Leaching of imidacloprid and procymidone in a greenhouse of southeast of Spain

The leaching processes of the insecticide imidacloprid [1-(6-chloro-3-pyridinylmethyl)-N-nitro-2-imidazolidinylideamine] and the fungicide procymidone [N-(3,5-dichlorophenyl)-1,2-dimethyl-1,2-cyclopropanedicarboximide] in a greenhouse soil from the southeastern of Spain were investigated. Four separate pesticide applications were made at dose rates considerably higher than the recommended in normal agronomic practice, representing a worst case scenario. Soils samples were taken to a depth of 40 cm at time intervals after each application and analyzed by high performance liquid chromatography (HPLC). The partition coefficients (K-d) of the samples for imidacloprid and procymidone were calculated by carrying out batch experiments and fitting the experimental data point to the linear isotherm equation. Soil tension, water content; and temperature measurements were also determined during all the experiments. Although the results show a high degree of variability, rapid transport of pesticides through the soil occurred which increases the possibility of groundwater pollution. The leaching of these pesticides, particularly procymidone, generally thought of as immobile, might be possible through formation of stable soluble organic fraction-pesticide interactions in solution, allowing an increased groundwater contamination potential.