TY - JOUR

T1 - Isoprene photo-oxidation products quantify the effect of pollution on hydroxyl radicals over Amazonia

AU - Liu, Yingjun

AU - Seco, Roger

AU - Kim, Saewung

AU - Guenther, Alex B.

AU - Goldstein, Allen H.

AU - Keutsch, Frank N.

AU - Springston, Stephen R.

AU - Watson, Thomas B.

AU - Artaxo, Paulo

AU - Souza, Rodrigo A.F.

AU - McKinney, Karena A.

AU - Martin, Scot T.

PY - 2018

Y1 - 2018

N2 - Nitrogen oxides (NOX) emitted fromhuman activities are believed to regulate the atmospheric oxidation capacity of the troposphere. However, observational evidence is limited for the low-to-median NOX concentrations prevalent outside of polluted regions. Directly measuring oxidation capacity, represented primarily by hydroxyl radicals (OH), is challenging, and the span in NOX concentrations at a single observation site is often not wide. Concentrations of isoprene and its photo-oxidation productswere used to infer the equivalent noontime OHconcentrations. 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 (NOy), indicative of NOX exposure during the preceding few hours, spanned from 0.3 to 3.5 parts per billion. Accompanying the increase of NOy concentration, the inferred equivalent noontimeOHconcentrations increased by at least 250%from0.6 × 106 to 1.6 × 106 cm-3. The conclusion is that, compared to background conditions of low NOX concentrations over the Amazon forest, pollution increased NOX concentrations and amplified OH concentrations, indicating the susceptibility of the atmospheric oxidation capacity over the forest to anthropogenic influence and reinforcing the important role of NOX in sustaining OH concentrations.

AB - Nitrogen oxides (NOX) emitted fromhuman activities are believed to regulate the atmospheric oxidation capacity of the troposphere. However, observational evidence is limited for the low-to-median NOX concentrations prevalent outside of polluted regions. Directly measuring oxidation capacity, represented primarily by hydroxyl radicals (OH), is challenging, and the span in NOX concentrations at a single observation site is often not wide. Concentrations of isoprene and its photo-oxidation productswere used to infer the equivalent noontime OHconcentrations. 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 (NOy), indicative of NOX exposure during the preceding few hours, spanned from 0.3 to 3.5 parts per billion. Accompanying the increase of NOy concentration, the inferred equivalent noontimeOHconcentrations increased by at least 250%from0.6 × 106 to 1.6 × 106 cm-3. The conclusion is that, compared to background conditions of low NOX concentrations over the Amazon forest, pollution increased NOX concentrations and amplified OH concentrations, indicating the susceptibility of the atmospheric oxidation capacity over the forest to anthropogenic influence and reinforcing the important role of NOX in sustaining OH concentrations.

U2 - 10.1126/sciadv.aar2547

DO - 10.1126/sciadv.aar2547

M3 - Journal article

C2 - 29651460

AN - SCOPUS:85045741888

VL - 4

JO - Science advances

JF - Science advances

SN - 2375-2548

IS - 4

M1 - eaar2547

ER -