Evaluation of Heavy Metals in Soil Using Modified BCR Sequential Extraction

Hafsat Tukur Rumah

doi:10.11648/j.ijmpem.20170205.13

Abstract

Recent studies have shown that strong acid digestions for the determination of heavy metals in soils and sediments can be misleading when assessing environmental effects. Therefore, this study adopted the use of modified community bureau of reference (BCR) sequential extraction scheme in order to overcome the limitation. The physicochemical properties of the soil such as pH, cation exchange capacity (CEC) and soil organic matter (SOM) were determined. The pH, CEC and SOM were found to be 5.90, 0.0023 cmol/kg and 99.8% respectively. The concentrations of the heavy metals in the solution were also measured using atomic absorption spectrophotometry. Pseudo total metal content in the soil (aqua-reqia digestions) for cadmium, lead, chromium, nickel, zinc and copper were 0.12, 0.74, 0.48, 0.26, 15.9 and 11.0 mg/kg respectively. These concentrations are within the World Health Organization (WHO) permissible limit in agricultural soils. The heavy metals were partitioned into four fractions (exchangeable, reducible, oxidizable and residual fractions) in the soil using modified BCR sequential extraction. Cd, Zn and Cu were predominantly in the first two fractions, thus, mobile and bioavailable for plant uptake, while Pb, Cr and Ni were found in the last two fractions (less mobile and immobile residual fractions). Thus, Cd, Zn and Cu may pose high environmental risk. The results indicate the reliability of the Modified BCR scheme in risk assessment of heavy metals in soils.

Highlights

Soil contamination is any addition of compounds in the soil that results in detectable adverse effect on soil functioning
Soil pollution is the soil contamination that has become severe and the adverse effects have become unacceptable resulting in malfunctioning of the soil and consequent soil degradation [1]
This work is aimed at assessing the efficiency of modified BCR sequential extraction technique in partitioning of heavy metals in the soil

Summary

Introduction

Soil contamination is any addition of compounds in the soil that results in detectable adverse effect on soil functioning. Waste produced naturally from plants and animals adds to the fertility of the soil [2]. These leave elevated levels of heavy metals, hydrocarbons, nutrients and other compounds on land and possibly in the ground water. Heavy metals constitute an ill-defined group of inorganic chemical hazard. Those most commonly found at contaminated sites are Cd, Pb, Cr, Ni, Zn, Hg and Cu. Rapid industrialization and urbanization are majorly responsible for the soil pollution commonly observed in recent time [6]

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Conclusion