黄土丘陵沟壑区退耕地面源污染物负荷变化研究

Study on change of the non-point source pollution load in the returned farmland on loess hilly and gully area

【目的】研究在黄土丘陵沟壑地区实施退耕还林还草工程对水土流失及土壤面源污染的防治效果.【方法】在3个坡级、4种退耕还林草土地利用方式下(乔木林、灌木林、人工草地和坡耕地)布设12个径流小区,对4种土地利用方式下污染物输入量、地表径流、主要面源污染物负荷和林草地拦蓄效率进行研究.【结果】年径流系数坡耕地(3.23%)、人工草地(2.91%)明显地高于油松林(2.74%)和沙棘林(0.91%);坡耕地N、P、K投入量分别是需要量的282%、115%、369%;坡耕地、油松林地、沙棘林地和人工草地CODMn、BOD5、NH3-N、TN、F-、NO2-N、TP含量超标,污染物负荷分别为3.05、3.37、1.07、0.26kg/hm2.【结论】林草植被有效地减少了地表径流的产生数量,整地工程极大地提高了对地表径流的拦截效率.与坡耕地相比,油松林地、沙棘林地面源污染物输出数量减少了64.85%和88.80%,人工草地减少了16.02%.

【Objective】To evaluate control effect of returning farmland to forest or grassland project on soil and water erosion and non-point source pollution in loess hilly and gully area.【Method】12 runoff plots were arranged in 3 slope grades with 4 patterns of returned farmland to forest and grassland（i.e.,arbors,shrubs,artificial grassland and sloping land）,and the input of pollutants,surface runoff,main non-point source pollution load and the efficiency of soil conservation by forest and grassland were measured.【Result】The annual runoff coefficients in sloping farmland（3.23%）and the artificial grassland（2.91%）are significantly higher than those in Pinus tabulaeformis forest（2.74%）and Hippophae rhamnoides forest（0.91%）.The inputs of N,P and K in slope farmland are 282%,115%and 369% of required amounts.The contents of CODMn,BOD5,NH3-N,TN,F-,NO2-N and TP in 4 patterns of returned farmland are all beyond the national standard,the load of non-point source pollution in the sloping land,Pinus tabulaefor-mis forest,Hippophae rhamnoides forest and artificial grassland were 3.05,3.37,1.07 and 0.26 kg/hm^2,respectively.【Conclusion】The forest and grass vegetation effectively reduced the surface runoff,and the soil preparation project greatly improved the interception efficiency of surface runoff.Compared with that in cultivated land,the output of groundwater pollutants in Pinus tabulaeformis,Hippophae rhamnoides forest and grown grassland decreased by 64.85%,88.80% and 16.02%,respectively.