Seasonal levels of pesticide residues in the main and the Blue Nile waters in Sudan

Levels of twenty-two commonly used pesticides were monitored three times a year (autumn, winter, and summer) in 54 water samples collected from six sites representing the main and Blue Nile. These sites were selected to reflect any attributes from main drainage canals from agricultural schemes in Sudan as well as any impact from upstream sources. Collected samples were subject to gas chromatographic analysis equipped with FID/ECD, and results were expressed in ng/l water. Analysis of Blue Nile water indicated the presence of OCs in 45% of the samples, OPs in 11%, pyrethroids in 22%, and none of the tested herbicides. Heptachlor and DDTs were the most prevalent followed by the pyrethroids. Levels detected were not high. Water of the main Nile showed the presence of OCs in 22% of the samples, pyrethroids in 4%, and none of the tested OPs and herbicides. DDT is the most prevalent followed by heptachlor. Total concentration in main Nile is relatively higher than the Blue Nile. Residues of DDD, λ cyhalothrin, deltamethrin, oxyfluorfen, HCH, and endosulfan isomers were not detected in the analyzed samples. Generally levels were least in autumn, followed by summer and winter. Sources of contamination might include some drains from agricultural lands in central Sudan and/or upstream sources. Both recent and old contaminations were indicated.