长江口悬浮颗粒有机碳的稳定同位素

STABLE ISOTOPE OF SUSPENDED PARTICULATE ORGANIC CARBON IN YANGTZE ESTUARY AND ADJACENT WATERS

对长江口及邻近海区的悬浮颗粒有机碳(POC)进行了稳定同位素^(13)C/^(12)C比值研究。结果表明:冬季调查区POC的δ^(13)C值范围在-25.64×10^(-3)～22.64×10^(-3),且POC主要来自陆源;夏季,调查区域内以25等盐线为界,分布着两组δ^(13)C值范围不同的POC。一组分布在表层盐度低于25的水域,POC的δ^(13)C值范围为-26.39×10^(-3)～-22.03×10^(-3),与冬季的δ^(13)C值相近;另一组分布在表层盐度大于25的水域,其δ^(13)C值在-21.79×10^(-3)～-18.64×10^(-3)范围内变化,表明这组POC的主要来源为海洋浮游生物。这两种不同源POC的分布格局与长江冲淡水羽状流的分布特征对比发现,夏季羽状流对这种分布格局的形成起着决定作用。

The13 C/12 C ratio of the paniculate organic carbon (POC) in the Yangtze estuary and adjacent coastal waters has been studied. The result shows that the POC of the area in January 1986 (low discharge period) has δ13C range of -25. 28 × 10-3--22. 64 × 10-3 ,dominated by terrestrial carbon contribution. There are two groups of POC with different δ13C ranges during the period of high water discharge (July 1986). One has δ13C range of -26. 39×1013-22. 03 × 103, appearing in the area where salinity is lower than 25. The second one distributes in the area where the salinity is higher than 25 and has the δ13C range of -21. 79×1013-18. 65 × 10-3,suggesting a doinant marine plankton source. The Yangtze plume front in summer controlls the distribution pattern of POC with different sources.