亚热带地区典型水库流域氮、磷湿沉降及入湖贡献率估算

为了探究汤浦水库流域氮、磷湿沉降对水库水体营养的贡献率,本研究对2014 2015年的汤浦水库流域4个采样点的雨水及3条溪流进行样品收集,测定其中磷和不同形态氮的质量浓度,分析汤浦水库流域大气湿沉降中氮、磷营养盐的分布特征,并估算氮、磷营养盐湿沉降对汤浦水库入库负荷的贡献率.结果表明:湿沉降中总氮(TN)平均浓度为1.02±0.58 mg/L,氨氮、硝态氮和有机氮浓度占TN浓度的比例分别为60.65%、34.07%和5.28%;总磷(TP)平均浓度为0.033±0.028 mg/L.4个采样点湿沉降中氮、磷浓度均表现为冬春季(少雨季)高、夏秋季(多雨季)低.空间上,王化点位的各形态氮和总磷浓度显著高于其他3个采样点.TN和TP年均湿沉降通量约为18.15和0.62 kg/(hm~2·a),年均沉降总量为834.94和28.39 t;库区TN和TP水面湿沉降量为24.14和0.82 t,直接贡献率占河流输入的1.77%和3.07%.湿沉降来源的氮、磷营养盐随河流输入的间接贡献率为8.3%和4.6%.综上所述,氮、磷湿沉降是水库外源营养的重要输入部分,深入掌握其时空分布特征及入库贡献率是进一步加强流域管理和减轻水库外源营养输入的重要前提.

Wet atmospheric deposition of nitrogen and phosphorus and estimation of their contributions to the lake in typical subtropical reservoir basins

To understand seasonal and spatial wet deposition characteristics of nutrients input to the Tangpu Reservior Basin, precipitation samples at four sites and stream water samples at three sites were collected from the basin during 2014-2015. The mass concentration of total nitrogen(TN), nitrate nitrogen (NO₃^--N), ammonia nitrogen and total phosphorus(TP) in the wet deposition were measured, and the precipitation characteristics of nitrogen and phosphorus nutrients, the deposition rates and their contributions compared with their counterparts from external loading of streams to the reservoir were studied. The results showed that the annual wet deposition concentration of TN was 1.02±0.58 mg/L, and the percentages of ammonium, nitrate and organic nitrogen contributed 60.65%, 34.07% and 5.28% of TN, respectively. The annual wet deposition concentration of TP was 0.033±0.028 mg/L. Seasonally, the concentrations of TN and TP in wet deposition were higher in winter and spring than in summer and autumn. Spatially, the concentrations of TN and TP were the highest at Wanghua site. The annual wet deposition rates of TN and TP were about 18.151 and 0.62 kg/(ha·a), and their average annual budgets reached 834.94 and 28.39 t, respectively. The wet depositions of water surface into Tangpu Reservoir were 24.14 and 0.82 t, and the direct contributions as 1.77% and 3.07% of the stream input. The indirect contributions of nitrogen and phosphorus from wet deposition sources accounted for 8.3% and 4.6% of the stream input. In summary, the nutrient load from the wet deposition plays a crucial role in the nutrient input of reservoirs. Understanding the nutrient load from the wet deposition will help us to better manage the reservoir basin and reduce the external nutrient loads to the basin.