研究典型沙源区水库大气氮、磷湿沉降时空分布特征及水环境污染效应对水生态环境的治理与修复具有重要意义.以往的研究多集中在沿海地区、长江流域及南方地区,而对于干旱少雨、多大风天气、蒸发量远远大于降水量的沙源区水库则鲜有报道.以京蒙沙源区大河口水库为研究对象,于2014年3月—2016年2月在水库周围5个不同区域湿沉降采样点收集样品80个,测定TN、各形态氮和TP浓度,分析湿沉降中N、P营养盐的沉降特征,估算大气氮、磷湿沉降率及湿沉降对水库富营养化的贡献,探讨氮、磷湿沉降对水库水环境所产生的影响.结果表明,大河口水库湿沉降中N沉降所占比例最大,总氮质量浓度年均值为0.50 mg?L-1,其中NH4+-N高于NO3--N,两者共占约70%;P沉降较少,总磷质量浓度年均值为0.08 mg?L-1.湿沉降中氮、磷营养盐主要来源于畜禽养殖,农业化肥施用及秸秆和牛粪焚烧等.大气氮、磷湿沉降率呈明显的季节性变化特征,表现为夏季最大,夏、秋两季TN、TP的湿沉降率分别占全年的75%和80%.水库周围各区域湿沉降呈现西北库区各季节沉降率较东南库区高的特征.通过大气湿沉降进入大河口水库的TN年负荷量为1.89 t?a-1,TP年负荷量为0.10 t?a-1,分别为同期河流入库负荷的5.27%和7.14%,这主要与北方沙源区多风少雨的典型气候特征和当地环境条件有关.尽管大河口水库大气氮、磷沉降仍以干沉降为主,但湿沉降对地处生态环境极其脆弱的沙源区水库水环境的影响及可能带来的水生态环境问题不容小视.%Spatiotemporal variations of nitrogen (N) and phosphorus (P) and its impact on water pollution are significant to water ecosystem govern and recovery in sand source area. Most previous studies are performed in coastal areas, the Yangtze River Basin and southern of China. While for reservoirs in sand source with more drought, less precipitation, more windy, and evaporation is far greater than precipitation are rarely reported. In this study, five sites around Dahekou Reservoir which located in the sand source area of Beijing and Inner Mongolian, were chosen to collect 80 precipitation samples from March 2014 to February 2016. Mass concentration of total nitrogen (TN), nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N), ammonia nitrogen (NH4+-N) and total phosphorus (TP) in each precipitation samples were measured to understand seasonal and spatial nutrients variations of wet deposition. The wet deposition rates of N and P were quantified, and the contribution of wet deposition to eutrophication of Dahekou Reservoir was estimated as well. The results indicated that TN deposition accounted for the largest proportion in wet deposition. Annual average mass concentration of TN was 0.50 mg?L-1, in which the content of NH4+-N was higher than NO3--N and those two components accounted for about 70%. The mass concentrations of TP deposition were relatively lower, with an annual average value of 0.08 mg?L-1. In wet deposition, N and P nutrient salt mainly came from livestock and poultry, chemical fertilizer application for agricultural, the burning of straw and manure, and so on. Seasonally, the deposition rates of nutrients in five sites were high in summer. Wet deposition rate of TN and TP in the two seasons of summer and autumn accounted for 75% and 80%. Spatially,the deposition rates were relatively higher in the northwestern than southeastern of Dahekou Reservoir. The annual wet deposition of TN and TP was 1.89 t and 0.10 t, respectively, which accounting to 5.27% and 7.14% of the annual loading of rivers into Dahekou Reservoir. This was mainly related to the typical climate characteristics of windy and less precipitation and to the local environmental conditions of the northern sand source area of Beijing and Inner Mongolia. Although dry deposition was still the main component of atmospheric nitrogen and phosphorus deposition, much attention should be paid to wet deposition which was significant to water ecosystem and environment of reservoir that located in extremely vulnerable ecological environment.
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