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Contributions of coastal megacities to environmental changes at regional and global scales
Published in Mark Pelling, Sophie Blackburn, Megacities and the Coast, 2014
The scale at which pollutants have an effect extends from local (human health, building materials, ecosystem) to regional (acidification, euthrophication) to global (atmospheric composition, climate change). The impacts of megacities vary in space and time as a function of the prevailing winds. The mean transport distance for most megacities (from source location to pollution plume centre) for black carbon and other primary fine PM is of the order of 100–200 kilometres (MegaPoli, 2011). Whereas secondary PM species can be transported much further with sulphate and secondary organic aerosol often over 400 kilometres on average. Maximum transport distances are significantly higher, with secondary particulate matter impacts reaching as far as 2, 000 kilometres away. As one example the Boston-New York-Washington region has a relatively weak influence on the European atmosphere. To date no significant above-average concentration event has been observed associated with pollution coming from there (Eckhardt et al., 2011). The range of megacities’ effect on regional air quality may be limited by orography; e.g. Po Valley, one of the most polluted areas in Europe, rarely impacts air quality outside the confined north Italy region. The location and surrounding topography of the coastal megacities relative to predominant synoptic conditions impact the region that is influenced. For example, Los Angeles with mountains to the west has a large amount of recirculation back onto the urban area itself.
Mutagenicity of Inhalable Particulate Matter at Four Sites in New Jersey
Published in Paul J. Lioy, Joan M. Daisey, Toxic Air Pollution, 1987
Judith B. Louis, Thomas B. Atherholt, Joan M. Daisey, Leslie J. McGeorge, Gerard J. McGarrity
Formation of secondary organic aerosol, via photochemical oxidation of gaseous precursors and gas-to-particle conversion, has long been of concern in the Los Angeles area. During the Summer 1981 ATEOS campaign, there is evidence of secondary organic aerosol formation at all four sites during air pollution episodes characterized by high concentrations of particulate matter, sulfate, and ozone. Secondary organic aerosol was estimated to have increased ambient levels of polar (ACE) particulate organic matter by 15 to 36% (Daisey et al., 1984). Because the mutagenic activity of this additional secondary organic aerosol was of interest, the activity of ACE fractions collected during an extended episode of photochemical smog was compared to that of composites of nonepisode days. This extended episode period in Summer 1982 was selected on the basis of three criteria which distinguished such periods during the earlier Summer 1981 study: (1) elevated concentrations of IPM, FPM, sulfate, ozone, and EOM, (2) higher proportions of polar (ACE) organics in the total EOM (ACE greater than 60% of EOM), and (3) stagnation conditions.
Particle/Gas Distribution of Semivolatile Organic Compounds: Field and Laboratory Experiments with Filtration Samplers
Published in Douglas A. Lane, Gas and Particle Phase Measurements of Atmospheric Organic Compounds, 2020
Terry F. Bidleman, Renee L. Falconer, Tom Harner
In Equation (9), fom is the fraction of the particle mass that consists of absorbing organic matter having molecular weight M(g/mol). A substantial portion of this organic matter may be “secondary organic aerosol”, which is formed by oxidation of hydrocarbons and is therefore polar [72]. The combined relationship for both adsorption and absorption is: Kp=(1/pLo){RTNsAtspexp[(Qd−Qv)/RT]}+10−6RTfom/Momγom
Wildfire and prescribed burning impacts on air quality in the United States
Published in Journal of the Air & Waste Management Association, 2020
Daniel A. Jaffe, Susan M. O’Neill, Narasimhan K. Larkin, Amara L. Holder, David L. Peterson, Jessica E. Halofsky, Ana G. Rappold
Once released, organic aerosol can lose mass, through evaporation or volatilization, or gain mass, through formation of secondary organic aerosol (SOA). SOA formation occurs due to oxidation of VOCs. Oxidation adds organic functional groups, which lowers the vapor pressure of the compounds, or it can cleave C-C bonds, which can increase the vapor pressure of the existing aerosol compounds (Kroll et al. 2009). SOA production from biomass burning aerosols can also occur in the aqueous phase, when aerosols deliquesce or are associated with fog, although a clear mechanistic understanding is presently lacking (Gilardoni et al. 2016). As the aerosol moves with a smoke plume, we can monitor the enhancement ratio (ER) as ΔX/ΔCO to identify physical or chemical production or loss of components (e.g., ΔX). CO is typically used in the denominator of this ratio, because CO concentrations are strongly enhanced in the smoke plume compared to background concentrations, and CO undergoes only slow loss by reaction with OH (the CO lifetime with respect to loss is ~2 weeks). Thus, CO can act as a relatively inert indicator for dilution. For plumes with no production or loss of component X, dilution affects both compounds similarly, and the enhancement ratio remains constant.
Complex refractive index, single scattering albedo, and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors
Published in Aerosol Science and Technology, 2019
Justin H. Dingle, Stephen Zimmerman, Alexander L. Frie, Justin Min, Heejung Jung, Roya Bahreini
The Intergovernmental Panel on Climate Change (IPCC) (Myhre et al. 2013) reported that the most significant sources of uncertainty in the total estimated anthropogenic radiative forcing are due to aerosol direct and indirect interactions with solar radiation. In the most recent IPCC report (Myhre et al. 2013), the average global climate forcing for direct and indirect aerosol effects were estimated to be −0.35 Wm−2 (−0.85 to +0.15 Wm−2) and −0.45 (−1.2 to 0.0) Wm−2, respectively. Sub-micron aerosols, those that are longest lived and most important for radiative forcing, are mainly comprised of organic aerosols (OA). It is estimated that 70–90% of OA is secondary organic aerosols (SOA) (Hallquist et al. 2009). SOA particles are produced from chemical reactions of volatile and semi-volatile organic species in the atmosphere, leading to compounds with a lower vapor pressure that partition to the particle phase (Hallquist et al. 2009; Volkamer et al. 2006). Prevalence of oxygenated organic aerosol, representing SOA particles, has been observed in urban centers, downwind of urban sites, and at remote locations (Zhang et al. 2007). Typically, OA efficiently scatters light in the visible range and has negative direct radiative forcing values.
Computational simulation of the dynamics of secondary organic aerosol formation in an environmental chamber
Published in Aerosol Science and Technology, 2018
A. M. Sunol, S. M. Charan, J. H. Seinfeld
Understanding the chemical mechanisms by which volatile organic compounds (VOCs) are oxidized to low volatility products and secondary organic aerosol (SOA) is a major area of atmospheric chemistry research. The principal source of data on mechanisms of SOA formation is derived from laboratory chamber experiments, in which VOCs are caused to undergo oxidation, most frequently by the hydroxyl (OH) radical, to generate the low volatility products that condense into the particle phase (Schwantes et al. 2017). The SOA yield (Y) is determined as the ratio of the mass of organic aerosol formed to the mass of VOC reacted. To promote condensation of VOC oxidation products into the aerosol phase in the chamber, inert seed particles are customarily introduced to serve as sites for vapor condensation. Inevitably, the laboratory chamber contains walls, and interactions of vapors and particles with chamber walls must be accounted for in interpretation of data. For example, VOC oxidation products can condense onto growing aerosol or deposit onto the chamber wall, and even in the presence of seed aerosol, low volatility oxidation products may accumulate to a level at which they nucleate to form aerosol if the rate of generation of such products is sufficiently rapid to overcome the condensation sink. If an appreciable fraction of the VOC oxidation products deposits on the wall, then the SOA yield derived from the chamber data will be understated, perhaps significantly so. When such data are translated to the atmosphere, SOA yields would be correspondingly understated.