Characteristics of Diffuse Source N Pollution in Lean River Catchment

This paper analyzes the spatiotemporal characteristics of diffuse source N pollution in Lean River catchment. The water sampling points were set up on the main stream and tributary on Lean River, and water samples were taken in wet season, dry season, normal season and in the agricultural busy season; the chemical analysis has been carried out in the laboratory. The results indicate that the peak concentration of total nitrogen (TN), dissolved nitrogen (DTN), nitrate nitrogen (NO3--N) appear in December, and the lowest concentration in September, while the concentration of ammonia nitrogen (NH4 + -N) follows converse trend, it is highest in wet season, and lowest in dry season. Furthermore, the concentration of diffuse N is generally higher in downstream area compared to upstream area, and it increased dramatically after rainstorm and intensive agriculture activities. The main finding of this work is that rainfall and runoff are the primary driving factors to cause non-point source N exported from the catchment. Meanwhile fertilizer application causes a great quantity of N into environment, and agricultural activities accelerate the N transformation to water bodies.