澄江尖山河小流域不同土地利用类型面源污染输出特征

Characteristics of Non-point Source Pollution Output of Different Lands Utilization Pattern in Small Watersheds in Jianshan River,Chengjiang

研究了自然降雨条件下澄江尖山河小流域4种不同土地利用类型径流小区中面源污染输出特征。结果表明，不同土地利用类型径流小区中面源污染物输出量不同，农地的全磷输出量最大，其次是人工林，次生林和灌草丛较小；氨氮和COD输出量表现出农地和人工林大于次生林和灌草丛。不同土地利用类型径流中面源污染物输出浓度没有显著差异．但从总体上来看，植被覆盖度越高，径流水中的氮、磷浓度越高，而COD、氨氮浓度越低，硝态氮浓度是亚硝态氮浓度的8．5～111倍，可溶态氮以硝态氮形式流失为主；侵蚀泥沙有富集养分的特征，且次生林和灌草丛的富集率高于农地。不同土地利用类型侵蚀泥沙中全氮和全磷的输出量依次为：农地〉人工林〉灌草丛〉次生林，速效氮和速效磷则为：农地〉人工林〉次生林〉灌草丛。与氮相比，表层土壤中的磷更容易随径流流失，磷的输出以泥沙结合态为主，特别是速效磷。

This study mainly studied the characteristics of non-point source pollution output of runoff areas of four different lands use pattern in Jianshan river, Chengjiang, under natural precipitation condition. The result showed that the total phosphorous outputs were different at various runoff areas of the lands use pattern, and the farmland had the maximum total phosphorous output among the four different runoff areas, and followed by planted forest, the secondary forest and shrub-grassland. The COD and NH4^＋ -N outputs at planted forest and farmland were higher than the secondary forest and shrub-grassland. The non-point source pollution output at the four different runoff areas of different lands use pattern had no definate differences, however, on the whole view, the higher vegetation coverage caused the higher concentrations of phosphorous and nitrogen output in runoff, while leaded to the lower COD and NH4^＋ -N, NO3^- -N concentrations. The nitrate concentration reached 8.5 - 111 times of the nitrite, and the soluble nitrate was the main loss form. The eroded sediment was capable to enrich nutrient, and the enrichment ratios at secondary forest and shrub-grassland were higher than the farmland. The total phosphorous and nitrogen outputs at the eroded sediments of different lands use pattern were orderly followed as farmland, planted forest, shrub-grassland and secondary forest, but the available nitrogen and phosphorus concentrations were followed as farmland, planted forest, secondary forest and shrub-grassland. Compared with nitrogen, the surface soil phosphorus was more easily to be lost with the runoff activity, and the phosphorous output was mainly connected with sediment, particularly for the available phosphorus.