流域磷素面源污染产生与输移空间分异特征

Contrasting spatial distribution of the emission and export of phosphorus loss from a typical watershed in Yunnan Plateau Lakes Area

甶于面源污染物从坡面产生后至向流域出口输出过程会发生一系列变化,如在河道迁移过程发生的沉降衰减,基于污染物产生与输出空间分布识别关键区会存在一定的差异.因此,本研究选取面源污染较为严重的高原湖泊洱海典型小流域,以子流域为空间分析单元,采用经实测数据验证后的定量模拟工具-SWAT模型和数学统计方法,分析流域面源磷产生与输出的空间分布及差异,评估河道迁移过程对两者空间分布差异的影响.结果表明:流域面源流失磷产生强度存在明显的空间分异特征,不同子流域流失磷的产生强度在1.52~1.82kg/hm^2之间变化,高强度区主要集中在有坡耕地分布的水文敏感区和植被覆盖度差的土壤侵蚀敏感区;不同子流域流失的磷经河道迁移后发生了-25.6%~21.6%的变化,导致流失磷的输出与产生空间分布出现差异,较高产生强度区,磷流失高输出强度区缩小为土壤侵蚀敏感区;不同子流域流失磷经河道迁移后发生的不同变化受流失磷产生强度与径流迁移时间的综合影响.

Understanding the spatial distribution of phosphorus(P)loss is of value to identify the critical source areas(CSAs)fordiffuse pollution control,but little is known about difference between the emission amount thatemitted to the reach and exportamount that exported out from reach.Taking Fengyu River watershed,a typical sub-basin of Erhai Lake basin in Yunnan plateaulake area,as the case study area,this work studied on the spatial distribution of the emission and export of P loss using SWAT,furthermore,evaluated the role of P delivery through the reaches in the spatial distribution of P loss.High emission intensity oftotal Ploss was mostly located in the hydrological sensitive areas or soil erosion sensitive areas with slope arable lands.Thehighest emission intensity of total Ploss was1.52~1.82kg/hm2.Moreover,the delivery process of emitted P toreaches decreasedthe distribution area of the highest export intensity of total P.The highest export intensity of total Ploss reduced to bethe soilerosion sensitive area.The retention coefficients of reaches in different sub-watersheds ranged from-25.6%to21.6%because ofthe variation of transporting processes between sub-watersheds,which changed the spatial features of P loss.