Abstract：
Reservoirs located in middle and high latitudes freeze for months in winter, where the accumulation characteristics of pollutants are changed by superimposed influence of salt exclusion from ice on the surface and pollution release from sediments at the bottom. Taking total nitrogen (TN) of Biliuhe reservoir in Northeast China as an example, we developed a model to simulate TN accumulation characteristics influenced by ice and sediments during the freezing period (NACISF), and quantified contributions of TN from ice and sediments. Model parameters of ice and sediments were determined by laboratory freeze-up simulation experiment and sediment release flux simulation experiment, and water quality data were obtained from field investigations. Results showed that the annual average amount of TN input during the ice-covered period from 2015 to 2020 was 220.77 t, the output was 400.11 t, and the accumulated amount was 589.52 t. TN excluded from ice and released from sediments contributed 8.12% and 7.17% of the total TN inputs in winter, respectively. Analysis showed that the TN excluded from ice was positively correlated with ice thickness and initial TN concentration. The maximum ice thickness of Biliuhe reservoir had a 13 year cyclic feature, and the proportion of TN excluded from ice to the total TN inputs in different periods ranged from 10.68% to 17.30% (mean 13.18%). Meanwhile, TN accumulated seasonally as summer > autumn > winter > spring. The TN exclusion effect in 2050 would be weakened when considering the combined effects of climate change and human activities, with a reduction of about 40.85% compared to the current. It is concluded that the NACISF model took into account the influences of both ice and sediments, which provided a detailed understanding of the accumulation characteristics of TN during freezing period, and had important reference significance for water quality management in winter.
摘要：
位于中高纬度地区的水库冬季冻结数月,其中污染物的积累特征是由于表面冰层的盐排除和底部沉积物的污染释放的叠加影响而改变的。以东北碧流河水库总氮(TN)为例,我们开发了一个模型来模拟冰期（NACISF）中冰和沉积物影响的TN积累特征，以及冰和沉积物对TN的量化贡献。通过实验室冻结模拟实验和沉积物释放通量模拟实验确定了冰和沉积物的模型参数,水质数据是从实地调查中获得的。结果表明,2015-2020年冰封期间TN年平均投入量为220.77t,输出为400.11t，累积量为589.52t。冬季，从冰中排除并从沉积物中释放的TN占总TN输入的8.12％和7.17％，分别。分析表明，冰层中排除的TN与冰层厚度和初始TN浓度呈正相关。碧流河水库的最大冰层厚度具有13年的循环特征，在不同时期，冰排除的TN占总TN输入的比例为10.68％至17.30％（平均13.18％）。同时,TN按季节累积为夏季>秋季>冬季>春季。考虑到气候变化和人类活动的综合影响，2050年的TN排斥效应将会减弱，与目前相比减少了约40.85%。结论是，NACISF模型考虑了冰和沉积物的影响，详细了解了凝固期TN的积累特性，对冬季水质管理具有重要的参考意义。
