Decomposition of Urban CO2 Fluxes into Fossil and Biogenic Components using a novel Relaxed Eddy Accumulation System

The aim of this thesis is the characterization of a novel relaxed eddy accumulation (REA) system for collection of 14CO2 air samples and its first application in the city of Zurich, Switzerland. The REA system, developed within the ICOS (Integrated Carbon Observation System) Cities project, selects air based on a 20 Hz vertical wind signal into an upwind and a downwind sample, allowing for the first time 14CO2-based decomposition of CO2 fluxes into fossil and biogenic components. This is prerequisite for independent eddy covariance-based top-down assessment of urban fossil fuel CO2 (ffCO2) emissions. Quality control tests during the Zurich campaign show that there is no significant bias between upwind and downwind sampling and that concentration differences between the flask pairs agree with the differences of in situ measurements within (0.02 +- 0.21) ppm. In total, 300 flask pairs were collected, of which 95 were analyzed for 14CO2. These were grouped and interpreted according to atmospheric sampling conditions. The potential of 14CO2-based CO2 flux separation was demonstrated for samples with ffCO2 differences greater than 1.2 ppm. However, for the majority of the collected samples, evaluating ffCO2 estimates is limited by large uncertainties due to the precision of 14CO2 measurements. Exploiting the full potential of the ICOS REA flask sampling system requires larger signals, which could potentially be achieved by lower sampling heights.

Level thesis:degree_level

master

Grantor dc:publisher

Universität Heidelberg

Year

2023

Author dc:creator

• Kunz, Ann-Kristin

Contributors dc:contributor

• Levin, Ingeborg

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/39077

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:39077