Pesticide residues in four rivers running through an intensive agricultural area, Kilimanjaro, Tanzania

Organochlorine pesticide (OCP) residues were determined in water and bottom-sediments from four rivers running through sugarcane plantations in Kilimanjaro Tanzania. The aim was to assess the levels of pesticide contamination as the rivers are important sources of domestic water in the area. Water samples were extracted by liquid–liquid extraction method, and ultrasonic-assisted liquid-solid extraction coupled with gel permeation chromatography was employed in sediment preparation, before analysis by GC-ECD and GC-MS. Blank and spiked recovery tests were used to validate the analytical procedure. Data were assessed by using descriptive statistics and multivariate analysis to study correlations between different parameters, evaluate the contamination patterns and describe their spatial and seasonal trends. The percentage recoveries ranged from 75.0 ± 2.4 to 89.8 ± 1.5 in water, and 70.5 ± 1.7 to 86.2 ± 2.3 in sediments, which are within the acceptable ranges. The OCP concentrations ranged from trace (endrin) to 120 ng/l (p,p’-DDD) in water, and from trace (aldrin) to 132 ng/g-dry weight (p,p’-DDD) in sediments, and were higher during the dry season. A notable water contamination that exceeded the European Union maximum acceptable concentration for the protection of human health was detected in river Kikavu.