周边土地利用类型对川西平原西河氮素的影响

Impact of surrounding land use types on nitrogen in Xihe River of West Sichuan Plain

以四川盆地西部典型农业小流域为研究区,于2015年3月～2016年2月持续监测河流氮素(NH_4^+-N、NO_3^--N、TN)和pH,结合遥感解译、地理信息系统和相关性分析等技术,探讨了监测断面周边流域土地利用类型与河流氮素及pH值的关系.结果表明,研究区河流氮素浓度的季节变化均表现为冬季最高(2.063mg/L)、春秋次之(1.536mg/L;1.432mg/L)、夏季最低(1.085mg/L),同时月均NO_3^--N浓度(0.891mg/L)显著高于NH_4^+-N(0.425mg/L)(P<0.01),且NO_3^--N受到典型土地利用类型的显著影响.随着缓冲区半径的增加,耕地、城乡建设用地和水域的面积与NO_3^--N和TN浓度相关性逐渐降低,且在250m缓冲区内,城乡建设用地面积与NO_3^--N浓度呈显著正相关(P<0.05);交通运输用地面积与所有氮组分的相关性均增大,且在750m缓冲区内,交通运输用地面积与NO_3^--N和TN浓度呈极显著正相关(P<0.01).城乡建设用地和交通运输用地可能是河流NO_3^--N的"源".

This research was conducted in a typical agricultural small watershed in the western Sichuan Basin.The nitrogen(NH4^+-N,NO3^--N,TN)concentration and pH in Xihe river were continuously monitored from March2015to February2016.Using different techniques,such as remote-sensing interpretation,geographic information systems,and correlation analysis,the relationship between nitrogen concentration and pH in the river with surrounding land use typed area was explored.Results showed that river nitrogen concentration was higher in the winter(2.063mg/L)than in spring and autumn(1.536mg/L;1.432mg/L),followed by summer(1.085mg/L).Concurrently,the monthly average concentration of NO3^--N(0.891mg/L)was significantly higher than that of NH4^+-N(0.425mg/L)(P<0.01),and NO3^--N was remarkably affected by typical land use types.As the buffer zone radius increased,the correlation of cultivated land,urban-rural construction land,and water area with NO3^--N and TN concentrations gradually decreased.In the250m buffer zone,the area of urban-rural construction land was significantly positively correlated with NO3^--N concentration(P<0.05),and the transportation land was increasingly correlated with all nitrogen components.In the750m buffer zone,the area of transportation land was significantly positively correlated with NO3^--N and TN concentrations(P<0.01).Urban-rural construction land and transportation land may be the“source”of river NO3^--N.