Heavy Metals and Polycyclic Aromatic Hydrocarbons in Soil from E-waste Dumpsites in Lagos and Ibadan, Nigeria

Abstract

Background.Soil contamination from heavy metals and polycyclic aromatic hydrocarbons (PAHs) released during informal e-waste processing and disposal poses human and ecological health risks in Nigeria.Objectives.This study assesses the levels of heavy metals and PAHs in soils of e-waste dumpsites in Lagos and Ibadan, Nigeria.Methods.Composite soil samples were collected at depths of 0–15 cm, 15–30 cm and 30–45 cm from major e-waste dumpsites in Lagos and Ibadan and analyzed for lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr) and PAHs to evaluate the potential contaminant contribution from e-waste activities. Control samples were collected at the Botanical Garden, University of Ibadan. Samples were analyzed for heavy metals after acid digestion using atomic absorption spectrophotometry, while PAHs were extracted using cold solvent extraction and quantified by gas chromatography-mass spectrometry. Blank determination and recovery studies were carried out for each metal. Contamination and ecological risks were assessed using soil contamination indices such as contamination factor, geo-accumulation and pollution load indices, and potential ecological risk index to categorize contaminant concentrations and associated impacts. Soil physico-chemical characteristics such as pH and total organic matter were also determined.Results.Metals concentrations in the dumpsite soils ranged from 114–2,840 mg/kg and not detectable - 6.50 mg/kg for Pb and Cd, and 42.8–5,390 mg/kg, 27.5–3,420 mg/kg, 11.0–128 mg/kg and 94.0–325 mg/kg for Cu, Zn, Ni and Cr, respectively. Serious metals accumulation was observed at every e-waste dumpsite, as shown by the pollution load index. The potential ecological risk values were between 584 and 10,402 at all of the dumpsites, signifying very high ecological risk. The total PAHs ranged from 1,756–2,224 μg/kg at the 0–15 cm level, 1,664–2,152 μg/kg at 15–30 cm and 278 μg/kg in the top- and sub-soil of the control site.Discussion.The total PAHs in the soil of e-waste dumpsites was significantly higher than in the control soil.Conclusions.The results of this study indicate that indiscriminate dumping and open burning of e-waste are potential sources of PAH and toxic metal emissions, which can pose serious human health and ecological risks.

A Survey of Concentrations and Source Characterization of Polycyclic Aromatic Hydrocarbons in Surface Waters of the Imiringi River System

“…Hence, PAHs have been described as the anthropogenic micro-pollutant with most environmental influence [11]. In the same manner, incineration of waste tends to release semi-volatile hydrocarbon compounds, such as PAHs into the atmosphere [7,12,13], thereby increasing the exposure routes for PAHs in the environment. Overall, the poor waste management practise of dumping un-segregated wastes along river banks tends to release inorganic and organic micro-pollutants directly into the water body, thereby enhancing the movement of such contaminants along coastal waters, before emptying them into the open sea waters.…”

“…Naturally occurring sources of pyrogenic PAHs release nominal levels in the environment, which emanates mainly from volcanic lava eruptions and incomplete burning of woodland fires, etc [22]. Other sources of PAHs include coal tar and crude oil [21] and electronic wastes [13], amongst others.…”

Impact of informal electronic waste recycling on metal concentrations in soils and dusts

“…Comparing the metal levels to those reported in previous studies in the same areas, it is found that metal concentrations are increasing (Olafisoye et al, 2013;Isimekhai et al, 2017;Adesokan and Gilbert, 2016;Adeyi, 2017). The metal concentration at the burning sites were also higher than the concentration reported in studies in China (Yekeen et al, 2016;Awasthi et al, 2016a).…”

“…The strengths of this study are its focus on different e-waste sites in each city, analyses of more number of metals that are not usually reported in other studies, the comparison of metal concentrations in various environmental samples (top soils, floor dusts, roadside dust, and direct dust from electronics) from different e-waste recycling sites and corresponding control sites, and the comparison of the extent of metal pollution at ewaste sites across the three cities in two different geopolitical zones in Nigeria. So far most studies (Isimekhai et al, 2017;Adesokan and Gilbert, 2016;Adeyi, 2017;Adaramodu et al, 2012) on metal pollution due to informal e-waste recycling sites focused on one location and usually on one type of environmental sample only. Therefore, these did not provide a comprehensive view on the extent to which heavy metal pollution from these activities is a problem.…”

Quantitative Analysis of Heavy Metals and Organic Compounds in Soil from Deir Kanoun Ras El Ain Dump, Lebanon

“…In the soil, these organic compounds have low mobility, high durability, and high affinity to soil organic matter [6]. It has been reported as well that, at dumpsites where solid wastes are burned, contamination by heavy metals is often accompanied by contamination by organic compounds [7,8].…”