Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 6611-6629, 2017
https://doi.org/10.5194/acp-17-6611-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Jun 2017
Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia
Suzane S. de Sá1, Brett B. Palm2, Pedro Campuzano-Jost2, Douglas A. Day2, Matthew K. Newburn3, Weiwei Hu2, Gabriel Isaacman-VanWertz4,a, Lindsay D. Yee4, Ryan Thalman5, Joel Brito6,b, Samara Carbone6, Paulo Artaxo6, Allen H. Goldstein4, Antonio O. Manzi7, Rodrigo A. F. Souza8, Fan Mei9, John E. Shilling3,9, Stephen R. Springston5, Jian Wang5, Jason D. Surratt10, M. Lizabeth Alexander3, Jose L. Jimenez2, and Scot T. Martin1,11 1School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
2Department. of Chemistry & Biochemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
3Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA
4Dept. of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
5Brookhaven National Laboratory, Upton, New York, USA
6Departamento de Física Aplicada, Universidade de São Paulo, São Paulo, Brazil
7Instituto Nacional de Pesquisas da Amazonia, Manaus, Amazonas, Brazil
8Escola Superior de Tecnologia, Universidade do Estado do Amazonas, Manaus, Amazonas, Brazil
9Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA
10Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
11Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
anow at: Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
bnow at: Laboratory for Meteorological Physics (LaMP), University Blaise Pascal, Aubière, France
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 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 h 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. The IEPOX-SOA factor loadings 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). 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 NOy 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 NOy 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. The pollution from Manaus elevated NOy 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.

Citation: de Sá, S. S., Palm, B. B., Campuzano-Jost, P., Day, D. A., Newburn, M. K., Hu, W., Isaacman-VanWertz, G., Yee, L. D., Thalman, R., Brito, J., Carbone, S., Artaxo, P., Goldstein, A. H., Manzi, A. O., Souza, R. A. F., Mei, F., Shilling, J. E., Springston, S. R., Wang, J., Surratt, J. D., Alexander, M. L., Jimenez, J. L., and Martin, S. T.: Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia, Atmos. Chem. Phys., 17, 6611-6629, https://doi.org/10.5194/acp-17-6611-2017, 2017.
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