三峡库区农业化肥流失污染及其成因分析

农业化肥流失是三峡库区最主要的非点源污染源之一，其污染成因分析对有效控制三峡库区非点源污染具有重要的指导意义。通过对三峡库区19个区县化肥用量、施肥强度、品种、比例结构、流失负荷的统计资料分析，明确了库区化肥流失非点源污染的基本情况;接着随机性选取石柱县、开县、宜昌市、兴山县4库区县市12个监测点进行监测分析．同时结合秭归县15个人工模拟降雨试验。得出库区化肥施用强度高，分布不均匀，施用品种单一，重氮肥、磷肥轻钾肥，化肥N，P流失非点源污染有加重的趋势，且化肥N，P的流失量与土壤肥力成正比N：R2=0.51〉0.468（n=16，95％）；P：R^2=0．68〉0．549（n=19.99％）]，与农田地表中粉粒（0．002—0．02mm）和粘粒（〈0．002mm）浓度成正比，与施肥强度呈显著性正相关；降雨强度越大、地表植被越少，化肥N，P流失越大R^2=0．98 R^2〉765（n=8.99％）]。

Current Pollution Situation and Causes Analysis of Chemical Fertilizer Losses in Three Gorges Reservoir Region

Chemical fertilizer losses is one of the main sources of non-point source pollution. This paper analyzed current situation of non-point source pollution from chemical fertilizer losses according to dosage, amount in unit area, types, structure proportion of chemical fertilizer and burden of non-point source pollution from chemical fertilizer losses in 19 counties of Three Gorges Reservoir Region from 1996 to 2001. As the same time, this paper summarized the causes of non-point source pollution from chemical fertilizer losses by observing 12 monitoring points in 4 counties （Shizhu, Kaixian, Yichang, Xingshan） and 15 artificial rainfall districts in the county of Zigui. It concludes that the amount of chemical fertilizer is high in unit area and distributes asymmetry, types of chemical fertilizer is monotonous, the dosage of nitrogenous and phosphorescence fertilizer is much more than kainite fertilizer, and the burden of non-point source pollution from Chemical fertilizer N, P losses is higher and higher. Chemical fertilizer N, P losses is positive correlated with the amount of chemical fertilizer in unit areaN： R^2 = 0.51 〉 0.468（n = 16, 95%）; P： R^2 = 0.68 〉 0.549（n = 19.99%）] and the contents of granule （0.002 - 0.02 mm） and soil clay （〈0.002 mm） on farmland. The greater rainfall intensity and less vegetation on the earth＇s surface cause more N and P losses R^2 = 0.98R^2 〉 765（n = 8, 99%）].