Methodology for Measuring Greenhouse Gas Emissions from Agricultural Soils Using Non-isotopic Techniques
Mohammad Zaman, Kristina Kleineidam, Lars R. Bakken, Jacqueline Berendt, Conor Bracken, Klaus Butterbach‐Bahl, Zucong Cai, Scott X. Chang, Timothy J. Clough, Khadim Dawar, Weixin Ding, Peter Dörsch, M. dos Reis Martins, C. Eckhardt, Sebastian Fiedler, Torsten Frosch, J. P. Goopy, Carolyn‐Monika Görres, Apoorv Gupta, Sina Henjes, Magdalena E. G. Hofmann, Marcus A. Horn, M. M. R. Jahangir, Anne Jansen‐Willems, Katharina Lenhart, Lee Heng, Dominika Lewicka‐Szczebak, G. Lucic, Lutz Merbold, Joachim Mohn, Lars Molstad, Gerald M. Moser, Paul Murphy, Alberto Sanz-Cobeña, Petr Šimek, Segundo Urquiaga, Reinhard Well, N. Wrage-Mönnig, S. Zaman, Jinbo Zhang, Christoph Müller
Abstract
Abstract Several approaches exist for measuring greenhouse gases (GHGs), mainly CO 2 , N 2 O, and CH 4 , from soil surfaces. The principle methods that are used to measure GHG from agricultural sites are chamber-based techniques. Both open and closed chamber techniques are in use; however, the majority of field applications use closed chambers. The advantages and disadvantages of different chamber techniques and the principal steps of operation are described. An important part of determining the quality of the flux measurements is the storage and the transportation of the gas samples from the field to the laboratory where the analyses are carried out. Traditionally, analyses of GHGs are carried out via gas chromatographs (GCs). In recent years, optical analysers are becoming increasingly available; these are user-friendly machines and they provide a cost-effective alternative to GCs. Another technique which is still under development, but provides a potentially superior method, is Raman spectroscopy. Not only the GHGs, but also N 2 , can potentially be analysed if the precision of these techniques is increased in future development. An important part of this chapter deals with the analyses of the gas concentrations, the calculation of fluxes, and the required safety measures. Since non-upland agricultural lands (i.e. flooded paddy soils) are steadily increasing, a section is devoted to the specificities of GHG measurements in these ecosystems. Specialised techniques are also required for GHG measurements in aquatic systems (i.e. rivers), which are often affected by the transfer of nutrients from agricultural fields and therefore are an important indirect source of emission of GHGs. A simple, robust, and more precise methodof ammonia (NH 3 ) emission measurement is also described.