降雨和施肥对秦岭北麓俞家河水质的影响

为了探讨小流域内种植业的施肥措施对流域内地面水质的影响机制,选取秦岭北麓的俞家河小流域为研究对象,设置8个覆盖整个流域特征的监测断面,并于该流域主要经济作物猕猴桃的3个典型施肥时期的不同降雨条件下对河流水质进行监测,分析水体中氮、磷和有机污染物含量的时空分布特征以及降雨和施肥对其产生的影响。结果表明:俞家河流域总氮浓度的变化范围是4.53~11.45 mg·L~(-1),平均值为6.51 mg·L~(-1);总磷平均浓度的变化范围是0.004~1.377 mg·L~(-1),平均值为0.312 mg·L~(-1);CODMn浓度的变化范围为0.89~11.23 mg·L~(-1),平均值为3.15 mg·L~(-1)。早春基肥期总氮平均负荷为227.03 g·d-1,流域负荷增加了73.34%;盛夏追肥期总磷平均负荷为11.36 g·d-1,流域负荷增加了117.36%。大雨时期总氮、总磷、COD_(Mn)负荷分别为228.10、9.94、174.53 g·d-1,对应增加的百分比为35.93%、84.31%、69.65%。水体总氮、总磷浓度与降雨密切相关,雨强越大,浓度和负荷增加越显著,雨强是造成该流域氮素流失的主要气象参数。早春基肥期果园施加氮肥是水体总氮的主要来源,盛夏追施肥会增加水体磷素污染风险,早春施肥期大雨后存在较高的COD_(Mn)污染风险,降雨和施肥的叠加效应是导致面源污染发生的主要因素。河流污染负荷较高的区域集中于中部,主要由两岸猕猴桃园施肥引起,居民的生活污染也有一定贡献。

Effects of rainfall and fertilization on water quality of the Yujia River watershed in the northern Qinling Mountains

With the purpose of investigating the mechanisms of how rainfall and fertilization affected the quality of ground water, we selected a typical Yujia River watershed in which eight water-sampling sections representing the watershed characteristics. Water quality(N, P and COD_Mn) was monitored after various rainfall intensities on Kiwifruit plots(main economical crop for the local) with three key fertilization time-points in early-spring, summer and late autumn. The results show that in Yujia River watershed the concentration of total N averages 6.51 mg·L^-1(range:4.53~11.45 mg·L^-1), the mean values for the concentrations of total P and COD_Mn are 0.312 mg·L^-1(range:0.004~1.377 mg·L^-1)and 3.15 mg·L^-1(range:0.89~11.23 mg·L^-1) respectively. As for the load of fertilization applications to water quality, the mean load of total N during early-spring fertilization is 227.03 g·d^-1, with an increase of 73.34% to the whole watershed, the average load of total P during the summer fertilization is 11.36 g·d^-1, with an increase of 117.36%. With regard to rainfall, the loads of the total N, total P and COD_Mn, during heavy rainfall period are 228.10 g·d^-1, 9.94 g·d^-1 and 174.53 g·d^-1, with an increase of 35.93%, 84.31% and 69.65%, correspondingly. The concentration of total nitrogen and total phosphorus show a positive relationship with rainfall intensity. Therefore, as revealed by our data, rainfall is a main meteorological parameter to cause nitrogen loss in this region. Fertilization during early-spring contributes substantially to the increased N concentration, and the risk of water P pollution becomes stronger especially in summer fertilization. There is higher COD_Mn contamination after heavy rain in early-spring. The combined effect of the rainfall and fertilization is the main factor causing the non-point pollution in Yujia River watershed. The main polluting area of the watershed was middle-part concentrated, which was mainly caused by kiwifruit fertilization, additionally, pollution from local living-residents may also be a reason to the total pollution.