Lead, Zinc and Cadmium Accumulation, and Associated Health Risks, in Maize Grown near the Kabwe Mine in Zambia in Response to Organic and Inorganic Soil Amendments.

Patricia N Mwilola,Victor Shitumbanuma,Ikabongo Mukumbuta,Yoshitaka Uchida,Shouta Nakayama,Benson H Chishala,Hokuto Nakata,Mayumi Ishizuka

doi:10.3390/ijerph17239038

Patricia N Mwilola, Victor Shitumbanuma + Show 6 more

Open Access

https://doi.org/10.3390/ijerph17239038

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Abstract

Health risks due to heavy metal (HM) contamination is of global concern. Despite concerns of high levels of HMs in soils near Kabwe mine in Zambia, edible crop production is common, posing potential health risks. This study assessed the potential of chicken manure (CM), triple superphosphate (TSP) and a blended fertilizer (BF; consisting of Nitrogen, Phosphorous and Potassium (NPK) fertilizer and composted chicken manure) to reduce lead (Pb), zinc (Zn) and cadmium (Cd) in soils and their accumulation in maize grown near the Kabwe mine. Maize was grown to maturity and its HM concentrations and associated health risk indices were calculated. All soil amendments decreased bioavailable soil Pb concentrations by 29–36%, but only CM decreased Zn, while the amendments increased or had no effect on Cd concentrations compared to the control. The amendments reduced Pb (>25%) and Zn concentrations (>18%) in the maize stover and grain. However, Cd concentrations in maize grain increased in the BF and TSP treatments. Bioaccumulation factors showed that Cd had the highest mobility from the soil into maize stover and grain, indicating the need for greater attention on Cd in Kabwe despite its apparently lower soil concentration compared to Pb and Zn. The hazard quotients for Pb and Cd were much greater than one, indicating a high risk of possible exposure to toxic levels by people consuming maize grain grown in this area. This study demonstrated the significant potential of manure and phosphate-based amendments to reduce Pb and Zn, and to some extent Cd, uptake in maize grain and consequently reduce associated health risks.

Highlights

Contamination of the environment due to heavy metals (HMs) from mining and other industrial activities is of major concern globally due to their effect on water and food quality and the resulting effect on human healthy [1,2,3]
The main goals of this study were to: (i) assess the levels of accumulation of Pb, Zn and Cd in the roots, stover and grain of maize (Zea mays), a crop widely grown and consumed in the study area, and the associated health risks, based on the joint United Nations Food and Agricultural Organization (FAO) and World Health Organization (WHO) limits for human health, and (ii) evaluate the effect of phosphate-bearing organic and inorganic soil amendments: chicken manure, triple super phosphate and an NPK fertilizer mixed with chicken manure on the bioavailable concentrations of Pb, Zn and Cd in the soil and their uptake by maize
All three soil amendments decreased bioavailable soil Pb concentrations, but only chicken manure decreased Zn and Cd in soil compared to the control

Summary

Introduction

Contamination of the environment due to heavy metals (HMs) from mining and other industrial activities is of major concern globally due to their effect on water and food quality and the resulting effect on human healthy [1,2,3]. Heavy metals accumulate in soils following the disposal of tailings, dust emission, through water transport or pesticide use [4,5,6,7,8]. Res. Public Health 2020, 17, 9038; doi:10.3390/ijerph17239038 www.mdpi.com/journal/ijerph

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