The Experts below are selected from a list of 25860 Experts worldwide ranked by ideXlab platform
O R Cooper - One of the best experts on this subject based on the ideXlab platform.
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increasing springtime ozone mixing ratios in the free troposphere over western north america
Nature, 2010Co-Authors: V. Thouret, Jean-pierre Cammas, O R Cooper, D D Parrish, Andreas Stohl, M Trainer, Philippe Nedelec, Samuel J Oltmans, Bryan J JohnsonAbstract:Anthropogenic emissions of ozone precursors, chiefly nitrogen oxides and volatile organic compounds, have caused widespread increases in lower-atmosphere concentrations of ozone since the late 1800s. In the lowermost part of the atmosphere ozone is a greenhouse gas that can have detrimental effects on plant and animal life. At present East Asia has the fastest rate of growth in such emissions and much of its pollution is exported towards North America. A compilation of springtime ozone measurements from across western North America now provides evidence for a strong increase in ozone mixing ratios during 1995–2008. The rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. This phenomenon, previously suspected but not confirmed, may make it more difficult for the United States to meet its own ozone Air Quality Standard. High concentrations of ozone in the troposphere are toxic and act as a greenhouse gas. Anthropogenic emissions of ozone precursors have caused widespread increases in ozone concentrations since the late 1800s, with the fastest-growing ozone precursor emissions currently coming out of east Asia. Much of the springtime east Asian pollution is exported towards western North America; a strong increase in springtime ozone mixing ratios is now found in the free troposphere over this region. In the lowermost layer of the atmosphere—the troposphere—ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases1. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity1. Moreover, tropospheric ozone itself acts as an effective greenhouse gas2. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors3 resulting in widespread increases in ozone concentrations since the late 1800s3,4,5,6,7. At present, east Asia has the fastest-growing ozone precursor emissions8. Much of the springtime east Asian pollution is exported eastwards towards western North America9. Despite evidence that the exported Asian pollution produces ozone10, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s5,11,12. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995–2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes13, with western North America being particularly sensitive to rising Asian emissions14. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA’s compliance with its ozone Air Quality Standard.
Haimeng Zhao - One of the best experts on this subject based on the ideXlab platform.
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urban Air Quality evaluations under two versions of the national ambient Air Quality Standards of china
Atmospheric Pollution Research, 2016Co-Authors: Wei Chen, Hongzhao Tang, Haimeng ZhaoAbstract:Abstract The Air Quality of urban areas is of a great concern for residents living in cities. China has released a new National Ambient Air Quality Standard (NAAQS) in 2012 to improve the Air Quality evaluation index because the reported Air Quality situation from governments is inconsistent with public sensing. In total, 190 cities' hourly monitoring data are publicized in the national web platform. By using the above data, the Air pollution indexes (APIs) under the previous NAAQS and Air Quality indexes (AQI) for all 190 cities' were calculated. With the new NAAQS, the national attainment rate has fallen from 73.63% to 59.62% with regional differences. 8 of the 10 cities with the worst Air Quality are located in North China around Beijing, while 9 of the 10 cities with the best Air Quality are located in South China. These results indicate that cities in North China, including Beijing, need to address the Air pollution together as the pollution in North China is a regional issue and not a local issue.
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diurnal weekly and monthly spatial variations of Air pollutants and Air Quality of beijing
Atmospheric Environment, 2015Co-Authors: Wei Chen, Hongzhao Tang, Haimeng ZhaoAbstract:Abstract Under the National Ambient Air Quality Standard released in 2012 (NAAQS-2012), Beijing began to publicize hourly Air Quality Index as well as real time concentrations of 6 pollutants in its web platform to provide detailed information for Air Quality assessment from 2013. In this study, hourly Air Quality monitoring data from May 2014 to April 2015 were collected for all 35 monitoring stations in Beijing to analyze the temporal and spatial variations of Air pollutants and Air Quality. It is found that in spatial pattern, the Air qualities in southern and northern Beijing are totally different. The association between heavy pollution concentrations and wind situations suggested that neighboring area's Air Quality has an important role in the Air Quality of Beijing combining with Air Quality attainment rates in all 35 monitoring stations and northern China. For temporal variations, late night and early morning are the most polluted time while afternoon is the least polluted time for all pollutants except O3 with most polluted time in afternoon. Summer time in Beijing has the best Air Quality while winter time has the worst Air Quality coinciding with the heating season in the winter.
Daniel J Jacob - One of the best experts on this subject based on the ideXlab platform.
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improved estimate of the policy relevant background ozone in the united states using the geos chem global model with 1 2 2 3 horizontal resolution over north america
Atmospheric Environment, 2011Co-Authors: Lin Zhang, Daniel J Jacob, Nicole Downey, Dana A Wood, D Blewitt, C Carouge, Aaron Van Donkelaar, Dylan B A Jones, Lee T Murray, Yuxuan WangAbstract:The policy-relevant background (PRB) ozone is defined by the US Environmental Protection Agency (EPA) as the surface ozone concentration that would be present over the US in the absence of North American anthropogenic emissions. It is intended to provide a baseline for risk and exposure assessments used in setting the National Ambient Air Quality Standard (NAAQS). We present here three-year statistics (2006e2008) of PRB ozone over the US calculated using the GEOS-Chem global 3-D model of atmospheric composition with 1/2
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effect of climate change on Air Quality
Atmospheric Environment, 2009Co-Authors: Daniel J Jacob, Darrell A WinnerAbstract:Air Quality is strongly dependent on weather and is therefore sensitive to climate change. Recent studies have provided estimates of this climate effect through correlations of Air Quality with meteorological variables, perturbation analyses in chemical transport models (CTMs), and CTM simulations driven by general circulation model (GCM) simulations of 21st-century climate change. We review these different approaches and their results. The future climate is expected to be more stagnant, due to a weaker global circulation and a decreasing frequency of mid-latitude cyclones. The observed correlation between surface ozone and temperature in polluted regions points to a detrimental effect of warming. Coupled GCM-CTM studies find that climate change alone will increase summertime surface ozone in polluted regions by 1-10 ppb over the coming decades, with the largest effects in urban areas and during pollution episodes. This climate penalty means that stronger emission controls will be needed to meet a given Air Quality Standard. Higher water vapor in the future climate is expected to decrease the ozone background, so that pollution and background ozone have opposite sensitivities to climate change. The effect of climate change on particulate matter (PM) is more complicated and uncertain than for ozone. Precipitation frequency and mixing depth are important driving factors but projections for these vari- ables are often unreliable. GCM-CTM studies find that climate change will affect PM concentrations in polluted environments by � 0.1-1 m gm
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sensitivity of us Air Quality to mid latitude cyclone frequency and implications of 1980 2006 climate change
Atmospheric Chemistry and Physics, 2008Co-Authors: Eric M Leibensperger, Loretta J Mickley, Daniel J JacobAbstract:We show that the frequency of summertime mid-latitude cyclones tracking across eastern North America at 40°–50° N (the southern climatological storm track) is a strong predictor of stagnation and ozone pollution days in the eastern US. The NCEP/NCAR Reanalysis, going back to 1948, shows a significant long-term decline in the number of summertime mid-latitude cyclones in that track starting in 1980 (−0.15 a −1 ). The more recent but shorter NCEP/DOE Reanalysis (1979–2006) shows similar interannual variability in cyclone frequency but no significant long-term trend. Analysis of NOAA daily weather maps for 1980–2006 supports the trend detected in the NCEP/NCAR Reanalysis 1. A GISS general circulation model (GCM) simulation including historical forcing by greenhouse gases reproduces this decreasing cyclone trend starting in 1980. Such a long-term decrease in mid-latitude cyclone frequency over the 1980–2006 period may have offset by half the ozone Air Quality gains in the northeastern US from reductions in anthropogenic emissions. We find that if mid-latitude cyclone frequency had not declined, the northeastern US would have been largely compliant with the ozone Air Quality Standard by 2001. Mid-latitude cyclone frequency is expected to decrease further over the coming decades in response to greenhouse warming and this will necessitate deeper emission reductions to achieve a given Air Quality goal.
Roy M Harrison - One of the best experts on this subject based on the ideXlab platform.
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carcinogenic potential levels and sources of polycyclic aromatic hydrocarbon mixtures in indoor and outdoor environments and their implications for Air Quality Standards
Environment International, 2011Co-Authors: Juana Maria Delgadosaborit, Christopher Stark, Roy M HarrisonAbstract:Both the World Health Organization and the UK Expert Panel on Air Quality Standards (EPAQS) have considered benzo(a)pyrene (BaP) as a marker of the carcinogenic potency of the polycyclic aromatic hydrocarbons (PAH) mixture, when recommending their respective guidelines for PAHs in outdoor Air. The aim of this research is to compare the concentrations and relative abundance of individual PAH and their contribution to the overall carcinogenic potential of the PAH mixture in indoor and outdoor environments to assess the suitability of the UK Air Quality Standard derived for outdoor Air for use as a guideline for indoor environments. Samples were collected onto filters using active sampling in different indoor and outdoor microenvironments. The ratio of individual compounds to BaP, the BaP equivalent concentrations and the percentage contribution of each individual compound to the total carcinogenic potential of the PAH mixture were calculated. Mean concentrations were generally lower indoors (BaP=0.10 ng/m(3)) than outdoors (BaP=0.19 ng/m(3)), with the exception of indoor environments with wood burners (BaP=2.4 ng/m(3)) or ETS (BaP=0.6 ng/m(3)). The ratio of individual PAHs to BaP showed no significant differences between indoors (e.g. DahA/BaP=0.27) and outdoors (DahA/BaP=0.31). The relative contribution of BaP to the PAH overall carcinogenic potency is similar indoors (49%), outdoors (54%) and in the smelter environment (48%) used by EPAQS to derive the UK Air Quality Standard for ambient Air. These results suggest the suitability of BaP as a marker for the carcinogenic potential of the PAH mixture irrespective of the environment. Despite small differences in PAH mixture composition indoors and outdoors, the level of protection afforded by the present EPAQS Standard is likely to be similar whether it is applied to indoor or outdoor Air.
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receptor modeling for Air Quality management
1997Co-Authors: R E Hester, Roy M Harrison, Philip K HopkeAbstract:1. An Introduction to Receptor Modeling (P.K. Hopke). 2. Sampling and Analysis Methods for Ambient PM-10 Aerosol (T.G. Dzubay and R.K. Stevens). 3. Source Sampling for Receptor Modeling (J.E. Houck). 4. Chemical Mass Balance (J.G. Watson, J.C. Chow and T. G. Pace). 5. Multivariate Receptor Models (R.C. Henry). 6. Scanning Electron Microscopy (P.K. Hopke and G.S. Casuccio). 7. Receptor Modeling for Volatile Organic Compounds (P.A. Scheff and R.A. Wadden). 8. Receptor Modeling in the Context of Ambient Air Quality Standard for Particulate Matter (T.G. Pace). 9. Application of Receptor Modeling to Solving Local Air Quality Problems (J.E. Core). Index.
Bryan J Johnson - One of the best experts on this subject based on the ideXlab platform.
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increasing springtime ozone mixing ratios in the free troposphere over western north america
Nature, 2010Co-Authors: V. Thouret, Jean-pierre Cammas, O R Cooper, D D Parrish, Andreas Stohl, M Trainer, Philippe Nedelec, Samuel J Oltmans, Bryan J JohnsonAbstract:Anthropogenic emissions of ozone precursors, chiefly nitrogen oxides and volatile organic compounds, have caused widespread increases in lower-atmosphere concentrations of ozone since the late 1800s. In the lowermost part of the atmosphere ozone is a greenhouse gas that can have detrimental effects on plant and animal life. At present East Asia has the fastest rate of growth in such emissions and much of its pollution is exported towards North America. A compilation of springtime ozone measurements from across western North America now provides evidence for a strong increase in ozone mixing ratios during 1995–2008. The rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. This phenomenon, previously suspected but not confirmed, may make it more difficult for the United States to meet its own ozone Air Quality Standard. High concentrations of ozone in the troposphere are toxic and act as a greenhouse gas. Anthropogenic emissions of ozone precursors have caused widespread increases in ozone concentrations since the late 1800s, with the fastest-growing ozone precursor emissions currently coming out of east Asia. Much of the springtime east Asian pollution is exported towards western North America; a strong increase in springtime ozone mixing ratios is now found in the free troposphere over this region. In the lowermost layer of the atmosphere—the troposphere—ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases1. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity1. Moreover, tropospheric ozone itself acts as an effective greenhouse gas2. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors3 resulting in widespread increases in ozone concentrations since the late 1800s3,4,5,6,7. At present, east Asia has the fastest-growing ozone precursor emissions8. Much of the springtime east Asian pollution is exported eastwards towards western North America9. Despite evidence that the exported Asian pollution produces ozone10, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s5,11,12. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995–2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes13, with western North America being particularly sensitive to rising Asian emissions14. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA’s compliance with its ozone Air Quality Standard.