Extended database of SO2 column densities over Pakistan by exploiting satellite observations

Increasing levels of atmospheric SO2 is a major threat and is now widely included in health risk assessment studies. An annual estimation of SO2 has been conducted for both anthropogenic and natural activities at country level. Satellite observations of atmospheric sulfur dioxide (SO2) are obtained over Pakistan during the time span of 2005-2016. The data was acquired from the Ozone Monitoring Instrument (OMI) onboard NASA's Aura satellite. DOAS (Differential Optical Absorption Spectroscopy) based algorithm was utilized to retrieve SO2 column densities. In addition to spatio-temporal analysis of SO2 column, seasonal cycles over major areas of Pakistan are evaluated and discussed. Year 2007, 2011 exhibited anomalous high levels of SO2 attributed to trans-boundary volcanic plumes observed in Pakistan. SO2 plumes were caused by Dallafilla and Nabro volcanic eruption and spread over East African, the Middle Eastern and South Asian regions. A temporal increase of about 78% was observed in anthropogenic SO2 levels for a period of 2005-2016 across Pakistan. Further, the relative change was maximum in Khyber Pakhtoon Khwa (KPK region 46%) followed by Punjab (38%), Sindh (28%) and Baluchistan (18%), respectively. The economic prosperity in recent years resulted in increased demand for energy by both the industrial and domestic sector, and consequent increase in SO2 emissions in Pakistan.