紫色土丘陵区典型生态-水文单元径流与氮磷输移特征

通过对紫色土丘陵区典型农业-集镇-林地复合型小流域3次降雨-径流全过程的连续监测，测定径流过程中泥沙含量和不同形态氮磷浓度，以期认识典型农村生态-水文单元降雨径流过程中氮磷迁移规律。结果表明：降雨-径流过程中悬浮泥沙的流失主要集中在径流前期，其峰值出现在雨强最大时；集镇径流污染的影响主要表现在径流前期，是径流前期铵态氮偏高的主因；降雨-径流过程中，颗粒态氮与可溶态氮比（PN/DN）、颗粒态磷与可溶态磷比（PP/DP）的峰值均出现在雨强较大时：其中PN/DN多小于1，而PP/DP范围为1.1~30.2，说明氮素流失主要通过可溶态的方式，而磷的迁移以颗粒态磷为主。因此在紫色丘陵区建议利用湿地植物与沉砂池等综合措施控制土壤侵蚀和非点源污染以保护当地生态环境安全。

Characteristics of Nitrogen and Phosphorus Transportation Through Runoff in a Typical Ecological-hydrological Unit of Hilly Area of Purple Soil

This study was carried out at an agriculture-town-forestry headwater watershed in Hilly area of purple soil. In order to understand the hydrological pathways of nitrogen and phosphorus loss in this Typical Ecology-Hydrology Unit, water flow, sediment, N and P were monitored continuously in three storms. Results showed that suspended sediment loss mainly occurred in the early stormflow and SS concentration peaks was synchronous with rainfall intensity. The impact of the N and P pollution from town mainly contributed to the early runoff which was the reason for high ammonium-nitrogen (AN). Particulate nitrogen/dissolved nitrogen ratio (PN/DN) of most samples was less than 1 and particulate phosphorus/dissolved phosphorus ratio (PP/DP) ranged from 1.1 to 30.2 indicating that nitrogen loss was mainly in dissolved form and the phosphorus loss was mainly though sediment. Both peaks of the two ratios occurred when the rain intensity was high. Construction of wetland in ditches combined with grit chamber could be effective on N and P loss control in this region.