亚热带典型农林流域面源磷负荷估算与源解析

Estimation and sources apportionment of nonpoint source phosphorus load in a typical subtropical agricultural and forestry watershed

选取亚热带典型农林流域——金井河流域为研究对象,构建流域面源磷负荷估算模型,对流域面源磷负荷进行估算,并解析各形态磷负荷的空间分布特征。采用改进的输出系数模型和修订的通用土壤流失方程(RUSLE)分别建立模型的溶解态磷和吸附态磷模块,同时利用贝叶斯统计反演得到输出系数模型的参数后验分布以提高模型模拟精度。模型总磷负荷模拟值与观测值的误差绝对值为3.3%~27.1%,溶解态磷的决定系数(R^(2))和纳什效率系数(NSE)分别为0.84和0.82,吸附态磷的R^(2)和NSE分别为0.68和0.65,模型对溶解态磷负荷的模拟效果优于吸附态磷。流域面源总磷负荷平均为64.3 kg·km^(-2)·a^(-1),其中溶解态磷为29.6 kg·km^(-2)·a^(-1),其空间高值区主要集中在农田和村镇区域,林地、农田、居民地溶解态磷负荷分别为13.4、40.5、31.1 kg·km^(-2)·a^(-1);流域吸附态磷负荷平均为34.7 kg·km^(-2)·a^(-1),其空间高值区多分布在林坡地,林地、农田、居民地吸附态磷负荷分别为43.1、16.5、4.5 kg·km^(-2)·a^(-1)。研究表明,亚热带丘陵区面源磷负荷的治理需要根据不同形态磷负荷输出空间分布差异有针对性地开展管控措施。

Jinjing watershed,a subtropical watershed primarily used for agriculture and forestry,is the focus of this study.Specifically,we constructed a nonpoint source phosphorus load estimation model to estimate phosphorus load.Moreover,we also analyzed the spatial distribution characteristics of each form of phosphorus load.The modified output coefficient model and the revised universal Soil Loss Equation(RUSLE)were used to establish the dissolved and adsorbed phosphorus modules of the model;simultaneously,the posterior distribution of parameters of the output coefficient model was obtained through Bayesian statistical inversion to improve the accuracy of the model′s simulations.The absolute error between the modeled and observed values of total phosphorus ranged from 3.3%to 27.1%.The coefficient of determination(R^(2))and Nash efficiency coefficient(NSE)of dissolved phosphorus were 0.84 and 0.82,respectively;while the R^(2)and NSE of adsorbed phosphorus were 0.68 and 0.65,respectively.The results showed that the average of the total phosphorus load of nonpoint sources was 64.3 kg·km^(-2)·a^(-1),whereas the dissolved phosphorus load was 29.6 kg·km^(-2)·a^(-1).Spatially,phosporus loads were mostly concentrated in farmlands and residential areas.Specifically,the dissolved phosphorus load of forests,farmlands,and residential areas were 13.4,40.5 kg·km^(-2)·a^(-1),and 31.1 kg·km^(-2)·a^(-1),respectively.The average adsorption phosphorus load of the basin was 34.7 kg·km^(-2)·a^(-1),and it was mostly concentrated in forest slopes.The adsorbed phosphorus load of forests,farmlands,and residential areas was 43.1,16.5 kg·km^(-2)·a^(-1),and 4.5 kg·km^(-2)·a^(-1),respectively.The control of nonpoint source phosphorus load in subtropical hilly regions should to be conducted through targeted control measures,considering spatial distribution differences of different forms of phosphorus output.