Systematic review of papers on atmospheric sulphate formation to understand recent trends in cloud behaviour due to anthropogenic emissions and other determinants

Condensation of water vapour on tiny air borne particles, which are also identified as Cloud Condensation Nuclei (CCN) result into formation of cloud. Sulphate aerosols are most abundant CCN. In this period of rapidly changing weather and increasing air pollution it is crucial to understand the pathways of sulphate formation for more accurate forecasting of cloud formation. A systematic review of publications on sulphate formation pathways and subsequent cloud formation has been done in present work. 25 papers were selected for this work and 18 papers have been considered after AI enabled screening with a set of criteria like: work is a peer reviewed journal paper, work has direct relevance to SO2 oxidation to sulphate with at least one or more than one pathway(s), mechanistic or quantitative content like reaction schemes, rate laws, kinetic parameters, or regime diagrams are available, interpretations or modelling explains and conform to the observational results, work is representative of atmospheric sulphate formations, and work is mostly done between 2015 -2025, early 2026). Few works are excluded to avoid duplicity, overlapping, insufficient focus on SO2 to sulphate pathways, lack of transparency. Authors differ in explaining mechanisms of sulphate pathways but there are commonalities in observations and conclusions. Most of the work showed that cloud pH, water content, oxidant levels in air, presence of transition metal ions (Fe, Mn) for catalysing oxidation, presence of aqueous aerosols are the governing factors for sulphate formation followed by cloud formations dynamics, laboratory experiments, kinetic or box or global models. In addition to conventional sources of sulphur like volcanic eruptions and anthropogenic fossil fuel combustions, multiple sources including biogenic asubstances in copious volume alter cloud formation at scale. Even in this year of Super El Nino, there shall be pockets where cloud cover stays longer and allow to enjoy cooler temperature.