scholarly journals Baseline levels and trends of ground level ozone in Canada and the United States

2010 ◽  
Vol 10 (18) ◽  
pp. 8629-8647 ◽  
Author(s):  
E. Chan ◽  
R. J. Vet
Keyword(s):  
United States ◽  
Ground Level ◽  
Western Canada ◽  
Eastern Canada ◽  
Ground Level Ozone ◽  
Mixing Ratios ◽  
Western Us ◽  
The Us ◽  
Baseline Levels ◽  
Ozone Precursor

Abstract. A statistical method was developed to extract baseline levels of ground level ozone in Canada and the US, and to quantify the temporal changes of baseline ozone levels on annual, seasonal, diurnal and decadal scales for the period 1997 to 2006 based on ground-level observations from 97 non-urban monitoring sites. Baseline ozone is defined here as ozone measured at a given site in the absence of strong local influences. The quantification of baseline levels involved using a Principal Component Analyses (PCA) to derive groups of commonly-varying sites in contiguous regions by season, followed by using backward air parcel trajectories to systematically select ozone mixing ratios associated with the baseline condition in each of the PCA-derived regions. Decadal trends were estimated by season for each of the regions using a generalized linear mixed model (GLMM). Baseline ozone mixing ratios determined by this method were found to vary geographically and seasonally. For the 1997–2006 period, baseline mixing ratios were calculated for annual and seasonal periods in seven regions of North America based on multi-site multi-year averages of the baseline data sets. The annual average (±1 standard deviation) baseline mixing ratios for the regions are as follows: Continental Eastern Canada=30±9 ppb, Continental Eastern US=30±10 ppb, Coastal Eastern Canada=27±9 ppb, Coastal Western Canada=19±10 ppb; Coastal Western US=39±10 ppb, Continental Western Canada=28±10 ppb and Continental Western US=46±7 ppb. Trends in the baseline mixing ratios were also found to vary by season and by geographical region. On a decadal scale, increasing baseline ozone trends (temperature-adjusted) were observed in all seasons along the Pacific coasts of Canada and the US, although the trends in California were not statistically significant. In the coastal zone of Pacific Canada, positive trends were found with a rate of increase of 0.28±0.26, 0.72±0.55, and 0.93±0.41 ppb/a in spring (MAM), summer (JJA) and winter (DJF), respectively. In the Atlantic coastal region, the trends were also positive in 3 of the 4 seasons (but only significantly so in MAM). In the high ozone precursor emission areas of the Eastern United States, decadal trends in baseline ozone are, in general, negative in the spring, summer and fall and appear to be controlled by the strong within-region changes induced by decreasing ozone precursor emissions.

scholarly journals Climate-driven ground-level ozone extreme in the fall over the Southeast United States

2016 ◽  
Vol 113 (36) ◽  
pp. 10025-10030 ◽  
Author(s):  
Yuzhong Zhang ◽  
Yuhang Wang
Keyword(s):  
United States ◽  
Climate Models ◽  
Weather Condition ◽  
Ground Level ◽  
Field Studies ◽  
The United States ◽  
Fire Emissions ◽  
Ground Level Ozone ◽  
Ozone Concentrations ◽  
Ozone Precursor

Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades (1980–2010). Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.

scholarly journals First Report of Phytophthora infestans Genotype US23 Causing Late Blight in Canada

Plant Disease ◽  
2011 ◽  
Vol 95 (7) ◽  
pp. 873-873 ◽  
Author(s):  
L. M. Kawchuk ◽  
R. J. Howard ◽  
R. D. Peters ◽  
K. I. Al-Mughrabi
Keyword(s):  
United States ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
The United States ◽  
Western Canada ◽  
Eastern Canada ◽  
Disease Symptoms ◽  
Metalaxyl Sensitivity ◽  
Epidemiological Characteristics

Late blight is caused by the oomycete Phytophthora infestans (Mont.) de Bary and is one of the most devastating diseases of potato and tomato. Late blight occurs in all major potato- and tomato-growing regions of Canada. Its incidence in North America increased during 2009 and 2010 (2). Foliar disease symptoms appeared earlier than usual (June rather than July) and coincided with the identification of several new P. infestans genotypes in the United States, each with unique characteristics. Prior to 2007, isolates collected from potato and tomato crops were mainly US8 or US11 genotypes (1). However, P. infestans populations in the United States have recently experienced a major genetic evolution, producing isolates with unique genotypes and epidemiological characteristics in Florida and throughout the northeastern states (2). Recent discoveries of tomato transplants with late blight for sale at Canadian retail outlets prompted an examination of the genotypes inadvertently being distributed and causing disease in commercial production areas in Canada. Analysis of isolates of P. infestans from across Canada in 2010 identified the US23 genotype for the first time from each of the four western provinces (Manitoba, Saskatchewan, Alberta, and British Columbia) but not from eastern Canada. Allozyme banding patterns at the glucose phosphate isomerase (Gpi) locus indicated a 100/100 profile consistent with US6 and US23 genotypes (4). Mating type assays confirmed the isolates to be A1 and in vivo metalaxyl sensitivity was observed. Restriction fragment length polymorphic analysis of 50 isolates from western Canada with the multilocus RG57 sequence and EcoRI produced the DNA pattern 1, 2, 5, 6, 10, 13, 14, 17, 20, 21, 24, 24a, 25 that was indicative of US23 (3). The recently described P. infestans genotype US23 appears to be more aggressive on tomato, and although isolates were recovered from both tomato and potato, disease symptoms were often more severe on tomato. Results indicate that movement and evolution of new P. infestans genotypes have contributed to the increased incidence of late blight and that movement of the pathogen on retail plantlets nationally and internationally may provide an additional early season source of inoculum. A major concern is that the introduced new A1 populations in western Canada have established a dichotomy with the endogenous A2 populations in eastern Canada, increasing the potential for sexual recombination producing oospores and additional genotypes should these populations merge. References: (1) Q. Chen et al. Am. J. Potato Res. 80:9, 2003. (2) K. Deahl. (Abstr.) Phytopathology 100(suppl.):S161, 2010. (3) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (4) S. B. Goodwin et al. Phytopathology 88:939, 2004.

scholarly journals Regional stratospheric warmings in the Pacific-Western Canada (PWC) sector during winter 2004/2005: implications for temperatures, winds, chemical constituents and the characterization of the Polar vortex

2008 ◽  
Vol 26 (11) ◽  
pp. 3597-3622 ◽  
Author(s):  
A. H. Manson ◽  
C. E. Meek ◽  
T. Chshyolkova
Keyword(s):  
Chemical Constituents ◽  
Thermal Characteristics ◽  
Polar Vortex ◽  
Latitudinal Gradients ◽  
Western Canada ◽  
Heterogeneous Chemistry ◽  
High Latitudes ◽  
Eastern Canada ◽  
Mixing Ratios ◽  
The Pacific

Abstract. The vortex during winter 2004/2005 was interesting for several reasons. It has been described as "cold" stratospherically, with relatively strong westerly winds. Losses of ozone until the final warming in March were considerable, and comparable to the cold 1999–2000 winter. There were also modest warming events, indicated by peaks in 10 hPa zonal mean temperatures at high latitudes, near 1 January and 1 February. Events associated with a significant regional stratospheric warming in the Pacific-Western Canada (PWC) sector then began and peaked toward the end of February, providing strong longitudinal variations in dynamical characteristics (Chshyolkova et al., 2007; hereafter C07). The associated disturbed vortex of 25 February was displaced from the pole and either elongated (upper) or split into two cyclonic centres (lower). Observations from Microwave Limb Sounder (MLS) on Aura are used here to study the thermal characteristics of the stratosphere in the Canadian-US (253° E) and Scandinavian-Europe (16° E) sectors. Undisturbed high latitude stratopause (55 km) zonal mean temperatures during the mid-winter (December–February) reached 270 K, warmer than empirical-models such as CIRA-86, suggesting that seasonal polar warming due to dynamical influences affects the high altitude stratosphere as well as the mesosphere. There were also significant stratopause differences between Scandinavia and Canada during the warming events of 1 January and 1 February, with higher temperatures near 275 K at 16° E. During the 25 February "PWC" event a warming occurred at low and middle stratospheric heights (10–30 km: 220 K at 253° E) and the stratopause cooled; while over Scandinavia-Europe the stratosphere below ~30 km was relatively cold at 195 K and the stratopause became even warmer (>295 K) and lower (~45 km). The zonal winds followed the associated temperature gradients so that the vertical and latitudinal gradients of the winds differed strongly between Scandinavia-Europe and Canada-US. The data-archive of Aura-MLS was also used to produce height versus latitude contours of ozone and related constituents, using mixing ratios (r) for ClO, N2O and HCl, for the 16° E and 253° E sectors. The Q-diagnostic was used to display the positions of the cyclonic (polar) vortex, using data from the UK Meteorological Office (MetO) analyses. ClO/HCL maxima/minima occurred on 1 February in both sectors, consistent with loss of ozone by heterogeneous chemistry. Low N2O values at high latitudes indicated that both sectors were inside the polar vortex, Time-difference plots show greater reductions in O3 in the Canadian sector. For the 25 February PWC warming event, O3-rich air from lower latitudes continued to be excluded from Europe, while O3 penetrated to at least 82° N over the Canadian sector. The contours for ClO, N2O and HCl at 16° E are consistent with continued ozone loss within the vortex during the event. Finally the thermal and chemical changes at these 16° E and 253° E sectors are placed into a hemispheric context using polar-cylindrical plots, with the following results. Firstly, the mixing ratios of O3, ClO, HNO3, HCL and the temperatures from Aura-MLS were consistent with consensus views of heterogeneous chemistry. Secondly, and consistent with the polar plots of C07, the vortices and their edges were strongly distorted during the 1 January, 1 and 25 February warming events, with sinusoidal shapes consistent with stationary planetary waves of wave-numbers 1 and 2. Thirdly, the distributions of the chemicals followed the curvatures (cyclonic and anticyclonic) of the vortex edges with O3 losses occurring at the cold cyclonic locations. During February these were over Scandinavia-Western Europe and Central-Eastern Canada. Trajectory analysis was applied to the two February warming events. For the 1 February event, the rotation time for air parcels within the peanut-shaped vortex was 3–4 days; while the O3-rich low latitude air that entered the Pacific-Western Canada sector during the 25 February event, showed no signs of becoming trapped within the highly distorted but still strong remnant of the polar vortex.

scholarly journals How emissions, climate, and land use change will impact mid-century air quality over the United States: a focus on effects at National Parks

2014 ◽  
Vol 14 (19) ◽  
pp. 26495-26543 ◽  
Author(s):  
M. Val Martin ◽  
C. L. Heald ◽  
J.-F. Lamarque ◽  
S. Tilmes ◽  
L. K. Emmons ◽  
...  
Keyword(s):  
United States ◽  
Land Use ◽  
Air Quality ◽  
National Parks ◽  
Land Use Changes ◽  
The United States ◽  
Western Us ◽  
The Us ◽  
Us Epa ◽  
Surface O3

Abstract. We use a global coupled chemistry-climate-land model (CESM) to assess the integrated effect of climate, emissions and land use changes on annual surface O3 and PM2.5 on the United States with a focus on National Parks (NPs) and wilderness areas, using the RCP4.5 and RCP8.5 projections. We show that, when stringent domestic emission controls are applied, air quality is predicted to improve across the US, except surface O3 over the western and central US under RCP8.5 conditions, where rising background ozone counteracts domestic emissions reductions. Under the RCP4.5, surface O3 is substantially reduced (about 5 ppb), with daily maximum 8 h averages below the primary US EPA NAAQS of 75 ppb (and even 65 ppb) in all the NPs. PM2.5 is significantly reduced in both scenarios (4 μg m−3; ~50%), with levels below the annual US EPA NAAQS of 12 μg m−3 across all the NPs; visibility is also improved (10–15 deciviews; >75 km in visibility range), although some parks over the western US (40–74% of total sites in the US) may not reach the 2050 target to restore visibility to natural conditions by 2064. We estimate that climate-driven increases in fire activity may dominate summertime PM2.5 over the western US, potentially offsetting the large PM2.5 reductions from domestic emission controls, and keeping visibility at present-day levels in many parks. Our study suggests that air quality in 2050 will be primarily controlled by anthropogenic emission patterns. However, climate and land use changes alone may lead to a substantial increase in surface O3 (2–3 ppb) with important consequences for O3 air quality and ecosystem degradation at the US NPs. Our study illustrates the need to consider the effects of changes in climate, vegetation, and fires in future air quality management and planning and emission policy making.

scholarly journals Assessment of the effect of air pollution controls on trends in shortwave radiation over the United States from 1995 through 2010 from multiple observation networks

2013 ◽  
Vol 13 (9) ◽  
pp. 23719-23755 ◽  
Author(s):  
C.-M. Gan ◽  
J. Pleim ◽  
R. Mathur ◽  
C. Hogrefe ◽  
C. N. Long ◽  
...  
Keyword(s):  
United States ◽  
Cloud Cover ◽  
Surface Concentration ◽  
The United States ◽  
Air Pollutant ◽  
Shortwave Radiation ◽  
Clear Sky ◽  
Western Us ◽  
The Us ◽  
Increasing Trends

Abstract. Long term datasets of all-sky and clear-sky downwelling shortwave (SW) radiation, cloud cover fraction and aerosol optical depth (AOD) are analyzed together with surface concentration from several networks (e.g. SURFRAD, CASTNET, IMPROVE and ARM) in the United States (US). Seven states with varying climatology are selected to better understand the effects of aerosols and clouds on SW radiation. This analysis aims to assess the effects of reductions in anthropogenic aerosol burden resulting from substantial reductions in emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) over the past 16 yr across the US on trends in SW radiation. The SO2 and NOx emission data show decreasing trends from 1995 to 2010 which indirectly validates the effects of the Clean Air Act (CAA) in the US. Meanwhile, the total column AOD and surface total PM2.5 observations also show decreasing trends in the eastern US but slightly increasing trends in the western US. Moreover, measured surface concentrations of several other pollutants (i.e. SO2, SO4 and NOx) have the same behavior as the AOD and total PM2.5. First, all-sky downwelling SW radiation is assessed together with the cloud cover. Results of this analysis show strong increasing trends in all-sky downwelling SW radiation with decreasing trends in cloud cover. However, since observations of both all-sky direct and diffuse SW radiation are increasing, there may be other factors contributing to the radiation trends in addition to the decreasing trends in overall cloud cover. To investigate the role of direct radiative effects of aerosols, clear-sky downwelling radiation is analyzed so that cloud effects are eliminated. However, similar increasing trends in clear-sky direct and diffuse SW radiation are observed. While significantly decreasing trends in AOD and surface concentration along with increasing SW radiation (both all-sky and clear-sky) in the eastern US during 1995–2010 imply the occurrence of direct aerosol mediated "brightening", the increasing trends of both all-sky and clear sky diffuse SW radiation contradicts this conclusion since diffuse radiation would be expected to decrease as aerosols direct effects decrease. After investigating several confounding factors, the increasing trend in diffuse SW may be due to more high-level cirrus from increasing air traffic over the US. In contrast to the eastern US, radiation observations in the western US do not show any indication of "brightening" which is consistent with the observations (e.g. AOD, PM2.5 and surface concentration) that show the aerosol loading increasing slightly. This outcome is not unexpected because the CAA controls were mainly aimed at reducing air pollutants emission in the eastern US and air pollutant level in the western US are much lower.

Coal

2020 ◽  
pp. 81-119
Author(s):  
Paul F. Meier
Keyword(s):  
United States ◽  
Coal Combustion ◽  
Electricity Generation ◽  
Ground Level ◽  
The United States ◽  
Pulverized Coal ◽  
Ground Level Ozone ◽  
Energy Applications ◽  
Residential Heating ◽  
Coal Technology

Coal has two main energy applications, with about 90% used for electricity generation and 10% used for commercial and residential heating. In terms of electricity generation in the United States, coal is responsible for about 28%, a significant decrease from 53% twenty years earlier when it was the leading energy for producing electricity. There are two primary commercial methods for generating electricity from coal including pulverized coal combustion and fluidized bed coal combustion. To safely burn coal, sulfur, nitrogen, and heavy metals are removed at the electric plant. The sequestering of sulfur and nitrogen are important steps for limiting acid rain and ground level ozone. To generate electricity, the United States has about 360 coal plants with about 790 generators, of which greater than 90% use pulverized coal technology. Most coal is transported by rail.

scholarly journals How emissions, climate, and land use change will impact mid-century air quality over the United States: a focus on effects at national parks

2015 ◽  
Vol 15 (5) ◽  
pp. 2805-2823 ◽  
Author(s):  
M. Val Martin ◽  
C. L. Heald ◽  
J.-F. Lamarque ◽  
S. Tilmes ◽  
L. K. Emmons ◽  
...  
Keyword(s):  
United States ◽  
Land Use ◽  
Air Quality ◽  
National Parks ◽  
Land Use Changes ◽  
The United States ◽  
Western Us ◽  
The Us ◽  
Emission Controls ◽  
Surface O3

Abstract. We use a global coupled chemistry–climate–land model (CESM) to assess the integrated effect of climate, emissions and land use changes on annual surface O3 and PM2.5 in the United States with a focus on national parks (NPs) and wilderness areas, using the RCP4.5 and RCP8.5 projections. We show that, when stringent domestic emission controls are applied, air quality is predicted to improve across the US, except surface O3 over the western and central US under RCP8.5 conditions, where rising background ozone counteracts domestic emission reductions. Under the RCP4.5 scenario, surface O3 is substantially reduced (about 5 ppb), with daily maximum 8 h averages below the primary US Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS) of 75 ppb (and even 65 ppb) in all the NPs. PM2.5 is significantly reduced in both scenarios (4 μg m−3; ~50%), with levels below the annual US EPA NAAQS of 12 μg m−3 across all the NPs; visibility is also improved (10–15 dv; >75 km in visibility range), although some western US parks with Class I status (40–74 % of total sites in the US) are still above the 2050 planned target level to reach the goal of natural visibility conditions by 2064. We estimate that climate-driven increases in fire activity may dominate summertime PM2.5 over the western US, potentially offsetting the large PM2.5 reductions from domestic emission controls, and keeping visibility at present-day levels in many parks. Our study indicates that anthropogenic emission patterns will be important for air quality in 2050. However, climate and land use changes alone may lead to a substantial increase in surface O3 (2–3 ppb) with important consequences for O3 air quality and ecosystem degradation at the US NPs. Our study illustrates the need to consider the effects of changes in climate, vegetation, and fires in future air quality management and planning and emission policy making.

Unraveling the sources of ground level ozone in the Intermountain Western United States using Pb isotopes

2015 ◽  
Vol 530-531 ◽  
pp. 519-525 ◽  
Author(s):  
John N. Christensen ◽  
Peter Weiss-Penzias ◽  
Rebekka Fine ◽  
Charles E. McDade ◽  
Krystyna Trzepla ◽  
...  
Keyword(s):  
United States ◽  
Ground Level ◽  
Pb Isotopes ◽  
Western United States ◽  
Ground Level Ozone
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