Occurrence and Remediation of Polychlorinated Biphenyls in Soil from Jos, Plateau State, Nigeria

Ezekiel Gube Ibrahim^1*, Salami Sunday John¹, Gushit John S², Dalen MB¹ and Gube-Ibrahim MA^3
*Correspondence: Ezekiel Gube Ibrahim, Department of Chemistry, University of Jos, P.M.B. 2084 Jos, Nigeria, Tel: +2348032900356, Email:

Keywords

Remediation • Polychlorinated biphenyl • Mon-oammonium phosphate • Chromatography and soil

Introduction

Polychlorinated biphenyls (PCBs) are persistent and toxic pollutants that have been widely distributed into the environment [1]. They are classified as persistent organic pollutants (POPs) under the Stockholm Convention due to their persistence bioaccumulation, high toxicity and long-range atmospheric transport with potential carcinogenicity [2]. Research evidence has revealed that long range transport is a major source of this contaminant in a remote area [3].

Polychlorinated biphenyls are mainly synthetic chemicals with 2-10 atoms of chlorine attached to the biphenyls molecules and were produced several years ago with annual production estimation of 1.5millions tones [4]. Although banned in most of the countries in 1980, yet its emission still continues from old electrical equipment, inadequate management of wastes and electronic equipment leakage or improper disposal of transformer and capacitor oil [5].

They are 209 compounds often known as PCBs congeners. Their properties such as heat resistance, low electrical conductivity and thermal degradation performance make them excellent in use as insulators mediums, flame retardant agents, plasticizers and pesticides additives since 1930s [6-8]. Out of the 1.5million tones production globally, 48% production of the PCBs is used for transformer oils, 21% for small capacitors, 10% for other closed system, these include heat transfer fluids, hydronic fluids, liquid filled cables and circuit breakers and approximately 21% for open systems as paints and pesticides [4]. They have also been used as organic diluents, plasticizers, adhesives, dust reducing agent cutting oils, flame retardants, sealants and in carbonless copy paper. Some of these PCBs uses have resulted in them directs introduction into the environment.

Contamination of the environmental compartments by polychlorinated biphenyls is a matter of great concern to the environmentalists worldwide. They have been reported to have adverse effects on the environment, human and ecosystem. They enter the environment as a mixture containing different individual congeners [9].

Despite their phase out in 1970, PCBs residues still have been reported in soil, water and air all over the world [10-13] and their levels are not expected to decrease significantly in the next few decades [14].

Soil has been an important sink for PCBs and can also acts as a source of pollution [15]. Soil contamination has led to the reduction of agricultural areas which is a growing problem in many countries. Meijer et al. reported that nearly 21,000 tons of PCBs have been discharged to the soil in the world. This can be accumulated gradually through the food chain and have a detrimental effect on human [16].

The distribution of PCBs in soil can help to assess the level of pollution, infer the source of the emission and evaluate the human health risk [17]. Therefore, the aim of this research is to investigate the occurrence of PCBs in soil and remediate using locally produced activated carbon from Coconut shell and Moringa seed on contaminated soil from Transformer Installation Sites in Jos, Plateau State Nigeria with the objective of evaluating the efficiency of remediation between the activated carbon and the Moringa seed.

Materials and Methods

Sample collection and treatment

The soil samples were collected in March 2019 from transformer installation site in Jos, Plateau State, Nigeria within the depth of 15 cm from different sites. The stones, weeds, leave and roots were removed after which it was taken to laboratory. All the samples were dried at ambient temperature crushed through a sieve of 10mm aperture and stored in the refrigerator for further analysis [18].

For the remediation studies the activated carbon was produced according to Soideide with slight modification whereby the final product was air-dried after addition of distilled water for two weeks at room temperature instead of oven drying. This was packed in polyethylene bottles for further use. The Moringa seed was purchased in local market cleaned from debris and crushed with pestle and mortal to obtain the powder seed, which was stored in polythene leather for further use. Ten grams each of the contaminated soil was mixed with five grams each of prepared activated carbon, Moringa seed and Moringa seed powder; and allowed to stand for two weeks, after which it was extracted and analysed.

Sample extraction and cleaned up

Twenty grams of the soil samples (that is moisture free) were mixed thoroughly with 10 g of anhydrous sodium sulphate each sample was ultrasonicated with 30 mL of n-hexane/acetone (1:1 v/v) for 30 minutes. The extract was cleaned with column chromatography packed with silica gel and concentrated to 2 mL using rotary evaporator.

Instrumental analysis

The final extract of 2.0 ml was analysed for PCBs using a gas chromatograph equipped with 63Ni electron capture detector GC - ECD model CP 3800.

The capillary column used was VF 5ms 30 m × 0.25 mm id × 0.25 μm film thickness. The GC conditions were as follows: injection point temperature: 270°C; oven temperature programme:

70°C (hold 2 min) to 180°C at a rate of 25°C/min (hold 1min) to 300°C at a rate of 5°C/min. Temperature of detector was 300°C; carrier gas-nitrogen at flow rate: 1.0 ml/min; make-up gas flow rate 29.0 ml/min. The total runtime was 31.368 min.

The PCBs congeners were identified by the comparison of retention time of the PCBs in the samples with those of the standard while the quantification of individual congeners in mg/kg was calculated on dry weight basis.

Conclusion

The results of the total PCBs concentration in the soil from the two sites of the transformer installations exceeded the maximum required baseline of 2 mg/kg for cleanup. Both activated carbon and Moringa seed can be used for remediation, preferably Moringa seed powder probably due to increased in the surface area. Due to the economic importance of Moringa seed which served as a source of immune boaster the researcher recommend that PCB transformer should be replaced with non PCB releasing transformers.

Acknowledgement

The authors express their appreciation to TETFUND University of Jos Institution Based Research through the Office of Research and Development (ORD) for their financial support in this research work, Ikukplasi Laboratory Services (Nig.) Ltd for their facilities and Jos Electricity Distribution Company for availing us opportunity to use their facilities.

Authors Contributions

E.G. Ibrahim performed the experiment, wrote the manuscript and collect the samples, S.J. Salami designed the experiment, J.S. Gushit analysed the data and contributed in provision of materials, M.B. Dalen contributed reagents/ analysis tools and M.A. Gube-Ibrahim proof read and edit the manuscript.

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