Impact of Holika Dahan on ambient PM2.5 and associated health risks in an urban environment of Lucknow, India.

Large-scale biomass-mix burning of Holika Dahan (HD) is celebrated before the Indian traditional festival Holi, which has adverse effects on air quality and health. This study aimed to assess chemical characteristics of airborne PM2.5, source contributions, emission dispersions, and related health risks during pre-HD, HD, and post-HD sequential nights for a residential area and a commercial area in Lucknow. Compared with pre-HD night, concentrations of ambient PM2.5 were higher during HD night by factors of 2.0 and 1.4 in the respective residential and commercial areas. Tracer signatures of PM2.5 emissions from HD biomass-mix combustion ranged from 1.2 to 2.7 times higher during HD night than during pre-HD night. Further, the peaks in the spectrum of ATR-FTIR functional group markers of PM2.5 samples indicate the impact of HD biomass-mix combustion on local air quality. In addition to peaks in marker species of HD emission, PCA and HCA statistics further confirmed that HD biomass-burning is the predominant source of PM2.5 at both study sites. The HYSPLIT simulated the HD emission transport paths towards primary eastward and south-eastward. The AERMOD dispersion hotspot isopleths indicated the extent of localised propagation of HD emissions up to 1.2 km and 1.5 km for residential and commercial areas, respectively. The hazard index (HI) values were found below the USEPA permissible limit, indicating negligible non-carcinogenic health risk despite the record of high HIs on HD night. Whereas the cancer risk (CR) exceeded USEPA safe limits due to HD impact at both the sites, however, peak CR was observed during HD night. The findings of the study highlighted short-term air quality degradation and potential long-term health concerns associated particularly with Holi festival-related HD combustion.