沱江流域典型农业小流域氮和磷排放特征

Emission Characteristics of Nitrogen and Phosphorus in a Typical Agricultural Small Watershed in Tuojiang River Basin

小流域非点源污染氮和磷流失是河流水体污染的重要来源,而且氮和磷流失强度与气候、人为活动有密切的关系.因此,本文以长江上游沱江水系花椒沟小流域为研究对象,对小流域径流量、氮磷流失浓度以及流失量进行定位连续监测,结合降雨分析氮和磷输出变化特征及其响应过程.结果表明:(1)小流域2012年和2013年的7~9月径流量分别为10.05×10^5 m3和3.34×10^5 m3,分别占全年径流量的76.58%和56.51%,而且径流量与降雨量呈正相关关系;(2)铵态氮最大排放浓度在4~6月,2012年和2013年最高分别能够达到11.51 mg·L^-1和4.44 mg·L^-1,流失风险期为4~7月,2012年和2013年流失量分别占全年流失量的78.45%和62.24%;总氮、硝态氮最大排放浓度、流失风险期都为7~9月,硝态氮为总氮的最主要排放形式,2012年和2013年硝态氮最大排放浓度分别为6.06 mg·L^-1和11.43 mg·L^-1,7~9月流失量分别占全年流失量的88.74%和65.55%;(3)总磷、可溶性总磷和颗粒态磷流失风险期为7~9月,颗粒态磷为总磷最主要的排放形式,2012年和2013年7~9月流失量占全年流失的36%和68%,且总磷中颗粒态磷的比例会受到降雨的影响.

The emission of nitrogen and phosphorus via non-point source pollution from a small watershed has become the main pollution source of river waters,while climatic conditions and human activities directly affect the changes in rainfall-runoff and types of land use that are closely related to nitrogen and phosphorus pollution.In this study,we explore the runoff loss,nitrogen and phosphors concentration,and nitrogen and phosphorus emission in Huajiaogou small watershed on the upper reaches of Yangtze River.The rainfall,runoff,and temporal changes of nitrogen and phosphorus were analyzed using the continuous position monitoring data.The results showed that:(1)the runoff volumes were 10.05×10^5 m3 and 3.34×10^5 m3 from July 1st to September 30th,accounting for 76.58%and 56.51%in 2012 and 2013,respectively,and they were positively correlated to rainfall.The peak concentrations of ammonia nitrogen(NH4^+-N)from April 1st to June 30th were 11.51 mg·L^-1 and 4.44 mg·L^-1in 2012 and 2013,respectively.(2)The NH4^+-N emission risk period was from July 1st to September 30th,accounting for 78.45%and 62.24%in 2012 and 2013,respectively.The peak concentration and emission risk period of total nitrogen(TN)and nitrate nitrogen(NO3^--N)were from July 1st to September 30th,and NO3^--N was the main form of the total nitrogen emission.The peak concentration of NO3^--N was 6.06 mg·L^-1 and 11.43 mg·L^-1in 2012 and 2013,respectively,and the loss in NO3^--N from July 1st to September 30th accounted for 88.74%and 65.55%in 2012 and 2013,respectively.(3)The emission risk period of total phosphorus(TP),dissolved total phosphorus(DTP),and particulate phosphorus(PP)was also from July 1st to September 30th,and the particulate phosphorus was the main form of the total phosphorus emission.The particulate phosphorus emission from July 1st to September 30th accounted for 36%and 68%in 2012 and 2013,respectively,and the ration of particle phosphorus to total phosphorus was easily affected by rainfall.