青海湖沉积物稳定碳同位素常常被用来指示古环境的变化,然而准确地解译其信号需要充分认识溶解无机碳同位素比值(δ13CDIC)变化及其控制因素.本文利用沉积物捕获器连续一年收集的青海湖湖水及颗粒物,通过其中湖水的(δ13CDIC)和细颗粒沉积物中碳酸盐稳定碳同位素δ13Ccarb的同步分析,结合湖水δ13CDIC的垂直分布和表层沉积物δ13Ccarb及有机碳同位素(δ13CDIC),探讨了有机质分解在δ13CDIC和δ13Ccarb中的调节作用.结果表明,从沉积物捕获器中获得的湖水δ13CDIC的变化主要受控于与外界隔绝后(微)生物对有机质的分解作用,但这种(微)生物分解作用并不会影响到δ13Ccarb比值.这些现象反映了(1)还原环境下(微)生物对有机质的分解作用对水体δ13CDIC有重要影响和(2)青海湖自生碳酸盐主要从上层湖水沉淀,且形成后不再与周围水体发生交换作用. “,”The stable carbon isotopes in sediment have been widely used to indicate the paleo-environment changes in Lake Qinghai. A better understanding of the controlling factors of dissolved inorganic carbon (DIC) isotopic composition (δ13CDIC) is of significance to withdraw the sedimentary carbon isotopic signal. In this study, the samples of lake water and settling particles collected in situ by a time-series sediment trap over a whole year in Lake Qinghai were used to synchronously measure stable carbon isotopic compositions of DIC in waters (δ13CDIC) and fine-grain carbonates in sediments (δ13Ccarb). The impacts of organic-matter degradation on δ13CDIC of lake water and δ13Ccarb of authigenic carbonates in the sediment trap were discussed, by combining with δ13Ccarb profile of lake water with water depth and δ13Ccarb, and organic carbon isotopic ratios (δl3Corg) of surface sediments in Lake Qinghai. The results indicated that the δ13Ccarb of lake water samples in the sediment trap was regulated by the organic-matter degradation by (micro-)organism after the sample bottles were sealed when the collection was completed, but not for δ13Ccarb of authigenic carbonates of the settling particles. These observations suggested (1) that there was significant impact of organic-matter degradation by (micro-)organism on water δ13CDIC under a closed reducing (micro-)environment and (2) that the precipitation of authigenic carbonate was precipitated mostly in the surface water, with limited interaction with ambient water after its precipitation.