Development of methods for measurement of biosphere -atmosphere exchange of carbon and nitrogen
Abstract
The complexity of biosphere-atmosphere exchange of carbon and nitrogen requires direct measurement of these processes to fully understand the feedback mechanisms that ultimately get incorporated into and evaluate biospheric and atmospheric process models. The direct measurement of such exchanges can be analytically challenging because exchange processes can occur on multiple temporal and spatial scales and concentrations can be small. In this thesis, a disjunct eddy accumulation sampling system (DEA) is tested in the field by measuring the fluxes of speciated alkyl nitrates. Although the DEA performed adequately, the measured fluxes were not statistically significantly different from zero. A lack of precision in the measurements, in part, due to excessive handling of the samples is hypothesized for the insignificant fluxes. An airborne flux measurement platform was tested above a forest canopy by measuring sensible heat and CO2 fluxes. Fluxes agreed well with tower-based platforms. The measured fluxes are shown to vary with the underlying surface type, turbulence characteristics, and boundary layer depth. Finally, a method incorporating Lagrangian sampling with a convective boundary layer budget approach was conducted on an airborne platform to measure exchange of CO2 on a regional scale. The region was adequately homogeneous with respect to land-use types and anthropogenic emissions so that a pseudo-Lagrangian experiment could be conducted and evaluated in a simplistic environment with supporting high-precision tower-based measurements. Airborne regional-scale CO2 fluxes agree well with tower-based measurements when land-use distributions, anthropogenic emissions, and subsidence are considered.
Degree
Ph.D.
Advisors
Shepson, Purdue University.
Subject Area
Atmospheric Chemistry|Analytical chemistry
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