Sources and properties of Amazonian aerosol particles

Martin, Scot T.; Andreae, Meinrat O.; Artaxo, Paulo; Baumgardner, Darrel; Chen, Qi; Goldstein, Allen H.; Guenther, Alex; Heald, Colette L.; Mayol-Bracero, O. L.; McMurry, Peter H.; Pauliquevis, Theotônio; Pöschl, Ulrich; Prather, Kimberly A.; Roberts, Grégory; Saleska, S. R.; Dias, M. A. Silva; Spracklen, Dominick V.; Swietlicki, Erik; Trebs, Ivonne

doi:10.1029/2008rg000280

Cited by 354 publications

(492 citation statements)

References 253 publications

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“…Background air, meaning the Amazon basin in the nominal absence of the pollution plume of Manaus, had significant variability associated with it, especially with respect to effective photochemical age. Background variability arose from variations of in-basin emissions and transformations integrated across several days of meteorology as well as, at times, from significant out-of-basin influences and variability tied to transport from the Atlantic Ocean and Africa (28,29). Even so, the effect of the plume, when present, dominated over this background variability for the measured quantities of the present study.…”

Section: Significancementioning

confidence: 76%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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103

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Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2 ) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO 2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.isoprene photochemistry | Amazon | organic hydroperoxides

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Section: Significancementioning

confidence: 76%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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103

165

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“…During the dry season, the lower atmosphere is polluted by high aerosol concentrations caused by both biomass burning and prolonged aerosol suspension associated with reduced precipitation Martin et al, 2010). During the wet season, the atmosphere is mostly clean and convective, and the landscape is referred to as the Green Ocean (Roberts et al, 2001;Williams et al, 2002;Andreae et al, 2004) because the convection there resembles storms over blue oceans, where the warm phase in clouds generally produces rain.…”

Section: The Amazon Forest Climatementioning

confidence: 99%

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

et al. 2018

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Abstract. This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. This study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the massweighted mean diameter) were quantified over both seasons.The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only durPublished by Copernicus Publications on behalf of the European Geosciences Union. L. A. T. Machado et al.: Overview: Precipitation characteristics and sensitivities to environmental conditionsing the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.

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“…Much of this organic material is thought to be of biogenic origin, especially in heavily vegetated areas such as the southeastern United States (6) and the Amazon basin (7). Recent analyses have shown that conversion of biogenic volatile organic compounds (VOCs) to aerosol material can be promoted by anthropogenic pollution (6,8), and chamber studies have revealed a number of biogenic aerosol formation mechanisms in both polluted and clean environments.…”

mentioning

confidence: 99%

Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass

Froyd

Murphy²,

Murphy³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

227

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Recent laboratory studies have demonstrated that isoprene oxidation products can partition to atmospheric aerosols by reacting with condensed phase sulfuric acid, forming low-volatility organosulfate compounds. We have identified organosulfate compounds in free tropospheric aerosols by single particle mass spectrometry during several airborne field campaigns. One of these organosulfates is identified as the sulfate ester of IEPOX, a second generation oxidation product of isoprene. The patterns of IEPOX sulfate ester in ambient data generally followed the aerosol acidity and NO x dependence established by laboratory studies. Detection of the IEPOX sulfate ester was most sensitive using reduced ionization laser power, when it was observed in up to 80% of particles in the tropical free troposphere. Based on laboratory mass calibrations, IEPOX added >0.4% to tropospheric aerosol mass in the remote tropics and up to 20% in regions downwind of isoprene sources. In the southeastern United States, when acidic aerosol was exposed to fresh isoprene emissions, accumulation of IEPOX increased aerosol mass by up to 3%. The IEPOX sulfate ester is therefore one of the most abundant single organic compounds measured in atmospheric aerosol. Our data show that acidity-dependent IEPOX uptake is a mechanism by which anthropogenic SO 2 and marine dimethyl sulfide emissions generate secondary biogenic aerosol mass throughout the troposphere.acid-catalyzed particle phase reactions | epoxides | free troposphere | secondary organic aerosol

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Sources and properties of Amazonian aerosol particles

Cited by 354 publications

References 253 publications

Isoprene photochemistry over the Amazon rainforest

Isoprene photochemistry over the Amazon rainforest

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass

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