Spatial Characteristics and Sources of Organic Matter in Top Sediment Layers of Lakes Datun and Changqiao

ZHANG Longwu; ZHANG Hucai; JIAO Yuanmei; LI Ting; DUAN Lizeng

doi:10.19672/j.cnki.1003-6504.2535.22.338

Abstract：To elucidate the organic matter in top sediment layer of shallow lakes in the Mengzi Basin with respect to its spatial distribution characteristics and its source,the organic carbon/nitrogen stable isotopes of 65 top sediment layer samples from two shallow lakes,Lake Datun and Changqiao,were measured and C/N values were calculated,and the sources of organic matter under the influences of human activities were analyzed in association with the characteristics of human activities in the Basin.As a result,TOC contents of top sediments of Lake Datun and Changqiao were in the range of 1.91％～8.78％and 0.17％～4.70％,respectively,which were mainly distributed and enriched in the lakes'central areas with concen-tric spatial distribution characteristics;and δ13C and δ15N contents of Lake Datun were in the ranges from-30.49‰ to-21.46‰ and from 4.11‰ to 9.07‰,respectivly,and C/N values ranged from 8.12 to 12.55;while δ13C and δ15N contents of Lake Changqiao were in the ranges from-30.42‰ to-21.7‰,and from 8.43‰ to 13.97‰,respectively with C/N values ranging from 8.63 to 14.80.In addition,there were significant discrepancies in their spatial distribution characteristics.It was found that organic matter in the top sediment layer of the two lakes had mainly come from the terrestrial sources(e.g.sewage)and phytoplankton,and a portion of the terrestrial sources being the soil organic matter.So it was clear that the sources of organic matter in the lakes'top sediment layer in this study area were controlled by the combined action of exogenous and endogenous sources of the lakes,and the order in decreasing magnitude of the contribution of organic matter in Lake Datun was fsew(sewage)＞fp(phytoplankton)＞fsoil,while that in Lake Changqiao wasfsoil＞fsew＞fp.In brief,the terrestrial sewage and soil were the major exogenous input to the lakes'sediments,and the exogenous input was greater than the endogenous contribution.