高清质谱解析河岸带湿地溶解有机质分子组成特征及其环境意义

High resolution mass spectrometry reveals molecular composition of dissolved organic matter from riparian wetland and its environmental implications

河岸带湿地土壤溶解有机质(Dissolved organic matter,DOM)对陆源污染物的迁移和对河流水体富营养化进程均具有重要影响.本研究以典型河口冲积岛——崇明岛河岸带湿地DOM为研究对象,采用液相四级杆飞行时间质谱(Liquid chromatography quadrupole time-of-flight mass spectrometry,LC-Q-TOF-MS)技术分析河岸带湿地土壤DOM的分子组成特征,探究河岸带湿地DOM可能的主要来源.研究结果表明:LC-QTOF-MS技术成功地解析了复杂混合物DOM的分子组成特征,其中脂类化合物是崇明岛河岸带湿地土壤DOM的主要组分,占到28.87%~43.87%,其次为蛋白类物质和羰基类化合物,分别占到总DOM的17.46%~36.54%和19.13%~31.28%,最少的是脂肪酸类、糖类和氨基酸类物质,其三者之和仅为12%左右.同时,崇明岛河岸带湿地DOM分子主要来源于河岸带湿地植物光合生产和陆上区域农业面源径流、生活污水和工业废水的排放,其空间分布受小流域土地利用类型影响.研究结果为复杂混合物的分子组成解析和河岸带湿地管理提供一种新思路.

Dissolved organic matter（ DOM） extracted from riparian wetland soil plays important roles on the migration of terrestrial contaminants and eutrophication for fluvial water body. In our study,molecular compositions of DOM extracted from riparian wetland soil in Chongming Island was detected using liquid chromatography quadrupole time-of-flight mass spectrometry（ LC-Q-TOF-MS）,and their probable sources were discussed through the previous literatures. The results showed that LC-Q-TOF-MS could reveal DOM molecular composition precisely. Lipid was the predominant fraction for DOM,which accounted for 28.87% - 43.87%,followed by proteins and carbonyl compounds（ 17. 46% - 36. 54%,19. 13% - 31. 28% respectively）. However,all of fatty acids,sugars and amino acids only accounted for 12%,approximately. Simultaneously,DOM was mainly originated from the autochthonous debris within riparian wetland and allochthonous sources carried by runoff,including agricultural non-point runoff,discharges of demostic seawage and industrial wastewater. Furthermore,we found that the spatial distribution of DOM molecular composition was controlled by its adjacted land use patterns. These results can provide a new idea to reveal the chemical compositions of wetland soil DOM at molecular level,and implications for ripirain wetland management.