Heavy Metal Pollution of Soils and Their Ecological Risk in Suburban Areas

Abstract

In this study, soils of five suburban areas of Nairobi, Kenya where vegetables were irrigated with wastewater were assayed for heavy metals and resultant concentrations compared to the predefined permissible levels. Using multivariate statistical analyses, relationships among the assayed metals were established. Furthermore, pollution and ecological risk indices were used to rate pollution levels from assayed metal contaminants. Findings showed that concentrations of As, Cd, Cr, Co, Hg and Mn were higher than permissible levels, which was indicative of pollution. All metals except Co and Ni came from similar sources based on their positive Pearson's correlation coefficient values. Based on the computed pollution and ecological risk indices, Cd and Hg had the greatest pollution contribution in the soils. Pollution in the study area was largely a result of anthropogenic activities in the vicinity. Affirmative action is imperative to regulate the release and reuse of wastewater for agricultural purposes.