SF6 gas, capable of trapping 23,500 times more heat than carbon dioxide over a century, sees its concentrations rising in Beijing while other atmospheric pollutants show stabilization or decline. This unexpected divergence, highlighted by a study published in Environmental Science & Technology, raises serious concerns about the effectiveness of local depollution policies.
What the study reveals: SF6 rise despite decline in other pollutants
Analysis of atmospheric data from the Beijing region shows that fine particulate (PM2.5) and nitrogen dioxide (NO₂) concentrations have reached their lowest levels in two decades, thanks to strict measures on transport and industry. Conversely, SF6, used primarily as an electrical insulator in high-voltage substations, has shown a steady upward trend since the early 2000s. Researchers emphasize that, although the absolute volume of the gas remains low, its global warming potential (GWP) places it among the most dangerous contributors to climate change.
The GWP of SF6, estimated at 23,500 times that of CO₂ over a hundred-year period, means that each kilogram of this gas is equivalent to 23,500 kilograms of CO₂ in terms of greenhouse effect. Thus, even a marginal increase in its concentration can have a disproportionate impact on the global radiative balance. The study indicates that SF6's contribution to China's total greenhouse gas emissions has increased by several percentage points over the past decade, a figure that, while modest at the national scale, represents a growing share of the local problem.
The article's authors stress that this increase occurs despite air cleanup efforts that have reduced particulates and nitrogen oxides by 30% on average since 2015. They explain that SF6 is not directly linked to combustion sources but comes mainly from leaks in electrical equipment, a sector that has undergone rapid expansion to support the megacity's energy demand. This dissociation between the trajectories of traditional pollutants and SF6 highlights a gap in current policies, which focus more on CO₂ and particulate emissions than on greenhouse gases with very high GWP.