| dc.description.abstract | The levels of heavy metals were determined in environmental samples; water, flora and
sediments along the Thika River, specifically, to investigate their distribution and to determine
the extent of pollution. Water, sediment and algae (Cladophora) samples were each collected
from thirty-two (32) sampling sites identified along the river’s profile and each analyzed for the
selected heavy metal content using TXRF and EDXRF.
In general, the concentration levels of heavy metals in water samples ( gl-1) were determined as
follows; Mn (53.5 -605), Cu (< 10 -303), Zn (22-325), Ni(< 15 - 77), Pb (< 10 -84) while those
in sediment samples (mg kg-1) were; Mn (2230-8659), Cu (51 -115), Zn (153-432), Ni (67 -
172), Pb (32-177). The results of the concentration levels of heavy metals in Cladophora (mg kg-
1) ranged as follows; Mn (3719 - 21200), Cu (65-129), Zn (153-434), Ni (35 -235), Pb (17 - 72).
There was a significant difference in heavy metal concentrations between the three media for all
elements studied.
Based on results of enrichment factors, geoaccumulation indices, pollution load index (PLI),
contamination factors and modified degree of contamination, all sampled sediments were
generally contaminated with, Cu, Zn, Mn and Ni to a moderate degree, hence requires
intervention to curb on the rising levels of pollutants.
Statistically significant interrelationship was observed between sediments and Cladophora,
which supports the idea that, Cladophora is an appropriate bio-indicator for heavy metal
pollution. Heavy metal contamination levels in water samples, in this study, is variously impacted by;
nearby industries, dust from the nearby mining activities and the chemical fertilizers used in the
nearby commercial pineapple farms and combustion of fuel from the vehicles plying the nearby
roads and therefore unsuitable for drinking.
The study consequently, recommends for the introduction of heavy metal bio-accumulators such as bamboo plants grown along Thika River basin and for enforcement of measures to restrict direct release of untreated waste waters and industrial effluents, into the river.
Further studies should also be carried out to determine the other sources contributing to the
pollution of the river ecosystem. | en_US |
