Physico-Chemical Parameters, Levels of Selected Heavy Metals and Nutrients during Wet and Dry Seasons Along River Ewaso Narok, Laikipia County, Kenya
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Date
2023-10
Authors
Maisa, Thadius Nyamweya
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
River water pollution is a growing problem especially in developing countries
where population growth and urbanization are never adequately checked.
Effluents from chemical industries and dumping of toxic solid wastes from urban
settlements find their way into rivers. Run-offs from agricultural fields
downstream and other anthropogenic activities result in heavy pollution of rivers.
Downstream most urban areas live huge communities of humans and animals who
rely on water from these rivers for survival. There are reports of environmental
degradation, water related discases in both animals and humans all of which are
cvidence of water pollution. The objective of this study was to assess the extent of
water pollution by determining the levels of selected heavy metals namely: Pb,
Cu, Mn & Cd and selected nutrients (NO3 and PO3~) along river Ewaso Narok,
Laikipia County, Kenya, during wet and dry seasons. Sampling was done along
the river to obtain samples of water, sediment and soil in both seasons, and each
sample was analyzed for the concentrations of each parameter along with
determination of selected Physico-chemical parameters of water including pH, T,
Ce, TDS and TSS. Soil and sediment samples were digested using nitric and
hydrochloric acid. Samples were then analyzed for heavy metals using FAAS and
for nutrients using UV-vis Spectrophotometry. Data was analyzed using ANOVA
and t-tests. The results obtained were as follows: The mean pH varied downstream
across the two scasons; 7.46 1.02 wet, 8.56 + 0.51 dry, with a lower pH in the
wet season, an indication of presence of heavy metals. Temperature was generally
lower than the set limit by WASREB (20-35°C) in both seasons; 13.91 + 1.96°C
wet, 15.57 £ 2.13°C dry. The same trend was observed with electrical conductivity
Ce; 153+ 198.5pS/em wet, 164 + 206.23pS/cm dry, and TDS; 113.6 = 133.5mg/L
wet, 122.8 + 144.5mg/L dry. Noticeably, T, Ce and TDS were generally higher in
the dry season albeit falling below set limits by WHO. Ce, just like TDS, is a
factor of temperature. TSS was slightly above set limit by WASREB in the wet
season; 30.4 + 17.36mg/L wet, 224 = 14.74mg/L dry. Pb concentration was
higher in the wet season; 0.0529 0.0830mg/L, being significantly higher than set
limit by WHO (p<0.05). The same trend was noted with Cu; 2.6057 +
3.2705mg/L in the wet season The wet season is associated with run-offs and
heavy agricultural activities. Mn was not detected in the wet season. Manganese
Carbonate, a fertilizer, is insoluble in water thus not easily detectable. However, in
the dry season a mean of 0.06524 = 0.03666mg/L was recorded falling within the
limit set by WHO. Cd was higher in the wet season (0.0051 £ 0.0044mg/1) than in
the dry season (0.0002 = 0.0006mg/l), but was within WHO limit (0.003mg/1).
The concentration of nitrate was significantly higher in the wet season; 1 10.3122
+ 62.1294mg/L, than in the dry season (25.5787 £ 1.4487mg/l) being significantly
higher (p<0.05) than standard WHO value in both seasons. Similarly the
concentration of phosphate was significantly higher than WHO set limit in both
seasons: wet season; 0.1068 + 0.07249mg/L, dry season; 0.1376 = 0.0957mg/L.
This is because of wash-off of agricultural residues during downpour. These
results signify clevated levels of heavy metals and nutrients in R. Ewaso Narok,
especially in the wet scason, potentially from urbanization, agriculture and other
anthropogenic activities along the river, which may lead to health and
environmental implications. NEMA, WRA, KFS and other relevant bodies need to
combine effort to control human activities along the river which will lead to
availability of clean drinking water for residents in order to protect the river and
lives.
Description
A Thesis Submitted In Partial Fulfillment of the Requirements for the Award of The Degree of Master of Science (Chemistry) in the School of Pure and Applied Sciences Of Kenyatta University, October 2023
Keywords
Physico-Chemical Parameters, Levels, Heavy Metals, Nutrients, Wet and Dry Seasons, Ewaso Narok, Laikipia County, Kenya