Concentrations, transport characteristics, and health risks of PM2.5-bound trace elements over a national park in central India

Abstract

Fine particulate matter (PM2.5) mass and its chemical constituents were measured over Van Vihar National Park (VVNP) in Bhopal, central India. Fine PM collected over two years onto Teflon filters using a Mini-Vol® sampler were analyzed for trace elements using an Energy Dispersive X-ray fluorescence (ED-XRF) spectrometer. The temporal behaviour, dry deposition fluxes and transport pathways of elements, in addition to their health risks were examined in this study. S, K, Si, Al, Ca, and Fe accounted for most of the PM2.5-bound trace elements (~88% on average). Pronounced seasonality was observed for major elements (S, K, and Cl) and reconstructed soil (estimated as the sum of oxides of crustal elements, i.e., Si, Al, Ca, Fe, and Ti), with winter and post-monsoon season highs, potentially due to source strengths and favourable metrology during these seasons. The synoptic meteorology during these seasons favoured the fetch of particles from highly polluted regions such as the Indo-Gangetic Plain. The estimated average dry depositional flux of each element in this study was comparable to those measured/estimated for each of these species over other urban areas. The sum of the dry deposition flux for crustal elements (1301.9 ± 880.7 μg m−2 d−1) was in agreement with global dust cycle models. Air-parcel trajectory cluster analysis revealed that S, K, and Cl were influenced by biomass and coal burning in predominantly in central, and northwestern India, while reconstructed soil was influenced by air masses from the Arabian and Thar deserts. Finally, human exposure risk assessment to carcinogens (As, Cr, Cd, Pb and Ni) and non-carcinogens (Cu, Zn, Mn, V, Hg, Se and Al) revealed that no significant risk was posed by these elements. The assessment in this study was a screening for severe adverse effects, rather than a speciated health assessment. Thus, over the study region, monitoring, health risk assessment and mitigation measures, where needed, must be enhanced to ensure that trace elements induced health effects continue to be within safe levels.