草海沉积物有机质空间分布与来源识别

The Distribution Characteristics and Sources of Organic Carbon in Sediments of Caohai Lake

本文选取草海湿地这一典型高原湖泊湿地作为研究对象,分析了17个表层沉积物和3根代表性湖区沉积物柱芯总有机碳(TOC)含量、有机碳δ^(13)C及C/N值,探讨了草海湿地表层沉积物和三个重点湖区不同深度沉积物有机质的主要来源,并利用有机碳δ^(13)C和C/N值对表层沉积物有机碳来源进行定量分析.结果表明:草海表层沉积物中TOC含量、δ^(13)C和C/N值变化范围分别为6.86%~34.85%,-28.49%^-18.19%,7.36~11.12;表层沉积物有机碳主要来源于藻类生产和沉水植物,沉水植物贡献率为49.7%,藻类初级生产的贡献率为48.8%,而陆源输入只对东部湖区有较小影响;东部湖区上部沉积物有机碳主要来源于藻类,底部受到藻类生长、陆源输入及沉水植物共同影响。

This study focused on the distribution characteristics and sources of organic carbon in sediments of Caohai Lake,a typical plateau lake in China. Stable carbon isotope（ δ^13C）,C： N ratio,total organic carbon（ TOC） contents of 17 surface sediments and three sediment cores were analyzed. Our results showed that the contents of TOC in surface sediments varied from 6. 86% to 34. 85%,with a median of 23. 30 ± 7. 80%. The δ^13C ranged from-28. 49% to-18. 19%,averaged 23. 30 ± 2. 88%,while the C： N ratio ranged from 7. 36-11. 12,averaged 9. 13 ± 1. 17. The results indicated that primary production of phytoplankton was the main source of organic carbon in surface sediments in the east areas of Caohai Lake,the effect of terrestrial input and submerged plant was negligible. However,primary production of phytoplankton and submerged plants were the main sources in other lake areas. The contribution of submerged plants to TOC in surface sediments accounted for 49. 7%,while the contribution of primary production of phytoplankton was 48. 8%. The results of sediment cores in the east area showed that organic carbon in the upper sediments mainly originated from algae,but in bottom sediments from algae,terrestrial input and submerged plants. Besides,organic carbon in center area sediment core mainly came from algae and submerged plants,while in the outlet area almost came from submerged plants.