A method for estimating carbon dioxide leakage rates in controlled-environment chambers using nitrous oxide

Abstract

Naturally sunlit, outdoor controlled-environment chambers provide an important research tool for studying the effects of environmental variables on crop physiological processes. Typically these types of chambers are semi-closed and are capable of continuously monitoring canopy scale gas exchanges. Accurately determining chamber CO 2 leakage rate is essential for correcting measurements of photosynthesis and respiration in these kinds of chambers. The purpose of this study was to evaluate the ability of a new CO 2 leak quantification system which used N 2 O as a tracer gas to estimate chamber CO 2 leakage rates in a recently constructed outdoor, controlled-environment chamber facility at Beltsville, MD. Chamber CO 2 leakage rates as determined by the loss of CO 2 (C L ) from the chamber were compared with CO 2 leakage rates determined using N 2 O as a tracer gas (C LN ). These two methods of determining leakage rates were compared in two different types of chambers: smaller and more tightly sealed Daylit chambers and larger more leaky Soil-Plant-Atmosphere-Research (SPAR) chambers. Comparisons of C L with C LN indicated that C LN was an excellent predictor of C L . However, over a wide range of internal to external concentration gradients, the analysis did show a slight but consistent overestimation of C L by C LN that averaged 0.3, 1.4, and 1.1 mol CO 2 m −2 s −1 for the Daylit chambers, the SPAR chambers and all data combined, respectively. These results indicate that N 2 O can be used as a tracer gas to accurately and reliably estimate chamber CO 2 leakage rates in real time during experiments in the presence of plants and when it is necessary to maintain specific chamber CO 2 treatment set points that make estimation of C L difficult. Published by Elsevier B.V.

Canopy photosynthesis, evapotranspiration, leaf nitrogen, and transcription profiles of maize in response to CO2 enrichment

“…Pioneer 3733) were grown from individual seeds in sunlit soil–plant–atmosphere research (SPAR) chambers located at the Beltsville Agricultural Research Center (Beltsville, MD, USA). A physical description of these SPAR chambers and methods of operation and monitoring have been described previously (Baker et al , 2004). Six SPAR chambers were randomly assigned to ambient (370 μmol mol −1 ) or elevated C a (750 μmol mol −1 ) treatment.…”

“…Injection rates of CO 2 were regulated by mass flow controllers (FMA‐766‐V‐CO 2 , Omega Engineering Inc., Stanford, CT, USA) located in the air handling system of each chamber using a feed‐forward, feed‐back proportional–integral–differential (PID) control algorithm. Canopy CO 2 exchange rates ( A can ) were calculated from mass balance equations, solved every 30 s, averaged, and recorded every 300 s. To correct A can for chamber leakage, chamber CO 2 leakage rates were determined daily using a N 2 O drawdown method (Baker et al , 2004). Canopy evapotranspiration rates (ET can ) were determined by collecting the condensate from cooling coils used to control air temperature and relative humidity and passing the condensate through a conduit connected to pressure transducers.…”

Response of Potato Gas Exchange and Productivity to Phosphorus Deficiency and Carbon Dioxide Enrichment

“…Each SPAR chamber formed a semiclosed system for measurement of CO 2 and water vapor (H 2 O) fl uxes. Carbon dioxide leakage rates were estimated on a daily basis using an N 2 O tracer gas system (Baker et al, 2004). Whole plant CO 2 exchange rate (CER) (μmol CO 2 m −2 s −1 ) was calculated at 30-s intervals based on the amount of CO 2 injected, the amount leaking from the chamber, and the amount injected but not used by the plants.…”

CO2 uptake by a soil microcosm

“…Environmental growth chambers have been utilised for this type of study for various related sample types (Fleisher et al, 2008;Ferguson and Williams, 1974;Nakanoa et al, 2004) but few studies make attempts at quantifying the volume of CO 2 taken up during incubation. The integrity of the data from chamber studies relies heavily on the reliability of measurements (Baker et al, 2004). At present, we were only able to locate a single study in the literature that assessed the accuracy of a sealed chamber when making estimates of CO 2 uptake (Acock and Acock, 1989), with the majority of studies not discussing this experimental aspect despite its relevance to CO 2 uptake determinations (De Morais and Costa, 2007;Ohashi et al, 2005;Pringault et al, 1996).…”