IIT Madras-Led team uncovers link between power plant emissions and cloud formation

A multinational group of scientists, spearheaded by researchers from the Indian Institute of Technology (IIT) Madras, has conducted an extensive investigation into the influence of power plant emissions on cloud creation through the atmospheric conversion of gaseous discharges. This conversion gives rise to particulate matter (PM) composed primarily of sulfate, resulting in particles that exhibit heightened potential for cloud formation in comparison to their natural counterparts.

The outcomes of this study, which have been detailed in the esteemed npj Climate and Atmospheric Science journal, carry significant implications for shaping policies concerning the management of PM2.5 pollutants. The collaborative effort, comprising 27 scientists hailing from 17 distinct institutions across eight countries, delved into the repercussions of emissions from the Neyveli coal-fired power station located approximately 200 kilometers south of Chennai, Tamil Nadu. Their focus was on the evolution of aerosols and cloud-forming characteristics within the vicinity.

Professor Sachin S. Gunthe, Coordinator of the Centre for Atmospheric Sciences within the Department of Civil Engineering at IIT Madras, underscored the importance of the findings. "Our study offers a unique opportunity to assess the sensitivity of aerosol particles that contribute to cloud formation, particularly in relation to the formation and growth induced by sulfur dioxide (SO2) emissions from a coal-fired power plant operating under relatively cleaner conditions," he remarked. Gunthe added, "These discoveries carry significant implications for gauging the climate impact of human-generated aerosols and underscore the necessity of comprehensive emission control measures."

The research was executed during the period of Covid-19 lockdown in India, when anthropogenic emissions from sources such as vehicular traffic and industries were notably curtailed. Notably, the researchers revealed that the discontinuation of local anthropogenic emissions didn't lead to a decline in PM2.5 concentrations. On the contrary, emissions of SO2 from the power plant were shown to contribute to the augmentation of PM2.5 mass through the creation of novel particles—an observation that challenges prevailing assumptions.

The study disclosed that the transformation of gaseous SO2 emissions into particulate matter via power plant activities contributed to an increased concentration of aerosols rich in sulfates, fostering a heightened potential for cloud formation within the atmosphere. These aerosol particles play a crucial role in the formation of clouds, ensuring the availability of freshwater essential for sustaining life on Earth. Moreover, their interaction with incoming solar radiation significantly influences the planet's radiative balance.

Of particular interest was an intriguing event wherein long-range transport of SO2 gas emitted by the Neyveli power plant spurred the creation of new particles, commonly referred to as 'secondary aerosols', in Chennai. These particles were characterized by their rich sulfate content and rapid growth, eventually reaching sizes conducive to cloud formation. This growth was accompanied by a pronounced ability to absorb water, thereby intensifying the aerosol particles' potential for catalyzing cloud formation—an outcome that contrasts with conventional scenarios.

The study also accentuated that, in cleaner conditions characterized by reduced human activities, the presence of low-volatility vapors from specific gases enhances the likelihood of new aerosol particle formation and growth. This stands in contrast to typical urban environments like Chennai, where these low-volatile gases tend to condense on pre-existing aerosol particles stemming from human activities.

Professor Gunthe remarked on the policy implications of the study's findings, stating, "The results of this study necessitate a comprehensive reevaluation of existing strategies aimed at reducing PM2.5 levels arising from traffic and industries in India's densely populated coastal regions."