Study of ice nucleating particles in fog-haze weather at New Delhi, India: A case of polluted environment

Ice nucleating particles (INPs) concentration in deposition mode was measured and reported for a polluted urban site in New Delhi, India. The measurements were carried out during the winter period from December 2016 to January 2017. The INPs data, sampled under different meteorological conditions, were analysed using a thermal gradient static diffusion chamber. The observed INPs concentration ranges from 0.05 to 9.55 L-1 at mean nucleation temperature - 18.49 degrees C (SD = 0.27 degrees C). The mean INPs number concentration observed under three meteorological conditions was significantly different. No correlation was observed between particles size 0.5 mu m, Particulate Matter and BC for the entire observation period, but correlation (r(2) = 0.27, p < 0.001) was observed between INPs and BC under foggy conditions for January 2017 period. The activation fraction was ranges from 1:10(6) to 1:10(8) for the entire campaign. Scanning electron microscopy analyses revealed that particles chemistry was diverse, and particles were a mixture of BC, mineral dust, and soot. The enrichment factor indicates that elements like Nitrogen, Sulphur, and Chloride were of anthropogenic origin.