Alpine Wetlands as an Overlooked Source of Dimethyl Sulfide (DMS) on the Tibetan Plateau

Abstract

Dimethyl sulfide (DMS) emitted from the ocean is the largest natural source of sulfur to the atmosphere. In the sulfur-limited, near-pristine terrestrial regions, the rapid oxidation of DMS and subsequent formation of sulfur species also play critical roles in sustaining the sulfur cycle. However, measurements and quantifications of terrestrial DMS sources remain limited and are absent in the Tibetan Plateau (TP). Here, we present the first in situ field measurements of DMS at the TP alpine wetlands (3429 m above sea level) using Vocus proton transfer reaction time-of-flight mass spectrometry (Vocus PTR-ToF-MS). We detected evident DMS mixing ratios (up to 48.1 pptv) with strong diurnal cycles, in concert with methane (CH₄) and carbon dioxide (CO₂) that originate from microbial source in anaerobic sediments. An annual wetland-DMS emission from 2.3 × 10^–5 to 6.5 × 10^–4 Tg S yr^–1 is estimated based on our measurements, comparable to other globally significant terrestrial DMS sources. Thus, the extensive alpine wetlands across the TP represent a previously overlooked biogenic DMS source in the TP region, potentially crucial for understanding the global DMS budget in the near-pristine, preindustrial terrestrial environment.