scholarly journals Anthropogenic enhancements to production of highly oxygenated molecules from autoxidation

2019 ◽  
Vol 116 (14) ◽  
pp. 6641-6646 ◽  
Author(s):  
Havala O. T. Pye ◽  
Emma L. D’Ambro ◽  
Ben H. Lee ◽  
Siegfried Schobesberger ◽  
Masayuki Takeuchi ◽  
...  
Keyword(s):  
Fine Particulate Matter ◽  
Peroxy Radicals ◽  
Dominant Component ◽  
Fine Particulate ◽  
Biogenic Voc ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Climate Interactions ◽  
Urban Plume

Atmospheric oxidation of natural and anthropogenic volatile organic compounds (VOCs) leads to secondary organic aerosol (SOA), which constitutes a major and often dominant component of atmospheric fine particulate matter (PM2.5). Recent work demonstrates that rapid autoxidation of organic peroxy radicals (RO2) formed during VOC oxidation results in highly oxygenated organic molecules (HOM) that efficiently form SOA. As NOxemissions decrease, the chemical regime of the atmosphere changes to one in which RO2autoxidation becomes increasingly important, potentially increasing PM2.5, while oxidant availability driving RO2formation rates simultaneously declines, possibly slowing regional PM2.5formation. Using a suite of in situ aircraft observations and laboratory studies of HOM, together with a detailed molecular mechanism, we show that although autoxidation in an archetypal biogenic VOC system becomes more competitive as NOxdecreases, absolute HOM production rates decrease due to oxidant reductions, leading to an overall positive coupling between anthropogenic NOxand localized biogenic SOA from autoxidation. This effect is observed in the Atlanta, Georgia, urban plume where HOM is enhanced in the presence of elevated NO, and predictions for Guangzhou, China, where increasing HOM-RO2production coincides with increases in NO from 1990 to 2010. These results suggest added benefits to PM2.5abatement strategies come with NOxemission reductions and have implications for aerosol–climate interactions due to changes in global SOA resulting from NOxinteractions since the preindustrial era.

scholarly journals A Prototype Sensor for In Situ Sensing of Fine Particulate Matter and Volatile Organic Compounds

Sensors ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 265 ◽  
Author(s):  
Chee-Loon Ng ◽  
Fuu-Ming Kai ◽  
Ming-Hui Tee ◽  
Nicholas Tan ◽  
Harold Hemond
Keyword(s):  
Particulate Matter ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Fine Particulate Matter ◽  
Fine Particulate ◽  
Volatile Organic ◽  
In Situ Sensing

scholarly journals Characterization of ozone production in San Antonio, Texas, using measurements of total peroxy radicals

2019 ◽  
Vol 19 (5) ◽  
pp. 2845-2860 ◽  
Author(s):  
Daniel C. Anderson ◽  
Jessica Pavelec ◽  
Conner Daube ◽  
Scott C. Herndon ◽  
Walter B. Knighton ◽  
...  
Keyword(s):  
San Antonio ◽  
Peroxy Radical ◽  
Ozone Production ◽  
Peroxy Radicals ◽  
Entire Region ◽  
Volatile Organic ◽  
In Situ Observations ◽  
Study Sites

Abstract. Observations of total peroxy radical concentrations ([XO2] ≡ [RO2] + [HO2]) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made on board the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas, region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv h−1, a factor of 2 higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv h−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO2, suggest that the region was predominantly NOx-limited. Only approximately 20 % of observations were in the VOC-limited regime, predominantly before 11:00 EST, when ozone production was low. Biogenic volatile organic compounds (VOCs) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

scholarly journals Formation of Secondary Organic Aerosols by Germicidal Ultraviolet Light

Environments ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 17
Author(s):  
Eureka Choi ◽  
Zhongchao Tan ◽  
William Anderson
Keyword(s):  
Uv Light ◽  
Fine Particulate Matter ◽  
Particle Formation ◽  
Uv Exposure ◽  
Indoor Environments ◽  
Fine Particulate ◽  
Volatile Organic ◽  
Solar Uv ◽  
Commercial Environment ◽  
Number Of Particles

Ultraviolet (UV) light with a wavelength of 254 nm is known to be germicidal, and thus has been increasingly employed as a method of disinfection for indoor environments. Solar UV wavelengths (300 to 400 nm) are known to initiate the formation of secondary organic aerosol (SOA) particles from the photo-oxidation of volatile organic compounds (VOC) in the atmosphere, but germicidal wavelengths have not been extensively studied for indoor environments. In this work, toluene was exposed to 254 nm UV light in a laboratory photoreactor while varying the conditions of the air, the duration of UV exposure, and the duration of post-UV time. The number of particles formed in the fine particulate matter (PM2.5) size range was measured, and significant levels of particle formation were observed for UV exposure periods of as short as 5 min. The particle formation ranged from 2.4 × 106 particles/m3 for 5 min of UV exposure, to 163.2 × 106 particles/m3 for 15 min of UV exposure, for toluene concentrations in the range of 55 to 85 mg/m3. Particle formation was found to increase at a relative humidity of approximately 20% and higher. Variations in the initial number of particles present did not appear to have a significant effect on the particle formation, suggesting that nucleation was not a controlling factor under these conditions. However, tests in a commercial environment at much lower VOC concentrations and lower UV fluence rates showed no detectable PM2.5 formation, indicating that SOA formation during the intermittent use of germicidal UV may not significantly affect indoor air quality under normal conditions.

scholarly journals In situ, satellite measurement and model evidence on the dominant regional contribution to fine particulate matter levels in the Paris megacity

2015 ◽  
Vol 15 (16) ◽  
pp. 9577-9591 ◽  
Author(s):  
M. Beekmann ◽  
A. S. H. Prévôt ◽  
F. Drewnick ◽  
J. Sciare ◽  
S. N. Pandis ◽  
...  
Keyword(s):  
Air Pollution ◽  
Particulate Matter ◽  
Air Quality ◽  
Fine Particulate Matter ◽  
Organic Aerosol ◽  
Satellite Measurement ◽  
Fine Particulate ◽  
Wood Burning ◽  
Air Pollution Regulation

Abstract. A detailed characterization of air quality in the megacity of Paris (France) during two 1-month intensive campaigns and from additional 1-year observations revealed that about 70 % of the urban background fine particulate matter (PM) is transported on average into the megacity from upwind regions. This dominant influence of regional sources was confirmed by in situ measurements during short intensive and longer-term campaigns, aerosol optical depth (AOD) measurements from ENVISAT, and modeling results from PMCAMx and CHIMERE chemistry transport models. While advection of sulfate is well documented for other megacities, there was surprisingly high contribution from long-range transport for both nitrate and organic aerosol. The origin of organic PM was investigated by comprehensive analysis of aerosol mass spectrometer (AMS), radiocarbon and tracer measurements during two intensive campaigns. Primary fossil fuel combustion emissions constituted less than 20 % in winter and 40 % in summer of carbonaceous fine PM, unexpectedly small for a megacity. Cooking activities and, during winter, residential wood burning are the major primary organic PM sources. This analysis suggests that the major part of secondary organic aerosol is of modern origin, i.e., from biogenic precursors and from wood burning. Black carbon concentrations are on the lower end of values encountered in megacities worldwide, but still represent an issue for air quality. These comparatively low air pollution levels are due to a combination of low emissions per inhabitant, flat terrain, and a meteorology that is in general not conducive to local pollution build-up. This revised picture of a megacity only being partially responsible for its own average and peak PM levels has important implications for air pollution regulation policies.

Satellite-based observations of ground-level fine particulate matter and comparison to a regional air quality model

2020 ◽  
Author(s):  
Jana Handschuh ◽  
Frank Baier ◽  
Thilo Erbertseder ◽  
Martijn Schaap
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Air Pollutants ◽  
Fine Particulate Matter ◽  
Ground Level ◽  
In Situ Measurements ◽  
Satellite Observations ◽  
Optical Parameters ◽  
Fine Particulate

<p>Particulate matter and other air pollutants have become an increasing burden on the environment and human health. Especially in metropolitan and high-traffic areas, air quality is often remarkably reduced. For a better understanding of the air quality in specific areas, which is of great environment-political interest, data with high resolution in space and time is required. The combination of satellite observations and chemistry-transport-modelling has proven to give a good database for assessments and analyses of air pollution. In contrast to sample in-situ measurements, satellite observations provide area-wide coverage ​​of measurements and thus the possibility for an almost gapless mapping of actual air pollutants. For a high temporal resolution, chemistry-transport-models are needed, which calculate concentrations of specific pollutants in continuous time steps. Satellite observations can thus be used to improve model performances.</p><p>There are no direct satellite-measurements of fine particulate matter (PM2.5) but ground-level concentrations of PM2.5 can be derived from optical parameters such as aerosol optical depth (AOD). A wide range of methods for the determination of PM2.5 concentrations from AOD measurements has been developed so far, but it is still a big challenge. In this study a semi-empirical approach based on the physical relationships between meteorological and optical parameters was applied to determine a first-guess of ground-level PM2.5 concentrations for the year 2018 and the larger Germany region. Therefor AOD observations of MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the NASA Aqua satellite were used in a spatial resolution of 3km. First results showed an overestimation of ground-level aerosols and quiet low correlations with in-situ station measurements from the European Environmental Agency (EEA). To improve the results, correction factors were calculated using the coefficients of linear regression between satellite-based and in-situ measured particulate matter concentrations. Spatial and seasonal dependencies were taken into account with it. Correlations between satellite and in-situ measurements could be improved applying this method.</p><p>The MODIS 3km AOD product was found to be a good base for area-wide calculations of ground-level PM2.5 concentrations. First comparisons to the calculated PM2.5 concentrations from chemistry-transport-model POLYPHEMUS/DLR showed significant differences though. Satellite observations will now be used to improve the general model performance, first by helping to find and understand regional and temporal dependencies in the differences. As part of the German project S-VELD funded by the Federal Ministry of Transport and Digital Infrastructure BMVI, it will help for example to adjust the derivation of particle emissions within the model.</p>

scholarly journals Chemical characterization of fine particulate matter emitted by peat fires in Central Kalimantan, Indonesia, during the 2015 El Niño

2018 ◽  
Vol 18 (4) ◽  
pp. 2585-2600 ◽  
Author(s):  
Thilina Jayarathne ◽  
Chelsea E. Stockwell ◽  
Ashley A. Gilbert ◽  
Kaitlyn Daugherty ◽  
Mark A. Cochrane ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Fine Particulate Matter ◽  
Water Soluble ◽  
Central Kalimantan ◽  
Fine Particulate ◽  
Soluble Ions ◽  
Water Soluble Ions ◽  
Mass Fractions

Abstract. Fine particulate matter (PM2.5) was collected in situ from peat smoke during the 2015 El Niño peat fire episode in Central Kalimantan, Indonesia. Twenty-one PM samples were collected from 18 peat fire plumes that were primarily smoldering with modified combustion efficiency (MCE) values of 0.725–0.833. PM emissions were determined and chemically characterized for elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble ions, metals, and organic species. Fuel-based PM2.5 mass emission factors (EFs) ranged from 6.0 to 29.6 g kg−1 with an average of 17.3 ± 6.0 g kg−1. EC was detected only in 15 plumes and comprised  ∼ 1 % of PM mass. Together, OC (72 %), EC (1 %), water-soluble ions (1 %), and metal oxides (0.1 %) comprised 74 ± 11 % of gravimetrically measured PM mass. Assuming that the remaining mass is due to elements that form organic matter (OM; i.e., elements O, H, N) an OM-to-OC conversion factor of 1.26 was estimated by linear regression. Overall, chemical speciation revealed the following characteristics of peat-burning emissions: high OC mass fractions (72 %), primarily water-insoluble OC (84 ± 11 %C), low EC mass fractions (1 %), vanillic to syringic acid ratios of 1.9, and relatively high n-alkane contributions to OC (6.2 %C) with a carbon preference index of 1.2–1.6. Comparison to laboratory studies of peat combustion revealed similarities in the relative composition of PM but greater differences in the absolute EF values. The EFs developed herein, combined with estimates of the mass of peat burned, are used to estimate that 3.2–11 Tg of PM2.5 was emitted to atmosphere during the 2015 El Niño peatland fire event in Indonesia. Combined with gas-phase measurements of CO2, CO, CH4, and volatile organic carbon from Stockwell et al. (2016), it is determined that OC and EC accounted for 2.1 and 0.04 % of total carbon emissions, respectively. These in situ EFs can be used to improve the accuracy of the representation of Indonesian peat burning in emission inventories and receptor-based models.

scholarly journals Formation of Secondary Organic Aerosols by Germicidal Ultraviolet Light

2018 ◽  
Author(s):  
Eureka Choi ◽  
Zhongchao Tan ◽  
William A. Anderson
Keyword(s):  
Uv Light ◽  
Fine Particulate Matter ◽  
Particle Formation ◽  
Uv Exposure ◽  
Indoor Environments ◽  
Fine Particulate ◽  
Volatile Organic ◽  
Solar Uv ◽  
Commercial Environment ◽  
Number Of Particles

Ultraviolet (UV) light with a wavelength of 254 nm has proven to be effective at inactivating microorganisms, and thus has been increasingly employed as a method of disinfection for indoor environments. Solar UV wavelengths (300 to 400 nm) are known to initiate the formation of secondary organic aerosol (SOA) particles from photo-oxidation of volatile organic compounds in the atmosphere, but germicidal wavelengths have not been extensively studied for indoor environments.  In this work, toluene was exposed to 254 nm UV light in a laboratory photoreactor, with varying conditions of the air, the duration of UV exposure, and the duration of post-UV time. The number of particles formed in the fine particulate matter (PM2.5) size range was measured, and significant levels of particle formation were observed for UV exposure periods of as short as 5 minutes. The particle formation ranged from 2.4x106 particles/m3 for 5 minutes of UV exposure, to 1449.8x106 particles/m3 for 15 minutes of UV exposure. Particle formation was found to increase with increasing concentrations of gas phase toluene, and at relative humidity of approximately 20% and higher. Variations in the initial number of particles present did not appear to have a significant effect on the particle formation, suggesting that nucleation was not a controlling factor. However, tests in a commercial environment showed no significant detectable PM2.5 formation, indicating that SOA formation during the intermittent use of germicidal UV may not significantly affect indoor air quality.

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