Urban flux measurements reveal a large pool of oxygenated volatile organic compound emissions

Karl, T.; Striednig, Marcus; Graus, M.; Hammerle, Albin; Wohlfahrt, Georg

doi:10.1073/pnas.1714715115

Cited by 100 publications

(78 citation statements)

References 60 publications

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“…emerging VOC sources from oil and gas facilities (Li et al, 2017;Pfister et al, 2017), ii) volatile chemical products (McDonald et al, 2018), and iii) unexpectedly large urban OVOC fluxes (Karl et al, 2018). It is possible that such sources are not well captured in current inventories such as those used here, which in turn could alter the budget understanding above.…”

Section: Discussionmentioning

confidence: 91%

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

Chen¹,

Millet²,

Singh³

et al. 2019

Preprint

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Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to i) characterize the VOC budget, and ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs, over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70&#8201;% and 95&#8201;% of annually emitted VOC-carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2&#215; larger source of non-methane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC-abundance (R2&#8201;=&#8201;0.36) and reactivity (R2&#8201;=&#8201;0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (~&#8201;60&#8201;%), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL&#8201;:&#8201;FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene&#8201;+&#8201;oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.

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Section: Discussionmentioning

confidence: 91%

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

Chen¹,

Millet²,

Singh³

et al. 2019

Preprint

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“…The code, along with a test dataset, can be downloaded from the website of the University of Innsbruck Atmospheric Physics and Chemistry (APC) group: https://www.atm-phys-chem. at/innflux (Karl, 2020).…”

Section: Results Filementioning

confidence: 99%

InnFLUX – an open-source code for conventional and disjunct eddy covariance analysis of trace gas measurements: an urban test case

et al. 2020

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Abstract. We describe and test a new versatile software tool for processing eddy covariance and disjunct eddy covariance flux data. We present an evaluation based on urban non-methane volatile organic compound (NMVOC) measurements using a proton transfer reaction quadrupole interface time-of-flight mass spectrometer (PTR-QiTOF-MS) at the Innsbruck Atmospheric Observatory. The code is based on MATLAB® and can be easily configured to process high-frequency, low-frequency and disjunct data. It can be applied to a wide range of analytical setups for NMVOC and other trace gas measurements, and is tailored towards the application of noisy data, where lag time corrections become challenging. Several corrections and quality control routines are implemented to obtain the most reliable results. The software is open source, so it can be extended and adjusted to specific purposes. We demonstrate the capabilities of the code based on a large urban dataset collected in Innsbruck, Austria, where three-dimensional winds and ambient concentrations of NMVOCs and auxiliary trace gases were sampled with high temporal resolution above an urban canopy. Concomitant measurements of 12C and 13C isotopic NMVOC fluxes allow testing algorithms used for determination of flux limits of detection (LOD) and lag time analysis. We use the high-frequency NMVOC dataset to generate a set of disjunct data and compare these results with the true eddy covariance method. The presented analysis allows testing the theory of disjunct eddy covariance (DEC) in an urban environment. Our findings confirm that the disjunct eddy covariance method can be a reliable tool, even in complex urban environments when fast sensors are not available, but that the increase in random error impedes the ability to detect small fluxes due to higher flux LODs.

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“…These results suggest that NOx is dominated by vehicular traffic emissions and that CO2 is partitioned more equally between the traffic and RCP sectors. In contrast, urban NMVOC emissions are generally more diverse (Karl et al, 2018). Here we investigate aromatic NMVOC, that are closely linked to combustion processes and fossil fuel use (EPA, 1998).…”

Section: Discussionmentioning

confidence: 99%

Decoupling of urban CO2 and air pollutant emission reductions during the European SARS-CoV2 lockdown

Lamprecht¹,

Graus²,

Striednig³

et al. 2020

Preprint

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Abstract. Lockdown and the associated massive reduction in people’s mobility imposed by SARS-CoV-2 mitigation measures across the globe provide a unique sensitivity experiment to investigate impacts on carbon and air pollution emissions. We present an integrated observational analysis based on long-term in-situ multispecies eddy flux measurements, allowing to quantify near real time changes of urban surface emissions for key air quality and climate tracers. During the first European SARS-CoV-2 wave we find that the emission reduction of classic air pollutants decoupled from CO2 and was significantly larger. These differences can only be rationalized by the different nature of urban combustion sources, and point towards a systematic bias of extrapolated urban NOx emissions in state-of the art emission models. The analysis suggests that European policies, shifting residential, public and commercial energy demand towards cleaner combustion, have helped to improve air quality more than expected, and that the urban NOx flux remains to be dominated (e.g. > 90 %) by traffic.

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Urban flux measurements reveal a large pool of oxygenated volatile organic compound emissions

Cited by 100 publications

References 60 publications

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

InnFLUX – an open-source code for conventional and disjunct eddy covariance analysis of trace gas measurements: an urban test case

Decoupling of urban CO<sub>2</sub> and air pollutant emission reductions during the European SARS-CoV2 lockdown

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Urban flux measurements reveal a large pool of oxygenated volatile organic compound emissions

Cited by 100 publications

References 60 publications

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

InnFLUX – an open-source code for conventional and disjunct eddy covariance analysis of trace gas measurements: an urban test case

Decoupling of urban CO&lt;sub&gt;2&lt;/sub&gt; and air pollutant emission reductions during the European SARS-CoV2 lockdown

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Product

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About

Decoupling of urban CO<sub>2</sub> and air pollutant emission reductions during the European SARS-CoV2 lockdown