Global Research Alliance N₂O chamber methodology guidelines: Introduction, with health and safety considerations

Abstract

Non-steady-state (NSS) chamber techniques have been used for decades to measure nitrous oxide (N 2 O) fluxes from agricultural soils. These techniques are widely used because they are relatively inexpensive, easy to adopt, versatile, and adaptable to varying conditions. Much of our current understanding of the drivers of N 2 O emissions is based on studies using NSS chambers. These chamber techniques require decisions regarding multiple methodological aspects (e.g., chamber materials and geometry, deployment, sample analysis, and data and statistical analysis), each of which may significantly affect the results. Variation in methodological details can lead to challenges in comparing results between studies and assessment of reliability and uncertainty. Therefore, the New Zealand Government, in support of the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases (GRA), funded two international projects to, first, develop standardized guidelines on the use of NSS chamber techniques and, second, refine them based on the most up to date knowledge and methods. This introductory paper summarizes a collection of papers that represent the revised guidelines. Each article summarizes existing knowledge and provides guidance and minimum requirements on chamber design, deployment, sample collection, storage and analysis, automated chambers, flux calculations, statistical analysis, emission factor estimation and data reporting, modeling, and "gap-filling" approaches. The minimum requirements are not meant to be highly prescriptive but instead provide researchers with clear direction on best practices and factors that need to be considered. Health and safety considerations of NSS chamber techniques are also provided with this introductory paper.

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

“…A recommended minimum set of ancillary measurements for N 2 O EF studies would improve the potential for subsequent meta‐analyses (de Klein, Alfaro, et al., 2020; López‐Aizpún et al., 2020). If the goal is to understand temporal patterns in N 2 O emissions, or for model development or verification, then a wider range of (frequent) ancillary measurements are necessary (de Klein, Alfaro, et al., 2020; Dorich et al., 2020; Giltrap et al., 2020).…”

“…The 2015 Nitrous Oxide Chamber Methodology Guidelines (de Klein, Harvey, et al., 2020) provided guidance on chamber methodologies for sampling N 2 O emitted from soils. The papers presented in this special section provide updates on the 2015 guidelines.…”

Global Research Alliance N2O chamber methodology guidelines: Statistical considerations, emission factor calculation, and data reporting

“…This section summarizes the minimum requirements for reporting of data for calculating EFs and for development of process‐based models (Table 1). The recommendations are a combination of those listed in the earlier version of the Global Research Alliance guidelines (refer to de Klein et al., 2020) and those suggested by Buckingham et al. (2014).…”

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

“…This work was funded by the New Zealand Government to support the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases towards mitigation of agricultural greenhouse gases (https://globalresearchalliance.org/research/livestock/). The background to and development of the N 2 O chamber methodology guidelines is described in the accompanying introductory paper of this special section (de Klein et al., 2020).…”

“…The background to and development of the N 2 O chamber methodology guidelines is described in the introductory paper by de Klein et al. (2020). 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).…”