Effect Of Leguminous Mixed Graminaceous Herbage Interacted With Biochar On Removing The Pollutants In Runoff

The non-point source pollution was more and more serious and became the focus of water environment pollution control after the point pollution was effectively controlled. As the last protection measure before receiving waters, vegetation buffer strips(VFS) are becoming a research hotspot in the field of environmental science. Lots of research and reports of VFS are found. But reports that using leguminous mixed gramineous herbage or changing the texture of the soil to improve the interception of the VFS are rarely seen. In order to improve the efficiency of interception, VFS were built using the mixture of leguminous with gramineous herbage, and biochar was introduced to change the texture of the soil, which could provide some theoretical basis for the new construction techniques of building VFS along rivers.By the method of laboratory simulation test, this paper studied the effect of different amount(0%、2%、4%、8%and16%) of biochar on exogenous nitrogen and phosphorus interception. The result indicated that the biochar application in cinnamon soil could significantly improve the ability to intercept the exogenous pollutants in soil. During the efficient operation, the infiltration rate of the column of 16% biochar added was 9.43 times of CK, the interception speed of TN could be 9.05 times of CK, and the interception speed of COD was 16.34 times of CK. Each treatment could intercept TN and COD efficiently(the averaged interception rate of TN and COD were 95%and63%).In addition, the content of effective phosphorus in biochar could significantly affect the interception of exogenous phosphorus, we should use the biochar of little content of phosphorus to build VFS.By the method of laboratory simulation test, this paper studied the effect of different combination of herbage on exogenous nitrogen and phosphorus interception with 16% biochar added. Except the blank, seven treatments were studied in this experiment, such as the Trifolium repens L 、Lolium.perenne 、Festuca rubra 、Poapretensis、mixture of Trifolium repens L and Lolium.perenne by 1:3、mixture of Trifolium repens L and Festuca rubra by 1:3、mixture of Trifolium repens L and Poapretensis by 1:3. The results showed that the addition of herbage could improve the interception capacity of soil significantly. And the treatment of Trifolium repens L and Lolium.perenne mixed had the best performance, whose interception rate of TN and COD were 93%and90%. Compared with the blank, this treatment could improve the interception of the amount of sewage by 127.16%, and improve the interception of the total amount of the pollutants.VFS were built of 4m length 、2m width and 7 slope with different herbage combinations and 16% biochar added. There treatments were the same as before except the blank. Results showed that the treatment of Trifolium repens L and Lolium.perenne mixed really had the best performence. Compared with Trifolium repens L 、Lolium.perenne 、Festuca rubra 、Poapretensis、mixture of Trifolium repens L and Festuca rubra by 1:3、mixture of Trifolium repens L and Poapretensis by 1:3, this vegetation buffer strip could improve the total amount of pollutants intercepted by 3.29%、5.31%、5.56%、8.26%、3.98% and 5.28%.This study showed that the Trifolium repens L and Lolium.perenne mixed by1:3 could improve the interception capacity of soil significantly with the 16% biochar added. And the result of this experiment offered a reference data for the research of VFS.