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India's Hidden Air Threat: SO2 Fuels PM2.5
24 Dec
Summary
- Secondary particulate matter, primarily ammonium sulfate, forms up to 42% of India's PM2.5.
- 78% of coal power plants are exempt from SO2 control systems.
- Delhi's worst pollution episodes are driven by regional SO2 emissions.
A significant portion of India's PM2.5 air pollution originates from precursor gases, with secondary particulate matter, mainly ammonium sulfate, accounting for up to 42 percent. Coal-fired power plants are the largest national source of sulfur dioxide (SO2), a key component in forming this secondary pollution.
Despite this, a substantial 78 percent of these power plants are exempt from installing flue gas desulphurisation systems, weakening controls at the source. Current air quality strategies often overlook SO2 and other precursor gases, focusing instead on visible pollutants like PM10 and road dust.
States such as Chhattisgarh and Odisha show high ammonium sulfate contributions. Delhi experiences severe pollution episodes, particularly in post-monsoon and winter, where ammonium sulfate constitutes a major part of PM2.5, underscoring the national scale of secondary sulfate formation.
