基于水动力学的紫色土区植物篱控制面源污染的临界带间距确定

Confirmation of critical distance between hedgerows for non-point pollution control based on hydro-dynamics in purple soil area

为了分析确定紫色土区植物篱控制面源污染合适的带间距,该研究基于坡面水流动力学,利用四川省遂宁市水土保持试验站多年观测资料,分析了紫色土区新银合欢植物篱带间距对10°、15°农耕地面源污染的控制机理。结果表明:紫色土区在天然降雨条件下,为保证植物篱带间距能有效地控制篱带间的土壤流失,坡面发生细沟侵蚀时的径流流速应不大于颗粒粒径<0.02mm土粒的起动流速。通过对坡面细沟发育过程推导表明,紫色土区坡度为10°、15°的坡面布设植物篱时带间距最大分别应为13.73、9.00m。当坡面开始产生细沟侵蚀时的径流流速与颗粒粒径<0.02mm土粒的起动流速刚好处于临界状态时,10°、15°坡面产生细沟侵蚀的最小径流流速分别为0.183、0.190m/s。坡面表土养分流失主要是通过土壤颗粒流失的,植物篱控制坡面土壤颗粒的流失对控制农业面源污染具有重要意义。

To confirm suitable distance between hedgerows for controlling non-point pollution in purple soil area,its control mechanism for the cropland under different distance between L.leucocephala hedgerows of 10° and 15° gradient cropland was analyzed based on hydro-dynamics and observed data of many years in Suining soil and water conservation experimental station.The results indicated that the hedgerows could effectively control soil erosion between hedgerows under the natural precipitation condition if runoff velocity was less than or equal to the start-up velocity of the soil particle（0.02 mm） while rill erosion was occurring in purple soil area.Through studying the derivation of rill erosion process,it showed that the largest distance between hedgerows for 10° and 15° gradient sloping cropland was 13.73 and 9.00 m respectively. When runoff velocity and start-up velocity of soil particle （0.02 mm） were in the critical starting condition at the time of rill erosion occurring, the smallest runoff velocity of 10° and 15° gradient slope was 0.183 and 0.190 m/s respectively. It was the main nutrient loss way through soil particle loss on the surface soil, controlling soil particle loss by hedgerow played an important role in the process of non-point pollution control.