Isotopic constraints on atmospheric sulfate formation pathways in the Mt. Everest region, southern Tibetan Plateau

Abstract. As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, the ecological environment, and human health. The Tibetan Plateau (TP), identified as “Third Pole”, contains largest land ice masses outside poles has attracted widespread attention for its environment climatic change. However, mechanisms of formation in this specific region still remain poorly characterized. An oxygen-17 anomaly (?17O) been used a probe to constrain relative importance different pathways leading formation. Here, we report ?17O values atmospheric collected at remote site Mt. Everest decipher possible such pristine environment. Throughout sampling campaign (April–September 2018), non-dust show average 1.7 ‰±0.5 ‰, which is higher than most existing data modern sulfate. seasonality exhibits high pre-monsoon low monsoon, opposite both nitrate (i.e., minima warm season maxima cold season) observed from diverse geographic sites. This found clearly indicates role S(IV)+O3 pathway promoted by conditions cloud water pH. Overall, our study provides observational constraint acidity altering pathways, particularly dust-rich environments, identification key processes basis better understanding sulfur cycle TP.