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

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
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  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:
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
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
European Geosciences Union
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)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1363989