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Development and validation of inexpensive, automated, dynamic flux chambers
Citation:
Almand-Hunter, B., Johnt Walker, N. Masson, L. Hafford, AND M. Hannigan. Development and validation of inexpensive, automated, dynamic flux chambers. Atmospheric Measurement Techniques. Copernicus Publications, Katlenburg-Lindau, Germany, 8(1):267-280, (2015).
Impact/Purpose:
Inexpensive flux measurement methods are needed to support the secondary NAAQS for NOx and SOx as well as O3 and other atmospheric compunds that adverseley affect ecosystem health. This paper assesses the performance of a low-cost chamber based method for measuring air-surface fluxes of gas phase compounds over short vegetation.
Description:
We developed and validated an automated, inexpensive, and continuous multiple-species gas-flux monitoring system that can provide data for a variety of relevant atmospheric pollutants, including O3, CO2, and NOx. Validation consisted of conducting concurrent gas-phase dry deposition experiments, using both dynamic flux chambers and an eddy-covariance system, in a grassy clearing in the Duke Forest (Chapel Hill, NC). Experiments were carried out in June and September, under a variety of meteorological conditions. Ozone-deposition measurements from the two methods matched very well (4-10% difference in mean flux rate) when the leaf-area index (LAI) inside the chambers was representative of the average LAI in the field. The dynamic flux chambers can be considered an accurate measurement system under these conditions. CO2 measurements were conducted for one 20-hour period, and the flux chamber captured the diurnal trend in CO2 flux well, although the quantity of the data was not sufficient to validate chamber performance. Flux-chamber NOx measurements could be calculated when ambient NOx concentrations were above 1 ppb. Unfortunately, the eddy-covariance system for measuring NOx was not available during this field campaign, so comparisons cannot be made. NOx fluxes were in a reasonable range for the field site.
