Effect of solid olive-mill waste amendment on pesticide sorption and leaching in soil

Abstract

Organic amendment addition to soil is an agricultural practice that can greatly influence pesticide sorption and movement through the soil profile. In this work, we have investigated the effects of the addition of a solid olive-mill waste (SOMW) on the sorption and leaching of the herbicide simazine in a sandy loam soil. The effect of SOMW addition on soil porosity was also assessed. The soil was amended in the laboratory with SOMW at two different rates (5°/0and 10°/0 w/w). Simazine sorption isotherms showed a great increase in herbicide sorption after soil amendment with SOMW; sorption increased with the amount of SOMW added. Simazine sorption-desorption isotherms on unamended and amended soil were reversible. Breakthrough curves of simazine in unamended and amended soil columns showed that, upon SOMW addition, simazine concentrations in Ieachates were greatly reduced and the maximum concentration peak was shifted to larger volumes of water added, thus indicating reduced leaching of simazine in the amended soils. Total amounts of herbicide recovered from the soil columns indicated enhanced degradation and/or irreversible sorption of simazine in the amended soil. Mercury intrusion porosimetry data indicated that SOMW addition to soil gave rise to an increase in the volume of pores with radii about 10 ~m. The results showed that SOMW addition may reduce the risk of ground water contamination associated with rapid leaching of simazine in soils.