Computer-aided estimation of kinetic rate constant for degradation of volatile organic compounds by hydroxyl radical: An improved model using quantum chemical and norm descriptors

2021 ◽  
pp. 117244
Author(s):  
Yajuan Shi ◽  
Jin-Jin Li ◽  
Qiang Wang ◽  
Qingzhu Jia ◽  
Fangyou Yan ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Rate Constant ◽  
Quantum Chemical ◽  
Kinetic Rate Constant ◽  
Kinetic Rate ◽  
Volatile Organic ◽  
Computer Aided ◽  
Improved Model

scholarly journals Variability of hydroxyl radical (OH) reactivity in the Landes maritime pine forest: results from the LANDEX campaign 2017

2020 ◽  
Vol 20 (3) ◽  
pp. 1277-1300 ◽  
Author(s):  
Sandy Bsaibes ◽  
Mohamad Al Ajami ◽  
Kenneth Mermet ◽  
François Truong ◽  
Sébastien Batut ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Secondary Products ◽  
Strong Concentration ◽  
Volatile Organic ◽  
Warm Night ◽  
Photolysis Laser ◽  
Primary Emissions ◽  
Comparative Reactivity

Abstract. Total hydroxyl radical (OH) reactivity measurements were conducted during the LANDEX intensive field campaign in a coniferous temperate forest located in the Landes area, southwestern France, during July 2017. In order to investigate inter-canopy and intra-canopy variability, measurements were performed inside (6 m) and above the canopy level (12 m), as well as at two different locations within the canopy, using a comparative reactivity method (CRM) and a laser photolysis–laser-induced fluorescence (LP-LIF) instrument. The two techniques were intercompared at the end of the campaign by performing measurements at the same location. Volatile organic compounds were also monitored at both levels with a proton transfer time-of-flight mass spectrometer and online gas chromatography instruments to evaluate their contribution to total OH reactivity, with monoterpenes being the main reactive species emitted in this forest dominated by Pinus pinaster Aiton. Total OH reactivity varied diurnally, following the trend of biogenic volatile organic compounds (BVOCs), the emissions and concentrations of which were dependent on meteorological parameters. Average OH reactivity was around 19.2 and 16.5 s−1 inside and above the canopy, respectively. The highest levels of total OH reactivity were observed during nights with a low turbulence (u*≤0.2 m s−1), leading to lower mixing of emitted species within the canopy and thus an important vertical stratification characterized by a strong concentration gradient. Comparing the measured and the calculated OH reactivity highlighted an average missing OH reactivity of 22 % and 33 % inside and above the canopy, respectively. A day–night variability was observed on missing OH reactivity at both heights. Investigations showed that during daytime, missing OH sinks could be due to primary emissions and secondary products linked to a temperature-enhanced photochemistry. Regarding nighttime missing OH reactivity, higher levels were seen for the stable and warm night of 4–5 July, showing that these conditions could have been favorable for the accumulation of long-lived species (primary and secondary species) during the transport of the air mass from nearby forests.

scholarly journals Secondary organic aerosols from anthropogenic volatile organic compounds contribute substantially to air pollution mortality

2021 ◽  
Vol 21 (14) ◽  
pp. 11201-11224
Author(s):  
Benjamin A. Nault ◽  
Duseong S. Jo ◽  
Brian C. McDonald ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
...  
Keyword(s):  
Air Quality ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Urban Areas ◽  
Premature Mortality ◽  
Strongly Correlated ◽  
Premature Deaths ◽  
Volatile Organic ◽  
Order Of Magnitude ◽  
Improved Model

Abstract. Anthropogenic secondary organic aerosol (ASOA), formed from anthropogenic emissions of organic compounds, constitutes a substantial fraction of the mass of submicron aerosol in populated areas around the world and contributes to poor air quality and premature mortality. However, the precursor sources of ASOA are poorly understood, and there are large uncertainties in the health benefits that might accrue from reducing anthropogenic organic emissions. We show that the production of ASOA in 11 urban areas on three continents is strongly correlated with the reactivity of specific anthropogenic volatile organic compounds. The differences in ASOA production across different cities can be explained by differences in the emissions of aromatics and intermediate- and semi-volatile organic compounds, indicating the importance of controlling these ASOA precursors. With an improved model representation of ASOA driven by the observations, we attribute 340 000 PM2.5-related premature deaths per year to ASOA, which is over an order of magnitude higher than prior studies. A sensitivity case with a more recently proposed model for attributing mortality to PM2.5 (the Global Exposure Mortality Model) results in up to 900 000 deaths. A limitation of this study is the extrapolation from cities with detailed studies and regions where detailed emission inventories are available to other regions where uncertainties in emissions are larger. In addition to further development of institutional air quality management infrastructure, comprehensive air quality campaigns in the countries in South and Central America, Africa, South Asia, and the Middle East are needed for further progress in this area.

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