Near-highway aerosol and gas-phase measurements in a high-diesel environment

DeWitt, H. Langley; Hellebust, Stig; Temime-Roussel, Brice; Ravier, Sylvain; Polo, L.; Jacob, Véronique; Buisson, Christine; Charron, Aurélie; Meynier, André; Pasquier, Anaïs; Besombes, Jean-Luc; Jaffrezo, Jean-Luc; Wortham, Henri; Marchand, Nicolas

doi:10.5194/acp-15-4373-2015

Cited by 30 publications

(37 citation statements)

References 56 publications

(66 reference statements)

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“…Therefore, as a first-order approximation, ELVOCs measured in the near-highway environment are likely dominated by regional background aerosol, and thus a gradient downwind of the roadway is not expected. On the other hand, traffic emissions are a major contributor of BC in near-highway environments (Baldauf et al, 2008;Bond et al, 2013;DeWitt et al, 2015) and a rapid downwind decay of BC concentrations was observed in our site (Saha et al, 2018), which is consistent with past studies (Karner et al, 2010).…”

Section: Parameterizing Volatilitysupporting

confidence: 81%

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

2018

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Abstract. We present spatial measurements of particle volatility and mixing state at a site near a North Carolina interstate highway (I-40) applying several heating (thermodenuder; TD) experimental approaches. Measurements were conducted in summer 2015 and winter 2016 in a roadside trailer (10 m from road edge) and during downwind transects at different distances from the highway under favorable wind conditions using a mobile platform. Results show that the relative abundance of semi-volatile species (SVOCs) in ultrafine particles decreases with downwind distance, which is consistent with the dilution and mixing of traffic-sourced particles with background air and evaporation of semi-volatile species during downwind transport. An evaporation kinetics model was used to derive particle volatility distributions by fitting TD data. While the TD-derived distribution apportions about 20–30 % of particle mass as semi-volatile (SVOCs; effective saturation concentration, C∗ ≥ 1µm−3) at 10 m from the road edge, approximately 10 % of particle mass is attributed to SVOCs at 220 m, showing that the particle-phase semi-volatile fraction decreases with downwind distance. The relative abundance of semi-volatile material in the particle phase increased during winter. Downwind spatial gradients of the less volatile particle fraction (that remaining after heating at 180 °C) were strongly correlated with black carbon (BC). BC size distribution and mixing state measured using a single-particle soot photometer (SP2) at the roadside trailer showed that a large fraction (70–80 %) of BC particles were externally mixed. Heating experiments with a volatility tandem differential mobility analyzer (V-TDMA) also showed that the nonvolatile fraction in roadside aerosols is mostly externally mixed. V-TDMA measurements at different distances downwind from the highway indicate that the mixing state of roadside aerosols does not change significantly (e.g., BC mostly remains externally mixed) within a few hundred meters from the highway. Our analysis indicates that a superposition of volatility distributions measured in laboratory vehicle tests and of background aerosol can be used to represent the observed partitioning of near-road particles. The results from this study show that exposures and impacts of BC and semi-volatile organics-containing particles in a roadside microenvironment may differ across seasons and under changing ambient conditions.

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Section: Parameterizing Volatilitysupporting

confidence: 81%

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

2018

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“…Therefore, as a first order approximation, ELVOCs 25 measured in the near-highway environment are likely dominated by regional background aerosol, and thus a gradient downwind of the roadway is not expected. On the other hand, traffic emissions are a major contributor of BC in near-highway environments (Baldauf et al, 2008;Bond et al, 2013;DeWitt et al, 2015) and a rapid downwind decay of BC concentrations was observed in our site (Saha et al 2017a), consistent with past studies (Karner et al, 2010).…”

Section: Observed Evaporations In Td With Downwind Distancesupporting

confidence: 80%

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Saha¹,

Khlystov²,

Grieshop³

2017

Preprint

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Abstract. We present spatial measurements of particle volatility and mixing state at a site near a North Carolina interstate highway (I-40) applying several heating (thermodenuder; TD) experimental approaches. Measurements were conducted in summer 2015 and winter 2016 in a roadside trailer (10 m from road edge) and during downwind transects at different distances 10 from the highway under favorable wind conditions using a mobile platform. Results show that the relative abundance of semivolatile species (SVOCs) in ultrafine particles decreases with downwind distance, consistent with the dilution and mixing of traffic-sourced particles with background air and evaporation of semi-volatile species during downwind transport. An evaporation kinetics model was used to derive particle volatility distributions by fitting TD data. While the TD-derived distribution apportions about 20-30% of particle mass as semi-volatile (SVOCs; effective saturation concentration, C* ≥ 1µ 15 m-3) at 10 m from road edge, approximately 10% of particle mass is attributed to SVOCs at 220 m, showing that the particlephase semi-volatile fraction decreases with downwind distance. The relative abundance of semi-volatile material in the particle-phase increased during winter. Downwind spatial gradients of the less-volatile particle fraction (that remaining after heating at 180°C) was strongly correlated with black carbon (BC). BC size distribution and mixing state measured using a Single Particle Soot Photometer (SP2) at the roadside trailer showed that a large fraction (70-80%) of BC particles were 20 externally-mixed. Heating experiments with a volatility tandem differential mobility analyzer (V-TDMA) also showed that the non-volatile fraction in roadside aerosols are mostly externally mixed. V-TDMA measurements at different distances downwind from the highway indicate that mixing state of roadside aerosols does not change significantly (e.g., BC mostly remains externally mixed) within a few hundred meters from the highway. A preliminary analysis indicates that a superposition of volatility distributions measured in laboratory vehicle tests and of 'background' aerosol can be used to represent 25 the observed partitioning of near-road particles. The results from this study highlight that exposures and impacts of BC and semi-volatile organics containing particles in a near-road microenvironment may differ across seasons and under changing ambient conditions. 30 Atmos. Chem. Phys. Discuss., https://doi

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“…This difference in the eBC tr to HOA ratio at the two locations is most probably related to the higher percentage of gasoline vehicles in China compared to Europe. Specifically, according to DeWitt et al (2015), an eBCtr to HOA of around 0.8 corresponds to a diesel fuel share of about 40 to 50 %. This estimation is in good agreement with results from Gentner et al (2016), where a diesel fuel share of around 40 % was estimated for 2013 in China, dominated by heavy-and medium-duty vehicles.…”

Section: Ebc Source Apportionmentmentioning

confidence: 99%

“…As the vehicular fleet in China and Europe are significantly different, e.g., higher diesel contribution in Europe, the use of a European profile to apportion traffic emissions in China could introduce significant errors. However, the comparison between HOA spectra from Europe (fleet dominated by diesel) and from the United States (fleet dominated by gasoline), shows that the variability among two European spectra (Mohr et al, 2012;Crippa et al, 2013) is comparable to the variability among HOA spectra from the United States and Europe (Docherty et al, 2011;. This was evaluated by means of cosine similarity analysis, which resulted in O HOA(Europe-Europe) = 0.93 and O HOA(Europe-US) = 0.92.…”

Section: Interpretation and Optimization Of Oa Source Apportionmentmentioning

confidence: 99%

New insights into PM<sub>2.5</sub> chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry

Elser¹,

Huang²,

Wolf³

et al. 2015

Preprint

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During winter 2013-2014 aerosol mass spectrometer (AMS) measurements were conducted for the first time with a novel PM 2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) lens in two major cities of China: Xi'an and Beijing. We denote the periods with visibility below 2 km as extreme haze and refer to the rest as reference periods. During the measurements in Xi'an an extreme haze covered the city for about a week and the total non-refractory (NR)-PM 2.5 mass fraction reached peak concentrations of over 1000 µg m −3 . During the measurements in Beijing two extreme haze events occurred, but the temporal extent and the total concentrations reached during these events were lower than in Xi'an. Average PM 2.5 concentrations of 537 ± 146 and 243 ± 47 µg m −3 (including NR species and equivalent black carbon, eBC) were recorded during the extreme haze events in Xi'an and Beijing, respectively. During the reference periods the measured average concentrations were 140 ± 99 µg m −3 in Xi'an and 75 ± 61 µg m −3 in Beijing. The relative composition of the NR-PM 2.5 evolved substantially during the extreme haze periods, with increased contributions of the inorganic components (mostly sulfate and nitrate). Our results suggest that the high relative humidity present during the extreme haze events had a strong effect on the increase of sulfate mass (via aqueous phase oxidation of sulfur dioxide). Another relevant characteristic of the extreme haze is the size of the measured particles. During the extreme haze events, the AMS showed much larger particles, with a volume weighted mode at about 800 to 1000 nm, in contrast to about 400 nm during reference periods. These large particle sizes made the use of the PM 2.5 inlet crucial, especially during the severe haze events, where 39 ± 5 % of the mass would have been lost in the conventional PM 1 (particulate matter with aerodynamic diameter ≤ 1 µm) inlet. A novel positive matrix factorization procedure was developed to apportion the sources of organic aerosols (OA) based on their mass spectra using the multilinear engine (ME-2) controlled via the source finder (SoFi). The procedure allows for an effective exploration of the solution space, a more objective selection of the best solution and an estimation of the rotational uncertainties. Our results clearly show an increase of the oxygenated organic aerosol (OOA) mass during extreme haze events. The contribution of OOA to the Published by Copernicus Publications on behalf of the European Geosciences Union. 3208M. Elser et al.: OA chemical composition and sources during haze events in China total OA increased from the reference to the extreme haze periods from 16.2 ± 1.1 to 31.3 ± 1.5 % in Xi'an and from 15.7 ± 0.7 to 25.0 ± 1.2 % in Beijing. By contrast, during the reference periods the total OA mass was dominated by domestic emissions of primary aerosols from biomass burning in Xi'an (42.2 ± 1.5 % of OA) and coal combustion in Beijing (55.2 ± 1.6 % of OA). These two sources are also mostly responsible for extremely high polycy...

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Near-highway aerosol and gas-phase measurements in a high-diesel environment

Cited by 30 publications

References 56 publications

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

New insights into PM<sub>2.5</sub> chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry

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Near-highway aerosol and gas-phase measurements in a high-diesel environment

Cited by 30 publications

References 56 publications

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

Downwind evolution of the volatility and mixing state of near-road aerosols near a US interstate highway

New insights into PM&lt;sub&gt;2.5&lt;/sub&gt; chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry

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Product

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New insights into PM<sub>2.5</sub> chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry