Transfer of heavy metals from soils to curly mustard (Brassica juncea (L.) Czern.) grown in an agricultural farm in Brunei Darussalam

Adzrin Asikin Zunaidi,Lee Hoon Lim,Faizah Metali

doi:10.1016/j.heliyon.2021.e07945

Abstract

Determination of heavy metal concentrations in vegetables and agricultural soils is crucial because high levels of heavy metals could affect soil quality, crop production and safe consumption of crops. A field study was conducted to determine the heavy metal concentrations and their transfer from agricultural soils to different parts (leaf, stem, and root) of Brassica juncea (L.) Czern. In addition, potential health risks of contamination in the vegetables grown in the field were evaluated. Acid digestion method USEPA 3050B in combination with ICP-OES were used to analyze heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) contents in both pre- and post-harvest soils and vegetable samples. Results showed that none of the heavy metals in soils had concentrations above the maximum safety limits based on the WHO, USEPA and CCME guidelines. Calculated metal transfer factor (MTF >1) showed B. juncea accumulated Cd, Co, Ni, Pb and Zn in leaves, stems and roots, but Cu and Mn, as well as Cr were only accumulated in stems and roots, respectively. There were variations in heavy metal contents between the different parts of B. juncea, but only Cd and Pb contents were above the maximum allowable limit recommended by FAO/WHO. PCA analysis was able to identify 4 major components corresponding to 38.38%, 28.98%, 14.39% and 10.67% of the total variance and PC1 was clearly associated to leaves of B. juncea. Based on the MTF values, only Cd was found to have a value of HRI >1 compared to the other heavy metals, implying potential health risk associated with long-term ingestion of the vegetable.

Highlights

Over the years, heavy metal contamination has potentially become an increasing global environmental and health concern, in developing countries (Zhong et al, 2018; Rai et al, 2019; Yan et al, 2020)
This study found that Cd has the highest daily oral intake of metals (DIM), estimated daily exposure of metals (EDEM), and health risk index (HRI) for B. juncea with HRI of 3.294 and 5.180 in adults and children, respectively
The agricultural soils in this study did not contain heavy metals, whose concentrations are above the maximum safety limit according to the Council of Ministers of the Environment (CCME), United States Environmental Protection Agency (USEPA), and World Health Organization (WHO) guidelines

Summary

Introduction

Heavy metal contamination has potentially become an increasing global environmental and health concern, in developing countries (Zhong et al, 2018; Rai et al, 2019; Yan et al, 2020). Fe, Mn, Ni and Zn) and non-essential heavy metals Essential heavy metals are normally required at optimal levels by plants and may play a role in plant growth and development, at elevated concentrations, they produce severe toxicity symptoms in plants (Arif et al, 2016; Rout and Sahoo, 2015). Non-essential heavy metals have no biological and physiological functions in plants and are very toxic even at low concentrations (Singh et al, 2016a). Heavy metals in soils are derived from both natural and anthropogenic sources (Opaluwa et al, 2012; Alloway, 2013) where natural inputs are associated with minerals in the geological parent materials, while anthropogenic activities are linked to industrialization, urbanization and agricultural activities (Morgan, 2013; Zunaidi et al, 2020)

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