Browsing by Author "S. HASSAN, HASSAN"

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    Levels of Pesticide Residues in Water and Soil from Hydromorphic Rice Valleys in Pemba Island
    (SUZA, 2017-01-01) S. HASSAN, HASSAN
    Assessment of status of pesticide pollution in five hydromorphic rice valleys in Pemba Island revealed the presence of a total of ten pesticide residues belonging to organochlorine pesticides (OCPs), organophosphorous pesticides (OPPs) and herbicides. The total concentrations of OCPs during application period ranged from not detected (ND) - 5.51μg/l and 0.38 - 6.56ng/g dw (mean 3.25ng/g dw) in water and soil, respectively; while during harvesting, the concentrations of OCPs in soil ranged from 0.06 - 2.98ng/g dw (mean 1.25ng/g dw) and those in water ranged from ND - 1.94μg/l. The total concentration of OPPs in surface water and soil during application period ranged from 0.46 - 6.62μg/l (mean 2.15μg/l) and 2.65 - 4.44ng/g dw (mean 3.34ng/g dw), respectively; and concentrations of herbicides in surface water and soil in the same period ranged from 0.3 - 7.36μg/l (mean 2μg/l) and 1.09 - 5.03 ng/g dw, respectively. All ground water samples from Muhoro were contaminated with OPPs and herbicides but the pesticides were below detection in ground water samples from other valleys. During harvesting period, levels of both OPPs and herbicides were below detection. The study revealed combination of past use of OCPs and current use of lindane, OPPs and herbicides. There were strong temporal variations of OPPs and herbicides that were governed by pesticide use in the valleys while OCPs were quite stable throughout the study periods showing their persistence and ubiquitous nature. Among the surveyed rice valleys, Tibirinzi rice valley was the most contaminated with OCPs while Muhoro was dominated with OPPs and herbicides. In general the study sites are less polluted compared with related rice farms elsewhere. The study recommends the establishment of management and monitoring teams to oversee use of pesticides in these valleys to safeguard the health of valleys ecosystem.