Author(s): Fenghua Gao; Zhongbo Yu; Long Xiang; Cheng Chen; Xiaolu Wei
Linked Author(s): Zhongbo Yu
Keywords: Nitrogen; Phosphorus; Delivery; Catchment; Hydrological pathway
Abstract: Abstract: With the rapid development of economy, the environment endures the relevant negative effects in China. Water environment becomes worse, and the Lake Tai, eastern China suffers from dramatic eutrophication problems. The main reason is extensive application of pesticide, fertilizer and manure. It breaks the phosphorus and nitrogen balance in natural ecosystem, and the residual nutrient deliveries and transfers to the Lake Tai by hydrological pathways. This research was conducted in the Meilin catchment, a small mixed agricultural watershed (73.7 ha) in the hilly area, southwest Lake Tai. In this study, the characteristic and procedure of precipitation-runoff in this watershed were studied during two storm events. The characteristic and mechanics of phosphorus and nitrogen exporting from land by hydrological pathways were also investigated in different scales. During rain events water samples were collected, and the total nitrogen, ammonia nitrogen, nitrate nitrogen, dissolved phosphorus, phosphate and total phosphorus were measured in the catchment. The results indicated that the time for overland runoff reaching to the outlet was very short because of the small size of the catchment. The lag time of the rain starting and the runoff peak at outlet was about 4 hours. The response of groundwater was very large and rapid. Nitrate nitrogen transferred from land to river by surface runoff and subsurface flow, while ammonium nitrogen and phosphorus mainly by surface runoff. At hillslope scale, the regularity of nitrogen and phosphorus exporting by surface runoff was simple, affected mainly by rainfall intensity, rainfall lasting time and runoff yield. But at catchment scale, it became complex. The nitrogen and phosphorus exporting procedure was shown as cyclical fluctuation in concentration and several peaks with a main one in load, and the load peaks were resulted by the different time of nutrient transferred to outlet from the main land uses.