中文摘要：

采用超滤膜法对水溶解性有机物进行物理分级，研究长江常熟段水源水中不同分子质量区间DOC和UV254分布的变化特征及其原因。结果表明，长江常熟段水源水总体水质较好，高锰酸盐指数、氨氮、总磷等指标均未超过地表Ⅲ类水体水质标准，符合饮用水源地卫生要求。2008年11月至2009年9月期间，水源水中分子质量小于1kDa的DOC所占比例平均为64．3％，分子质量小于lkDa的UV254所占比例平均为45．2％，表明长江水源水中水溶解性有机物主要以小分子质量的有机物为主，汛期水源水中分子质量在3～10kDa区间的DOC和UV254比例较枯水期有显著提高。

英文摘要：

To study the variation characteristics and influence factors of dissolved organic matter （DOM） and UV254 in the Changshu Section of the Yangtze River, physical classification of DOM was carried out by the method of uhra-fihration. The results show that the water quality in the Changshu Section of the Yangtze River is good and meets the standard of drinking water. CODMn, NH3-N , and TP content of the river water meet the surface water quality standard Ⅲ. During November 2008 to September 2009, the contents of DOC and UV254 with a molecular mass lower than lkDa are 64. 3% and 45.2%, respectively, suggesting that the main DOM is organic matter with a smaller molecular mass. The contents of DOC and UV254 with the molecular mass of 3 ~-10 kDa increase significantly during the flood season.