A Portable, Low-Power Cavity Ring-Down Analyzer and Automated Soil Flux Chamber System for Measuring Wetland GHG Emissions.

Preservation and restoration of wetlands have the potential to help sequester large amounts of carbon due to the naturally high primary productivity and slow turnover of stored soil carbon. However, the anoxic environmental conditions present in wetland soils are also the largest natural contributor to global methane emissions. Therefore, uptake, storage, and loss of CO₂ and CH₄ need to be carefully considered when evaluating the climate effects of land-use change.

Methodologically, it is relatively challenging to measure methane emissions from wetlands with currently available techniques because of the temporally and spatially sporadic nature of the processes involved (methanogenesis, methane oxidation, ebullition, etc.). For example, manual soil flux chambers can only capture a portion of either the spatial or temporal variability and have other disadvantages associated with soil atmosphere disturbance during their deployment. On the other hand, automated chamber systems offer the advantage of collecting high-resolution time series of gaseous fluxes while reducing human- and method-induced biases.

Additionally, new laser-based analyzers that can be used in situ alongside automated chambers, offer a greater minimum detectable flux than those from alternative instruments such as Gas Chromatography. However, until recently these types of automated measurements were limited to areas that had good power coverage as laser-based systems were power intensive and could not easily be supplemented with power from field-available sources such as solar. Recent developments in laser technology have reduced the power consumption of the analyzers and have made these systems more field portable in the process.

Here we present data using an automated chamber system coupled to a new low power and portable laser-based greenhouse gas analyzer (Picarro GasScouter, G4301). The focus of this presentation will be on the methodological and field deployment benefits of the automated system over the manual system including; improved ability to run on limited field-based power resources; reduced disturbance on the soil during chamber closure; good spatial coverage (30 meters radially); excellent temporal resolution; and, enhanced minimum detectable flux limits. These advantages will be demonstrated through the deployment of the instrumentation at a tidal estuary in Nova Scotia, Canada, where the system will monitor CO2 and CH4 fluxes continuously over a 10-day period.