博斯腾湖有色可溶性有机物来源及季节变化特征

博斯腾湖是中国西北地区最大的外流湖，近年来随着湖区周边废水排入量的增加，严重威胁到湖泊周边地区居民的饮用水安全.对博斯腾湖开展有色可溶性有机物（CDOM）的来源及季节变化研究对该湖水质保护具有非常重要的意义.通过平行因子分析法解析博斯腾湖CDOM三维荧光光谱，得到类腐殖酸组分C1（255 nm/420 nm），类酪氨酸组分C2（270 nm/324 nm）和类色氨酸组分C3（230 nm/340 nm）.2018年夏季盐度与C1呈显著负相关（r=－0.64，p<0.01），与C2呈显著正相关（r=0.65，p<0.01），这表明河流等外界输入是夏季湖水中类蛋白质和类腐殖质荧光组分的主要来源，夏季强烈的蒸发作用使得微生物活性增强.而2019年秋季盐度与C3呈显著正相关（r=0.70，p<0.01），与C2呈显著负相关（r=－0.51，p<0.05），意味着淡水输入直接稀释河口区CDOM中的类蛋白组分.整体上，博斯腾湖CDOM浓度在黄水区附近最大，且夏季CDOM浓度较秋季更大（t-test，p<0.001），意味着夏季水质更差.河口区各指标的变异程度较大，受淡水输入影响较其他湖区大，这在2018年夏季表现得尤为显著.博斯腾湖CDOM具有高度空间异质性，2018年夏季该湖西部入湖河口区C1组分的贡献较大且该组分贡献率向东部水体交换弱的湖区方向逐渐减小，相应C2组分的贡献率逐步增大.2019年秋季各荧光组分占比表现为由黄水沟河口区以C1为主向东部湖区快速转变为以C2为主.

Sources and seasonal variation of chromophoric dissolved organic matter in Lake Bosten

Lake Bosten is the largest outflow lake in northwestern China. In recent years, with increasing wastewater discharge from the lake watershed, the drinking water supply safety of Lake Bosten has been seriously threatened. Therefore, the sources and seasonal variability of chromophoric dissolved organic matter (CDOM) in Lake Bosten are of great significance for understanding carbon cycling and for water quality protection of the lake. In this study, three-dimensional fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) was used to analyze the sources of CDOM in Lake Bosten. Three fluorescent components, including a terrestrial humic-like C1(255 nm/420 nm), a tyrosine-like C2(270 nm/324 nm) and a tryptophan-like C3(230 nm/340 nm) were obtained using PARAFAC. In the summer of 2018, we found a significant negative correlation between salinity and C1(r= -0.64, p<0.01), and a significant positive correlation with C2(r= 0.65, p<0.01), suggesting that external inputs via rivers were the main source of protein-like and humic-like fluorescent components, and intense evaporation resulted in enhanced microbial activity. In the autumn of 2019, salinity was significantly and positively correlated with C3 (r= 0.70, p<0.01), and significantly and negatively correlated with C2 (r = -0.51, p<0.05), implying that freshwater input diluted protein-like components. Overall, the highest CDOM concentration was found in the estuary of the Huangshuigou River, northwestern of the lake, varying in seasons. The mean of a(350) in the lake was higher in the summer than in the autumn (t-test, p<0.001), indicating that water quality in the summer was worse than in the autumn. The variation of the CDOM parameters was greater in the inflowing estuaries, and the influence of fresh water input was more significant in the summer of 2018 than that in the autumn of 2019. High spatial heterogeneity of CDOM was observed in Lake Bosten. CDOM fluorescence was dominated by C1 in the inflowing estuaries and the fluorescence intensity of C1 decreased eastward in the summer of 2018. While in the autumn of 2019, C1 contributed more in the estuary of River Huangshui than in the remaining lake regions.