基于二元模型和贝叶斯混合模型的青海湖表层沉积物有机碳来源解析OA

Determining the sources of organic carbon in lake sediments is key to unraveling carbon cycling in lakes and the evolution of watershed environments.Currently,quantitative studies on sources of organic carbon in sediments from Lake Qinghai remain relatively limited,and disparate source-tracing proxies often yield incon-sistent conclusions.Drawing on the published carbon-nitrogen ratio(C/N)of organic matter and organic carbon isotope(δ13Corg)data for surface sediments from Lake Qinghai,this study employed the Binary model and Bayes-ian mixing model to quantitatively resolve the contribution of terrestrial-derived and autochthonous organic car-bon to the surface sediments,demonstrating that(1)Organic carbon in the surface sediments of Lake Qinghai is predominantly derived from terrestrial inputs,with an average contribution rate of 70.2%,as estimated using the MixSIAR model;the autochthonous part is mainly from the genus Cladophora(with an average contribution rate of 26.0%),and the contribution of submerged plants is relatively low(with a mean value of 3.8%).(2)The com-position of organic carbon sources in the sediments displays distinct spatial heterogeneity,where the terrestrial contribution is negatively correlated with the water depth.(3)Comparison of the models indicates that the δ13Corg-based MixSIAR model exhibits higher reliability in quantifying sources of organic carbon,whereas the C/N-based Binary model is prone to uncertainties in selecting the end-member value and early diagenesis.This study revealed the source,composition,and spatial distribution patterns of organic carbon in the surface sediments of Lake Qinghai,providing a reference for evaluating the organic carbon burial mechanism in alpine saltwater lakes.