Wambua Mwenzwa

Abstract

Heavy metal pollution is a major concern globally. Anthropogenic activities are believed to lead to accumulation of heavy metals in soil and water over time. This may lead to serious health problems affecting microorganisms, plants and higher order animals such as man. The objective of this study was to analyze the concentration of heavy metals in soil, water and vegetables and their potential human health risk.32 samples were collected from eight sampling stations for soil, vegetables and water samples separately following standard APHA procedures. Samples were collected using a composite sampling method in January and April 2023.Soil and vegetable samples were collected using plastic bags while water samples were collected using clean plastic bottles. Heavy metal concentration analysis was done using atomic absorption spectroscopy for Pb, Cr, As, and Zn. Data analysis was done using descriptive statistics of changes in concentrations, ANOVA, Pearson correlation co efficient and principal component analysis. The mean concentration of heavy metals in soil, water and vegetables was analyzed. Among the heavy metals analyzed the results showed Zn with highest levels of, 7.22 mg/kg and 5.01 mg/kg for vegetables and soil samples, respectively. The maximum Target Cancer Risk (TCR), the highest value of Estimated Daily Intake (EDI) and the maximum value of Bioconcentration factor (BCF) value recorded were 8.46 × 10 ⁵ 0.001, and 18.37, for As, Cr and Zn, respectively. Hazard index (HI) indicated no potential health risk. The concentration of heavy metals in the soil sample showed that Cr and As were strongly positively correlated with the concentration of Pb in vegetables during month of January. As concentration in the water sample was also strongly positively correlated with the concentration of Pb during January. The application of proper policy framework for the reduction of contaminants from wood treatment industries and suitable irrigation methods with treated wastewater is essential. The study can provide a basis for the ministry of environment to properly protect the soil and water quality and provide a reference for proper disposal of chemicals and wastewater around wood treatment industries in the country.