目的：目前关于地表水冰封的研究主要集中于冰封期重金属、营养盐在冰-水体系的分布特征，室内模拟实验则侧重于研究冻融过程中污染物在冰-水体系中的迁移规律及其影响因素。冻融条件下污染物在冰-水-沉积物体系中的迁移规律，尚未明了。因此本文以溶解性有机物（DOM）为研究对象，探究溶解性污染物在冰-水-沉积物体系中的分布变化规律。结合总氮（TN）、总磷（TP）等指标分析不同物质在冻融过程中的关联特征，以环境雌激素类非挥发性有机微污染物为特征污染物，剖析其在冰水相变过程中的浓度变化动态特征。 方法：设置室内控制实验，测定冻融过程中冰水两相的三维荧光光谱（EEMs）、比紫外吸光度（SUVA254）、总氮（TN）、总磷（TP）、溶解有机碳（DOC），并对三维荧光特征指数、SUVA254、TN、TP、DOC进行相关性分析。在排除沉积物影响的前提下，测定冻融过程中冰水两相双酚A（BPA）、雌二醇（E2）、炔雌醇（EE2）的浓度。 结果：1）冻结过程中水相的三维荧光光谱中类色氨酸峰、类酪氨酸峰、类腐殖酸峰的荧光强度增强，TN、TP浓度增加至原水样的1.47、1.13倍，说明在冻结过程中由于冷冻浓缩效应，类色氨酸、类酪氨酸、类腐殖酸三类溶解性有机物、TN、TP由冰相向水相迁移。在水体完全冻结时，冰相的类色氨酸峰、类酪氨酸峰、类腐殖酸峰荧光强度小于原水样，TN、TP浓度降低至原水样的0.76、0.87倍，说明三类溶解性有机物、TN、TP进一步向沉积物迁移，最后在溶解过程中，由沉积物向水体释放。但溶解过程中沉积物向水体释放的三类溶解性有机物、TP的量少于冻结过程中迁移的量，意味着部分污染物在此过程中富集在沉积物中。2）通过测定冻融条件下冰水两相中BPA、E2、EE2的浓度发现，在冻结过程中BPA、E2、EE2向水相中迁移，但迁移速率有所不同。3）相关性分析结果表明，在冻融过程中SUVA254和TP显著正相关，在冻融的影响下，芳香族物质与含P溶解性物质迁移趋势的关联较为紧密。 结论：在冻结过程中，污染物尤其是芳香类污染物向沉积物迁移并富集在沉积物中。冰体融化过程中，在温度、外界扰动的影响下污染物由沉积物向水体释放。因此在地表水冰层形成过程中，冰下水体中污染物浓度升高，同时水体中污染物向沉积物迁移，停留在沉积物中。春季冰层融化，停留在沉积物中的污染物向水体释放，导致春季地表水中污染物浓度升高，可能对水生生态系统健康构成潜在风险。

Objectives: At present, the research on the freezing of surface water mainly focuses on the distribution characteristics of heavy metals and nutrients in ice-water systems during the freezing period. The indoor simulation experiments focus on the migration and influencing factors of pollutants in ice-water systems during freeze-thaw process. However, the migration of pollutants in ice-water-sediment systems under freeze-thaw alternating conditions remain unclear. In the current study, the dissolved organic matter (DOM) was selected as the study object to explore the distribution and migration of dissolved pollutants in an ice-water-sediment system. Combined with total nitrogen (TN), total phosphorus (TP) and other indicators, the correlation characteristics of different substances in freeze-thaw process were analyzed. In addition, environmental estrogens were chosen as represented microorganic pollutants to illustrate the variation on concentrations between ice and water phase during the freeze-thaw alternating process. Methods: Indoor control experiments were set up to measure the three-dimensional fluorescence spectra (EEMs), specific ultraviolet absorbance (SUVA254), and concentrations of total nitrogen (TN), total phosphorus (TP) and dissolved organic carbon (DOC) in ice and water during freeze-thaw process, and the correlation analysis among three-dimensional fluorescence characteristic index, SUVA254, TN, TP and DOC was performed. Simultaneously, the concentrations of bisphenol A (BPA), estradiol (E2) and ethinyl estradiol (EE2) in an ice-water system during freeze-thaw process were measured. Results: 1) The fluorescence intensity peaks of tryptophan-like, tyrosine-like and humic acid-like compounds in the three-dimensional fluorescence spectrum of aqueous phase increased during freezing process, and the concentrations of TN and TP increased to 1.47 and 1.13 times of the raw water sample. The results indicated that tryptophan-like, tyrosine-like and humic acid-like dissolved organic matters, TN and TP migrated from ice phase to aqueous phase due to the freeze concentration effect. When the water was completely frozen, the fluorescence intensity peaks of tryptophan-like, tyrosine-like and humic acid-like compounds at ice phase was lower than that of the raw water sample, and the concentrations of TN and TP were reduced to 0.76 and 0.87 times as compared to the raw water sample, which indicates that those three kinds of dissolved organic matters, TN and TP migrated to the sediment, and then released from the sediment to the water body during dissolution process. However, the amount of those three kinds of dissolved organic matters and TP released from sediment to water in the process of dissolution was less than that transferred in the process of freezing, which means that some pollutants were enriched in sediment in this process. 2) By measuring the concentrations of BPA, E2 and EE2 in the ice-water phase under freeze-thaw alternating conditions, it was found that BPA, E2 and EE2 migrated to the water phase during freezing, but the migration rates were different. 3) The results of correlation analysis showed that SUVA254 was positively correlated with TP during freeze-thaw process. Under the influence of freezing and thawing, the migration trend of aromatic substances and phosphorus-containing dissolved substances is closely related. Conclusions: During the freezing process, pollutants, especially aromatic pollutants, were migrated to and accumulated in sediments. In the process of ice melting, pollutants are released from sediments to water under the influence of temperature and external disturbance. Therefore, during the formation of the surface water ice layer, the concentration of pollutants in the water under the ice increases, while pollutants migrated to the sediment and stay in the sediment. When the ice melts in spring, pollutants staying in sediments will release into water, which lead to the increase of pollutant concentration in surface water in spring and may pose potential risks to aquatic ecosystem health.

X522

国家重点研发计划课题(2019YFD1100501)