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Title: Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia

Abstract

The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO 2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 hours downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Mass spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor (“IEPOX-SOA factor”) was associated with PM production by the IEPOX pathway. Loadings of this factor correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C 5-alkene triols and 2-methyltetrols (R = 0.96 and 0.78, respectively). Factor loading, as well as the ratio of the factor loading to organic PM mass concentration, decreased under polluted compared to background conditions. For the study period, sulfate concentration explained 37 % of the variability in the factor loading. After segregation ofmore » the data set by NO y concentration, the sulfate concentration explained up to 75 % of the variability in factor loading within the NO y subsets. The sulfate-detrended IEPOX-SOA factor loading decreased by two- to three-fold for an increase in NO y concentration from 0.5 to 2 ppb. Here, the suppressing effects of elevated NO dominated over the enhancing effects of higher sulfate with respect to the production of IEPOX-derived PM. Relative to background conditions, the Manaus pollution contributed more significantly to NO y than to sulfate. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.« less

Authors:
 [1];  [2]; ORCiD logo [2];  [2];  [3];  [2]; ORCiD logo [4];  [5];  [6]; ORCiD logo [7];  [8]; ORCiD logo [8];  [5];  [9];  [10];  [3];  [3];  [6]; ORCiD logo [6];  [11] more »;  [3];  [2];  [1] « less
  1. Harvard Univ., Cambridge, MA (United States)
  2. Univ. of Colorado, Boulder, CO (United States)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  4. Univ. of California, Berkeley, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  5. Univ. of California, Berkeley, CA (United States)
  6. Brookhaven National Lab. (BNL), Upton, NY (United States)
  7. Univ. de Sao Paulo, Sao Paulo (Brazil); Univ. Blaise Pascal, Aubiere (France)
  8. Univ. de Sao Paulo, Sao Paulo (Brazil)
  9. Instituto Nacional de Pesquisas da Amazonia, Amazonas (Brazil)
  10. Univ. do Estado do Amazonas, Amazonas (Brazil)
  11. The Univ. of North Carolina, Chapel Hill, NC (United States)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1341692
Report Number(s):
BNL-113437-2017-JA; PNNL-SA-125341
Journal ID: ISSN 1680-7375; R&D Project: 2016-BNL-EE630EECA-Budg; KP1701000
Grant/Contract Number:
SC0012704; AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Atmospheric Chemistry and Physics Discussions (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics Discussions (Online); Journal Volume: 17; Journal ID: ISSN 1680-7375
Publisher:
European Geosciences Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

de Sa, Suzane S., Palm, Brett B., Campuzano-Jost, Pedro, Day, Douglas A., Newburn, Matthew K., Hu, Weiwei, Isaacman-VanWertz, Gabriel, Yee, Lindsay D., Thalman, Ryan, Brito, Joel, Carbone, Samara, Artaxo, Paulo, Goldstein, Allen H., Manzi, Antonio O., Souza, Rodrigo A. F., Mei, Fan, Shilling, John E., Springston, Stephen R., Wang, Jian, Surratt, Jason D., Alexander, M. Lizabeth, Jimenez, Jose L., and Martin, Scot T. Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia. United States: N. p., 2017. Web. doi:10.5194/acp-17-6611-2017.
de Sa, Suzane S., Palm, Brett B., Campuzano-Jost, Pedro, Day, Douglas A., Newburn, Matthew K., Hu, Weiwei, Isaacman-VanWertz, Gabriel, Yee, Lindsay D., Thalman, Ryan, Brito, Joel, Carbone, Samara, Artaxo, Paulo, Goldstein, Allen H., Manzi, Antonio O., Souza, Rodrigo A. F., Mei, Fan, Shilling, John E., Springston, Stephen R., Wang, Jian, Surratt, Jason D., Alexander, M. Lizabeth, Jimenez, Jose L., & Martin, Scot T. Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia. United States. doi:10.5194/acp-17-6611-2017.
de Sa, Suzane S., Palm, Brett B., Campuzano-Jost, Pedro, Day, Douglas A., Newburn, Matthew K., Hu, Weiwei, Isaacman-VanWertz, Gabriel, Yee, Lindsay D., Thalman, Ryan, Brito, Joel, Carbone, Samara, Artaxo, Paulo, Goldstein, Allen H., Manzi, Antonio O., Souza, Rodrigo A. F., Mei, Fan, Shilling, John E., Springston, Stephen R., Wang, Jian, Surratt, Jason D., Alexander, M. Lizabeth, Jimenez, Jose L., and Martin, Scot T. 2017. "Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia". United States. doi:10.5194/acp-17-6611-2017. https://www.osti.gov/servlets/purl/1341692.
@article{osti_1341692,
title = {Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia},
author = {de Sa, Suzane S. and Palm, Brett B. and Campuzano-Jost, Pedro and Day, Douglas A. and Newburn, Matthew K. and Hu, Weiwei and Isaacman-VanWertz, Gabriel and Yee, Lindsay D. and Thalman, Ryan and Brito, Joel and Carbone, Samara and Artaxo, Paulo and Goldstein, Allen H. and Manzi, Antonio O. and Souza, Rodrigo A. F. and Mei, Fan and Shilling, John E. and Springston, Stephen R. and Wang, Jian and Surratt, Jason D. and Alexander, M. Lizabeth and Jimenez, Jose L. and Martin, Scot T.},
abstractNote = {The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 hours downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Mass spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor (“IEPOX-SOA factor”) was associated with PM production by the IEPOX pathway. Loadings of this factor correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C5-alkene triols and 2-methyltetrols (R = 0.96 and 0.78, respectively). Factor loading, as well as the ratio of the factor loading to organic PM mass concentration, decreased under polluted compared to background conditions. For the study period, sulfate concentration explained 37 % of the variability in the factor loading. After segregation of the data set by NOy concentration, the sulfate concentration explained up to 75 % of the variability in factor loading within the NOy subsets. The sulfate-detrended IEPOX-SOA factor loading decreased by two- to three-fold for an increase in NOy concentration from 0.5 to 2 ppb. Here, the suppressing effects of elevated NO dominated over the enhancing effects of higher sulfate with respect to the production of IEPOX-derived PM. Relative to background conditions, the Manaus pollution contributed more significantly to NOy than to sulfate. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.},
doi = {10.5194/acp-17-6611-2017},
journal = {Atmospheric Chemistry and Physics Discussions (Online)},
number = ,
volume = 17,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
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  • The atmospheric chemistry of isoprene contributes to the production of a substantial mass fraction of the particulate matter (PM) over tropical forests. Isoprene epoxydiols (IEPOX) produced in the gas phase by the oxidation of isoprene under HO 2-dominant conditions are subsequently taken up by particles, thereby leading to production of secondary organic PM. The present study investigates possible perturbations to this pathway by urban pollution. The measurement site in central Amazonia was located 4 to 6 h downwind of Manaus, Brazil. Measurements took place from February through March 2014 of the wet season, as part of the GoAmazon2014/5 experiment. Massmore » spectra of organic PM collected with an Aerodyne Aerosol Mass Spectrometer were analyzed by positive-matrix factorization. One resolved statistical factor ("IEPOX-SOA factor") was associated with PM production by the IEPOX pathway. The IEPOX-SOA factor loadings correlated with independently measured mass concentrations of tracers of IEPOX-derived PM, namely C 5-alkene triols and 2-methyltetrols ( R = 0.96 and 0.78, respectively). The factor loading, as well as the ratio f of the loading to organic PM mass concentration, decreased under polluted compared to background conditions. For an increase in NO y concentration from 0.5 to 2 ppb, the factor loading and f decreased by two to three fold. Overall, sulfate concentration explained 37 % of the variability in the factor loading. After segregation of factor loading into subsets based on NO y concentration, the sulfate concentration explained up to 75 % of the variability. Considering both factors, the data sets show that the suppressing effects of increased NO concentrations dominated over the enhancing effects of higher sulfate concentrations. Furthermore, the pollution from Manaus elevated NO y concentrations more significantly than sulfate concentrations relative to background conditions. In this light, increased emissions of nitrogen oxides, as anticipated for some scenarios of Amazonian economic development, could significantly alter pathways of PM production that presently prevail over the tropical forest, implying changes to air quality and regional climate.« less
  • Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accountedmore » by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C 5H 6O + ( m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine f C5H6O ( f C5H6O= C 5H 6O +/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher f C5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. f C5H6O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations, which is shown to reflect large variations in its detailed molecular composition. The low f C5H6O (< 3 ‰) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX-SOA, and is not a tracer for all SOA from isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of f CO2 vs. f C5H6O. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of ~ 2, if the f C5H6O of the local IEPOX-SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX-SOA and will enable improved characterization of this OA component.« less
    Cited by 36
  • During the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) campaign, size-resolved cloud condensation nuclei (CCN) spectra were characterized at a research site (T3) 60km downwind of the city of Manaus, Brazil, in central Amazonia for one year (12 March 2014 to 3 March 2015). Particle hygroscopicity (κCCN) and mixing state were derived from the size-resolved CCN spectra, and the hygroscopicity of the organic component of the aerosol (κorg) was then calculated from κCCN and concurrent chemical composition measurements. The annual average κCCN increased from 0.13 at 75 nm to 0.17 at 171&thinsp;nm, and the increase was largely duemore » to an increase in sulfate volume fraction. Also, during both wet and dry seasons, κCCN, κorg, and particle composition under background conditions exhibited essentially no diel variations. The constant κorg of ~0.15 is consistent with the largely uniform and high O:C value (~0.8), indicating that the aerosols under background conditions are dominated by the aged regional aerosol particles consisting of highly oxygenated organic compounds. For air masses strongly influenced by urban pollution and/or local biomass burning, lower values of κorg and organic O:C atomic ratio were observed during night, due to accumulation of freshly emitted particles, dominated by primary organic aerosol (POA) with low hygroscopicity, within a shallow nocturnal boundary layer. The O:C, κorg, and κCCN increased from the early morning hours and peaked around noon, driven by the formation and aging of secondary organic aerosol (SOA) and dilution of POA emissions into a deeper boundary layer, while the development of the boundary layer, which leads to mixing with aged particles from the residual layer aloft, likely also contributed to the increases. The hygroscopicities associated with individual organic factors, derived from PMF analysis of AMS spectra, were estimated through multi-variable linear regression. For the SOA factors, the variation of the κ value with O:C agrees well with the linear relationship reported from earlier laboratory studies of SOA hygroscopicity. On the other hand, the variation in O:C of ambient aerosol organics is largely driven by the variation in the volume fractions of POA and SOA factors, which have very different O:C values. As POA factors have hygroscopicity values well below the linear relationship between SOA hygroscopicity and O:C, mixtures with different POA and SOA fractions exhibit a steeper slope for the increase of κorg with O:C, as observed during this and earlier field studies. Our finding helps better understand and reconcile the differences in the relationships between κorg and O:C observed in laboratory and field studies, therefore providing a basis for improved parameterization in global models, especially in a tropical context.« less
  • Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically-relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptakemore » by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of water has a weaker impact on IEPOX-derived SOA yield, but significantly enhanced formation of 2-methyltetrols, consistent with offline filter analysis. In contrast, IEPOX uptake by ABS particles coated by AP-derived SOA is strongly dependent on particle size and composition. IEPOX uptake occurred only when weight fraction of AP-derived SOA dropped below 50 %, effectively limiting IEPOX uptake to larger particles.« less
  • Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to organic aerosol (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, for 16–36 % of the submicron OA in the southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that the volatility of ambient IEPOX-SOA is lower than that of bulk OA and also much lower than that of known monomer IEPOX-SOA tracer species, indicating that IEPOX-SOA likely exists mostly as oligomers in the aerosol phase. The OH aging process of ambient IEPOX-SOA was investigated withmore » an oxidation flow reactor (OFR). New IEPOX-SOA formation in the reactor was negligible, as the OFR does not accelerate processes such as aerosol uptake and reactions that do not scale with OH. Simulation results indicate that adding  ∼  100 µg m −3 of pure H 2SO 4 to the ambient air allows IEPOX-SOA to be efficiently formed in the reactor. The heterogeneous reaction rate coefficient of ambient IEPOX-SOA with OH radical ( k OH) was estimated as 4.0 ± 2.0  ×  10 −13 cm 3 molec −1 s −1, which is equivalent to more than a 2-week lifetime. A similar k OH was found for measurements of OH oxidation of ambient Amazon forest air in an OFR. At higher OH exposures in the reactor (&gt;  1  ×  10 12 molec cm −3 s), the mass loss of IEPOX-SOA due to heterogeneous reaction was mainly due to revolatilization of fragmented reaction products. We report, for the first time, OH reactive uptake coefficients ( γ OH =  0.59 ± 0.33 in SE US and γ OH =  0.68 ± 0.38 in Amazon) for SOA under ambient conditions. A relative humidity dependence of k OH and γ OH was observed, consistent with surface-area-limited OH uptake. No decrease of k OH was observed as OH concentrations increased. These observations of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.« less
    Cited by 6