April.The suspended particulate organic matter mainly comes from phytoplankton(51.59%),silt of the inflow canal(34.60%)and macrophyte(13.76%).Theδ13 C TOC value of the bottom sediment organic carbon varies from-27.58‰to-22.68‰,with a tendency of April<October<July.The TOC/TON ratio of the bottom sediment ranges from 3.06 to 23.77,with obvious temporal and spatial variations.The primary source of organic carbon of the bottom sediment is the silt carried by the inflow canal(>72.79%),while the contribution rate of phytoplankton and macrophyte is relatively low(11.85%and 15.36%,respectively).This study estimates the sources of organic carbon in the suspended particulates and bottom sediments in a eutrophic lake affected by the inflow canal,and provides an in-depth understanding for improving the lake pollution and studying organic carbon sources.