Authors : Kithure J. G. N.; Abong'o D. A.; Wangui J. W.

Volume/Issue : Volume 11 - 2026, Issue 7 - July

Google Scholar : https://tinyurl.com/tmy2eydt

Scribd : https://tinyurl.com/az799h2b

DOI : https://doi.org/10.38124/ijisrt/26jul137

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Abstract : Heavy metal contamination in soil is a significant environmental concern due to its potential risks to human health and ecosystem integrity. This study determined heavy metal levels in soil samples collected from two petrol stations and one control site with limited human activities in Mukuruwe-ini Sub County, Nyeri County, Kenya. The sampling sites were Muhito Petrol Station (operational for 15 years), Zinc Petrol Station (operational for 4 years), and Mugumoini, a control site away from petrol stations. Soil samples were collected from the surface layer (0–15 cm), digested using aqua regia (3:1 HCl:HNO₃), and analyzed by flame Atomic Absorption Spectroscopy (AAS) for lead (Pb), cadmium (Cd), chromium (Cr), zinc (Zn), and copper (Cu). Physicochemical parameters — pH, electrical conductivity, moisture content, and organic matter — were also determined. The mean Pb concentrations were 7.16 ± 0.78, 5.90 ± 0.63, and 2.09 ± 0.54 mg/kg at Muhito, Zinc, and Mugumoini respectively. Mean Cr concentrations were 16.72 ± 2.03, 5.04 ± 0.98, and 1.78 ± 0.65 mg/kg, while Cd was detected only at the petrol stations (0.13 ± 0.04 and 0.02 ± 0.003 mg/kg). Zn concentrations were 10.72 ± 1.02, 5.28 ± 0.89, and 7.44 ± 0.75 mg/kg, and Cu was 0.38 ± 0.07, 0.25 ± 0.05, and 0.62 ± 0.09 mg/kg respectively. Chromium had the highest concentration at Muhito Petrol Station (16.72 ± 2.03 mg/kg), likely due to stationary fuel combustion. All heavy metal concentrations were within WHO and KEBS permissible limits; however, regular monitoring is recommended to prevent escalation. Soil pH ranged from 5.70 to 8.30, electrical conductivity from 15 to 175 µS/cm, and moisture content was lowest at the petrol stations, indicating that contamination adversely affects soil physicochemical properties.

Keywords : Heavy Metals, Soil Contamination, Petrol Stations, Atomic Absorption Spectroscopy, Mukuruwe-Ini, Nyeri County, Lead, Cadmium, Chromium, Zinc, Copper, Heavy Metals, Soil Samples, WHO, KEBS.

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