Study of clarification for riparian-buffer to non-point pollution

In this non-point pollution control experiment,three local swards: Cynodon dactylon,Festuca Arundinace,and Trifolium repens,and four gradients: 2,3,4,and 5% are selected to construct the buffer strips test base.The final results show that: the riparian buffer strips can effectively remove SS in runoff water and the nutrients in seepage water; the differences of sward and gradient have notable influence on the pollutants purification of buffer strips.The SS retention rate of the 2% gradient buffer strip,19 m long is 14% higher than 5% gradient strip; that of the Cynodon dactylon buffer,19 m long is 11% higher than Trifolium repens strip.When the TN concentration of influent is lower than 10 mg/L,that of seepage effluent of 2% gradient Cynodon dactylon strip is lower than Grade V of Surface Water Environmental Quality Standards (SWQS) (Chinese EPA,2002).When the TP concentration of influent is about 0.6 mg/L,that of seepage effluent of Cynodon dactylon,Festuca Arundinace,Trifolium repens and 2,3,and 4% gradient strips is lower than Grade Ⅲ of SWQS 1 According to the approach used in this paper,the optimal width of 5% gradient buffer strip is 8.6 m longer than 2% strip; and the optimal width of Trifolium repens buffer strip is 4.3 m longer than Cynodon dactylon strip.