Nitrogen And Phosphorus Transport By Surface Runoff From Upland In Taihu Lake Catchments

Taihu is an eutrophication lake, the eutrophication has lead to the decreasing of the biology species and seriously destroying ecology environment. It produced great threat to the health of people and development of economics. After the point pollution sources around the Taihu catchments have been controlled effectively in recent years, water quality doesn't become better, because non-point pollution of agriculture has become the main pollution sources, and at the same time storm water runoff is the most pathway of non-point pollution entering Taihu lake, so control the surface runoff of upland ground in Taihu catchments has important signification to relieve the eutrophication.This project "The technology of lower nitrogen and phosphorus in farmland" is a subproject of the project "Non-point pollution control in the Taihu catchments", which is a project in the Key Technologies R&D Programme in the Tenth Five-Year Plan (NO.2002AA6012) .The characteristics and the composing of surface runoff from upland ground in the Taihu catchments were investigated and analyzed. By built up a pilot-plant and the experiment of artificial rainfall, we researched the effect of different cover patterns and fertilization patterns in control the pollution of nitrogen and phosphorus from surface runoff. The results showed that:The loads of nitrogen and phosphorus transport by surface runoff from upland ground in Taihu Lake Catchments are 12.66kg/hm~2 and 4.05kg/hm~2, accounting for 5.63% and 4.13% of annual fertilization, respectively. Abut 3.86t of total nitrogen and 1.24t of total phosphorus discharged into water body of experiment area from upland, and it has obviously season characteristics, summer and autumn is high loads season, Jun-Nov accounting for 83.35% and 79.79% of total loads.The concentration of nitrogen and phosphorus changed greatly, about 5-6 times. Nitrate-N is the main form of nitrogen losses, and is account for 48.74% of total nitrogen. With the rainfall process, the concentration of Nitrate-N rose gradually, but Ammonium-N declined. Particle phosphorus is the main form of phosphorus losses, and is account for 76% of total phosphorus. It is enriched in SS, and the particle phosphorus has directly correlation with SS.The accumulated nitrogen loading and runoff volume has power correlation: TN=aQ~b; the accumulated phosphorus loading and runoff volume has linearity correlation: TP=aQ+b; and the time of rainfall and the accumulated runoff volume has logarithm correlation: L=a Ln(t)-b. Surface overlay and deep placement can lower the risk of nitrogen and phosphorus discharged into water body effectively. Film coverage can lower 59.76% of nitrogen and 90.49% of phosphorus; straw coverage can lower 59.83% of nitrogen and 86.52% of phosphorus; subsurface layer can lower 50.07% of nitrogen and 80.20% of phosphorus; deep layer can lower 52.41% of nitrogen and 80.25% of phosphorus, respectively. Every treatment has the advantage of low cost and high efficiency. This technology is suitable for the conditions of China, and has good prospect in the area of non-point pollution control.