Heavy Metal Contamination of Water, Soil and Vegetables in Urban Streams in Machakos Municipality, Kenya
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Date
2020
Authors
Tomno, Rose M.
Nzeve, Julius K.
Mailu, Stephen N.
Shitanda, Douglas
Waswa, Fuchaka
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
Pollution of the environment by heavy metals emanating from rapid economic growth and
improper waste and effluent disposal is a major concern. In this study, heavy metal concentrations (Cd, Cu, Pb, Zn and Cr) in vegetables, soil and water in two urban streams in
Machakos municipality were analyzed. Physicochemical parameters; pH, temperature, total
dissolved solids (TDS) and electrical conductivity (EC) were also measured on-site. Oneway Analysis of variance (ANOVA) was used to test for the significant difference (p ≤ 0.05)
of heavy metal concentrations in the vegetables, soil, and water across the different sampling sites. The relationship between the heavy metals in the soil, water and vegetables
was investigated using Pearson correlation. Temperature (21.58 – 23.05 °C), pH (7.5 – 8.45)
and TDS (577.5 – 865.83 mg/L) mean values were found to be within WHO acceptable
limits for surface water while EC (864 – 1778.5 μS/cm) exceeded the set limits. Results
showed that the mean concentrations (mg/kg) of Cd (BDL – 0.0011), Cu (0.0034 – 0.0055),
Pb (0.0012 – 0.007), Zn (0.0232 - 0.1351), and Cr (0.0036 - 0.0292) in water and Cd (0.0058
- 0.0534), Cu (10.39 – 27.5), Pb (4.23 - 8.35), Zn (20.1 – 28.8) and Cr (8.17 – 10.03) in soil
were within WHO permissible limits. Mean concentration values of (Zn (9.05 – 11.8), Pb
(0.28 – 0.636), Cr (BDL – 1.002)) in spinach exceeded WHO permissible limits while Cd
(BDL – 0.1285) and Cu (3.07 – 14.5) were within recommended levels. Cd (0.004 – 0.243),
Cu (0.909 – 3.60) and Pb (BDL – 0.458) concentration levels in kale were within WHO safe
limits for human consumption while Zn (12.06 – 18.8) and Cr (BDL – 1.62) exceeded WHO
set limits. Presence of heavy metals (Zn, Pb, Cr) in the vegetables signifies a health risk
hazard from consumption of these vegetables. Continuous monitoring of heavy metals in
stream water, soil and vegetables is critical towards safeguarding public health.
Description
Research Article
Keywords
Heavy metals, Urban effluent, Water, Soil, Vegetables
Citation
Tomno, R. M., Nzeve, J. K., Mailu, S. N., Shitanda, D., & Waswa, F. (2020). Heavy Metal Contamination of Water, Soil and Vegetables in Urban Streams in Machakos Municipality, Kenya. Scientific African, e00539.