不同坡度缓冲带滞缓径流及污染物去除定量化

Quantitative study of the damping effect of buffer strips with different slopes on runoff and pollutant removal efficiency

利用构建的东风港缓冲带现场试验基地和设计的径流流量测定装置,模拟上海地区农业面源污染物浓度和典型单次降雨历时及降雨量,对不同坡度缓冲带滞缓径流和农田氮磷污染物去除能力开展定量化试验研究。结果表明:相同植被缓冲带,坡度越小,其滞缓径流和土壤水力渗透的能力越强,19 m长的2%坡度缓冲带径流初始出水时间比5%坡度缓冲带延长了7.3 m in,两者的渗流水量比值达到1.74;不同坡度缓冲带渗流氮磷污染物去除量显著高于径流,2%、3%、4%和5%坡度缓冲带对于氮磷污染物的渗流去除量与径流去除量的比值分别为2.32、2.15、1.82和1.64;坡度的变化对缓冲带净化面源氮磷污染物效果的影响显著,坡度越小,缓冲带渗流水量越大,其氮磷污染物的总去除率和单位面积去除负荷也越高,2%坡度缓冲带对氮磷污染的总去除率和单位面积污染去除负荷分别是5%坡度的1.56倍和1.66倍,2%坡度缓冲带对TN、NH3-N、TP的单位面积去除负荷均最高,分别达到0.661 g/m2、0.672 g/m2和0.044 g/m2。

Using the constructed buffer strip experimental site and the hydrometric devices in the Dongfeng Port of Shanghai, a quantitative study is conducted to investigate the damping effect of buffer strips with different slopes on runoff and the pollutant removal efficiency of nitrogen （N） and phosphorous （P） from agricultural lands. The result shows that for a similar configuration of vegetation structure, the gentler the slope gradient is in relation to the damping effect of buffer strips, the slower the runoff moves, and the greater the hydraulic permeability is. For example, on a 19-m long buffer strip with a 2% slope, there will be a delay of 7.3 minutes for runoff starting to flow out of the strip compared to that with a 5% slope. The two slope configurations can lead to a ratio of 1 ： 1.74 with respect to the seepage water. The improvement in the pollutant removal efficiency of N and P would be more significant in comparison with the damping effect on runoff when the slope gradient increases. For instances, on the buffer strips with 2% , 3% , 4% and 5% slopes, the improvement ratio of the two elements are 2.32, 2.15, 1.82 and 1.64, respectively. The gentler the slope gradient is in relation to the pollutant removal efficiency of N and P, the greater the total efficiency and unit area improvements will be. For example, on the buffer strips with 2% and 5% slopes, the two improvement ratios are found to be 1.56 and 1.66, respectively. The buffer strip with a 2% slope would have the highest pollutant removal efficiency of total nitrogen （ TN）, ammonia nitrogen （ NH3-N） and total phosphorous （ TP）, which are 0. 661,0. 672 and 0. 044 g/m^2 , respectively.