Ozone Cracking in the Los Angeles Area

1959 ◽  
Vol 32 (4) ◽  
pp. 1134-1142 ◽  
Author(s):  
A. J. Haagen-Smit ◽  
M. F. Brunelle ◽  
J. W. Haagen-Smit
Keyword(s):  
Los Angeles ◽  
Ozone Concentration ◽  
Urban Areas ◽  
Crack Depth ◽  
Outdoor Exposure ◽  
Oxides Of Nitrogen ◽  
Chemical Measurements ◽  
Oxidizing Power ◽  
Large Fluctuations ◽  
The Difference

Abstract Cracking of rubber, due to the presence of ozone, was determined in the Los Angeles area by measuring the number of cracks and the crack depth after exposure of standardized bent rubber strips to the atmosphere. The cracking shows a daily and seasonal variation due to the difference in ozone concentration as well as difference in temperature. Results over a three year test period are presented, as well as a comparison with oxidant and ozone values measured in the same area. The ozone concentration usually reaches a maximum during the day and is highest during the summer months. Its origin has been traced to the action of sunlight on mixtures of organic material and oxides of nitrogen, common air pollutants in urban areas. A comparison with chemical measurements of the oxidizing power of the air shows a similar trend. The rubber test is useful in the correct interpretation of outdoor exposure tests of rubber goods, since it integrates the variable action of ozone due to large fluctuations in its concentration and the reaction rate due to climatological factors. The application of the test to area surveys in air pollution studies is suggested.

THE ROLE OF GAS IN ENVIRONMENTAL CONTROL

1973 ◽  
Vol 13 (1) ◽  
pp. 125
Author(s):  
Hanns F. Hartmann
Keyword(s):  
Air Pollution ◽  
Los Angeles ◽  
Natural Gas ◽  
Pollution Control ◽  
Urban Areas ◽  
Large Scale ◽  
Fossil Fuels ◽  
Environmental Control ◽  
Air Pollution Control ◽  
Oxides Of Nitrogen

The gases comprising the atmosphere are in dynamic balance both with the oceans and the dry land of the continents. The mechanisms which operate to keep the atmospheric content of oxygen, nitrogen, carbon and sulphur constant are now well defined. The capacity of the system to absorb excess gaseous impurities is adequate on a global basis with the exception of carbon dioxide.Air pollution is thus a local problem resulting from the overloading of a particular air space with contaminants. The greater part of air pollution is due to the combustion of fossil fuels. Ease of control and virtual freedom from sulphur give natural gas an advantage over liquid and solid fuels as far as air pollution control is concerned. Oxides of nitrogen are produced when natural gas is burned but in smaller quantities than in the combustion of other fuels. In high capacity industrial gas burners where oxides of nitrogen may be generated in large quantities control is easier and can achieve a lower level of oxides of nitrogen than is the case with other fuels.The large scale use of natural gas to solve the air pollution problems of Pittsburgh, Los Angeles and many other cities is proof of the usefulness of gas in this respect. Specialised applications include use in incinerators and industrial after burners. Advances in removal of impurities from fuels and of air pollutants from products of combustion combined with rising gas prices will in time displace gas from its preeminent position in air pollution control. It is, however, likely to retain its advantage in small installations and in dense urban areas. In public and private transport its use will probably remain limited.While technological developments in the distant future may eventually displace fossil fuels, gas will have a large share of the fuel market until that day comes and will contribute effectively to the control of air pollution.

scholarly journals Reducing secondary organic aerosol formation from gasoline vehicle exhaust

2017 ◽  
Vol 114 (27) ◽  
pp. 6984-6989 ◽  
Author(s):  
Yunliang Zhao ◽  
Rawad Saleh ◽  
Georges Saliba ◽  
Albert A. Presto ◽  
Timothy D. Gordon ◽  
...  
Keyword(s):  
Los Angeles ◽  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Peroxy Radicals ◽  
Oxides Of Nitrogen ◽  
Aerosol Formation ◽  
Vehicle Exhaust ◽  
Gasoline Vehicles

On-road gasoline vehicles are a major source of secondary organic aerosol (SOA) in urban areas. We investigated SOA formation by oxidizing dilute, ambient-level exhaust concentrations from a fleet of on-road gasoline vehicles in a smog chamber. We measured less SOA formation from newer vehicles meeting more stringent emissions standards. This suggests that the natural replacement of older vehicles with newer ones that meet more stringent emissions standards should reduce SOA levels in urban environments. However, SOA production depends on both precursor concentrations (emissions) and atmospheric chemistry (SOA yields). We found a strongly nonlinear relationship between SOA formation and the ratio of nonmethane organic gas to oxides of nitrogen (NOx) (NMOG:NOx), which affects the fate of peroxy radicals. For example, changing the NMOG:NOxfrom 4 to 10 ppbC/ppbNOxincreased the SOA yield from dilute gasoline vehicle exhaust by a factor of 8. We investigated the implications of this relationship for the Los Angeles area. Although organic gas emissions from gasoline vehicles in Los Angeles are expected to fall by almost 80% over the next two decades, we predict no reduction in SOA production from these emissions due to the effects of rising NMOG:NOxon SOA yields. This highlights the importance of integrated emission control policies for NOxand organic gases.

scholarly journals Findings From the Understanding Patterns of Healthy Aging Among Men Who Have Sex With Men Project

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 823-824
Author(s):  
Mark Brennan-Ing ◽  
Michael Plankey ◽  
Deborah Gustafson
Keyword(s):  
Los Angeles ◽  
Urban Areas ◽  
Healthy Aging ◽  
Research Policy ◽  
Disease Risk ◽  
Well Being ◽  
Hiv Status ◽  
Gay Community ◽  
Regulatory Strategies ◽  
Sex With Men

Abstract In 1984, the Multicenter AIDS Cohort Study (MACS) was started to identify factors in the HIV epidemic related to disease risk and treatment progression among gay, bisexual, and other men who have sex with men (MSM) in four urban areas in the US: Baltimore, MD/Washington, D.C.; Chicago, IL; Pittsburgh, PA, and Los Angeles, CA. MACS participants complete biannual study visits involving HIV testing, biometric screenings, and psychosocial data collection. In 2015 a MACS sub-study, the Understanding Patterns of Healthy Aging among MSM Project (HAMSM), was started to better understand resiliencies promoting well-being among MSM age 40 and older, including those with HIV. HAMSM has helped us to understand aging trajectories among MSM, and provides a unique combination of physiological and psychosocial data that can inform efforts to support MSM in healthy aging. This symposium will present emerging findings from the HAMSM study. Our first paper examines the relationships between psychological connection to the gay community (PSOC) and developmental regulatory strategies associated with health behaviors and more positive self-appraisals. The second paper examines how PSOC is related to HIV risk reduction behaviors, and if there are differences in such behaviors based on HIV status. Our third paper considers how self-perceptions of aging (age discrepancy, aging satisfaction) are related to frailty and frailty transitions, and if these relationships differ by HIV status. The final paper examines the relationship of social support to frailty among MSM by HIV status. Implications of these findings for research, policy, and programs targeting MSM will be discussed.

Toward CO2 and CH4 measurements by ground-based observations of surface-scattered sunlight

2021 ◽  
Author(s):  
Benedikt Hemmer ◽  
Christin Proß ◽  
Stanley P. Sander ◽  
Thomas J. Pongetti ◽  
Zhao-Cheng Zeng ◽  
...  
Keyword(s):  
Los Angeles ◽  
Urban Areas ◽  
Near Infrared ◽  
Chem Phys ◽  
Retrieval Algorithm ◽  
Los Angeles Basin ◽  
Satellite Measurements ◽  
Precise Knowledge ◽  
Extended Sources

<div> <div>Precise knowledge of sources and sinks in the carbon cycle is desired to understand its sensitivity to climate change and to account and verify man-made emissions. In this context, extended sources like urban areas play an important role. While in-situ measurements of carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) are highly accurate but localized, satellites measure column-integrated concentrations over an extended footprint. The CLARS-FTS [1, 2] stationed at the Mt. Wilson observatory looking downward into the Los Angeles basin has pioneered an innovative measurement technique that fills the sensitivity gap between in-situ and satellite measurements. The technique enables mapping the urban greenhouse gas concentration fields by collecting spectra of ground scattered sunlight and scanning through the region.</div> <div> </div> <div>Here, we report on progress developing a portable setup for a CLARS-FTS-like measurement geometry. The instrument is based on the EM27/SUN FTS with a modified pointing technique and a more sensitive detector. The retrieval algorithm is based on the RemoTeC software, previously employed for solar backscatter satellite measurements. We discuss first steps in terms of instrument performance and retrieval exercises. For the latter, we have carried out simulations on how the neglect of scattering by the retrieval affects the retrieved boundary layer concentrations of CO<sub>2</sub> and CH<sub>4</sub> for an ensemble of hypothetical scenes with variable complexity in aeorsol loadings and viewing geometry. We also report on a test to apply RemoTeC to a small set of CLARS-FTS spectra collected throughout the Los Angeles basin.</div> <div> </div> <div><em>References</em></div> <div>[1] Fu, D. et al., 2014: Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site, Atmos. Meas. Tech., 7, 713–729, https://doi.org/10.5194/amt-7-713-2014</div> [2] Wong, K. W. et al., 2015: Mapping CH4 : CO2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California, Atmos. Chem. Phys., 15, 241–252, https://doi.org/10.5194/acp-15-241-2015</div>

scholarly journals Household accessibility to heat refuges: Residential air conditioning, public cooled space, and walkability

2016 ◽  
Vol 44 (6) ◽  
pp. 1036-1055 ◽  
Author(s):  
Andrew M Fraser ◽  
Mikhail V Chester ◽  
David Eisenman ◽  
David M Hondula ◽  
Stephanie S Pincetl ◽  
...  
Keyword(s):  
Los Angeles ◽  
Public Space ◽  
Urban Areas ◽  
Air Conditioning ◽  
Regional Climate ◽  
Heat Exposure ◽  
Household Level ◽  
Private And Public ◽  
Residential Air Conditioning ◽  
Walking Speeds

Access to air conditioned space is critical for protecting urban populations from the adverse effects of heat exposure. Yet there remains fairly limited knowledge of the penetration of private (home air conditioning) and distribution of public (cooling centers and commercial space) cooled space across cities. Furthermore, the deployment of government-sponsored cooling centers is likely to be inadequately informed with respect to the location of existing cooling resources (residential air conditioning and air conditioned public space), raising questions of the equitability of access to heat refuges. We explore the distribution of private and public cooling resources and access inequities at the household level in two major US urban areas: Los Angeles County, California and Maricopa County, Arizona (whose county seat is Phoenix). We evaluate the presence of in-home air conditioning and develop a walking-based accessibility measure to air conditioned public space using a combined cumulative opportunities-gravity approach. We find significant variations in the distribution of residential air conditioning across both regions which are largely attributable to building age and inter/intra-regional climate differences. There are also regional disparities in walkable access to public cooled space. At average walking speeds, we find that official cooling centers are only accessible to a small fraction of households (3% in Los Angeles, 2% in Maricopa) while a significantly higher number of households (80% in Los Angeles, 39% in Maricopa) have access to at least one other type of public cooling resource such as a library or commercial establishment. Aggregated to a neighborhood level, we find that there are areas within each region where access to cooled space (either public or private) is limited which may increase heat-related health risks.

scholarly journals Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

2010 ◽  
Vol 10 (23) ◽  
pp. 11385-11399 ◽  
Author(s):  
N. Hudda ◽  
K. Cheung ◽  
K. F. Moore ◽  
C. Sioutas
Keyword(s):  
Los Angeles ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Urban Areas ◽  
Particle Number ◽  
Meteorological Conditions ◽  
Monitoring Station ◽  
Size Distributions ◽  
Central Monitoring ◽  
Seasonal And Diurnal Variations

Abstract. Ultrafine Particles (UFP) can display sharp gradients in their number concentrations in urban environment due to their transient nature and rapid atmospheric processing. The ability of using air pollution data generated at a central monitoring station to assess exposure relies on our understanding of the spatial variability of a specific pollutant associated with a region. High spatial variation in the concentrations of air pollutants has been reported at scales of 10s of km for areas affected by primary emissions. Spatial variability in particle number concentrations (PNC) and size distributions needs to be investigated, as the representativeness of a monitoring station in a region is premised on the assumption of homogeneity in both of these metrics. This study was conducted at six sites, one in downtown Los Angeles and five located about 40–115 km downwind in the receptor areas of Los Angeles air basin. PNC and size distribution were measured using Condensation Particle Counters (CPC) and Scanning Mobility Particle Sizer (SMPS). The seasonal and diurnal variations of PNC implied that PNC might vary significantly with meteorological conditions, even though the general patterns at the sites may remain generally similar across the year due to consistency of sources around them. Regionally transported particulate matter (PM) from upwind urban areas of Los Angeles lowered spatial variation by acting as a "homogenizing" factor during favorable meteorological conditions. Spatial variability also increased during hours of the day during which the effects of local sources predominate. The spatial variability associated with PNC (quantified using Coefficients of Divergence, CODs), averaged about 0.3, which was generally lower than that based on specific size ranges. Results showed an inverse relationship of COD with particles size, with fairly uniform values in the particle range which is associated with regional transport. Our results suggest that spatial variability, even in the receptor regions of Los Angeles Basin, should be assessed for both PNC and size distributions, and should be interpreted in context of seasonal and diurnal influences, and suitably factored if values for exposure are ascertained using a central monitoring station.

scholarly journals Differential Column Measurements Using Compact Solar-Tracking Spectrometers

2016 ◽  
Author(s):  
Jia Chen ◽  
Camille Viatte ◽  
Jacob K. Hedelius ◽  
Taylor Jones ◽  
Jonathan E. Franklin ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Los Angeles ◽  
Urban Areas ◽  
Integration Time ◽  
Small Scale ◽  
Los Angeles Basin ◽  
Solar Tracking ◽  
Regional Sources ◽  
New Applications ◽  
Atmospheric Phenomena

Abstract. We demonstrate the use of compact solar-tracking Fourier transform spectrometers (Bruker EM27/SUN) for differential measurements of the column-averaged dry-air mole fractions of CH4 and CO2 within urban areas. Using Allan variance analysis, we show that the differential column measurement has a precision of 0.1 ‰ for XCO2 and XCH4 using an optimum integration time of 10 min, which corresponds to standard deviations of 0.04 ppm, and 0.2 ppb, respectively. The sensor system is very stable over time and after relocation across the continent. We report tests of the differential column measurement, and its sensitivity to emission sources, by measuring the downwind minus upwind column gradient ΔXCH4 across dairy farms in the Chino California area and using the data to verify emissions reported in the literature. Spatial column gradient ratios ΔXCH4/ΔXCO2 were observed across Pasadena within the Los Angeles basin, indicating values consistent with regional emission ratios from the literature. Our precise, rapid measurements allow us to determine significant short-term variations (5–10 minutes) of ΔXCO2 and ΔXCH4, and to show that they represent atmospheric phenomena. Overall, this study helps establish a range of new applications for compact solar-viewing Fourier transform spectrometers. By accurately measuring the small differences in integrated column amounts across local and regional sources, we directly observe the mass loading of the atmosphere due to the influence of emissions in the intervening locale. The inference of the source strength is much more direct than inversion modeling using only surface concentrations, and less subject to errors associated with small-scale transport phenomena.

scholarly journals Environmental Risk Assessment of Vehicle Exhaust Particles on Aquatic Organisms of Different Trophic Levels

Toxics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 261
Author(s):  
Konstantin Pikula ◽  
Mariya Tretyakova ◽  
Alexander Zakharenko ◽  
Seyed Ali Johari ◽  
Sergey Ugay ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Sea Urchin ◽  
Urban Areas ◽  
Aquatic Organisms ◽  
Artemia Salina ◽  
Trophic Levels ◽  
Submicron Particles ◽  
Vehicle Exhaust ◽  
Exhaust Particles ◽  
The Difference

Vehicle emission particles (VEPs) represent a significant part of air pollution in urban areas. However, the toxicity of this category of particles in different aquatic organisms is still unexplored. This work aimed to extend the understanding of the toxicity of the vehicle exhaust particles in two species of marine diatomic microalgae, the planktonic crustacean Artemia salina, and the sea urchin Strongylocentrotus intermedius. These aquatic species were applied for the first time in the risk assessment of VEPs. Our results demonstrated that the samples obtained from diesel-powered vehicles completely prevented egg fertilization of the sea urchin S. intermedius and caused pronounced membrane depolarization in the cells of both tested microalgae species at concentrations between 10 and 100 mg/L. The sample with the highest proportion of submicron particles and the highest content of polycyclic aromatic hydrocarbons (PAHs) had the highest growth rate inhibition in both microalgae species and caused high toxicity to the crustacean. The toxicity level of the other samples varied among the species. We can conclude that metal content and the difference in the concentrations of PAHs by itself did not directly reflect the toxic level of VEPs, but the combination of both a high number of submicron particles and high PAH concentrations had the highest toxic effect on all the tested species.

scholarly journals Characteristics of PM<sub>2.5</sub> speciation in representative megacities and across China

2011 ◽  
Vol 11 (1) ◽  
pp. 1025-1051 ◽  
Author(s):  
F. Yang ◽  
J. Tan ◽  
Q. Zhao ◽  
Z. Du ◽  
K. He ◽  
...  
Keyword(s):  
Los Angeles ◽  
Atmospheric Pollution ◽  
Urban Areas ◽  
Fine Particles ◽  
Chemical Species ◽  
Northern Region ◽  
Eastern Region ◽  
Mobile Source ◽  
Combustion Source ◽  
Geographical Regions

Abstract. Based on PM2.5 chemical database from literature and our observations, chemical species and reconstructed speciation of PM2.5 in several representative Chinese megacities and across China were compared to draw insights into the characteristics of PM2.5 speciation. PM2.5 mass and speciation varied substantially over geographical regions in China. Near six-fold variations in average PM2.5 concentrations (34.0–193.4 μg m−3) across China were found with high PM2.5 levels (>100 μg m−3) appearing along northern region and in western urban areas. At both urban and rural sites in eastern region, sum of sulfate, nitrate, and ammonia (SNA) typically constituted 40–57% of PM2.5 mass, indicative of the regional characteristics of fine particulate pollution and more intensive "complex atmospheric pollution" compared to western region. Particulate organic matter (POM) had constant and significant contribution to PM2.5 mass. POM plus SNA accounted for 62–90% of PM2.5 mass at most of the sites. PM2.5 speciation in China was also characterized by high content of mineral dust. In four representative megacities (i.e. Beijing, Chongqing, Shanghai, and Guangzhou) with substantially higher levels of all the species except that NO3−, NH4+, and EC in PM2.5 than those in Los Angeles, distinct differences in nitrate and sulfate levels and their mass ratio [NO3−]/[SO42−] imply that mobile source is likely more important than stationary (coal combustion) source in Guangzhou whereas in Chongqing the situation is contrary. The observed intra-city variations in PM2.5 mass and speciation indicate that local emissions and regional transportation both contributed significantly to high fine particles levels in Beijing, while local contribution likely played a predominant role in Chongqing. During the ten-year period from 1999 through 2008 in urban Beijing, both SNA and [NO3−]/[SO42−] exhibited steadily increasing trends, implying that the characteristic of "complex atmospheric pollution" and the contribution from mobile sources were both being enhanced.

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