Levels of Pesticide Residues in Water and Soil from Hydromorphic Rice Valleys in Pemba Island
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Date
2017-01-01
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SUZA
Abstract
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.
Description
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.
Keywords
Water and Soil from Hydromorphic Rice Valleys in Pemba Island