Physico-Chemical Parameters, Selected Heavy Metals and Nutrients in Water, Fish and Sediments from Lake Turkana, Turkana County, Kenya
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Date
2024-06
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Kenyatta University
Abstract
The degradation of aquatic ecosystems by ever-increasing pollutants from anthropogenic activities
aggravates health problems, safe water and food scarcity globally. Lake Turkana is an important
resource for water, food and recreation in Turkana County, Kenya. However, wastes from urban
areas, residential areas, transportation and agriculture could alter physico-chemical parameters,
heavy metal and nutrient levels in its water, fish and sediments. This study determined physico chemical parameters, selected heavy metals and nutrients in water, fish and sediments from Lake
Turkana, Turkana County, Kenya. Water physico-chemical quality parameters: temperature, pH,
electrical conductivity (EC), dissolved oxygen (DO), salinity, total dissolved solids (TDS) and
oxidation-reduction potential (ORP) levels using YSI Pro 1030 Multiparameter electrode were
determined. The study also analyzed lead, cadmium and chromium in water, Oreochromis
niloticus and sediments using Flame Atomic Absorption Spectroscopy (iCE3300 AA System).
Similarly, the study investigated nitrates and phosphates in water using visible spectrophotometer
(Vis 130 Spectrophotometer). Water and sediments from Napasinyang’ River Mouth, Impressa
Beach, Long’ech Beach, Lobu Beach and Turkwel/Kerio River Mouth were sampled and
analyzed for lead, cadmium and chromium. Additionally, flesh and liver samples from
Oreochromis niloticus in the lake were analyzed. The mean analyte levels were compared across
the sampling sites using ANOVA and also with WHO and USEPA standards as appropriate.
Heavy metal levels were also compared between fish and water and between water and sediments
using student’s T-test. The results indicated physico-chemical parameters of the lake water as
follows: temperature (28.24±0.96 to 28.86±0.38°C), pH (9.04±0.21 to 9.46±0.06), electrical
conductivity (281.57±0.41 to 289.46±3.95 Ωcm-1
), dissolved oxygen (6.3±0.79 to 7.04±0.05
mg/L), salinity (1.67±0.00 to 1.70±0.01 ppt), TDS (2093.4±0.39 to 2135.8±4.86 mg/L) and ORP
(-54.22±0.12 to 588.14±0.51 mV). The results also showed lead (0.11±0.01 to 0.12±0.00 mg/L),
cadmium (0.00±0.00 to 0.03±0.00 mg/L) and chromium (0.01±0.00 to 0.03±0.01 mg/L). The
water nutrient levels were: nitrates (5.52±0.31 to 10.04±1.82 mg/L) and phosphates (0.47±0.06 to
0.72±0.15 mg/L). The levels of studied heavy metals in Oreochromis niloticus’s flesh and liver
were: lead (0.57±0.08 and 3.34±1.26 mg/Kg), cadmium (0.02±0.00 and 0.32±0.15 mg/Kg) and
chromium (0.12±0.01 and 0.51±0.18 mg/Kg). The results of sediment heavy metal analysis were:
lead (0.56±0.11 to 1.01±0.03 mg/Kg), cadmium (0.02±0.00 to 0.24±0.10 mg/Kg) and chromium
(0.11±0.03 to 0.2±0.05 mg/Kg). The pH and TDS in Lake Turkana’s water exceeded the WHO
standards of 6.5-8.5 and 600.0 mg/L respectively. The water lead levels exceeded WHO standard
of 0.01 mg/L. Water cadmium levels surpassed WHO standard of 0.003 mg/L in Impressa Beach
and Long’ech Beach. The Lake Turkana’s water nitrate levels complied with WHO standard of
50.0 mg/L. The phosphate levels were beyond USEPA standard of 0.024 mg/L. The levels of lead
in the Oreochromis niloticus’s flesh and liver exceeded WHO limits of 0.5 mg/Kg and were
considerably loftier (p < 0.05) than in the water column. Furthermore, the levels of lead, cadmium
and chromium in Lake Turkana’s sediments complied with USEPA standards of <40.0, <6.0 and
<25.0 mg/Kg respectively. However, the lead, cadmium and chromium levels in sediments were
appreciably higher (p < 0.05) than in the overlying water. The study did not consider seasons,
time, tides, other fish organs and species. The study recommends that water for human use be
treated for pH, TDS, lead, cadmium and phosphates. Detoxification of heavy metals in
Oreochromis niloticus to be done. The sediments to be protected from accumulating lead,
cadmium and chromium beyond USEPA standards.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Applied Analytical Chemistry in the School of Pure and Applied Sciences of Kenyatta University, June 2024