Levels of pesticides residues in the White Nile water in the Sudan

Abstract

Twenty-two commonly used pesticides were monitored during autumn, winter, and summer of 2004–2005 in 27 water samples from three sites along the White Nile in Sudan (former Sudan). Sites were selected to reflect pesticides gathered from drainage canals in central Sudan and from upstream sources. Collected samples were extracted and subjected to gas chromatographic analysis. Pesticides levels were measured in nanograms per liter. Pesticides residues were detected in 96 % of the samples with a total residue burden of 4132.6 ng L⁻¹, and an overall mean concentration and range of 50.99 and not detected-1570 ng L⁻¹, respectively. Ororganochlorines were the most frequently detected contaminants, which were found in 70 % of the samples, causing a total burden of 2852.8 ng L⁻¹, followed by pyrethroids 15 % of the samples, with a total burden of 926.5 ng L⁻¹. The tested herbicides were detected in ˂4 % of the samples with a total burden of 353.3 ng L⁻¹, while organophosphorus levels were below the detection limit. The most frequent contaminants were the following: heptachlor and its epoxide (52 % of samples), followed by DDTs (dichlorodiphenyltrichloroethanes) (DDT and DDE, in 19 % of the samples), cypermethrin and fenvalerate (in 11 % of the samples), and pendimethalin (in <4 % of the samples). Residues of hexachlorocyclohexane (HCH) isomers (α, β, γ and δ), endosulfan (α and β), p, p-DDD, λ cyhalothrin, deltamethrin, and oxyfluorfen were not detected in the analyzed samples. Generally, levels were least in autumn, and followed by summer and winter. Sources of contamination might include agricultural lands in central Sudan and upstream sources. Both recent and old contaminations were indicated.