scholarly journals Review of "Secondary organic aerosol formation from ambient air in an oxidation flow reactor in central Amazonia"

2017 ◽  
Author(s):  
Anonymous
Keyword(s):  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Central Amazonia ◽  
Secondary Organic Aerosol Formation

scholarly journals Supplementary material to "Secondary organic aerosol formation from ambient air in an oxidation flow reactor in central Amazonia"

2017 ◽  
Author(s):  
Brett B. Palm ◽  
Suzane S. de Sá ◽  
Douglas A. Day ◽  
Pedro Campuzano-Jost ◽  
Weiwei Hu ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Central Amazonia ◽  
Supplementary Material ◽  
Secondary Organic Aerosol Formation

scholarly journals In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

2015 ◽  
Vol 15 (21) ◽  
pp. 30409-30471 ◽  
Author(s):  
B. B. Palm ◽  
P. Campuzano-Jost ◽  
A. M. Ortega ◽  
D. A. Day ◽  
L. Kaser ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Pine Forest ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Photochemical Aging

Abstract. Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative time scales of condensation of low volatility organic compounds (LVOCs) onto particles, condensational loss to the walls, and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 μg m-3 when LVOC fate corrected), with maximum formation observed at 0.4–1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene + p-cymene concentrations, including a substantial increase just after sunrise at 07:00 LT. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than could be explained by the VOCs measured in ambient air. Several recently-developed instruments quantified ambient semi- and intermediate-volatility organic compounds (S/IVOCs) that were not detected by a PTR-TOF-MS. An SOA yield of 24–80 % from those compounds can explain the observed SOA, suggesting that these typically unmeasured S/IVOCs play a substantial role in ambient SOA formation. Our results allow ruling out condensation sticking coefficients much lower than 1. Our measurements help clarify the magnitude of SOA formation in forested environments, and demonstrate methods for interpretation of ambient OFR measurements.

Secondary Organic Aerosol Formation from Ambient Air at an Urban Site in Beijing: Effects of OH Exposure and Precursor Concentrations

2018 ◽  
Vol 52 (12) ◽  
pp. 6834-6841 ◽  
Author(s):  
Jun Liu ◽  
Biwu Chu ◽  
Tianzeng Chen ◽  
Changgeng Liu ◽  
Ling Wang ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Urban Site ◽  
Aerosol Formation ◽  
Secondary Organic Aerosol Formation

scholarly journals Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

2015 ◽  
Vol 15 (15) ◽  
pp. 21907-21958 ◽  
Author(s):  
A. M. Ortega ◽  
P. L. Hayes ◽  
Z. Peng ◽  
B. B. Palm ◽  
W. Hu ◽  
...  
Keyword(s):  
Los Angeles ◽  
Real Time ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Vertical Mixing ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Scanning Mobility Particle Sizer ◽  
Heterogeneous Oxidation

Abstract. Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An Oxidation Flow Reactor (OFR) was deployed to study SOA formation in real-time during the CalNex campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent atmospheric aging from hours up to several weeks in 3 min of processing. OH radical concentration was continuously stepped, obtaining measurements of real-time SOA formation and oxidation at multiple equivalent ages from 0.8 days–6.4 weeks. Enhancement of OA from aging showed a maximum net SOA production between 0.8–6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry, and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived VOC correlation, indicates the importance of relatively reactive (τOH ∼ 0.3 day) SOA precursors in the LA-Basin. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ∼ -0.65). Oxidation state of carbon (OSC) in reactor SOA increased steeply with age and remained elevated (OSC ∼ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and also extends to higher ages where OA loss dominates. The mass added at low-to-intermediate ages is due primarily to condensation of oxidized species, not heterogeneous oxidation. The OA decrease at high photochemical ages is dominated by heterogeneous oxidation followed by fragmentation/evaporation. A comparison of urban SOA formation in this study with a similar study of vehicle SOA in a tunnel supports the dominance of vehicle emissions in urban SOA. Pre-2007 SOA models underpredict SOA formation by an order of magnitude, while a more recent model performs better but overpredicts at higher ages. These results demonstrate the value of the reactor as a tool for in situ evaluation of the SOA formation potential and OA evolution from ambient air.

Secondary organic aerosol formation from photo-oxidation of toluene with NO x and SO 2 : Chamber simulation with purified air versus urban ambient air as matrix

2017 ◽  
Vol 150 ◽  
pp. 67-76 ◽  
Author(s):  
Wei Deng ◽  
Tengyu Liu ◽  
Yanli Zhang ◽  
Shuping Situ ◽  
Qihou Hu ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Photo Oxidation ◽  
Secondary Organic Aerosol Formation
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