Effects of sewage sludge amendments on pesticide sorption and leaching through undisturbed Mediterranean soils

International audienceThe Gharb region in Morocco is an important agricultural zone where soils receive pesticide treatments and organic amendmentsto increase yields. The groundwater aquifer in the Gharb region is relatively shallow and thus vulnerable. The objective of this workwas to study the influence of organic amendments on diuron, cyhalofop-butyl and procymidone leaching through undisturbed soilcolumns. Two soils were sampled from the Gharb region, a Dehs (sandy soil) and a R’mel (loamy clay soil). Following elution (124.5mm), the amount of pesticide residues in the leachates of the sandy soil (0.06–0.21 %) was lower than in those of the loamy clay soil(0.20–0.36 %), which was probably due to preferential flow through the loamy clay soil. The amount of procymidone leached throughthe amended soil columns was greater than the control for the sandy soil only. The organic amendments did not significantly influencediuron and cyhalofop-butyl leaching in either of the soils. The application of organic amendments affected the amounts of dissolvedorganic matter (DOM) eluted and thus pesticide leaching as a function of soil-type. Nevertheless, in some case, the formation ofpesticide-DOM complexes appeared to promote pesticide leaching, thus increasing groundwater contamination risks