Sulfur Isotope Anomalies (?³³S) in Urban Air Pollution Linked to Mineral-Dust-Associated Sulfate

Sulfur isotope analysis provides a unique probe for source-specific information and certain atmospheric reactions. Globally, aerosols in urban locations exhibit significant sulfur mass-independent fractionation (i.e., S-MIF, ?33S ? 0). The origin(s) of these S-MIF anomalies remains unclear, thereby limiting the interpretation and/or application such signals. Here, we conducted dual-isotope (?33S ?34S) fingerprinting sulfate from summertime megacity Delhi south Asia. A shift toward concomitantly high (from 0.2‰ to 0.5‰) low ?34S 5‰ 1‰) values was observed with influx mineral dust. Fe:Al ratio showed correlations both loadings (R2 = 0.84) signatures 0.77). Contrary prevailing paradigm, this observational evidence suggests that mineral-dust-associated exhibits anomalies. Atmospheric processing dust plausibly leads production Our evaluation an inherent mechanism(s) elusive. Although hindered by end-member uncertainties, show signals can be source apportioned quantitatively constrain fraction locations. influence air pollution affecting quality human health as requires monitoring. Urban therefore used trace fraction, improving our understanding aerosol dynamics.