Real-time detection of atmospheric dimethyl sulfide at pptv levels using tunable infrared laser direct absorption spectroscopy

Dimethyl sulfide (DMS), a biogenic trace gas emitted by marine ecosystems, plays a critical role in aerosol formation and climate regulation. However, its low atmospheric abundance and rapid reactivity hinder real-time detection, limiting our understanding of its climatic impact under warming-driven environmental changes. Here, we present a laser-based optical system using tunable infrared laser direct absorption spectroscopy (TILDAS) for the real-time DMS measurement at pptv levels. This system uses a 3.37 μm interband cascade laser and a 413.4 m multipass cell, targeting a strong DMS absorption band at 2969.7 cm⁻¹ . It achieves a detection limit of 46 pptv (3σ) with 2 min averaging of the 1 Hz data, improving to 17 pptv with 30 min averaging, verified by Allan variance analysis. Compared with existing optical DMS sensors, the system offers substantially improved sensitivity while retaining the high temporal resolution needed to resolve rapid atmospheric variability. Instrumental performance and stability were confirmed through year-round calibrations, which yielded a mean campaign-specific slope of 1.01 ± 0.02 between expected and measured DMS mixing ratios. Concurrent ambient-air measurements using TILDAS and conventional gas chromatography also showed overall agreement (slope = 1.01; r = 0.94), demonstrating reliable field performance. By combining pptv-level sensitivity, continuous 1 Hz output, minimal sample processing, and long-term operational stability, DMS-TILDAS provides a powerful tool for resolving short-timescale DMS variability, with potential future applications in marine sulfur cycling and associated aerosol and climate-related processes.