Ecological and health risk assessment of heavy metals in roadside soil, dust and water of three economic zone in Enugu, Nigeria

Abstract

Heavy metals posed threat to humans and environment. Spatial distribution/source identifications of heavy metals in soil, dust and water along major road of three economic zone of Enugu: Enugu/PH road (Industrial area), Agbani Road (Residential) and Ogui New Layout Road (Commercial) were evaluated. Soil and dust samples were collected at 15 cm depth and 1 m from roads, underground water at 65 m from roadside between December 2020–April 2021. Heavy metals were quantified by AAS. Heavy metals (mg/kg) in roadside soil varied from 0.00 to 0.05 (Cr), 1.50–4.00 (As), 0.08–6.93 (Ni), 4.98–7.86 (Cu), 0.00–0.03 (Hg), 213.95–274.79 (Fe), 1.25–4.16 (Pb) and 8.49–16.23 (Mn) for Enugu/PH; 0.00–0.20 (Cr), 2.75–3.13 (As), 0.25–4.94 (Ni), 3.65–11.73 (Cu), 0.00–0.00 (Hg), 159.87–233.65 (Fe), 2.08–4.54 (Pb), 6.18–17.15 (Mn) for Agbani; 0.00–0.13 (Cr), 1.48–3.70 (As), 0.03–1.50 (Ni), 3.13–5.54 (Cu), 0.00–0.00 (Hg), 138.06–189.51 (Fe), 0.58–1.38 (Pb), 9.75–21.75 (Mn) for Ogui. The level of heavy metals (mg/kg) in roadside dust ranged from 0.00 to 0.18 (Cr), 0.00–2.33 (As), 0.85–2.05 (Ni), 4.54–16.93 (Cu), 0.00–0.00 (Hg), 137.36–247.03 (Fe), 0.88–4.99 (Pb), 17.65–26.43 (Mn) for Enugu/PH; 0.00–0.00 (Cr), 0.00–2.85 (As), 0.71–4.68 (Ni), 4.94–121.85 (Cu), 0.00–0.00 (Hg), 159.23–203.70 (Fe), 0.59–14.63 (Pb), 15.05–23.44 (Mn) for Agbani; 0.00–0.14 (Cr), 0.00–2.33 (As), 1.08–4.45 (Ni), 4.25–6.95 (Cu), 0.00–0.00 (Hg), 152.84–207.66 (Fe), 1.00–3.41 (Pb), 14.13–23.18 (Mn) for Ogui. As in water Enugu/PH (0.081 mg/L), Agbani (0.079 mg/L) and Ogui (0.150 mg/L). Principal component analysis indicated that Cr, As, Ni, Cu, Hg, Pb Fe and Mn distributions were affected by traffic, industrial release and natural sources, ecological analysis showed low to moderate pollution. Risk assessment (children/adults) via each pathway were HI <1. Estimated cancer risk of 75% heavy metals via CRing/inh/der (soil, dust water) below 1× 10−6 - 1 × 10−4, total cancer risk shows high probability of carcinogenic risk via ingestion as children > adult susceptibility on prolonged exposure to vehicular activity, hence alarming contamination status of heavy metals in Enugu and associated health risk.