Abstract
Heavy metal (Cr, Cu, Zn, As, Cd, and Pb) contamination in irrigation water, soil, and vegetables was investigated in farmland adjacent to a multi-industry zone in Bangladesh in dry and wet seasons. In the zone, many factories release wastewater into nearby irrigation canals, and vegetables cultivated with this water could be a major food chain route for human exposure. In the irrigation water and vegetables, heavy metal concentrations exceeded permissible levels in the two seasons, but this was not the case in soil. Zn had the highest concentration, and Cd had the lowest concentration in irrigation water, soil, and vegetables. All heavy metal concentrations were found to be lower in the wet than in the dry season, which is due to the dilution of water by rainfall, lower absorption of heavy metals from the diluted irrigation water, and heavy metal absorption from low concentrated irrigation water and/or soil. The cluster analysis data of irrigation water, soil, and vegetables revealed that the heavy metals in vegetables were considered to be absorbed from irrigation water in the wet season and from soil in the dry season. In the dry season, the high heavy metal concentrations in vegetables might be caused by a high bioconcentration factor (mostly > 20%).
Highlights
In developing countries, heavy metal contamination of farmland is occurring, which is a severe environmental problem due to the toxicity of heavy metals [1]
The mean heavy metal concentrations of the irrigation water are given in Table 1, together with the coefficient of variation (CV) of the concentration
In irrigation water and vegetables, heavy metal concentrations exceeded their permissible levels, while in soil, most concentrations were below permissible levels
Summary
Heavy metal contamination of farmland is occurring, which is a severe environmental problem due to the toxicity of heavy metals [1]. The concentrations of heavy metals and metalloids in irrigation water, soil, and vegetables have been greatly increasing on farmland due to anthropogenic activities including the expansion of industrialization and urbanization [2]. Irrigation water contaminated with industrial wastewater has caused significant heavy metal contamination in soils and crops. Due to unplanned industrialization and urbanization in the country, wastewater contaminated with heavy metals is continuously released into irrigation canals, soil and crops are contaminated with heavy metals, and many people consume the contaminated crops after they have been transported and sold in retail markets [5], and face the risk of health problems
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