中文摘要：

以西安市典型城市污水二级出水为对象，分别测定了溶解性有机物的分子质量分布、亲疏水性组分以及荧光性质等。结果表明，无论以TOC或UV254计，二级出水中溶解性有机物分子质量分布趋势基本相同，大部分为小分子有机物，〈10 ku的有机物分别占60%~75%和71%~79%，〉50 ku的大分子有机物分别占14%~28%和13%~16%，其他区间所占比例较小，整个区间成“双峰”状。二级出水中亲水性组分较疏水性组分多，出水中难降解物质包括腐殖酸、富里酸和蛋白质类物质。含腐殖质较多的水样SUVA较高，而含蛋白质类物质较多的水样SUVA较低，且腐殖质等大部分存在于疏水性有机物中。

英文摘要：

Taking the typical urban sewage secondary effluent in Xi’an as research target,dissolved organic matter （DOM） molecular weight distribution,hydrophilic/hydrophobic constituents and fluorescence etc. have been determined. The results show that the tendency of the molecular weight distribution of DOM is basically the same , whether demonstrated by TOC or UV254,and most of DOM are micromolecular organic matter. The organic matter whose molecular weight is smaller than 10 ku occupies 60%-75% and 71%-79%. The organic matter whose molecular weight is bigger than 50 ku occupies 14%-28%and 13%-16%,separately. The proportion of other sections is less,and the whole section appears as“twin peaks”. The hydrophilic constituents in secondary effluent are more than hydrophobic constituents. The refractory degradation substances of effluent consist of humic acids ,fulvic acids and proteins etc. The water samples that contain more humic substances have higher SUVA ,while the water samples that contain more protein have lower SUVA. And most of humic substances generally exist in hydrophobic organic matter.