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Heavy metals and organochlorine residues
were determined in water, sediment, fish muscle, and
freshwater shrimps from aquatic environments in urban
and peri-urban areas in Morogoro, Tanzania. Most of
the water samples had heavy metal concentrations
below WHO acceptable water quality guidelines. All
sediment samples had comparable heavy metal concen-
trations that suggest natural rather than anthropogenic
origin. Hexachlorobenzene, α-hexachlocychlohexane,
cis-chlordane, trans-nonachlordane, cis-nonachlor-
dane, pp′-DDE, op′-DDD, pp′-DDD, op′-DDT, and
pp′-DDT in hairy river prawn (Macrobrachium rude),
African sharptooth catfish (Clarias gariepinus), and
Wami tilapia (Oreochromis urolepis) were detected at
significant concentrations above the methods’ detec-
tion limits. The ratio of pp′-DDT to ∑DDTs was 0.4
in O. urolepis and 0.3 in C. gariepinus, which
indicated previous rather than current use of DDT.
In M. rude, only pp′-DDE was detected and inO. urolepis and C. gariepinus there were higher
levels of pp′-DDE than pp′-DDT, which demonstrate
uptake of pp′-DDE, rather than pp′-DDT, from the
environment. Bioaccumulation of organochlorines
and mercury was the highest in C. gariepinus,
cadmium in M. rude, and lead in both M. rude and
O. urolepis. Maximum detected levels of organochlo-
rine pesticides and heavy metals in M. rude, O.
urolepis, and C. gariepinus were below the maximum
permissible concentrations recommended by FAO/
WHO. It is concluded that, at present, the contribution
of anthropogenic sources in pollution of aquatic
environments in Morogoro urban and peri-urban areas
are low and that the concentrations of heavy metals
and organochlorine pesticides in water and fish do not
indicate a risk to the consumers. |
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