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Title: Isoprene photo-oxidation products quantify the effect of pollution on hydroxyl radicals over Amazonia

Nitrogen oxides (NO x) emitted from human activities are believed to regulate the atmospheric oxidation capacity of the troposphere. However, observational evidence is limited for the low-to-median NO x concentrations prevalent outside of polluted regions. Directly measuring oxidation capacity, represented primarily by hydroxyl radicals (OH), is challenging, and the span in NO x concentrations at a single observation site is often not wide. Concentrations of isoprene and its photo-oxidation products were used to infer the equivalent noontime OH concentrations. The fetch at an observation site in central Amazonia experienced varied contributions from background regional air, urban pollution, and biomass burning. The afternoon concentrations of reactive nitrogen oxides (NO y), indicative of NO x exposure during the preceding few hours, spanned from 0.3 to 3.5 parts per billion. Accompanying the increase of NO y concentration, the inferred equivalent noontime OH concentrations increased by at least 250% from 0.6 × 10 6 to 1.6 × 10 6 cm -3. The conclusion is that, compared to background conditions of low NO x concentrations over the Amazon forest, pollution increased NO x concentrations and amplified OH concentrations, indicating the susceptibility of the atmospheric oxidation capacity over the forest to anthropogenic influence and reinforcing themore » important role of NO x in sustaining OH concentrations.« less
ORCiD logo [1] ; ORCiD logo [2] ;  [2] ; ORCiD logo [2] ; ORCiD logo [3] ;  [4] ; ORCiD logo [5] ; ORCiD logo [5] ; ORCiD logo [6] ; ORCiD logo [7] ; ORCiD logo [8] ; ORCiD logo [9]
  1. Harvard Univ., Cambridge, MA (United States). School of Engineering and Applied Sciences (SEAS)
  2. Univ. of California, Irvine, CA (United States). Dept. of Earth System Science
  3. Univ. of California, Berkeley, CA (United States). Dept. of Environmental Science, Policy, and Management
  4. Harvard Univ., Cambridge, MA (United States). School of Engineering and Applied Sciences (SEAS) and Dept. of Chemistry and Chemical Biology
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Environmental and Climate Sciences
  6. Univ. of Sao Paulo (Brazil). Dept. of Applied Physics
  7. Amazonas State Univ., Manaus (Brazil). Dept. of Meterology
  8. Harvard Univ., Cambridge, MA (United States). School of Engineering and Applied Sciences (SEAS); Colby College, Waterville, ME (United States). Dept. of Chemistry
  9. Harvard Univ., Cambridge, MA (United States). School of Engineering and Applied Sciences (SEAS) and Dept. of Earth and Planetary Sciences
Publication Date:
Report Number(s):
Journal ID: ISSN 2375-2548
Grant/Contract Number:
SC0012704; 001030/2012-4; SC0011115; SC0011122; 1628491; 1321987; 2014/05014-0; 2017/17047-0
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 4; Journal Issue: 4; Journal ID: ISSN 2375-2548
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA); National Inst. of Amazonian Research (INPA); Amazonas State Univ., Manaus (Brazil); National Council for Scientific and Technological Development (CNPq); National Science Foundation (NSF); São Paulo Research Foundation (FAPESP)
Country of Publication:
United States
OSTI Identifier: