Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations

Millet, Dylan B.; Guenther, Alex; Siegel, David A.; Nelson, Norman B.; Singh, H. B.; Gouw, J. A. de; Warneke, C.; Williams, Jonathan; Eerdekens, G.; Sinha, Vinayak; Karl, T.; Flocke, F. M.; Apel, E. C.; Riemer, D. D.; Palmer, Paul I.; Barkley, M. P.

doi:10.5194/acp-10-3405-2010

Cited by 293 publications

(309 citation statements)

References 121 publications

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“…There was no correlation between methanol and the dissolved organic carbon (DOC) content of rainwater samples, indicating that the methanol makes up a variable fraction of the organic carbon pool. Methanol concentrations were strongly correlated with acetaldehyde, which has a primarily biogenic input (Millet et al, 2010), suggesting that the potential biogenic source of methanol is consistent with the larger concentration of methanol observed during the growing season (Fig. 5).…”

Section: Intercorrelationsupporting

confidence: 55%

Temporal variations in rainwater methanol

et al. 2014

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Abstract. This work reports the first comprehensive analysis of methanol concentrations in rainwater. Methanol concentrations measured in 49 rain events collected between 28 August 2007 and 10 July 2008 in Wilmington, NC, USA, ranged from below the detection limit of 6 nM to 9.3 µM with a volume-weighted average concentration of 1 ± 0.2 µM. Methanol concentrations in rainwater were up to ∼ 200 times greater than concentrations reported previously in marine waters, indicating wet deposition as a potentially significant source of methanol to marine waters. Assuming that these methanol concentrations are an appropriate proxy for global methanol rainwater concentrations, the global methanol wet deposition sink is estimated as 20 Tg yr −1 , which implies that previous methanol budgets underestimate removal by precipitation. Methanol concentrations in rainwater did not correlate significantly with H + , NO − 3 , and NSS, which suggests that the dominant source of the alcohol to rainwater is not anthropogenic. However, methanol concentrations were strongly correlated with acetaldehyde, which has a primarily biogenic input. The methanol volume-weighted concentration during the summer (2.7 ± 0.9 µM) was ∼ 3 times that of the winter (0.9 ± 0.2 µM), further promoting biogenic emissions as the primary cause of temporal variations of methanol concentrations. Methanol concentrations peaked in rainwater collected during the time period 12 p.m.-6 p.m. Peaking during this period of optimal sunlight implies a possible relationship with photochemical methanol production, but there are also increases in biogenic activity during this time period. Rain events with terrestrial origin had greater concentrations than those of marine origin, demonstrating the significance of the continental source of methanol in rainwater.

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Section: Intercorrelationsupporting

confidence: 55%

Temporal variations in rainwater methanol

et al. 2014

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“…The lack of an observed vertical gradient in ethanol concentrations over the ocean also precludes an oceanic source; reducing the oceanic sink by decreasing the deposition velocity over oceans (0.28 to 0.08 cm/s) does not explain the discrepancy. This inability to simulate high observed mixing ratios in the free troposphere has been shown to occur for acetaldehyde in another global chemical transport model (Millet et al, 2010), indicating a general inconsistency between the observations and our understanding of the budget of short-lived volatile organic compounds.…”

Section: Resultsmentioning

confidence: 90%

“…The dependence of ethanol emissions on root flooding or plant stress is not considered here. With the availability of more information, the calculation of biogenic ethanol emissions has recently been revised to include the dependence on light and root flooding in MEGANv2.1 (Millet et al, 2010). We calculate monthly mean emissions offline using average emission factors (Fig.…”

Section: Ethanol Sourcesmentioning

confidence: 99%

Observational constraints on the global atmospheric budget of ethanol

et al. 2010

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Abstract. Energy security and climate change concerns have led to the promotion of biomass-derived ethanol, an oxygenated volatile organic compound (OVOC), as a substitute for fossil fuels. Although ethanol is ubiquitous in the troposphere, our knowledge of its current atmospheric budget and distribution is limited. Here, for the first time we use a global chemical transport model in conjunction with atmospheric observations to place constraints on the ethanol budget, noting that additional measurements of ethanol (and its precursors) are still needed to enhance confidence in our estimated budget. Global sources of ethanol in the model include 5.0 Tg yr −1 from industrial sources and biofuels, 9.2 Tg yr −1 from terrestrial plants, ∼0.5 Tg yr −1 from biomass burning, and 0.05 Tg yr −1 from atmospheric reactions of the ethyl peroxy radical (C 2 H 5 O 2 ) with itself and with the methyl peroxy radical (CH 3 O 2 ). The resulting atmospheric lifetime of ethanol in the model is 2.8 days. Gas-phase oxidation by the hydroxyl radical (OH) is the primary global sink of ethanol in the model (65%), followed by dry deposition (25%), and wet deposition (10%). Over continental areas, ethanol concentrations predominantly reflect direct anthropogenic and biogenic emission sources. Uncertainty in the biogenic ethanol emissions, estimated at a factor of three, may contribute to Correspondence to: V. Naik (vaishali.naik@noaa.gov) the 50% model underestimate of observations in the North American boundary layer. Current levels of ethanol measured in remote regions are an order of magnitude larger than those in the model, suggesting a major gap in understanding. Stronger constraints on the budget and distribution of ethanol and OVOCs are a critical step towards assessing the impacts of increasing the use of ethanol as a fuel.

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“…Kieber et al (1990) showed that compounds like formaldehyde, acetaldehyde or glyoxylate are produced from the photochemical oxidation of Dissolved Organic Matter (DOM) in natural waters when exposed to sunlight. Millet et al (2010) recently parameterized data from Kieber et al (1990) and showed that DOM photochemistry in the ocean is the second largest global source for acetaldehyde (57 Tg/year). Relying on the satellite retrievals of CHOCHO, the spatial distribution of the acetaldehyde source indeed appears to somewhat resemble that of CHOCHO at tropical latitudes (Wittrock et al, 2006;).…”

Section: Discussionmentioning

confidence: 99%

Ship-based detection of glyoxal over the remote tropical Pacific Ocean

et al. 2010

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Abstract. We present the first detection of glyoxal (CHO-CHO) over the remote tropical Pacific Ocean in the Marine Boundary Layer (MBL). The measurements were conducted by means of the University of Colorado Ship Multi-Axis Differential Optical Absorption Spectroscopy (CU SMAX-DOAS) instrument aboard the research vessel Ronald H. Brown. The research vessel was on a cruise in the framework of the VAMOS Ocean-Cloud-Atmosphere-Land Study -Regional Experiment (VOCALS-REx) and the Tropical Atmosphere Ocean (TAO) projects lasting from October 2008 through January 2009 (74 days at sea). The CU SMAX-DOAS instrument features a motion compensation system to characterize the pitch and roll of the ship and to compensate for ship movements in real time. We found elevated mixing ratios of up to 140 ppt CHOCHO located inside the MBL up to 3000 km from the continental coast over biologically active upwelling regions of the tropical Eastern Pacific Ocean. This is surprising since CHOCHO is very short lived (atmospheric life time ∼2 h) and highly water soluble (Henry's Law constant H = 4.2 × 10 5 M/atm). This CHOCHO cannot be explained by transport of it or its precursors from continental sources. Rather, the open ocean must be a source for CHOCHO to the atmosphere. Dissolved Organic Matter (DOM) photochemistry in surface waters is a source for Volatile Organic Compounds (VOCs) to the atmosphere, e.g. acetaldehyde. The extension of this mechanism to very soluble gases, like CHOCHO, is not straightforward since the air-sea flux is directed from the atmosphere into the ocean. For CHOCHO, the dissolved concentrations would need to be extremely high in order to explain our gas-phase observations by this mechanism (40-70 µM CHOCHO, comparedCorrespondence to: R. Volkamer (rainer.volkamer@colorado.edu) to ∼0.01 µM acetaldehyde and 60-70 µM DOM). Further, while there is as yet no direct measurement of VOCs in our study area, measurements of the CHOCHO precursors isoprene, and/or acetylene over phytoplankton bloom areas in other parts of the oceans are too low (by a factor of 10-100) to explain the observed CHOCHO amounts. We conclude that our CHOCHO data cannot be explained by currently understood processes. Yet, it supports first global source estimates of 20 Tg/year CHOCHO from the oceans, which likely is a significant source of secondary organic aerosol (SOA). This chemistry is currently not considered by atmospheric models.

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Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations

Cited by 293 publications

References 121 publications

Temporal variations in rainwater methanol

Temporal variations in rainwater methanol

Observational constraints on the global atmospheric budget of ethanol

Ship-based detection of glyoxal over the remote tropical Pacific Ocean

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