西江流域硝酸盐氮输出规律研究

Study on nitrate-N export changes of the Xijiang River

以西江流域为研究对象,研究流域出口断面硝酸盐氮浓度时间变化规律,采用非平稳时间序列分析方法,分析流域系统行为对氮输出的影响,结果发现:西江硝酸盐氮浓度存在线性增加的确定性趋势,其季节增加量最大值出现在每年5月,与降雨季节增加量最大值时间基本一致,表明降雨造成的地表冲刷、土壤侵蚀以及5月施加的氮肥量大,是造成流域硝酸盐氮输出增大的主要原因。对西江高要断面输出的硝酸盐氮浓度建立了非平稳自回归-滑动平均混合模型,即ARIMA(1,0,1)(2,1,1)12模型,模型通过了高要站硝酸盐氮浓度实测数据的验证,利用模型,预测了西江硝酸盐氮输出的时间变化规律。

On the basis of the time series analysis, the changes of nitrate-N concentrations in Gaoyao section of Xijiang River are studied in this paper for the analysis of the integrated catchment＇s response. It is found that the nitrate-N time series has a linear increase trend. Besides, its peak nitrate-N seasonal index occurs in May, almost the same time as the peak precipitation seasonal index does. It can be concluded that the soil erosion from precipitation, as well as the increase use of nitrogen fertilizer in May are the main cause of the peak nitrate export in the Xijiang catchment. In order to predict the changes of nitrate-N concentration in the Xijiang River, an integrated autoregressive and moving average model of ARIMA（1,0,1） （2,1, 1 ）12 is developed in this paper. The model＇s responses are verified by the comparison to the measurements of nitrate-N concentration in Gaoyao station, and a favorable match is found between them. The model simulation is conducted for the prediction of the future nitrate-N export in Xijiang River. It is clear that this paper is beneficial for the water environment protection in the Xijiang catchment.