Processing of soot in an urban environment: case study from the Mexico City Metropolitan Area

Johnson, Kathleen R.; Zuberi, B.; Molina, Luisa T.; Molina, Mario J.; Iedema, Martin J.; Cowin, James P.; Gaspar, Daniel J.; Wang, Chong M.; Laskin, Alexander

doi:10.5194/acp-5-3033-2005

Cited by 177 publications

(77 citation statements)

References 72 publications

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“…The fact that our OOM particles (after being coated with a similar mass of OM as observed in previous studies; Section 3.2) remained highly aspherical after aging indicates that the particles produced by flaming wood combustion in such a stove may also remain highly aspherical, unless mixed with aerosols from other sources. This conclusion is consistent with atmospheric observations suggesting that such external mixing is often insufficient for BC-containing particles to appear spherical (Johnson et al 2005;Adachi et al 2010). Models that represent aged soot as coated spheres (Jacobson 2001) may therefore obtain biased estimates of light absorption by BC for well-operated wood stoves and other BC sources producing aerosols with similar fractions of organic mass.…”

Section: Wood-stove Particle Propertiessupporting

confidence: 78%

Organic Emissions from a Wood Stove and a Pellet Stove Before and After Simulated Atmospheric Aging

Corbin

Keller

Lohmann

et al. 2015

Aerosol Science and Technology

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Logwood and pellet stoves are popular heating sources around the world. The particulate matter emitted from such stoves contains organic particulate matter (OM), soot, and ash, each of which may have significant effects on climate and health. In this study, the primary OM (POM) emitted from a wood stove and a pellet stove operated according to standard Swiss testing protocols were characterized using aerosol mass spectrometry. The POM mass spectra were found to be highly reproducible, and contained CO C as the dominant ion. Because the POM emitted by such stoves is typically enhanced by the condensation of gaseous organics following atmospheric aging, the secondary OM (SOM) formation potential of these stoves was simulated using the Micro Smog Chamber (MSC) designed by Keller and Burtscher in 2012. In general, OM emission factors from MSCaged aerosols were comparable to lower-time-resolution results from the literature, although the MSC exposed aerosols to much higher concentrations of oxidants and therefore produced OM that was more oxidized than expected for atmospheric samples. In addition, the logwood-stove particles remained highly aspherical even after oxidation, indicating that mixing with an external aerosol is required for these particles to become spherical. The one exception to this observation occurred when the wood failed to ignite and appeared to generate tar-ball OM particles.

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Section: Wood-stove Particle Propertiessupporting

confidence: 78%

Organic Emissions from a Wood Stove and a Pellet Stove Before and After Simulated Atmospheric Aging

Corbin

Keller

Lohmann

et al. 2015

Aerosol Science and Technology

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“…During MILAGRO, the measurements at T0 site suggest that during daytime, the mixing of freshly emitted POA and BC particles with other hygroscopic species takes place in a few hours, owing to the rapid formation and condensation of secondary nitrate and SOA. This rapid transition was also observed from single-particle mass spectrometry data taken at the T0 site (Moffet et al, 2009), and in an earlier microscopy study in Mexico City (Johnson et al, 2005). By 12:00 p.m., most particles have growth factors greater than 1.16 at 85% RH, which corresponds to an overall κ value of 0.1.…”

Section: Impact Of Mixing State On Calculated N Ccn and Its Variationmentioning

confidence: 57%

The importance of aerosol mixing state and size-resolved composition on CCN concentration and the variation of the importance with atmospheric aging of aerosols

et al. 2010

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The aerosol size distribution and composition often showed strong diurnal variation associated with traffic emissions and aging of aerosols through coagulation and local photochemical production of secondary aerosol species. CCN concentrations (N CCN ) are derived using Köhler theory from the measured aerosol size distribution and various simplified aerosol mixing state and chemical composition, and are compared to concurrent measurements at five supersaturations ranging from 0.11% to 0.35%. The influence of assumed mixing state on calculated N CCN is examined using both aerosols observed during MILAGRO and representative aerosol types. The results indicate that while ambient aerosols often consist of particles with a wide range of compositions at a given size, N CCN may be derived within ∼20% assuming an internal mixture (i.e., particles at a given size are mixtures of all participating species, and have the identical composition) if great majority of particles has an overall κ (hygroscopicity parameter) value greater than 0.1. For a non-hygroscopic particle with a diameter of 100 nm, a 3 nm coating of sulfate or nitrate is sufficient to increase its κ from 0 to 0.1. The measurements during MILAGRO suggest that the mixing of non-hygroscopic primary organic aerosol (POA) and black carbon (BC) particles with photochemically produced hygroscopic species and thereby the increase of their κ to 0.1 take place in a few hours during daytime. This rapid process suggests that during daytime, a few tens of kilometers away for Correspondence to: J. Wang (jian@bnl.gov) POA and BC sources, N CCN may be derived with sufficient accuracy by assuming an internal mixture, and using bulk chemical composition. The rapid mixing also indicates that, at least for very active photochemical environments such as Mexico City, the timescale during daytime for the conversion of hydrophobic POA and BC to hydrophilic particles is substantially shorter than the 1-2 days used in some global models. The conversion time scale is substantially longer during night. Most POA and BC particles emitted during evening hours likely remain non-hygroscopic until efficiently internally mixed with secondary species in the next morning. The results also suggest that the assumed mixing state strongly impacts calculated N CCN only when POA and BC represent a large fraction of the total aerosol volume. One of the implications is that while physically unrealistic, external mixtures, which are used in many global models, may also sufficiently predict N CCN for aged aerosol, as the contribution of nonhygroscopic POA and BC to overall aerosol volume is often substantially reduced due to the condensation of secondary species.

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“…In 2003, as part of the MCMA-2003 campaign (Molina et al, 2007), a mobile laboratory was deployed at various locations around the city. Filter samples were evaluated with electron microscopy and aerosol mass spectrometry (Johnson et al, 2005) and eBC was derived from an aethalometer, a filter-based instrument like the PSAP (Jiang et al, 2005). Marley et al (2007) also made measurements of eBC during MCMA-2003 with an aethalometer and compared them with measurements that they had made in 1997.…”

Section: A Retama Et Al: Seasonal and Diurnal Trends In Black Carbomentioning

confidence: 99%

Seasonal and diurnal trends in black carbon properties and co-pollutants in Mexico City

et al. 2015

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Abstract. The Mexico City metropolitan area (MCMA) is a region that continues to grow in population and vehicular traffic as well as being the largest source of short-lived climate pollutants (SLCP) in Latin America. The local city government has made significant progress in controlling some of these pollutants, i.e., ozone (O 3) and carbon monoxide (CO), but particulate matter (PM 2.5 and PM 10 ) and black carbon (BC) have shown a less positive response to mitigation strategies that have been in place for almost 3 decades. For the first time, extended measurements of equivalent black carbon (eBC), derived from light absorption measurements, have been made using a Photoacoustic Extinctiometer (PAX) over a 13 month period from March 2013 through March 2014. The daily trends in workdays (Monday through Saturday) and Sunday eBC, PM 2.5 and the co-pollutants CO, O 3 and NO x are evaluated with respect to the three primary seasons in the MCMA: rainy, cold and dry and warm and dry.The maximum values in all of the particle and gas concentrations were significantly larger (Student's t test, P <0.05) during the dry periods than in the rainy season. The changes from rainy to dry seasons for eBC, PM 2.5 , CO, O 3 and NO x were 8.8 to 13.1 µg m −3 (40 %), 49 to 73 µg m −3 (40 %), 2.5 to 3.8 ppm (40 %), 73 to 100 ppb (30 %) and 144 to 252 ppb (53 %), respectively.The primary factors that lead to these large changes between the wet and dry seasons are the accelerated vertical mixing of boundary layer and free tropospheric air by the formation of clouds that dilutes the concentration of the SLCPs, the decreased actinic flux that reduces the production of ozone by photochemical reactions and the heavy, almost daily rain that removes particulate matter.A significant "weekend effect" was also identified, particularly the decrease in BC due to fewer large transport vehicles that are fueled by diesel, which produces a large fraction of the BC. The other co-pollutant concentrations are also significantly less on weekends except for O 3 that shows no change in maximum values from workdays to Sundays. This lack of change is a result of the balancing effects of lower precursor gases, i.e., VOCs, offset by lower concentrations of NO x , that is an O 3 inhibitor.A comparison of the average maximum value of eBC measured during the 1 year period of the current study, with maximum values measured in shorter field campaigns in 2000 and 2006, shows no significant change in the eBC emissions over a 14 year period. This suggests that new methods may need to be developed that can decrease potentially toxic levels of this particulate pollutant. BackgroundShort-lived climate pollutants (SLCP) are those gases and particles whose atmospheric lifetimes range from less than a day to a few years (Shindell et al., 2012;Bowerman et al., 2013) and exert a positive radiative forcing to the global climate. These pollutants, black carbon (BC), methane (CH 4 ), tropospheric ozone (O 3 ) and selected hydrofluorocarbons (HFCs), also impact the environment and ...

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Processing of soot in an urban environment: case study from the Mexico City Metropolitan Area

Cited by 177 publications

References 72 publications

Organic Emissions from a Wood Stove and a Pellet Stove Before and After Simulated Atmospheric Aging

Organic Emissions from a Wood Stove and a Pellet Stove Before and After Simulated Atmospheric Aging

The importance of aerosol mixing state and size-resolved composition on CCN concentration and the variation of the importance with atmospheric aging of aerosols

Seasonal and diurnal trends in black carbon properties and co-pollutants in Mexico City

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