Abstract
The aim of the present study was to quantify and monitor the effect of seasonal variation on the acaricide and herbicide residues in date palm soils in the Al-Kharj region of central Saudi Arabia. The acaricides studied belonged to the abamectin, formamidine, organothiophosphate and oxime carbamate groups and the herbicides to the aryloxyphenoxypropionic, chlorotriazine, dinitroaniline and nitrile chemical groups. Soil samples were collected from surface layers (0-30cm depth) and subsurface layers (30-60cm depth) from ten selected farms during both summer and winter to study the effect of seasonal variation on residue levels. A simple optimized microwave-assisted extraction (MAE) technique and Gas Chromatography with Electron Impact Mass Spectrometer (EI-GCMS) was modified and used as the extraction and analytical techniques respectively.
Nine pesticide residues were quantified in the soil samples and concentration ranges were as follows; bromoxynil 0.174-0.007 mg kg(-1), atrazine 0.366-0.102 mg kg(-1), bromophos methyl 0.182-0.022 mg kg(-1), abamectin 0.99-0.54 mg kg(-1), amitraz 0.381-0.057 mg kg(-1), cloroneb 0.255-0.012 mg kg(-1) and oxamyl 0.444-0.008 mg kg(-1) with pendiomethalin and diclofop methyl only being present at very low levels in the surface layer in summer. Residue levels were also found in subsurface layers in summer. The data were replicated in winter giving four datasets for the entire study.