中文摘要：

为了探讨长江口水体胶体有机碳含量的季节变化，按季度采集长江口南支表层水样，利用切向流超滤技术（TFF）分离水样中小胶体物质（1—5kD）、中胶体物质（5-500kD）和大胶体物质（500kD-0．45μm），测试分离后样品的有机碳浓度。结果表明：长江口水体中总胶体有机碳浓度有明显的季节变化，表现为冬季〉夏季〉秋季〉春季，其原因可能是冬季长江流域陆源输入增加，水生生物生物量和生物活性减弱双方面的共同作用使得含量最高，而春季流域陆源有机碳含量输入较少，且流域内春汛雨量多水量大对水体中有机碳浓度具有稀释作用，从而导致该季节胶体有机碳含量较少。总胶体有机碳在不同分子量的分配上季节差异不大，中胶体有机碳浓度及其在总胶体有机碳中所占的比例均高于小胶体有机碳和大胶体有机碳。由于长江口胶体有机碳的含量较高，并有明显的季节变化，对有机碳的入海通量和生物地球化学循环发挥重要的作用。

英文摘要：

To understand seasonal variation of colloidal organic carbon in Changjiang （Yangtze） River estuary, water samples were collected seasonally in March, July, November, and December in 2009. Colloids were isolated by mini tangential flow ultrafiltration at membrane pore-sizes of 500, 5, and 1 kD （1 kD=1000 Daltons）, representing large, medium, and small size groups, respectively, and the concentration of organic carbon was tested by TOC II. The results reveal significant seasonal variation of colloidal organic carbon in the estuary, and the order of the concentration is winter 〉 summer 〉 autumn 〉 spring. The order may be explained that in the winter, terrestrial input increased, while aquatic biomass and biological activity decreased, and hence the concentration of colloidal organic carbon peaked during the year. However, in the spring, terrigenous organic carbon reduced, while rainfall increased causing dilution, making the lowest concentrations in the spring. The seasonal changes of colloidal organic carbon are similar to each other of different molecular weights, and the medium-sized colloidal organic carbon concentration occupied more proportion than small- and large-size groups in all seasons. The high content of organic carbon in the estuary and the seasonal change are important to organic carbon flux and biogeochemical cycles in the estuary region.