Removing effects of grass filter strips on sediment and herbicide from runoff in simulated experiment

Abstract: Atrazine, an herbicide to kill broadleaf weeds affecting many different types of crops such as corn, sorghum, and sugarcane, is extensively used in agricultural production around the world in recent years. The worldwide use of atrazine did not only significantly increase crop yields but also result in serious aboveground- and belowground water pollutions. Grass filter strips, planted along streams, ponds, and lakes, were designed to remove sediments, organic materials, nutrients, and chemicals carried in runoff or waste water, and which were regarded as one of the best management practices in the controlling of agricultural non-point source pollution in many countries. However, the efficiency of grass filter strips in the removing of atrazine has not been adequately tested, especially on the Northern China. This study was conducted to evaluate the effects of herbaceous grass filter strips established by Pennisetum (Pennisetum alopecuroides (Linn.) Spreng and Arundinella (Arundinella hirta (Thunb.) C. Tanaka) on the removing of runoff, sediment, and atrazine in a simulated experiment on the soil boxes with runoff generator (water flow rate and speed were 0.22 L/s and 1.3 m/s, respectively). Three treatments, including T1 (inflow sediment content=20 g/L, inflow atrazine concentration=0.3 mg/L), T2 (inflow sediment content=40 g/L, inflow atrazine concentration=0.6 mg/L), and T3 (inflow sediment content=60 g/L, inflow atrazine concentration=0.9 mg/L), were set and each of them had three replications in this study. The differences between the inflow and outflow of runoff, sediment, and atrazine through the grass filter strips were examined to determine the efficiency of the grass filter strips in the decreasing of studied pollutants. The results showed that the grass filter strips significantly reduced runoff by up to 88%. The grass filter strips was also very efficient in reducing sediment and atrazine, but their effects were significantly influenced by sediment content and atrazine concentration in the inflow water through the grass filter strips. The outflow sediment was decreased by 95%, 93%, and 85% by the grass filter strips when the inflow sediment content was 20, 40 and 60 g/L, respectively. Similarly, the outflow atrazine was decreased by 95%, 92%, and 81% by the grass filter strips when the inflow atrazine concentration was 0.3, 0.6 and 0.9 mg/L, respectively. Additionally, the decreasing percentage of the sediment and atrazine was gradually decreased with the increasing time. The sediment was decreased by 97%, 95%, 93%, 91%, and 87% at the 1st, 10th, 20th, 40th, and 60th min, respectively; while the atrazine was decreased by 97%, 93%, 90%, 86%, and 84% at the 1st, 10th, 20th, 40th, and 60th min, respectively. At last, the result of the correlation analysis showed that the outflow concentration of atrazine was significantly correlated with the volume of outflow water (r1=0.88, r2=0.93, r3=0.94), which indicated that the outflow atrazine was mainly determined by the volume of outflow water. From these results we concluded that the herbaceous grass filter strips were very efficient in reducing the sediment and atrazine. This conclusion may be helpful for preventing atrazine and other agricultural non-point source pollution in the Northern China.