Global Research Alliance N₂O chamber methodology guidelines: Considerations for automated flux measurement

Abstract

Nitrous oxide (N 2 O) emissions are highly episodic in response to nitrogen additions and changes in soil moisture. Automated gas sampling provides the necessary high temporal frequency to capture these emission events in real time, ensuring the development of accurate N 2 O inventories and effective mitigation strategies to reduce global warming. This paper outlines the design and operational considerations of automated chamber systems including chamber design and deployment, frequency of gas sampling, and options in terms of the analysis of gas samples. The basic hardware and software requirements for automated chambers are described, including the major challenges and obstacles in their implementation and operation in a wide range of environments. Detailed descriptions are provided of automated systems that have been deployed to assess the impacts of agronomy on the emissions of N 2 O and other significant greenhouse gases. This information will assist researchers across the world in the successful deployment and operation of automated N 2 O chamber systems.

Global Research Alliance N2O chamber methodology guidelines: Recommendations for deployment and accounting for sources of variability

“…Given the episodic nature of N 2 O fluxes, high frequency or continuous measurement techniques such as automated chamber systems (Grace et al., 2020) or micrometeorological methods (e.g., eddy covariance; Cowan et al., 2020) can provide better estimates of integrated N 2 O emissions (Jones et al., 2011). However, these approaches require expensive equipment and experienced operators, beyond the scope of many project budgets.…”

Global Research Alliance N2O chamber methodology guidelines: Guidelines for gap‐filling missing measurements

“…However, the Journal of Environmental Quality special section in which this article is published attempts to cover the entirety of methodology relevant to sampling soil N 2 O with chamber systems. Future research is needed for a comprehensive treatment of gap‐filling that can account for issues related to diurnality in fluxes (Grace et al., 2020) and the choice of flux calculation method (Venterea et al., 2020). The methods described in this paper have also been used for gap‐filling non‐chamber‐based measurements (Taki et al., 2018).…”

Global Research Alliance N2O chamber methodology guidelines: Recommendations for air sample collection, storage, and analysis

“…An increasing variety of N 2 O detectors are available for determining concentrations, either directly in the field in online automatic systems (Grace et al., 2020) or from laboratory analysis of chamber headspace samples stored as described above. A third approach, directed towards maximizing data from campaigns in remote or hill country regions, has been to use manual chambers with a portable field analyzer (Debouk, Altimir, & Sebastià, 2018).…”

“…Photoacoustic trace‐gas detection is a spectroscopic technique where specific infrared absorption is converted to an acoustic signal for measurement. Automated online chamber–photoacoustic analyzer systems have been deployed with the advantages of more rapid and frequent analysis (see also Grace et al., 2020). The technique has been discussed in summary by Butterbach‐Bahl et al.…”

“…This paper on sampling and analysis draws on previous work by the Global Research Alliance (GRA, https://globalresearchalliance.org/) and guidelines for chambers of other networks, such as the USDA (Parkin & Venterea, 2010) and Integrated Carbon Observing System (ICOS, Pavelka et al., 2018). Related papers in this special section discuss static chamber design (Clough et al., 2020), automated systems (Grace et al., 2020), and flux calculation methods (Venterea et al., 2020).…”