Heavy Metals Contamination Levels in the Vegetables Grown around Riruwai Mining Area, Kano State, Nigeria

Abstract

Vegetables grown in mining areas can accumulate significant amounts of heavy metals (HMs), which can cause serious developmental disorders and have long-term negative effects on public health. In the present study, the HMs contamination level in vegetables grown around the Riruwai mining area in Kano State, Nigeria, was investigated. Fifteen (15) vegetable samples were collected, including lettuce (Lacuta sativa L.), tomato (Solanum lycopersicum L.), and bean (Phaseolus vulgaris L.), as well as their corresponding soils. The levels of As, Cd, Cr, Hg, Mn, Ni, Pb, and Zn in all the samples were determined using Microwave Plasma Atomic Emission Spectrometry, and the measured concentrations were used to calculate the bioaccumulation factor (BAF). The results of the study revealed that HMs concentrations in the investigated vegetables were found to be significantly high, with the majority of levels exceeding the WHO/FAO (2007) recommended limit, and the concentration of HMs in the soil decreased in the order of Zn > Mn > Cr > Pb > As > Ni > Cd > Hg, with As, Pb, and Zn exceeding the WHO/FAO (2001) recommended limit. Pollution levels were found to significantly differ between HMs and vegetable types. BAF results revealed that cadmium is an accumulator of all the studied vegetables (BAFs > 1), while mercury was found to be an accumulator of L. sativa. Higher concentrations of these metals in vegetables and soil, particularly arsenic, cadmium, lead, and zinc, necessitate immediate scientific attention and further research to determine the optimum concentration required for human health. Planting of vegetables for human and animal consumption should be stopped until this is accomplished.

Keywords

• BAF
• Heavy metals
• Microwave Plasma Atomic Emission Spectrometry
• Riruwai
• Vegetables