Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2009
Publication Date: 2/26/2010
Citation: Arnold, S.L., Tubbs, R.S., Arnold, N.S., Walker, A.E. 2010. Automated collector of terrestrial systems used for the gathering of soil atmospheric-gas emissions. Communications in Soil Science and Plant Analysis. 41(5):638-648.
Interpretive Summary: Measuring soil greenhouse gas emissions requires considerable sampling to study field variability. Manual and simple automated gas collection techniques used at different locations during specific time intervals are labor intensive. The objectives of this study were to construct an automated device that can independently collect greenhouse gas samples while maintaining the same accuracy and precision of manually drawn samples. An automated collector of terrestrial systems (ACTS) is a programmable sampler used in the field to gather and contain soil greenhouse gas emissions. ACTS opens and closes an exterior chamber, mixes and draws a gas sample from the chamber than injects it into an evacuated vial stored on a 30-vial carousel. Vial gases are taken to the laboratory and analyzed for CO2, CH4 and N2O. ACTS sampling results were as good as hand and simple automated techniques used. The sampler proved to be a realistic and inexpensive way to sample emissions while reducing Human error associated with adverse sampling conditions and fatique.
Technical Abstract: The complexity of soil greenhouse gas (GHG) emissions requires considerable sampling to study field spatial and temporal differences. Manual and simple automated gas collection techniques used at multiple sites during specific time intervals are labor intensive. The objectives were to construct a device that can independently collect GHG samples with the accuracy and precision of manually drawn samples. An automated collector of terrestrial systems (ACTS) is a 24 h – 7 d a week programmable sampler used in the field, for real time gathering and containment of soil GHG emissions. The sampler opens and closes an exterior soil gas chamber, mixes gases in the chamber by turning fans on/off and utilizes programmable circuits to purge the system and draw a sample from the chamber with a pneumatic-driven syringe. Each sample was stored in an evacuated vial held in a 30-vial capacity carousel. Vial content was analyzed for CO2, CH4 and N2O at the USDA-ARS Agroecosystem Management Research Unit (AMRU). A Tracor1 MT-220 gas chromatograph (GC) configured with a thermal conductivity detector (TCD) was used for CO2 analysis while an automated gas sampling system (AGSS) attached to a Varian1 3700 GC configured with flame ionization detection (FID) and electron capture detection (ECD) was used for CH4 and N2O analysis. Field and laboratory mean values and coefficients of variation (standards and field concentrations of CO2, CH4 and N2O ranging from ambient to 71 kg ha-1 d-1 had coefficients of variation ranging from 1.2 to 4.2%) were similar between ACTS and manually drawn samples. Results showed strong correlation (R2 =0.81 to 1.00) between sampling methods. The sampler design provides a realistic and inexpensive approach for collecting emission samples while reducing human error associated with adverse sampling conditions and fatigue. The ACTS has potential for use in monitoring and comparing management practices in terrestrial systems to determine their contribution to GHG emissions.