重要饮用水源地天目湖水库有色可溶性有机物来源与组成特征

天目湖作为重要集中式饮用水源地，水体水质变化会影响其生态系统服务功能.有色可溶性有机物（CDOM）是溶解性有机物的重要组成部分，其来源与组成直接影响水处理工艺与出水品质，因而研究天目湖CDOM来源及时空分异规律对其水质供应安全及生态系统功能维护有着重要的作用.基于2017年逐月野外采样数据，运用平行因子分析法（PARAFAC）等对CDOM光谱数据进行分析，揭示了天目湖CDOM来源和组成的空间及季节变化特征.PARAFAC结果表明，天目湖CDOM库中微生物作用类腐殖酸组分C1相对丰度最高（44.2%±9.8%），其次为类色氨酸组分C2（29.2%±4.3%）和类酪氨酸组分C3（17.2%±13.1%），陆源类腐殖酸组分C4相对丰度最低（9.4%±2.4%）.时空分布特征及主成分分析结果表明天目湖河口区CDOM丰度a（254）、C1和C2组分显著高于下游湖区，而光谱斜率S_275-295则显著低于下游湖区（t-test，P<0.05），意味着入湖河流输入造成天目湖河口区CDOM腐殖质化程度及相对分子量的升高.夏、秋季节的a（254）、C1、C2和C4组分荧光强度显著高于冬、春季节（t-test，P<0.05）.结果表明不同季节对CDOM组成的影响不仅要考虑降雨量和径流输入的差异，还应综合考虑水体温度、热分层和浮游植物生物量以及光和微生物降解对CDOM的矿化作用.

Characterizing Sources and Composition of Chromophoric Dissolved Organic Matter in a Key Drinking Water Reservoir Lake Tianmu

Lake Tianmu is an important source of drinking water, and its water quality can influence ecosystem service functions. Unraveling the sources and composition of chromophoric dissolved organic matter (CDOM) that can affect water treatment processes is necessary to maintain water supply safety and ecosystem service functioning of Lake Tianmu. Samples were collected monthly in 2017 and analyzed for CDOM absorbance and fluorescent spectra using parallel factor analysis (PARAFAC) to investigate the spatial and temporal variations of CDOM sources and composition in Lake Tianmu. PARAFAC results showed that CDOM in Lake Tianmu was mainly composed of a microbial humic-like component C1 (44.2%±9.8%), followed by a tryptophan-like component C2 (29.2%±4.3%), tyrosine-like component C3 (17.2%±13.1%), and terrestrial humic-like component, C4 was the lowest (9.4%±2.4%). The CDOM abundance a(254) and fluorescence intensities of C1 and C2 were significantly higher in the river mouths than in the downstream lake regions, whereas the spectral slope S_275-295 was significantly lower in the river mouths (t-test, P<0.05), indicating that allochthonous inputs cause an elevated degree of humification and relative increase in the molecular weight of CDOM in the inflowing river mouths. Seasonal differences in CDOM composition were mainly ascribed to the a(254) and fluorescence intensities of C1, C2, and C4 being significantly higher in the summer and autumn than in the winter and spring (t-test, P<0.05). Our results showed that the influences of different seasons on CDOM composition comprise differences in rainfall and runoff input, as well as water temperature, thermal stratification, phytoplankton biomass, and mineralization of CDOM by light and microbes.