scholarly journals Ozone response to emission reductions in the southeastern United States

2018 ◽  
Vol 18 (11) ◽  
pp. 8183-8202 ◽  
Author(s):  
Charles L. Blanchard ◽  
George M. Hidy
Keyword(s):  
Environmental Protection Agency ◽  
Study Data ◽  
Nox Emissions ◽  
Emission Rates ◽  
Emission Reductions ◽  
Mixing Ratios ◽  
Southeastern Us ◽  
Surface Measurements ◽  
Nitrate Deposition

Abstract. Ozone (O3) formation in the southeastern US is studied in relation to nitrogen oxide (NOx) emissions using long-term (1990s–2015) surface measurements of the Southeastern Aerosol Research and Characterization (SEARCH) network, U.S. Environmental Protection Agency (EPA) O3 measurements, and EPA Clean Air Status and Trends Network (CASTNET) nitrate deposition data. Annual fourth-highest daily peak 8 h O3 mixing ratios at EPA monitoring sites in Georgia, Alabama, and Mississippi exhibit statistically significant (p < 0.0001) linear correlations with annual NOx emissions in those states between 1996 and 2015. The annual fourth-highest daily peak 8 h O3 mixing ratios declined toward values of ∼ 45–50 ppbv and monthly O3 maxima decreased at rates averaging ∼ 1–1.5 ppbv yr−1. Mean annual total oxidized nitrogen (NOy) mixing ratios at SEARCH sites declined in proportion to NOx emission reductions. CASTNET data show declining wet and dry nitrate deposition since the late 1990s, with total (wet plus dry) nitrate deposition fluxes decreasing linearly in proportion to reductions of NOx emissions by ∼ 60 % in Alabama and Georgia. Annual nitrate deposition rates at Georgia and Alabama CASTNET sites correspond to 30 % of Georgia emission rates and 36 % of Alabama emission rates, respectively. The fraction of NOx emissions lost to deposition has not changed. SEARCH and CASTNET sites exhibit downward trends in mean annual nitric acid (HNO3) concentrations. Observed relationships of O3 to NOz (NOy–NOx) support past model predictions of increases in cycling of NO and increasing responsiveness of O3 to NOx. The study data provide a long-term record that can be used to examine the accuracy of process relationships embedded in modeling efforts. Quantifying observed O3 trends and relating them to reductions in ambient NOy species concentrations offers key insights into processes of general relevance to air quality management and provides important information supporting strategies for reducing O3 mixing ratios.

scholarly journals Ozone Response to Emission Reductions in the Southeastern United States

2017 ◽  
Author(s):  
Charles L. Blanchard ◽  
George M. Hidy
Keyword(s):  
Environmental Protection Agency ◽  
Nox Emissions ◽  
Emission Rates ◽  
Emission Reductions ◽  
Mixing Ratios ◽  
Surface Measurements ◽  
Clean Air ◽  
Annual Total ◽  
Nitrate Deposition

Abstract. Ozone (O3) formation in the southeastern U.S. is studied in relation to nitrogen oxide (NOx) emissions using long-term (1990s–2015) surface measurements of the Southeastern Aerosol Research and Characterization (SEARCH) network, U.S. Environmental Protection Agency (EPA) O3 measurements, and EPA Clean Air Status and Trends Network (CASTNet) nitrate deposition data. CASTNet data show declining wet and dry nitrate deposition since the late 1990s, with total (wet plus dry) nitrate deposition fluxes decreasing linearly in proportion to reductions of NOx emissions in in Alabama and Georgia. Annual nitrate deposition rates at Georgia and Alabama CastNet sites correspond to 30 % of Georgia emission rates and 36 % of Alabama emission rates, respectively. The fraction of NOx emissions lost to deposition has not changed over time. SEARCH and EPA CASTNet sites exhibit comparable downward trends in mean annual nitric acid (HNO3) concentrations. Mean annual total oxidized nitrogen (NOy) mixing ratios at SEARCH sites declined in proportion to NOx emission reductions. Annual 4th-highest daily peak 8-hour O3 mixing ratios at EPA monitoring sites in Georgia, Alabama, and Mississippi exhibit statistically-significant (p 

scholarly journals Effects of emission reductions on organic aerosol in the southeastern United States

2015 ◽  
Vol 15 (12) ◽  
pp. 17051-17092 ◽  
Author(s):  
C. L. Blanchard ◽  
G. M. Hidy ◽  
S. Shaw ◽  
K. Baumann ◽  
E. S. Edgerton
Keyword(s):  
Biomass Burning ◽  
Motor Vehicle ◽  
Organic Aerosol ◽  
Combustion Products ◽  
Emission Reductions ◽  
Southeastern Us ◽  
Motor Vehicle Emissions ◽  
Combustion Processes ◽  
The City

Abstract. Long-term (1999 to 2013) data from the Southeastern Aerosol Research and Characterization (SEARCH) network are used to characterize the effects of anthropogenic emission reductions on fine particle organic aerosol (OA) concentrations in the southeastern US. On average, 45 % (range 25 to 63 %) of the 1999 to 2013 mean organic carbon (OC) concentrations are attributed to combustion processes, including fossil-fuel use and biomass burning, through associations of measured OC with combustion products such as elemental carbon (EC), carbon monoxide (CO), and nitrogen oxides (NOx). The 2013 mean combustion-derived OC concentrations were 0.5 to 1.4 μg m−3 at the five sites operating in that year. Mean annual combustion-derived OC concentrations declined from 3.8 ± 0.2 μg m−3 (68 % of total OC) to 1.4 ± 0.1 μg m−3 (60 % of total OC) between 1999 and 2013 at the urban Atlanta, Georgia, site (JST) and from 2.9 ± 0.4 μg m−3 (39 % of total OC) to 0.7 ± 0.1 μg m−3 (30 % of total OC) between 2001 and 2013 at the urban Birmingham, Alabama, site (BHM). The urban OC declines coincide with reductions of motor-vehicle emissions between 2006 and 2010, which may have decreased mean OC concentrations at the urban SEARCH sites by > 2 μg m−3. BHM additionally exhibits a decline in OC associated with SO2 from 0.4 ± 0.04 μg m−3 in 2001 to 0.2 ± 0.03 μg m−3 in 2013, interpreted as the result of reduced emissions from industrial sources within the city. Analyses using non-soil potassium as a biomass-burning tracer indicate that biomass-burning OC occurs throughout the year at all sites. All eight SEARCH sites show an association of OC with sulfate (SO4) ranging from 0.3 to 1.0 μg m−3 on average, representing ~ 25 % of the 1999 to 2013 mean OC concentrations. Because the mass of OC associated with SO4 averages 20 to 30 % of the SO4 concentrations, the mean SO4-associated OC declined by ~ 0.5 to 1 μg m−3 as SO4 decreased throughout the SEARCH region. The 2013 mean SO4 concentrations of 1.7 to 2.0 μg m−3 imply that future decreases in mean SO4-associated OC concentrations would not exceed ~ 0.3 to 0.5 μg m−3. Seasonal OC concentrations, largely associated with ozone (O3), vary from 0.3 to 1.4 μg m−3 (~ 20 % of the total OC concentrations).

scholarly journals Effects of emission reductions on organic aerosol in the southeastern United States

2016 ◽  
Vol 16 (1) ◽  
pp. 215-238 ◽  
Author(s):  
C. L. Blanchard ◽  
G. M. Hidy ◽  
S. Shaw ◽  
K. Baumann ◽  
E. S. Edgerton
Keyword(s):  
Biomass Burning ◽  
Motor Vehicle ◽  
Organic Aerosol ◽  
Combustion Products ◽  
Emission Reductions ◽  
Southeastern Us ◽  
Motor Vehicle Emissions ◽  
Combustion Processes ◽  
The City

Abstract. Long-term (1999 to 2013) data from the Southeastern Aerosol Research and Characterization (SEARCH) network are used to show that anthropogenic emission reductions led to important decreases in fine-particle organic aerosol (OA) concentrations in the southeastern US On average, 45 % (range 25 to 63 %) of the 1999 to 2013 mean organic carbon (OC) concentrations are attributed to combustion processes, including fossil fuel use and biomass burning, through associations of measured OC with combustion products such as elemental carbon (EC), carbon monoxide (CO), and nitrogen oxides (NOx). The 2013 mean combustion-derived OC concentrations were 0.5 to 1.4 µg m−3 at the five sites operating in that year. Mean annual combustion-derived OC concentrations declined from 3.8 ± 0.2 µg m−3 (68 % of total OC) to 1.4 ± 0.1 µg m−3 (60 % of total OC) between 1999 and 2013 at the urban Atlanta, Georgia, site (JST) and from 2.9 ± 0.4 µg m−3 (39 % of total OC) to 0.7 ± 0.1 µg m−3 (30 % of total OC) between 2001 and 2013 at the urban Birmingham, Alabama (BHM), site. The urban OC declines coincide with reductions of motor vehicle emissions between 2006 and 2010, which may have decreased mean OC concentrations at the urban SEARCH sites by > 2 µg m−3. BHM additionally exhibits a decline in OC associated with SO2 from 0.4 ± 0.04 µg m−3 in 2001 to 0.2 ± 0.03 µg m−3 in 2013, interpreted as the result of reduced emissions from industrial sources within the city. Analyses using non-soil potassium as a biomass burning tracer indicate that biomass burning OC occurs throughout the year at all sites. All eight SEARCH sites show an association of OC with sulfate (SO4) ranging from 0.3 to 1.0 µg m−3 on average, representing  ∼  25 % of the 1999 to 2013 mean OC concentrations. Because the mass of OC identified with SO4 averages 20 to 30 % of the SO4 concentrations, the mean SO4-associated OC declined by  ∼  0.5 to 1 µg m−3 as SO4 concentrations decreased throughout the SEARCH region. The 2013 mean SO4 concentrations of 1.7 to 2.0 µg m−3 imply that future decreases in mean SO4-associated OC concentrations would not exceed  ∼  0.3 to 0.5 µg m−3. Seasonal OC concentrations, largely identified with ozone (O3), vary from 0.3 to 1.4 µg m−3 ( ∼  20 % of the total OC concentrations).

Quantify the regional methane emissions based on a new SCIAMACHY data set

2020 ◽  
Author(s):  
Mengyao Liu ◽  
Ronald Van der A ◽  
Haiyue Tan ◽  
Christian Frankenberg ◽  
Ilse Aben ◽  
...  
Keyword(s):  
Eastern China ◽  
Global Ocean ◽  
Background Concentration ◽  
Mountain Areas ◽  
Data Set ◽  
Cloud Data ◽  
Mixing Ratios ◽  
Regional Sources ◽  
Surface Measurements

&lt;p&gt;Methane (CH4) is the most important anthropogenic greenhouse gas after carbon dioxide, and it keeps increasing globally since 2007 after a period of relative stability, which is well-documented by surface measurements and satellites. Although satellites provide long-term global observations of CH4, the interpretation of column-averaged mixing ratios (xCH4) is difficult due to the influence of elevated terrains (i.e. mountain areas) and less abundant methane in the stratosphere. The lack of data over the ocean further limits global insights. Here we build a long-term global CH4 data set at a resolution of 0.25&amp;#176; &amp;#215; 0.25&amp;#176; &amp;#160;from SCIAMACHY, including the areas over the ocean, with the help of FRESCO cloud data. We dynamically consider the influence of elevations and contributions from the stratosphere through converting xCH4 to tropospheric xCH4 (trop_xCH4) by applying the daily ratios of tropospheric to stratospheric xCH4 in GEOS-Chem model.&lt;/p&gt;&lt;p&gt;The large increases occur in Trop_xCH4 over the source regions and mountain areas. The trend of SCIAMACHY Trop_xCH4 over the global ocean is comparable to the trend of NOAA globally averaged marine monthly mean data, showing the capability of SCIAMACHY in monitoring the ocean. After removing the latitudinally independent background concentration based on SCIAMACHY data over the ocean, we quantify the regional sources. A significant trend in Trop_ xCH4 relating to the background in Eastern China, India, tropical Africa, and tropical South America is further found from 2003 to 2011.&amp;#160;&lt;/p&gt;

scholarly journals Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

2009 ◽  
Vol 9 (22) ◽  
pp. 9083-9099 ◽  
Author(s):  
L. M. O'Brien ◽  
N. R. P. Harris ◽  
A. D. Robinson ◽  
B. Gostlow ◽  
N. Warwick ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Transport Model ◽  
Cape Verde ◽  
Background Concentration ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Model Studies ◽  
Mixing Ratios ◽  
Measurement Period

Abstract. A new gas chromatograph was used to make measurements of halocarbons at the Cape Verde observatory during late May and early June 2007. The instrument demonstrated its potential for long-term autonomous measurements. Bromoform (CHBr3) exhibits the most variability of all the halocarbons observed, ranging from a background concentration of about 4 ppt to a maximum of >40 ppt during the course of the measurement period. CH2Br2 correlates well with bromoform, suggesting a common regional source. Methyl iodide does not correlate with these bromocarbons, with base levels of around 1–2 ppt and some periods of much higher mixing ratios. Using published bromocarbon emission rates, our chemical transport model studies, presented here, do not reproduce the observations. Local emission magnitudes and CHBr3:CH2Br2 ratios must be increased more in line with the recent observations of Yokouchi et al. (2005) to improve the model to measurement comparison. Even when the model reproduces the observed bromocarbons, modelled BrO is much less than recent tropical observations (Read et al., 2008). A sea salt source seems the likely explanation. When high BrO is reproduced, the model agrees much better with the observed ozone changes, including diurnal variation, during the measurement period but it is suggested that a representation of iodine chemistry in the model is also required.

scholarly journals Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

2009 ◽  
Vol 9 (1) ◽  
pp. 4335-4379 ◽  
Author(s):  
L. M. O'Brien ◽  
N. R. P. Harris ◽  
A. D. Robinson ◽  
B. Gostlow ◽  
N. Warwick ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Cape Verde ◽  
Background Concentration ◽  
Emission Rates ◽  
Model Studies ◽  
Mixing Ratios ◽  
Local Emission ◽  
Regional Source ◽  
Measurement Period

Abstract. A new gas chromatograph was used to make measurements of halocarbons at the Cape Verde observatory during late May and early June 2007. The instrument demonstrated its potential for long-term autonomous measurements. Bromoform (CHBr3) exhibits the most variability of all the halocarbons observed, ranging from a background concentration of about 4 ppt to a maximum of >40 ppt during the course of the measurement period. Dibromomethane (CH2Br2) correlates well with CHBr3, suggesting a common regional source. Methyl iodide (CH3I) does not correlate with these bromocarbons, with base levels of around 1–2 ppt and some periods of much higher mixing ratios. Model studies with published bromocarbon emission rates do not reproduce the observations. Local emission magnitudes and CHBr3:CH2Br2 ratios must be increased more in line with the recent observations of Yokouchi et al. (2005) to improve the model to measurement comparison. Even when the model reproduces the observed bromocarbons, modelled BrO is much less than recent tropical observations (Read et al., 2008). A sea salt source seems the likely explanation. When high BrO is reproduced, the model agrees much better with the observed ozone changes, including diurnal variation, during the measurement period but it is suggested that a representation of iodine chemistry in the model is also required.

scholarly journals Long-term mortality due to infection associated with elevated liver enzymes: a population-based cohort study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tak Kyu Oh ◽  
Eun Sun Jang ◽  
In-Ae Song
Keyword(s):  
Cohort Study ◽  
Liver Enzymes ◽  
Adult Population ◽  
Population Based ◽  
Study Data ◽  
Point Increase ◽  
Elevated Liver Enzymes ◽  
Glutamyl Transpeptidase ◽  
Long Term Mortality

AbstractWe aimed to investigate whether elevated liver enzymes in the adult population were associated with mortality due to infection. As a population-based cohort study, data from the National Health Insurance Service Health Screening Cohort were used. Adult individuals (aged ≥ 40 years) who underwent standardized medical examination between 2002 and 2003 were included, and infectious mortality was defined as mortality due to infection between 2004 and 2015. Aspartate transaminase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), AST/ALT ratio, and dynamic AST/ALT ratio (dAAR) were included in multivariable Cox modeling. A total of 512,746 individuals were included in this study. Infectious mortality occurred in 2444 individuals (0.5%). In the multivariable model, moderate and severe elevation in AST was associated with 1.94-fold [hazard ratio (HR):1.94, 95% confidence interval (CI) 1.71–2.19; P < 0.001] and 3.93-fold (HR: 3.93, 95% CI 3.05–5.07; P < 0.001) higher infectious mortality respectively, compared with the normal AST group. Similar results were observed for moderate and severe elevation in ALT and mild, moderate, and severe elevation in γ-GTP. Additionally, a 1-point increase in the AST/ALT ratio and dAAR was associated with higher infection mortality. Elevated liver enzymes (AST, ALT, AST/ALT ratio, γ-GTP, and dAAR) were associated with increased infectious mortality.

scholarly journals Long-term O<sub>3</sub>–precursor relationships in Hong Kong: field observation and model simulation

2017 ◽  
Vol 17 (18) ◽  
pp. 10919-10935 ◽  
Author(s):  
Yu Wang ◽  
Hao Wang ◽  
Hai Guo ◽  
Xiaopu Lyu ◽  
Hairong Cheng ◽  
...  
Keyword(s):  
Hong Kong ◽  
Model Simulation ◽  
Ground Level ◽  
Effective Control ◽  
Photochemical Pollution ◽  
Mixing Ratios ◽  
The Past ◽  
Total Volatile Organic Compounds

Abstract. Over the past 10 years (2005–2014), ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e. nitrogen oxides (NOx =  NO + NO2), total volatile organic compounds (TVOCs), and carbon monoxide (CO). To explain the contradictory phenomena, an observation-based box model (OBM) coupled with CB05 mechanism was applied in order to understand the influence of both locally produced O3 and regional transport. The simulation of locally produced O3 showed an increasing trend in spring, a decreasing trend in autumn, and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease in NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease in NO titration. However, the decreased in situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and that the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, probably due to the effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provide updated information on photochemical pollution and its impact in Hong Kong.

scholarly journals Changes to the chemical state of the northern hemisphere atmosphere during the second half of the twentieth century

2016 ◽  
Author(s):  
Mike J. Newland ◽  
Patricia Martinerie ◽  
Emmanuel Witrant ◽  
Detlev Helmig ◽  
David R. Worton ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Major Influence ◽  
Secondary Products ◽  
Alkyl Nitrates ◽  
Mixing Ratios ◽  
Wide Range

Abstract. The NOX (NO and NO2) and HOX (OH and HO2) budgets of the atmosphere exert a major influence on atmospheric composition, controlling removal of primary pollutants and formation of a wide range of secondary products, including ozone, that can influence human health and climate. However, there remain large uncertainties in the changes to these budgets over recent decades. Due to their short atmospheric lifetimes, NOX and HOX are highly variable in space and time, and so the measurements of these species are of very limited value for examining long term, large scale changes to their budgets. Here, we take an alternative approach by examining long-term atmospheric trends of alkyl nitrates, the formation of which is dependent on the atmospheric NO / HO2 ratio. We derive long term trends in the alkyl nitrates from measurements in firn air from the NEEM site, Greenland. Their mixing ratios increased by a factor of 4–5 between the 1970s and 1990s. This was followed by a steep decline to the sampling date of 2008. Moreover, we examine how the trends in the alkyl nitrates compare to similarly derived trends in their parent alkanes (i.e. the alkanes which, when oxidised in the presence of NOX, lead to the formation of the alkyl nitrates). The ratios of the alkyl nitrates to their parent alkanes increase from around 1970 to the late 1990's consistent with large changes to the [NO] / [HO2] ratio in the northern hemisphere atmosphere during this period. These could represent historic changes to NOX sources and sinks. Alternatively, they could represent changes to concentrations of the hydroxyl radical, OH, or to the transport time of the air masses from source regions to the Arctic.

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