Elemental chemistry and geochemical partitioning of heavy metals in road dust from Dhanbad and Bokaro regions, India

Road dust collected from India's richest and oldest coal mining belt of Dhanbad and Bokaro regions was analysed for particle size characteristics and elemental composition. The particle size distribution pattern shows dominance of 500-250 mu m and 250-125 mu m size fractions, constituting 45-58% of the mass size spectrum. Si is the most dominant element and its concentration varied between 29.3 and 36.4% with the average value 34.3%. Fe, Ti and Mn are the dominant heavy metals followed by Zn, Cr, Pb, Cu, Ni and Co. No significant differences concentration of metals between sampling sites was apparent; however, some sites tend to accommodate relatively higher metals due to its proximity to industrial and mining sites. In general, finer fraction (< 63 mu m) tend to contain 1-3 times higher metals as compared with the bulk composition. Except Pb and Mn all the measured metals are generally lie below grade zero, suggesting that there is no pollution threat with respect to these metals in roadway dust from the studied sites. Geochemical speciation study shows that the lithogenic phase is the major sink for heavy metals. Fe-Mn oxide and organic are the major non-lithogenic phases and Pb and Zn are the major elements of the non-lithogenic phase.