From sources to solutions: Real world characterization of PM2.5 emissions in mining transport corridors and future mitigation scenarios

Introduction and background

Roadside environments in opencast coal mining regions represent some of the most emission-intensive transport corridors in India, characterised by heavy-duty diesel operated vehicles and strong contributions from both exhaust and non-exhaust sources. Despite their importance for health risk and climate impacts, real-world characterisation of fine particulate matter (PM2.5) emissions and mitigation scenarios for mining-related transport activities remains limited.  

Methodology

PM_2.5 sampling campaigns were conducted at roadside locations along an active coal haul road and an urban road in Easter Maharashtra, India. Collected PM samples were analysed for elemental and organic carbon (EC & OC) through thermo-gravimetric analysis, total metals through ICP-MS, ions using ion chromatography, and PAHs through GC-MS.

Results and conclusions

High PM_2.5 (~500 ± 190 µg/m³) levels were observed near coal-haul road and city road. Carbonaceous species and ions dominated the PM mass, and elevated OC and EC and both roads, with coal road showing a strong EC signature (30 ± 15 µg/m³), reflecting combustion and vehicular sources. High molecular weight PAHs, particularly BaP, dominated the PAHs fraction, indicating a stronger influence from vehicular sources alongside pyrogenic sources. The ionic fraction was characterised by Cl^-(20-30%), SO₄^2-(5-10%), NH₄⁺ (10-25%), K⁺, and NO₃^- (~10%), indicating secondary formation and coal burning. Roadside PM2.5 showed elevated concentration of crustal and non-exhaust metals (Ca, Mg, Fe, Cr, Ni, Pb) and trace metals linked to mining-allied activities (Cu, Co, Se, As). APCS-MLR attributed PM2.5 around the mining region to non-exhaust, crustal dust, and coal combustion (52%), vehicular emissions and coal combustion (32%), and biomass burning and secondary inorganic aerosols (20%). Traffic characterisation revealed that super emitters (overloaded, poorly maintained diesel trucks with visible plumes) were significantly correlated with both fine and coarse PM levels (r>0.6, p<0.05). Building on the source-resolved PM_2.5 profiles, various mitigation scenarios were examined, including baseline, targeted reductions in vehicular exhaust, control of non-exhaust and resuspended dust sources under current and future mining growth conditions. The scenario analysis strongly indicated that transport-focussed interventions, particularly reduction in diesel exhaust and non-exhaust emissions from mining fleet, can yield substantial reductions in fine PM and its associated toxic component levels. Therefore, this study highlights the critical role of real-world chemical characterisation and source measurements in mitigation of transport related emission in complex industrial settings with mixed-sources. The findings underscore the need for targeted mitigation strategies such as regulation of super emitters, fleet upgradation, and control of non-exhaust emissions to improve air quality in diesel transportation dominated mining corridors.