ISOTOPIC TRACING OF TERRESTRIAL CONTRIBUTION TO ORGANIC MATTER OF SEDIMENTS IN THE ESTUARY OF TAIHU LAKE BASIN
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摘要: 分析了太湖流域不同土地利用类型土壤、河口表层沉积物及主要生物的有机碳含量和同位素分布特征,并利用端元混合法求取了陆源输入对湖泊沉积物有机质的贡献及分布。研究结果表明,流域表层土壤有机质δ13C受植物群落的δ13C值影响,不同植被类型的土壤有机质δ13C值存在差异。茶园、菜地、林地和农田δ13Corg平均值分别为-25.4‰、-25.8‰、-27.1‰和-28.1‰,其中茶园有机碳同位素值最高。河口表层沉积物有机碳同位素变化范围为-27.5‰~-25.1‰,平均值为-25.7‰。河口近岸区域表层沉积物δ13Corg偏低,且以河口为轴心向湖心逐渐增大,呈扇形条状分布,其分布主要受低δ13C值的陆源有机质输入影响。利用端元混合法求得近河口表层沉积物中陆源有机质贡献高达70%~80%,随着离岸距离的增加,陆源有机质贡献量逐渐减少。Abstract: The authors analyzed characteristics of organic carbon content and isotope distribution of top soil in different Land use types within the Taihu Lake basin, as well as surface sediments and organisms within the estuary. The sources of organic matter of lake sediments were obtained by using two-member mixing model. The results showed that there were differences of organic δ13C in different plant types, which affected organic δ13C of top soil within the catchment. The average δ13Corg values of tea plantations, vegetable lands, forest lands and paddy fields were -25.4‰,-25.8‰,-27.1‰ and -28.1‰ respectively,and the highest δ13Corg value existed in tea plantations. The range of δ13Corg values of surface sediments within the estuary were -27.5‰~-25.1‰ with the average value of -25.7‰. The δ13Corg of surface sediments near the shore was low, and gradually decreased from the estuary to center. The reason was the effect of import of terrestrial source with lower δ13Corg values. By using two-member mixing model, the contribution ratios of terrestrial source was 70%~80% in the estuary, and gradually decreased with the distance to the lake shore.
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Keywords:
- organic sources /
- carbon isotope /
- land use types /
- sediments /
- Taihu basin
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