Abstract:

Nonpoint source pollution is one of the most important factors affacting the water quality of Danjiangkou Reservoir. In order to explore the variation of nonpoint source pollution,nitrogen concentrations were measured from January to December of 2008 within different types of land use and small watersheds in Hujiashan.The results showed that TN and NO-3N concentrations were high and steady; While NH+4N concentration was low,but fluctuated greatly in village.The dynamic process of nitrogen concentrations at the outlet of village was closely related to rainfall intensity.NO-3N was the main form of nitrogen loss,accounting for 6031% ~ 9655% of TN output,and it was correlated significantly with TN.Compared with nitrogen concentration in village,the concentrations of nitrogen was low in mixture of woodland and farmland,and TN showed a process from increase to decrease,and then from smooth to increase change with rainfall,and NO-3N and TN had a close relationship.From the saptial transporting,the concentration of nitrogen showed dilution and enrichment effects in the downstrean of small watersheds,while the village concentration of nitrogen had large effect on these two types.In temporal,the concentration of NO-3N and TN varied with season change,showing concentration of TN in spring>summer>autumn>winter,NO-3N in autumn>summer>spring>winter,which was closely related to agricultural systems and weather.The water quality of Hujiashan watershed was poorer than that of Danjiangkou Reservoir;thus the effective measures should be implemented to improve the water quality,especially in villages.