Laboratory evaluation of pesticide leaching from sand-based constructed root zones amended with activated carbon

Research was conducted to evaluate the installation of an activated carbon (AC) layer to reduce pesticide leaching from sand-base constructed root zones. Soil profile columns included unamended pure sand (PS), sand amended with 10% v/v peat moss (PM), sand overlying a 3-cm layer of AC (Ch-1), and sand overlying a 13-cm layer of sand mixed with the same amount of AC as that in the 3-cm layer (Ch-2). Soil profiles treatments included tebuconazole at 0.125 mg a.i. m^-2, ethoprophos at 300 mg a.i. m^-2 and ethoprophos at 1500 mg a.i. m^-2. Total detected leachate from the PS was 52 and 80% of applied tebuconazole and ethoprophos, respectively. Both materials were detected at <1% of applied from Ch-2 leachate. Peat moss was as good as or more effective than the AC profile (Ch-1) for capturing tebuconazole, but not ethoprophos. Tebuconazole was detected at <1% of applied in the PM leachate, whereas ethoprophos was detected at 27% of applied from PM leachate. Ethoprophos applied at 1500 mg m^-2 was detected at 97, 83, 45, and 5% of applied from PS, PM, Ch-1, and Ch-2 leachate, respectively. Th e amount of ethoprophos remaining in the columns treated at 1500 mg m^-2 after leaching was 1, 9, 52, and 89% in PS, PM, Ch-1, and Ch-2, respectively. Our results indicate that a proper installation of PM or AC layers may be effective in reducing the leaching of pesticides from sand-base constructed root zones