Vol.:(0123456789) 1 3 Environmental Earth Sciences (2019) 78:411 https://doi.org/10.1007/s12665-019-8406-x ORIGINAL ARTICLE Assessment of heavy metals in roadside dust along the Abu Dhabi–Al Ain National Highway, UAE Ahmed A. Al‑Taani 1,2  · Yousef Nazzal 3  · Fares M. Howari 3 Received: 13 October 2018 / Accepted: 5 July 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Concentrations of key heavy metals (Pb, Zn, Cd, Ni, Cr, Mn, As, and Hg) have been investigated in roadside dust collected from Abu Dhabi–Al Ain National Highway in UAE. The heavy metals contents were analyzed by atomic absorption spec- trometer. Heavy metal levels varied widely from 227.9 to 2765, 19 to 1540, 37.4 to 398.6, 20.1 to 123, 0.3 to 0.7, 0.1 to 0.9, 0.1 to 0.7, and 0.1 to 0.5 mg/kg for Mn, Cr, Zn, Pb, Cd, Hg, Ni, and As, respectively. The spatial distribution pattern showed that diferent sources of roadway metal emissions dominate at specifc locations. Peaks in heavy metal concentrations were frequently observed in locations with high trafc volume, road intersections and junctions, gas and bus stations. Decreased levels of heavy metals were measured in locations with low trafc loadings and in close proximity to farm and forest areas. In addition to trafc-related heavy metals, emissions from fossil fuel and industries remain of signifcance. Natural sources, through regular dust storms, are important contributors to the observed metal levels. Enrichment factor indicated that As and Ni were entirely originated from crustal sources. Cd, Zn, Pb, and Mn were moderately enriched and are probably derived from mixed sources (trafc fows, gas stations, construction and agricultural activities, among others). Road dust was sig- nifcantly enriched in Cr and Hg indicating their dominant anthropogenic origin. The average geo-accumulation index values suggested that road dust are uncontaminated with Mn, Ni, and As, uncontaminated to moderately contaminated with Zn and Pb, and moderately contaminated with Cr, Cd, and Hg. The contamination factors indicated very highly contaminated road dust with Cr and Hg, considerably contaminated with Cd, and moderately contaminated with Mn, Zn, and Pb. Results of ecological risk assessment revealed that all heavy metals in road dust pose low risk to local ecosystems, except for Cd and Hg, which constitute potentially considerable risk and high risk, respectively. Keywords Heavy metals · Roadside dust · Contamination factor · Geo-accumulation index · Ecological risk assessment · UAE Introduction Air pollution is a signifcant public health problem in the United Arab Emirates (UAE) (Al-Taani et al. 2018b) and has become a national health priority issue (Al Jaberi et al. 2010; Reid et al. 2004). The rapid economic and indus- trial development in UAE has severely impacted on the air quality, where huge quantities of gasses and dust are emitted into the air. In addition, the extremely arid climate of UAE, amid a vast desert, makes it vulnerable to intense and regular episodes of dust storms. Of signifcant importance are the emissions associated with the transportation sector, which is one of the fast-growing sectors in UAE. The contributions of roadside dust to air pollution and human health have gained a growing attention due to absence of legislation pertaining to non-exhaust pollution sources (Gope et al. 2018). A large number of studies inves- tigated the levels of contaminants associated with highways, of which heavy metals received a particular interest (Bretzel and Calderisi 2006; Christoforidis and Stamatis 2009; Wei and Yang 2010; Apeagyei et al. 2011; Li et al. 2013; Nazzal et al. 2014; Adamiec 2017; El-Radaideh and Al-Taani 2018). * Ahmed A. Al-Taani taaniun@hotmail.com 1 Department of Earth and Environmental Sciences, Faculty of Science, Yarmouk University, Irbid 21163, Jordan 2 Deanship of Scientifc Research and Graduate Studies, Yarmouk University, Irbid 21163, Jordan 3 College of Natural and Health Sciences, Zayed University, P.O. Box 144534, Abu Dhabi, United Arab Emirates