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Factors Affecting the Association between Ambient Concentrations and Personal Exposures to Particles and Gases

Sarnat, Stefanie Ebelt; Coull, Brent A.; Schwartz, Joel; Gold, Diane R.; Suh, Helen H.
Fonte: National Institute of Environmental Health Sciences Publicador: National Institute of Environmental Health Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.42%
Results from air pollution exposure assessment studies suggest that ambient fine particles [particulate matter with aerodynamic diameter ≤ 2.5 μg (PM2.5)], but not ambient gases, are strong proxies of corresponding personal exposures. For particles, the strength of the personal–ambient association can differ by particle component and level of home ventilation. For gases, however, such as ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2), the impact of home ventilation on personal–ambient associations is untested. We measured 24-hr personal exposures and corresponding ambient concentrations to PM2.5, sulfate (SO42−), elemental carbon, O3, NO2, and SO2 for 10 nonsmoking older adults in Steubenville, Ohio. We found strong associations between ambient particle concentrations and corresponding personal exposures. In contrast, although significant, most associations between ambient gases and their corresponding exposures had low slopes and R2 values; the personal–ambient NO2 association in the fall season was moderate. For both particles and gases, personal–ambient associations were highest for individuals spending most of their time in high- compared with low-ventilated environments. Cross-pollutant models indicated that ambient particle concentrations were much better surrogates for exposure to particles than to gases. With the exception of ambient NO2 in the fall...

Long-term concentrations of ambient air pollutants and incident lung cancer in California adults: results from the AHSMOG study.Adventist Health Study on Smog.

Beeson, W L; Abbey, D E; Knutsen, S F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1998 EN
Relevância na Pesquisa
36.25%
The purpose of this study was to evaluate the relationship of long-term concentrations of ambient air pollutants and risk of incident lung cancer in nonsmoking California adults. A cohort study of 6,338 nonsmoking, non-Hispanic, white Californian adults, ages 27-95, was followed from 1977 to 1992 for newly diagnosed cancers. Monthly ambient air pollution data were interpolated to zip code centroids according to home and work location histories, cumulated, and then averaged over time. The increased relative risk (RR) of incident lung cancer in males associated with an interquartile range (IQR) increase in 100 ppb ozone (O3) was 3.56 [95% confidence interval (CI), 1.35-9.42]. Incident lung cancer in males was also positively associated with IQR increases for mean concentrations of particulate matter <10 microm (PM10; RR = 5.21; CI, 1.94-13.99) and SO2 (RR = 2.66; CI, 1.62-4.39). For females, incident lung cancer was positively associated with IQR increases for SO2 (RR = 2.14; CI, 1.36-3.37) and IQR increases for PM10 exceedance frequencies of 50 microg/m3 (RR = 1.21; CI, 0.55-2.66) and 60 microg/m3 (RR = 1.25; CI, 0.57-2.71). Increased risks of incident lung cancer were associated with elevated long-term ambient concentrations of PM10 and SO2 in both genders and with O3 in males. The gender differences for the O3 and PM10 results appeared to be partially due to gender differences in exposure.

Response of macaque bronchiolar epithelium to ambient concentrations of ozone.

Harkema, J. R.; Plopper, C. G.; Hyde, D. M.; St George, J. A.; Wilson, D. W.; Dungworth, D. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1993 EN
Relevância na Pesquisa
46.33%
Recently, we reported that exposure to ambient concentrations of ozone, near the U.S. National Ambient Air Quality Standard (0.12 ppm), induced significant nasal epithelial lesions in a non-human primate, the bonnet monkey. The present study defines the effects of ambient concentrations of ozone on the surface epithelium lining respiratory bronchioles and on the underlying bronchiolar interstitium in these same monkeys. Bonnet monkeys were exposed to filtered air or to 0.15 or 0.30 ppm ozone 8 hours/day for 6 or 90 days. At the end of exposures, monkeys were anesthetized and killed by exsanguination. Microdissected bronchiolar airways of infusion-fixed lungs were evaluated morphometrically by light microscopy and quantitatively by scanning and transmission electron microscopy for ozone-induced epithelial changes. Hyperplasia of nonciliated, cuboidal epithelial cells and intraluminal accumulation of macrophages characterized ozone-induced lesions in respiratory bronchioles. There were no significant differences in epithelial thickness or cell numbers among ozone-exposed groups. Ozone-exposed epithelium was composed of 80% cuboidal and 20% squamous cells compared with 40% cuboidal and 60% squamous cells in filtered air controls. In addition...

A Community Woodstove Changeout and Impact on Ambient Concentrations of Polycyclic Aromatic Hydrocarbons and Phenolics

Ward, Tony J.; Palmer, Christopher P.; Houck, James E.; Navidi, William C.; Geinitz, Steve; Noonan, Curtis W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/07/2009 EN
Relevância na Pesquisa
46.1%
A large woodstove changeout program was carried out in Libby, Montana with the goal of reducing ambient levels of PM2.5. This provided researchers the opportunity to measure ambient concentrations of phenolic and Polycyclic Aromatic Hydrocarbons (PAHs) before, during, and after the changeout of nearly 1,200 stoves to evaluate the effectiveness of the intervention. Starting in the heating season of 2004/2005 and ending in heating season 2007/2008, 19 compounds were measured every three days using a hivol polyurethane foam (PUF) sampler, followed by Gas Chromatography / Mass Spectrometry analysis.

Modeling of Personal Exposures to Ambient Air Toxics in Camden, New Jersey: An Evaluation Study

Wang, Sheng-Wei; Tang, Xiaogang; Fan, Zhi-Hua (Tina); Wu, Xiangmei; Lioy, Paul J.; Georgopoulos, Panos G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/2009 EN
Relevância na Pesquisa
36.42%
This study presents the Individual Based Exposure Modeling (IBEM) application of MENTOR (Modeling ENvironment for TOtal Risk studies) in a hot spot area, where there are concentrated local sources on the scale of tens to hundreds of meters, and an urban reference area in Camden, NJ, to characterize the ambient concentrations and personal exposures to benzene and toluene from local ambient sources. The emission-based ambient concentrations in the two neighborhoods were first estimated through atmospheric dispersion modeling. Subsequently, the calculated and measured ambient concentrations of benzene and toluene were separately combined with the time-activity diaries completed by the subjects as inputs to MENTOR/IBEM for estimating personal exposures resulting from ambient sources. The modeling results were then compared with the actual personal measurements collected from over 100 individuals in the field study to identify the gaps in modeling personal exposures in a hot spot. The modeled ambient concentrations of benzene and toluene were generally in agreement with the neighborhood measurements within a factor of 2, but were underestimated at the high-end percentiles. The major local contributors to the benzene ambient levels are from mobile sources...

Ambient Site, Home Outdoor and Home Indoor Particulate Concentrations as Proxies of Personal Exposures

Brown, Kathleen Ward; Suh, Helen H.; Sarnat, Jeremy A.; Coull, Brent A; Spengler, John D.; Koutrakis, Petros
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.48%
Despite strong longitudinal associations between particle personal exposures and ambient concentrations, previous studies have found considerable inter-personal variability in these associations. Factors contributing to this inter-personal variability are important to identify in order to improve our ability to assess particulate exposures for individuals. This paper examines whether ambient, home outdoor and home indoor particle concentrations can be used as proxies of corresponding personal exposures. We explore the strength of the associations between personal, home indoor, home outdoor and ambient concentrations of sulfate, fine particle mass (PM2.5) and elemental carbon (EC) by season and subject for 25 individuals living in the Boston, MA, USA area. Ambient sulfate concentrations accounted for approximately 70 to 80% of the variability in personal and indoor sulfate levels. Correlations between ambient and personal sulfate, however, varied by subject (0.1 – 1.0), with associations between personal and outdoor sulfate concentrations generally mirroring personal-ambient associations (median subject-specific correlations of 0.8 to 0.9). Ambient sulfate concentrations are good indicators of personal exposures for individuals living in the Boston area...

Ambient concentrations and personal exposure to polycyclic aromatic hydrocarbons (PAH) in an urban community with mixed sources of air pollution

ZHU, XIANLEI; FAN, ZHIHUA (TINA); WU, XIANGMEI; JUNG, KYUNG HWA; OHMAN-STRICKLAND, PAMELA; BONANNO, LINDA J.; LIOY, PAUL J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.33%
Assessment of the health risks resulting from exposure to ambient polycyclic aromatic hydrocarbons (PAH) is limited by a lack of environmental exposure data among the general population. This study characterized personal exposure and ambient concentrations of PAH in the Village of Waterfront South (WFS), an urban community with many mixed sources of air toxics in Camden, New Jersey, and CopeWood/Davis Streets (CDS), an urban reference area located ~1 mile east of WFS. A total of 54 and 53 participants were recruited from non-smoking households in WFS and CDS, respectively. In all, 24-h personal and ambient air samples were collected simultaneously in both areas on weekdays and weekends during summer and winter. The ambient PAH concentrations in WFS were either significantly higher than or comparable to those in CDS, indicating the significant impact of local sources on PAH pollution in WFS. Analysis of diagnostic ratios and correlation suggested that diesel truck traffic, municipal waste combustion and industrial combustion were the major sources in WFS. In such an area, ambient air pollution contributed significantly to personal PAH exposure, explaining 44–96% of variability in personal concentrations. This study provides valuable data for examining the impact of local ambient PAH pollution on personal exposure and therefore potential health risks associated with environmental PAH pollution.

Occurrence and Concentrations of Toxic VOCs in the Ambient Air of Gumi, an Electronics-Industrial City in Korea

Baek, Sung-Ok; Suvarapu, Lakshmi Narayana; Seo, Young-Kyo
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 05/08/2015 EN
Relevância na Pesquisa
36.34%
This study was carried out to characterize the occurrence and concentrations of a variety of volatile organic compounds (VOCs) including aliphatic, aromatic, halogenated, nitrogenous, and carbonyl compounds, in the ambient air of Gumi City, where a large number of electronics industries are found. Two field monitoring campaigns were conducted for a one year period in 2003/2004 and 2010/2011 at several sampling sites in the city, representing industrial, residential and commercial areas. More than 80 individual compounds were determined in this study, and important compounds were then identified according to their abundance, ubiquity and toxicity. The monitoring data revealed toluene, trichloroethylene and acetaldehyde to be the most significant air toxics in the city, and their major sources were mainly industrial activities. On the other hand, there was no clear evidence of an industrial impact on the concentrations of benzene and formaldehyde in the ambient air of the city. Overall, seasonal variations were not as distinct as locational variations in the VOCs concentrations, whereas the within-day variations showed a typical pattern of urban air pollution, i.e., increase in the morning, decrease in the afternoon, and an increase again in the evening. Considerable decreases in the concentrations of VOCs from 2003 to 2011 were observed. The reductions in the ambient concentrations were confirmed further by the Korean PRTR data in industrial emissions within the city. Significant decreases in the concentrations of benzene and acetaldehyde were also noted...

Factors Affecting the Association between Ambient Concentrations and Personal Exposures to Particles and Gases

Sarnat, Stefanie Ebelt; Coull, Brent Andrew; Schwartz, Joel David; Gold, Diane R.; Suh MacIntosh, Helen H.
Fonte: National Institute of Environmental Health Sciences Publicador: National Institute of Environmental Health Sciences
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
56.43%
Results from air pollution exposure assessment studies suggest that ambient fine particles [particulate matter with aerodynamic diameter ≤ 2.5 μg (PM2.5)], but not ambient gases, are strong proxies of corresponding personal exposures. For particles, the strength of the personal–ambient association can differ by particle component and level of home ventilation. For gases, however, such as ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2), the impact of home ventilation on personal–ambient associations is untested. We measured 24-hr personal exposures and corresponding ambient concentrations to PM2.5, sulfate (SO42−), elemental carbon, O3, NO2, and SO2 for 10 nonsmoking older adults in Steubenville, Ohio. We found strong associations between ambient particle concentrations and corresponding personal exposures. In contrast, although significant, most associations between ambient gases and their corresponding exposures had low slopes and R2 values; the personal–ambient NO2 association in the fall season was moderate. For both particles and gases, personal–ambient associations were highest for individuals spending most of their time in high- compared with low-ventilated environments. Cross-pollutant models indicated that ambient particle concentrations were much better surrogates for exposure to particles than to gases. With the exception of ambient NO2 in the fall...

The Relationship Between Ambient Air Pollution and Heart Rate Variability Differs for Individuals with Heart and Pulmonary Disease

Wheeler, Amanda; Zanobetti, Antonella; Gold, Diane R.; Schwartz, Joel David; Stone, Peter Howard; Suh MacIntosh, Helen H.
Fonte: National Institute of Environmental Health Sciences Publicador: National Institute of Environmental Health Sciences
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.28%
Associations between concentrations of ambient fine particles [particulate matter < 2.5 μm aerodynamic diameter (PM(_{2.5}))] and heart rate variability (HRV) have differed by study population. We examined the effects of ambient pollution on HRV for 18 individuals with chronic obstructive pulmonary disease (COPD) and 12 individuals with recent myocardial infarction (MI) living in Atlanta, Georgia. HRV, baseline pulmonary function, and medication data were collected for each participant on 7 days in fall 1999 and/or spring 2000. Hourly ambient pollution concentrations were obtained from monitoring sites in Atlanta. The association between ambient pollution and HRV was examined using linear mixed-effect models. Ambient pollution had opposing effects on HRV in our COPD and MI participants, resulting in no significant effect of ambient pollution on HRV in the entire population for 1-, 4-, or 24-hr moving averages. For individuals with COPD, interquartile range (IQR) increases in 4-hr ambient PM(_{2.5}) (11.65 μg/m(^3)) and nitrogen dioxide (11.97 ppb) were associated with 8.3% [95% confidence interval (CI), 1.7–15.3%] and 7.7% (95% CI, 0.1–15.9%) increase in the SD of normal R-R intervals (SDNN), respectively. For individuals with MI...

Integrated Air Pollution Management in China : Developing Particulate Matter Control

World Bank
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
36.35%
This study is a joint effort of the Ministry of Environmental Protection (MEP), Chinese experts, and the World Bank to inform the policy-making process in line with the government of China s medium- and long-term objectives. Specifically the study aims to assist MEP, provincial governments, and municipalities by: (1) Proposing a national PM10 compliance plan to help non-compliant cities attain grade II - preferably by 2015 or in certain cases by 2020 at the latest - and already compliant cities to further reduce PM concentrations. The plan would include (a) policies and regulations and associated physical interventions/measures; (b) geographical scope; (c) sequencing of interventions; and (d) feasible environmental investments likely to have high benefit/cost ratios. (2) recommending a PM2.5 monitoring system and related data applications.

Breathing Clean : Considering the Switch to Natural Gas Buses

Kojima, Masami
Fonte: Washington, DC: World Bank Publicador: Washington, DC: World Bank
EN_US
Relevância na Pesquisa
46.25%
In response to emerging epidemiological evidence of the toxicity of diesel vehicular emissions, there is growing interest in substituting conventional diesel with much cleaner natural gas in cities where ambient concentrations of particulate matter are markedly higher than what is internationally considered acceptable. This paper compares the performance of natural gas and conventional diesel buses, and outlines the barriers to the adoption of natural gas buses in developing countries. In the absence of emissions standards that effectively require natural gas, natural gas-fueled buses are unlikely to be adopted because they are more expensive to operate relative to diesel buses. The social case for replacing diesel with natural gas a fuel for buses rests on environmental grounds. If a local government decides that the reduction in air pollution associated with the substitution of conventional diesel with natural gas for use in buses is worth the cost, then it needs to adopt policies to encourage the switch to natural gas. These might include emissions standards for buses...

Pakistan Clean Fuels

World Bank
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
46.16%
In the context of the Pakistan Clean Fuels Program, and subsequent workshops, the study reviews the proposed timetable for phasing lead out of gasoline, increasing the average of gasoline octane, and reducing sulfur in diesel, and fuel oil. Within South Asia, Pakistan remains one of the countries using leaded gasoline widely, and, given the extensive epidemiological evidence concerning the adverse impact of lead on public health, lead elimination is the highest priority for fuel quality improvement, in addition to the pollutant concern of high ambient concentrations of fine particles. Also examined is the aspect of particulate emissions: higher contribution by diesel vehicles to particulate emissions, a factor aggravated by the much lower pricing policy of diesel. Workshops findings suggest that incremental costs of reducing sulfur in diesel is low, compared to the cost of reducing sulfur in fuel oil which is substantial, arguing for an accelerated switch from fuel oil to natural gas. Conversely, the incremental cost of eliminating lead in gasoline...

Toward Cleaner Urban Air in South Asia: Tackling Transport Pollution, Understanding Sources

World Bank
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
EN_US
Relevância na Pesquisa
36.28%
This ESMAP study was undertaken to provide technical input to support the region-wide process of developing and adopting cost-effective and realistic policies and efficient enforcement mechanisms to reverse the deteriorating trend in urban air quality in South Asia. It focused mainly on fine particulate matter, estimated to account for most premature mortality and illnesses caused by outdoor air pollution. Through stakeholder feedback, the study examined two areas where more information and policy analysis could complement ongoing activities on air pollution control: making vehicle emissions inspection more effective and understanding sources of small particulate matter. Poorly maintained older technology vehicles contribute disproportionately to total vehicular emissions. A common approach to identifying gross polluters and ensuring that they are repaired or retired is a vehicle inspection and maintenance (I/M) program. The analysis carried out in this study recommends that limited resources be concentrated on applying more robust (but also costly) test protocols to vehicle categories in large cities likely to contain a disproportionately large fraction of high annual-kilometer...

PCDD/F and PCB Multi-media Ambient Concentrations, Congener Patterns and Occurrence in a Mediterranean Coastal Lagoon (Etang de Thau, France)

CASTRO JIMENEZ JAVIER; DEVILLER GENEVIEVE; GHIANI MICHELA; LOOS ROBERT; MARIANI GIULIO; SKEJO HELLE; UMLAUF GUNTHER; WOLLGAST JAN; LAUGIER T.; HEAS-MOISAN K.; LEAUTE F.; MUNSCHY C.; TIXIER C.; TRONCZYNSKI J.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
46.13%
Ambient concentrations, congener patterns and multi-media distribution of PCDD/Fs and PCBs were determined in air, water, sediment and mussels in a semi-enclosed marine ecosystem (Thau lagoon, France). ¿2,3,7,8- PCDD/Fs and ¿7PCBs air concentrations (0.2-1.4 and 31-57 pg m-3, respectively) were typical of rural areas. Concentrations in the water column were very low for PCDD/Fs (163-476 fg l-1) and low for PCBs (138-708 pg l-1). PCDD/F and PCB concentrations found in surface sediment (0.15-1.6 and 2.5-33 ng g-1 d.w., respectively) and mussel (13-21 pg g-1 d.w. and 10-39 ng g-1 d.w., respectively) were medium levels. PCDD/F congener patterns observed in air, water particulate phase and sediments were similar suggesting direct coupling among these compartments and atmospheric inputs of PCDD/Fs into the lagoon. Conversely, for the same set of samples, similar patterns were not observed for PCBs. A different behavior regarding the uptake of PCDD/Fs and PCBs by lagoon mussels was observed; JRC.H.5-Rural, water and ecosystem resources

Cleaning Pakistan's Air : Policy Options to Address the Cost of Outdoor Air Pollution

Sanchez-Triana, Ernesto; Enriquez, Santiago; Afzal, Javaid; Nakagawa, Akiko; Khan, Asif Shuja
Fonte: Washington, DC: World Bank Publicador: Washington, DC: World Bank
Tipo: Publications & Research :: Publication
ENGLISH; EN_US
Relevância na Pesquisa
36.31%
Pakistan's urban air pollution is among the most severe in the world and it engenders significant damages to human health and the economy. Air pollution, inadequate water supply, sanitation, and hygiene are the top environmental priority problems in Pakistan. Industrialization and urbanization, in conjunction with motorization, can result in further deterioration of urban air quality. This book examines policy options to strengthen the Pakistan clean air program (PCAP) to better address the cost imposed by outdoor air pollution upon Pakistan's economy and populace. The approach provided in this book recommends that the federal and provincial environmental protection agencies (EPAs) take on a limited number of high return, essential, and feasible interventions drawn largely from the PCAP. The objective of this book is to examine policy options to control outdoor air pollution in Pakistan. The findings of the analysis aim at assisting the Government of Pakistan (GoP) in the design and implementation of reforms to improve the effectiveness and efficiency of Pakistan's ambient air quality institutions. The overarching theme of this book is that prioritizing interventions is essential to address the cost of outdoor air pollution...

Clean Air and Healthy Lungs : Enhancing the World Bank's Approach to Air Quality Management

Awe, Yewande; Nygard, Jostein; Larssen, Steinar; Lee, Heejoo; Dulal, Hari; Kanakia, Rahul
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
ENGLISH; EN_US
Relevância na Pesquisa
36.33%
This report specifically deals with air pollution, which was reported, by the World Health Organization (WHO), as the single largest environmental health risk globally in 2012 (WHO, 2014a). Air pollution from outdoor and household sources jointly account for more than 7 million deaths (3.7 million from ambient air pollution and 4.3 million from household air pollution). The following sections of this chapter present the objectives of, and key aspects of the institutional context for, this report followed by an examination of some of the major drivers of deteriorating ambient air quality in developing countries; air pollution sources and impacts; and the status of air quality management in developing countries. Chapter two presents the results of a desk-based portfolio review of World Bank projects that are relevant to reduction of air pollution. This is followed, in chapter three, by an examination of case studies of World Bank projects whose objectives include addressing ambient air pollution, highlighting good practices and lessons for future work of the Bank in supporting clients. Chapter four presents possible approaches for enhancing future Bank support in helping clients to improve air quality and reduce the associated adverse health outcomes. Chapter five presents overall conclusions and recommendations.

Respiratory hospital admissions were associated with ambient airborne pollen in Darwin, Australia, 2004-2005

Hanigan, Ivan; Johnston, Fay H
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.99%
Background: Although the role of pollen and fungus in specific allergic disorders has been well established, the public health impacts of ambient concentrations of airborne pollen and fungal spores; the shapes of concentration-response relationships; and

Investigating the Effects of Mercury Emissions in the Four Corners Area on Local Deposition Levels and Ambient Concentrations

Weidner, Kristin
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project Formato: 6998431 bytes; application/pdf
Publicado em 11/09/2007
Relevância na Pesquisa
46.19%
In 2005, the United States Environmental Protection Agency (EPA) issued the Clean Air Mercury Rule (CAMR) as a means for regulating mercury emissions from coal-fired utility boilers in the United States. However, there is concern that this rule may result in local ‘hot spots’ of increased mercury in the environment surrounding these facilities. Citizens of the Four Corners region in the southwest are particularly concerned about this rule due to the presence of two of the highest mercury-emitting facilities in the country. While studies have shown that an increase in atmospheric levels of mercury lead to a global increase in mercury deposition, little is known on the effects air emissions from point sources on local mercury levels in the environment. In this study, mercury emissions from the Four Corners Power Plant and the San Juan Generating Station of New Mexico were investigated for their possible impacts on local mercury levels in the environment. The analysis included statistical and back trajectory analysis of deposition data at a nearby monitoring site, as well as SCREEN dispersion modeling of mercury emissions to calculate mercury concentrations in the ambient air. Results of the statistical analysis of the deposition data showed a relationship between precipitation and deposition levels...

Volatile organic compounds in the downtown area of Mexicali, México during the spring of 2005: analysis of ambient data and source-receptor modeling

MENDOZA,A.; GUTIÉRREZ,A. A.; PARDO,E. I.
Fonte: Centro de Ciencias de la Atmósfera, UNAM Publicador: Centro de Ciencias de la Atmósfera, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2009 EN
Relevância na Pesquisa
46.08%
The border city of Mexicali has some of the worst air pollution in México, mainly due to the high levels of fine particulate matter (PM) and O3 registered. This also impacts the air quality of communities across the border in California's Imperial Valley. A field campaign was conducted in April of 2005 to obtain ambient concentrations of volatile organic compounds (VOC), and thus obtain insight on the levels and sources of these O3 and fine PM precursors. Six-liter stainless steel canisters were deployed at a site located in the downtown area of the city to obtain ambient air samples that were then analyzed for 54 selected target species. Samples were collected on a daily basis at three different sampling times: 6-9, 13-16, and 20-23 h LT. Average total non-methane organic compounds (TNMOC) concentration was 560 ppbC, with the morning samples having the highest reported average concentration (795) and the afternoon the lowest (257 ppbC). Aromatics contributed around 24% to the TNMOC concentration. Correlation between different species indicates strong influence of local anthropogenic sources (e.g., xylenes-benzene ratio of 2.1). In addition, high correlations between typical products from internal combustion engines (e.g., acetylene-ethene R² = 0.90...