Automated Collector of Terrestrial Systems Used for the Gathering of Soil Atmospheric‐Gas Emissions

Abstract

Soil greenhouse gas (GHG) emissions are complex, and their study requires considerable sampling of field spatial and temporal differences. Manual and simple automated gas‐collection techniques used at multiple sites during specific time intervals are labor intensive. The objective of this work was 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/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 carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) at the U.S. Department of Agriculture (USDA)–Agricultural Research Services (ARS) Agroecosystem Management Research Unit (AMRU). A Tracor MT‐220 gas chromatograph (GC) configured with a thermal conductivity detector (TCD) was used for CO₂ analysis, and an automated gas‐sampling system (AGSS) attached to a Varian 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.

Keywords:

• Automated sampler
• gas analysis
• greenhouse gas emissions
• soil
• terrestrial systems

Acknowledgments

The authors thank David Scoby and Tim Arkebauer for their help with flux chambers.

Notes

Mention of commercial products in this article is solely to provide specific information for the reader. It does not constitute endorsement by the USDA's Agricultural Research Service or University of Nebraska Agricultural Research Division over other products that may be suitable.