Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production

Kaiser, Jennifer; Wolfe, G. M.; Bohn, Birger; Broch, Sebastian; Fuchs, Hendrik; Ganzeveld, L.; Gomm, Sebastian; Häseler, R.; Hofzumahaus, A.; Holland, F.; Jäger, Julia; Li, X.; Lohse, Insa; Lu, Keding; Prévôt, Andrê S. H.; Rohrer, Franz; Wegener, Robert; Wolf, Robert; Mentel, Thomas F.; Kiendler‐Scharr, Astrid; Wahner, Andreas; Keutsch, Frank N.

doi:10.5194/acp-15-1289-2015

Cited by 42 publications

(34 citation statements)

References 33 publications

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“…3.2) but may also reflect a missing primary source of HCHO in the model. Similar findings are reported from field observations in the Po Valley in Italy, where the discrepancy between modelled and measured OH reactivity was found to be small, but HCHO concentrations were substantially under-predicted by a one-dimensional model, demonstrating an unidentified non-photochemical groundlevel source of HCHO (Kaiser et al, 2015). The unidentified Figure 6.…”

Section: Ability Of the Model To Reconcile The Observed Formaldehyde supporting

confidence: 82%

Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production

et al. 2016

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Abstract. Near-continuous measurements of hydroxyl radical (OH) reactivity in the urban background atmosphere of central London during the summer of 2012 are presented. OH reactivity behaviour is seen to be broadly dependent on air mass origin, with the highest reactivity and the most pronounced diurnal profile observed when air had passed over central London to the east, prior to measurement. Averaged over the entire observation period of 26 days, OH reactivity peaked at ∼ 27 s −1 in the morning, with a minimum of ∼ 15 s −1 during the afternoon. A maximum OH reactivity of 116 s −1 was recorded on one day during morning rush hour. A detailed box model using the Master Chemical Mechanism was used to calculate OH reactivity, and was constrained with an extended measurement data set of volatile organic compounds (VOCs) derived from a gas chromatography flame ionisation detector (GC-FID) and a twodimensional GC instrument which included heavier molecular weight (up to C 12 ) aliphatic VOCs, oxygenated VOCs and the biogenic VOCs α-pinene and limonene. Comparison was made between observed OH reactivity and modelled OH reactivity using (i) a standard suite of VOC measurements (C 2 -C 8 hydrocarbons and a small selection of oxygenated VOCs) and (ii) a more comprehensive inventory including species up to C 12 . Modelled reactivities were lower than those measured (by 33 %) when only the reactivity of the standard VOC suite was considered. The difference between measured and modelled reactivity was improved, to within 15 %, if the reactivity of the higher VOCs ( C 9 ) was also considered, with the reactivity of the biogenic compounds of α-pinene and limonene and their oxidation products almost entirely responsible for this improvement. Further improvements in the model's ability to reproduce OH reactivity (to within 6 %) could be achieved if the reactivity and degradation mechanism of unassigned two-dimensional GC peaks were estimated. Neglecting the contribution of the higher VOCs ( C 9 ) (particularly α-pinene and limonene) and model-generated intermediates increases the modelled OH concentrations by 41 %, and the magnitude of in situ ozone production calculated from the production of RO 2 was significantly lower (60 %). This work highlights that any future ozone abatement strategies should consider the role that biogenic emissions play alongside anthropogenic emissions in influencing London's air quality.

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Section: Ability Of the Model To Reconcile The Observed Formaldehyde supporting

confidence: 82%

Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production

et al. 2016

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“…Silage, a fermented type of animal feed, emits an abundance of VOCs [ Hafner et al , ], some of which (e.g., aldehydes) could rapidly oxidize to form secondary HCHO. Primary HCHO may also be emitted directly from corn fields during harvesting [ Kaiser et al , ]. Elsewhere in the Corn Belt (e.g., Iowa, Nebraska, South Dakota, and North Dakota), however, we fail to find significant correlation between HCHO columns and production of either corn silage or grain, even in areas that show significant increases in HCHO over time (Figure ).…”

Section: Resultsmentioning

confidence: 57%

Long‐term (2005–2014) trends in formaldehyde (HCHO) columns across North America as seen by the OMI satellite instrument: Evidence of changing emissions of volatile organic compounds

Zhu

Mickley

Jacob

et al. 2017

Geophysical Research Letters

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Satellite observations of formaldehyde (HCHO) columns provide top‐down information on emissions of highly reactive volatile organic compounds (VOCs). We examine the long‐term trends in HCHO columns observed by the Ozone Monitoring Instrument from 2005 to 2014 across North America. Biogenic isoprene is the dominant source of HCHO, and its emission has a large temperature dependence. After correcting for this dependence, we find a general pattern of increases in much of North America but decreases in the southeastern U.S. Over the Houston‐Galveston‐Brazoria industrial area, HCHO columns decreased by 2.2% a−1 from 2005 to 2014, consistent with trends in emissions of anthropogenic VOCs. Over the Cold Lake Oil Sands in the southern Alberta in Canada, HCHO columns increased by 3.8% a−1, consistent with the increase in crude oil production there. HCHO variability in the northwestern U.S. and Midwest could be related to afforestation and corn silage production. Although NOx levels can affect the HCHO yield from isoprene oxidation, we find that decreases in anthropogenic NOx emissions made only a small contribution to the observed HCHO trends.

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“…The enhanced amount of O 3 in this air mass can be linked to a high concentration of volatile precursors which may have favoured the build-up of ozone during the plume evolution. In a recent work, Kaiser et al (2015) suggest that in the Po Valley the high content of formaldehyde, also observed by Junkermann et al (2009), may be responsible for the excess of O 3 production. Fresh layers in the FT up to ∼ 2000-3000 m possibly associated with pollution export from northern Italy were also observed during flights V21 and V52 (not shown).…”

Section: 3mentioning

confidence: 94%

Continental pollution in the western Mediterranean basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013

et al. 2015

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Abstract. In this study we present airborne observations of aerosol and trace gases obtained over the sea in the western Mediterranean basin during the TRAQA (TRansport and Air QuAlity) and SAFMED (Secondary Aerosol Formation in the MEDiterranean) campaigns in summer 2012 and 2013. A total of 23 vertical profiles were measured up to 5000 m above sea level over an extended area (40-45 • N and 2 • W-12 • E) including the Gulf of Genoa, southern France, the Gulf of Lion, and the Spanish coast. During TRAQA and SAFMED the study area experienced a wide range of meteorological conditions which favoured pollution export from different sources located around the basin. Also, several events of dust outflows were measured during the campaigns. Observations from the present study show that continental pollution largely affects the western Mediterranean both close to coastal regions and in the open sea as far as ∼ 250 km from the coastline. The measured aerosol scattering coefficient varies between ∼ 20 and 120 Mm −1 , while carbon monoxide (CO) and ozone (O 3 ) mixing ratios are in the range of 60-165 and 30-85 ppbv, respectively. Pollution reaches 3000-4000 m in altitude and presents a very complex and highly stratified structure characterized by fresh and aged layers both in the boundary layer and in the free troposphere. Within pollution plumes the measured particle concentration in the Aitken (0.004-0.1 µm) and accumulation (0.1-1.0 µm) modes is between ∼ 30 and 5000-6000 scm −3 (standard cm −3 ), which is comparable to the aerosol concentration measured in continental areas under pollution conditions. Additionally, our measurements indicate the presence of highly concentrated Aitken layers (10 000-15 000 scm −3 ) observed both close to the surface and in the free troposphere, possibly linked to the influence of new particle formation (NPF) episodes over the basin.

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Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production

Cited by 42 publications

References 33 publications

Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production

Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production

Long‐term (2005–2014) trends in formaldehyde (HCHO) columns across North America as seen by the OMI satellite instrument: Evidence of changing emissions of volatile organic compounds

Continental pollution in the western Mediterranean basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013

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