Assessment of Potentially Harmful Elements in Roadside Soils and Dusts of Offa, Northcentral Nigeria and their Ecological Implications

Abstract

Urbanisation has been identified as a major trigger in the quality deterioration of environmental media, necessitating regular monitoring and assessments in various locations in industrialized countries. To this end, a study was conducted to examine concentrations of selected potentially harmful elements (PHEs) in soils and road dusts of Offa, as well as the ecological consequences of these elements in the media. Fifty samples (30 soils and 20 road dusts) were collected. The sieved samples were digested with aqua regia, followed by determination of the elemental constituents using Inductively Coupled Plasma Optical Emission Spectroscopy. The pH, Electrical Conductivity (EC) and Total Dissolved Solids (TDS), were determined using standard methods. Microsoft Excel and IBM-SPSS (version 20.0) were used to analyze the results to ascertain the elemental relationships and quality of the media. The pH ranged from 6.6-7.1, and 6.3-7.5, indicating acidic to slightly alkaline media; EC ranged from 42.4-3130.2 μS/cm, and 34-1254 μS/cm, and TDS ranged from 0.4-89.0 mg/l, and 13-248.0 mg/l, for soils and road dusts respectively. The following concentrations (in mg/Kg) ranges were measured for the PHEs in the soils and road dusts; Cu, 17.0-654.0; Pb, below detection limit (bdl)-1151.0; Zn, 22.0-2129.0; Ni, 7.0-97.0; Mn, 422.0-1396.0 and; Cr, 30.0-266.0. The study revealed that a combination of anthropogenic and lithogenic factors contributed to the elemental constituents of the samples. The samples were moderately contaminated with Cu, Pb, and Zn, but uncontaminated with Ni, Mn, and Cr. Pb poses a moderate ecological risk relative to other elements which are of low risk.