Environmental Engineering Reference
In-Depth Information
Fig. 1
Map of the sampling area
Sampling and Analysis of Water and Sediment Samples
Water samples were collected in 2.5 L bottle from rivers around Thohoyandou -
Nzhelele, Luvuvhu, Mutale, Mutshundudi and Dzindi rivers (Fig.
1
) between
September 2005 and January 2006. Sediment samples were also collected from the
rivers. Run-off samples and runoff sediments were collected at riverbanks at points
where run-off enters the rivers, and at roadsides and parking lots around
Thohoyandou Town. Water samples were stored at < 4°C and analyzed as soon as
possible after collection. A 500 mL aliquot of water sample was saturated with 75 g
of NaCl. The mixture was transferred into a separating funnel and extracted three
times by shaking vigorously with 30 mL dichloromethane. The three extracts were
pooled together and washed three times with 30 mL of 0.1 M sodium carbonate in
a 100 mL separating funnel. The organic layer was separated and dried with anhy-
drous Na
2
SO
4
. The dried extract was reduced by evaporation and the extraction was
done in triplicate.
Soxhlet extraction was used for the extraction of sediment samples since it is
recommended by the US Environmental Protection Agency for the extraction of
semi-volatile and non-volatile organics from solid matrices. Sediment samples
were air dried, crushed with a mortar and pestle, and sieved through a 0.5 mm mesh
sieve. 10 g of sediment samples were weighed into an extraction thimble, which
