• 关键词：湖荡  溶解有机质  三维荧光光谱  平行因子分析  来源解析  时空分布特征

• 基金项目：

• 王爽
• 同济大学环境科学与工程学院，长江水环境教育部重点实验室，上海 200092

• 王三秀
• 同济大学环境科学与工程学院，长江水环境教育部重点实验室，上海 200092

• 黄清辉
• 同济大学环境科学与工程学院，长江水环境教育部重点实验室，上海 200092

• 摘要：在太湖流域广泛分布的湖荡是一种浅水草型湖泊生态系统，研究其中的溶解有机质（DOM），有助于更好地认识湖泊营养动力学.本研究以南白荡为例，于2019年12月—2021年6月期间采集了14次、共计106个表层水体样品，开展了溶解有机碳（DOC）、紫外-可见吸收光谱及三维荧光光谱等分析，探讨了湖荡中DOM光谱参数、组成、来源及时空分布特征.结果表明：南白荡表层水DOC浓度为2.26 ~ 6.10 mg?L^-1，平均浓度（3.87 mg?L^-1）低于太湖，呈夏高冬低的特征.有色溶解有机质（CDOM）的吸收系数（α₃₅₅）、比吸收系数（SUVA₂₅₄）、光谱斜率（S_275~295）和吸收系数比值（α₂₅₀/α₃₆₅）等参数空间差异不显著（p>0.01），但表现出与DOC浓度类似的季节变化规律，即CDOM含量、芳香性以及分子量也呈夏高冬低的特征.荧光溶解有机质（FDOM）由类酪氨酸组分（C1，激发波长Ex 277 nm， 发射波长Em 307.5 nm）、陆源类腐殖酸组分（C2，Ex 247/313 nm，Em 440.9 nm）以及类色氨酸组分（C3，Ex <241/289 nm，Em 349.1 nm）组成.C2的荧光强度夏秋高、冬春低，C1和C3的荧光强度冬春高、夏秋低.荧光指数（FI）为1.80 ±0.08，生物源指数（BIX）在春季、秋季、冬季分别为1.11 ±0.07、1.08 ±0.07、1.19 ±0.07，腐殖化指数（HIX）为0.36 ±0.10，说明南白荡FDOM生物内源的贡献相对较多，且腐殖化程度较低；夏季BIX为0.77±0.27，显著低于其他季节（p<0.05），说明夏季陆源输入降低了自生源的贡献比例.

• Abstract：Small and shallow grass lakes are widely distributed in the Taihu Lake basin. Investigation on the characteristics and source of dissolved organic matter （DOM） is helpful for better understanding of the nutrient dynamics in these lakes， thus providing critical information for maintaining the water quality and safety as drinking water sources. In this study， we collected 106 surface water samples in Nanbaidang lake （as a typical small and shallow grass lake） during 14 samplings conducted between December 2019 and June 2021. The spectral characteristics， source as well as temporal and spatial distributions of DOM of these water samples were explored based on analysis of dissolved organic carbon （DOC）， UV-visible absorption spectroscopy， and three-dimensional fluorescence excitation-emission matrix. The results show that the DOC concentration was higher in summer and lower in winter （ranged from 2.26 to 6.10 mg?L^-1）， and the mean concentration （3.87 mg?L^-1） was lower than that in the Taihu Lake. There was no significant spatial variation （p>0.01） in the absorption spectral parameters of chromophoric dissolved organic matter （CDOM）， including ultraviolent absorption coefficient at 355 nm （α₃₅₅）， specific ultraviolent absorbance at 254 nm （SUVA₂₅₄）， spectrum slope （S_275~295） and α₂₅₀/α₃₆₅. Similar with the seasonal variation of DOC concentration， the CDOM content， aromatization， as well as molecular weight were higher in summer and lower in winter. The fluorescent dissolved organic matter （FDOM） was composed of tyrosine-like component （C1， Ex 277 nm， Em 307.5 nm）， terrestrial humic-like component （C2， Ex 247 /313 nm， Em 440.9 nm）， and tryptophan-like component （C3，Ex <241/289 nm， Em 349.1nm）. The fluorescence intensity of C2 was higher in summer and autumn， and lower in winter and spring. In contrast， the fluorescence intensities of C1 and C3 were higher in winter and spring than in summer and autumn. The fluorescence index （FI， 1.80 ±0.08） and biological/autochthonous index （BIX） in spring （1.11 ±0.07）， autumn （1.08 ±0.07） and winter （1.19 ±0.07） indicated the large contribution of biological autochthonous to FDOM， while the humification index （HIX， 0.36±0.10） indicated low humification. The BIX in summer （0.77 ±0.27） was significantly lower than other seasons （p<0.05）， indicating the contribution of autochthonous source was reduced by the relatively larger terrestrial inputs in summer.

• Key words：lake  dissolved organic matter  3-dimensional fluorescence spectrum  parallel factor analysis （PARAFAC）  source analysis  spatial and temporal distribution characteristics

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