Sulfur isotope anomalies in coal combustion: Applications to the present and early Earth environments

Abstract

The observation of mass-independent sulfur isotope fractionations (S-MIF) in Archean–Paleoproterozoic rocks has been instrumental in constraining oxygen levels on early Earth. The S-MIF effect, experimentally demonstrated to result from photochemical reactions, has now been observed in coal combustion, expanding our understanding of this phenomenon. Our study reveals that the negative Δ33S anomalies produced by coal combustion are consistent with similar anomalies observed in present-day sulfate aerosols in Beijing, China, and the black crust sulfates formed on building stones, monument walls, and sculptures in Europe that contribute to carbonate stone deterioration and cultural heritage damage. This finding provides independent evidence for a critical role of atmospheric sulfate from coal combustion in maintaining isotopic balance and offers an effective method for tracing sulfate aerosol sources. These insights are vital for developing more effective regulatory policies to control air pollution and protect public health. Given that coal energy production remains a significant issue in climate science, accurately mapping the global distribution of its by-products is imperative.