Thesis (MTech (Environmental Health)--Cape Peninsula University of Technology, 2007 / The widespread use of lead (Pb) and especially Pb from vehicular
emissions arising from lead additives in petrol has resulted in high levels of
this metal found in various soil samples taken along the road verges of
Cape Town CBD. The accumulation of lead was investigated in roadside
surface soil by collecting soil samples at various sites along the three major
highways (N7, N2, N1), approximately three metres from the road verges
and at a depth of approximately 5 cm for a period of 12 months. After
digestion with 55"70 nitric acid the Pb concentrations were determined by
using an Inductively Coupled Plasma Atomic Emission Spectrophotometer
(ICP-AES).
Results have shown the Pb concentrations in the soil at busy intersections
to be higher than at other areas along the roadsides. Lead concentrations
found in the roadside soils of the N1 ranged between 200 and 2000 mg/kg
and these were of the highest concentrations found compared to the other
two highways and were even higher than found in other studies. The
roadside soils on the N1 highway, with the most traffic, according to car
count data obtained, seemed more contaminated than the other two
highways.
It was also investigated whether earthworms (Eisenia fetida) accumulated
Pb after being exposed to the contaminated soil from the sampling sites.
The earthworms in the highly contaminated soil accumulated on average
much higher concentrations of Pb than the earthworms in the lower Pb
contaminated soil.
A potential biomarker (cell membrane integrity) was applied to determine
whether the earthworms experienced toxic stress as a result of the
exposure to lead contaminated soil. Behavioural and morphological
changes in the earthworms were also observed. The Trypan blue exclusion
assay was used to measure the effect of lead exposure on the membrane
stability of the coelomocytes in the coelomic fluid of earthworms. In the highest exposure groups per highway, a significant decrease in percentage
viable cells were seen (N7, 36 ± 0.07%; N2 48 ± 0.09%; N1, 34 ± 0.08%).
The fact that clear statistically significant responses were seen after the five
week exposure period in the highest, as well as lowest exposure groups
indicate that these responses could serve as an early warning system of
lead exposure. The percentage cell viability (biomarker) used in this study
have been useful in identifying toxic stress in earthworms caused by lead in
roadside soils. The additional information obtained by using biomarkers
could not be obtained by chemical analysis of soil and earthworms alone.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/788 |
| Date | January 2007 |
| Creators | Kruger, Anne-Liese |
| Contributors | Odendaal, James, Dr, Snyman, Reinette, Dr |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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