Heavy metal concentration and its distribution analysis in urban road dust: A case study from most populated city of Indian state of Uttarakhand

The present work reports pollution level and spatial distribution of heavy metals (HMs) i.e. Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Lead (Pb), Chromium (Cr), Nickel (Ni), and Arsenic (As) in road dust of Dehradun city, Uttarakhand, India. Seventy samples in triplicates were collected from different land-use areas categorized as residential, commercial, national highways, and silent zones. The Concentrations of studied HMs were determined by the acid digestion method followed by inductively coupled plasma-mass spectrometry (ICP-MS). Pearson's significant correlation analysis is used to evaluate the relationship between heavy metal (HM) concentration and principal components analysis (PCA) was used for source identification of HMs in road dust. The average concentration of Mn, Zn, Cu, Pb, and Ni found higher when compared to the Indian soil background values. Among all studied HMs, Pb and Zn were found the most contaminated HMs in road dust. The degree of contamination shows the highest contamination of HMs found in commercial zones followed by National highways. The pollution load index (PLI) was found higher than 1 in all monitored 70 locations, showing the deterioration in the quality of road dust over the Dehradun city due to HMs. The principal component analysis result suggests that PC1 (Fe, Zn, Cu, and Ni) mainly comes from vehicular pollution, including tire wear and brake pad wear particles and corrosion of metallic components. PC2 (Mn and As) primarily comes from fossil fuel burning and pesticides and fertilizers containing Mn and As compounds. PC3 (Pb and Cr) mainly comes into road dust via fuel and lubrication oil residues and chrome-based paints. Spatial distribution maps of the HM concentration reveal that the city's central and eastern zone is the primary hotspot of high HM concentration, which links these zones to high vehicular volume and high population pressure.