标题：Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy
摘要：Portable open-path laser (OPL) instruments provide a way to measure real-time, in situ atmospheric methane (CH 4 ) concentrations at a variety of spatial and temporal scales. Our results suggest that OPL instruments may be simple and effective tools for monitoring atmospheric CH 4 dynamics near ground-level in Arctic landscapes. We used a CH 4 detecting OPL instrument at seven different field sites in southwest Greenland during the summer of 2012 to monitor atmospheric CH 4 concentrations in the presence of local CH 4 sources and sinks. Measurements with the OPL were conducted for deployments between 0.4 and 40 h over path lengths between 10 and 300 m. These measurements were checked against periodic grab samples analyzed in the field lab using cavity-enhanced absorption spectroscopy. Mean concentrations of atmospheric CH 4 measured with the OPL across all field sites ranged from 1.72 (±0.12) to 1.88 (±0.15) ppm by volume (ppmv). The median atmospheric CH 4 concentration measured using cavity-enhanced absorption spectroscopy was 1.82 ± 0.04 ppmv. Slightly elevated CH 4 concentrations were measured downwind of one lake and in a subglacial cave. OPL measurements of atmospheric CH 4 concentrations agreed with results from cavity-enhanced absorption spectroscopy (<3% difference). OPL technology may be a useful tool for extended CH 4 monitoring studies in the Arctic and may help in our understanding of atmospheric CH 4 concentrations at spatial and temporal scales not accessible to other forms of measurement.
