Shifting the fossil fuel dominated energy system to a sustainable hydrogen economy could mitigate climate change through reduction of greenhouse gas emissions. Because it is estimated that fossil ...fuels will remain a significant part of our energy system until mid-century, bridge technologies which use fossil fuels in an environmentally cleaner way offer an opportunity to reduce the warming impact of continued fossil fuel utilization. Methane cracking is a potential bridge technology during the transition to a sustainable hydrogen economy since it produces hydrogen with zero emissions of carbon dioxide. However, methane feedstock obtained from natural gas releases fugitive emissions of methane, a potent greenhouse gas that may offset methane cracking benefits. In this work, a model exploring the impact of methane cracking implementation in a hydrogen economy is presented, and the impact on global emissions of carbon dioxide and methane is explored. The results indicate that the hydrogen economy has the potential to reduce global carbon dioxide equivalent emissions between 0 and 27%, when methane leakage from natural gas is relatively low, methane cracking is employed to produce hydrogen, and a hydrogen fuel cell is applied. This wide range is a result of differences between the scenarios and the CH4 leakage rates used in the scenarios. On the other hand, when methane leakage from natural gas is relatively high, methane steam reforming is employed to produce hydrogen and an internal combustion engine is applied, the hydrogen economy leads to a net increase in global carbon dioxide equivalent emissions between 19 and 27%.
•Methane cracking-hydrogen economy has the potential to mitigate climate change.•Up to 27% global CO2-eq emissions decrease by methane cracking-hydrogen economy.•Strong influence of CH4 leakage from natural gas system on total global emissions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Amyotrophic lateral sclerosis (ALS) is characterized by selective degeneration of motor neurons. Current imaging studies have concentrated on areas of the brain and spinal cord that contain mixed ...populations of sensory and motor neurons. In this study,
ex vivo magnetic resonance microimaging (MRM) was used to separate motor and sensory components by visualizing individual dorsal and ventral roots in fixed spinal cords. MRM at 15
μm in plane resolution enabled the axons of pure populations of sensory and motor neurons to be measured in the lumbar region of the SOD1 mouse model of ALS. MRM signal intensity increased by 38.3% (
p
<
0.05) exclusively in the ventral motor nerve roots of the lumbar spinal cord of ALS-affected SOD1 mice compared to wildtype littermates. The hyperintensity was therefore limited to white matter tracts arising from the motor neurons, whereas sensory white matter fibers were unchanged. Significant decreases in ventral nerve root volume were also detected in the SOD1 mice, which correlated with the axonal degeneration observed by microscopy. These results demonstrate the usefulness of MRM in visualizing the ultrastructure of the mouse spinal cord. The detailed 3D anatomy allowed the processes of pure populations of sensory and motor neurons to be compared.
► Magnetic resonance microimaging can detect axonal spinal cord damage in SOD1 mice. ► MRM signal intensity is increased in ventral nerves of SOD1 mice. ► Increasing MRM signal intensity correlates with decreasing axon number. ► MRM motor nerve root volume is decreased in SOD1 mice. ► High resolution MRM at 10
μm provided close to optical microscopy resolution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Urban air pollution has become a major concern over the past decades. One of the largest conurbations in Sub-Saharan Africa is developed around the cities of Johannesburg and Pretoria (Jhb-Pta ...megacity). In this study, a photochemical box model with a detailed representation of ozone (O3) formation chemistry was used to investigate the state of current air quality and photochemical processes in the Jhb-Pta megacity, as well as scenarios that could possibly mitigate air pollution. Results indicated that the Jhb-Pta megacity is within a VOC-limited (or NOx-saturated) regime. Major sources of NOx include transport from the Mpumalanga Highveld and local traffic emissions. O3 levels in the Jhb-Pta megacity will be more effectively reduced if VOC (volatile organic compound) emissions are decreased. A reduction of NOx emissions leads to an increase in O3 because of a decrease in titration through the reaction with NO. The same effect was observed in various cities worldwide, where O3 levels increased when NOx emissions were reduced during emission control strategies.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tropospheric ozone (O.sub.3) is an important air pollutant that affects human health, ecosystems, and climate. The contributions of O.sub.3 precursor emissions from different geographical source ...regions to the O.sub.3 concentration can help to quantify the effects of local versus remotely transported precursors on the O.sub.3 concentration in a certain area. This study presents a "tagging" approach within the WRF-Chem model that attributes O.sub.3 concentration in several European receptor regions to nitrogen oxide (NO.sub.x) emissions from within and outside of Europe during April-September 2010. We also examine the contribution of these different precursor sources to various O.sub.3 metrics and their exceedance events. Firstly, we show that the spatial distributions of simulated monthly mean MDA8 from tagged O.sub.3 source regions and types for late spring, summer, and early autumn 2010 varies with season. For summer conditions, O.sub.3 production is dominated by national and intra-European sources, while in the late spring and early autumn intercontinental transported O.sub.3 is an important contributor to the total O.sub.3 concentration. We have also identified shipping activities in the Mediterranean Sea as an important source of O.sub.3 for the Mediterranean countries, as well as the main contributor to high modelled MDA8 O.sub.3 concentration in the Mediterranean Basin itself. Secondly, to have a better understanding of the origin of MDA8 O.sub.3 exceedances, we compare modelled and observed values of MDA8 O.sub.3 concentration in the Po Valley and Germany-Benelux receptor regions, revealing that the contribution from local sources is about 41 % and 38 % of modelled MDA8 O.sub.3 during the exceedance days, respectively. By examining the relative contributions of remote NO.sub.x sources to modelled and observed O.sub.3 exceedance events, we determine that model underrepresentation of long-range O.sub.3 transport could be contributing to a general underestimation of modelled O.sub.3 exceedance events in the Germany-Benelux receptor region. Thirdly, we quantify the impact of local vs. non-local NO.sub.x precursors on O.sub.3 production for each European receptor region using different O.sub.3 metrics. The comparison between mean, MDA8 and 95th percentile O.sub.3 metrics accentuates the importance of large contributions from locally emitted NO.sub.x precursors to the high end of the O.sub.3 distribution. When we compare the vegetation and health metrics, we notice that the SOMO35 and AOT40 indexes exhibit rather similar behaviour, while the W126 index accentuates the importance of local emissions. Overall, this study highlights the importance of a tagging approach to quantify the contribution of local and remote sources to the MDA8 O.sub.3 concentration during several periods as well to different O.sub.3 metrics. Moreover, this method could be applied to assess different mitigation options.
Due to the strong temperature dependence of surface ozone concentrations (O3), future warmer conditions may worsen ozone pollution levels despite continued efforts on emission controls of ozone ...precursors. Using long-term measurements of hourly O3 concentrations co-located with NOx concentrations in stations distributed throughout Germany, we assess changes in the climate penalty in summertime, defined as the slope of ozone-temperature relationship during the period 1999–2018. We find a stronger temperature sensitivity in the urban stations over the southwestern regions, especially in the first period of the study (1999–2008). We show a decrease in the climate penalty in most of stations during the second period of the study (2009–2018), with some exceptions (e.g. Berlin) where the climate penalty did not show significant changes. A key motivation of this study is to provide further insights into the impacts of NOx reductions in the O3-temperature relationship. For that, we propose a statisti-cal approach based on Generalized Additive Models (GAMs) to describe ozone production rates, inferred from hourly observations, as a function of NOx and temperature, among other variables relevant during the O3 production. The GAMs confirm lower O3 production rates during the second period (2009–2018) at most of the stations and a decreasing sensitivity to temperature. We observe that a large number of stations are transitioning to NOx-limited chemistry, consistent with a decreasing temperature dependence of O3 at moderate-high temperatures as a result of sustained NOx reductions. Moreover, the GAMs results showed changes in the shape of the function representing the O3-temperature relationship when comparing the first and second period, which suggest changes in VOC influencing the temperature dependence of O3. From these results, we infer effective VOC reductions over time that have also contributed to the observed decrease of O3 production rates. Thus, our analysis indicates that emissions reductions have been effective in a number of stations, particularly in the southwestern regions. However, we notice that in a few stations (e.g. Berlin) additional emission reductions should be required to effectively mitigate the temperature dependence of O3.
•The observed climate penalty of ozone has decreased over the past decades in a large number of German stations.•There is a decreasing temperature dependence of ozone at moderate-high temperatures.•Emissions reductions have been generally effective in the southwestern regions of Germany.•In Berlin, additional emission reductions should be required to mitigate the climate penalty of ozone.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Germany and the United Kingdom have domestic shale gas reserves which they may exploit in the future to complement their national energy strategies. However gas production releases volatile organic ...compounds (VOC) and nitrogen oxides (NOx), which through photochemical reaction form ground-level ozone, an air pollutant that can trigger adverse health effects e.g. on the respiratory system. This study explores the range of impacts of a potential shale gas industry in these two countries on local and regional ambient ozone. To this end, comprehensive emission scenarios are used as the basis for input to an online-coupled regional chemistry transport model (WRF-Chem). Here we simulate shale gas scenarios over summer (June, July, August) 2011, exploring the effects of varying VOC emissions, gas speciation, and concentration of NOx emissions over space and time, on ozone formation. An evaluation of the model setup is performed, which exhibited the model’s ability to predict surface meteorological and chemical variables well compared with observations, and consistent with other studies. When different shale gas scenarios were employed, the results show a peak increase in maximum daily 8-hour average ozone from 3.7 to 28.3 μg m–3. In addition, we find that shale gas emissions can force ozone exceedances at a considerable percentage of regulatory measurement stations locally (up to 21% in Germany and 35% in the United Kingdom) and in distant countries through long-range transport, and increase the cumulative health-related metric SOMO35 (maximum percent increase of ~28%) throughout the region. Findings indicate that VOC emissions are important for ozone enhancement, and to a lesser extent NOx, meaning that VOC regulation for a future European shale gas industry will be of especial importance to mitigate unfavorable health outcomes. Overall our findings demonstrate that shale gas production in Europe can worsen ozone air quality on both the local and regional scales.
A comprehensive overview is provided evaluating direct real-world CO2 emissions of both diesel and petrol cars newly registered in Europe between 1995 and 2015. Before 2011, European diesel cars ...emitted less CO2 per kilometre than petrol cars, but since then there is no appreciable difference in per-km CO2 emissions between diesel and petrol cars. Real-world CO2 emissions of diesel cars have not declined appreciably since 2001, while the CO2 emissions of petrol cars have been stagnant since 2012. When adding black carbon related CO2-equivalents, such as from diesel cars without particulate filters, diesel cars were discovered to have had much higher climate relevant emissions until the year 2001 when compared to petrol cars. From 2001 to 2015 CO2-equivalent emissions from new diesel cars and petrol cars were hardly distinguishable. Lifetime use phase CO2-equivalent emissions of all European passenger vehicles were modelled for 1995–2015 based on three scenarios: the historic case, another scenario freezing percentages of diesel cars at the low levels from the early 1990s (thus avoiding the observed “boom” in new diesel registrations), and an advanced mitigation scenario based on high proportions of petrol hybrid cars and cars burning gaseous fuels. The difference in CO2-equivalent emissions between the historical case and the scenario avoiding the diesel car boom is only 0.4%. The advanced mitigation scenario would have been able to achieve a 3.4% reduction in total CO2-equivalent emissions over the same time frame. The European diesel car boom appears to have been ineffective at reducing climate-warming emissions from the European transport sector.
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•Diesel cars had much higher CO2-equivalent emissions than petrol cars until the year 2001.•From 2001 to 2015 CO2-equivalent emissions from new diesel cars and petrol cars became hardly distinguishable.•Difference in modelled CO2-equivalent emissions between 1995 and 2015 and a scenario for the same period avoiding the diesel car boom is negligible.•An advanced mitigation scenario would have been able to achieve a 3.4% reduction in total CO2-equivalent emissions.•The European diesel car boom was ineffective at reducing climate-warming emissions from the European transport sector.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this article we review the physical and chemical properties of methane (CH4) relevant to impacts on climate, ecosystems, and air pollution, and examine the extent to which this is reflected in ...climate and air pollution governance. Although CH4 is governed under the UNFCCC climate regime, its treatment there is limited to the ways in which it acts as a “CO2 equivalent” climate forcer on a 100-year time frame. The UNFCCC framework neglects the impacts that CH4 has on near-term climate, as well its impacts on human health and ecosystems, which are primarily mediated by methane’s role as a precursor to tropospheric ozone. Frameworks for air quality governance generally address tropospheric ozone as a pollutant, but do not regulate CH4 itself. Methane’s climate and air quality impacts, together with its alarming rise in atmospheric concentrations in recent years, make it clear that mitigation of CH4 emissions needs to be accelerated globally. We examine challenges and opportunities for further progress on CH4 mitigation within the international governance landscapes for climate change and air pollution.
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•CH4’s impacts on climate, ecosystems, and air quality are significant.•The concept of “CO2 equivalence” does not adequately capture these impacts.•These impacts are not adequately treated under international climate or air policy.•Opportunities for improving methane governance are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tropospheric ozone (O3) is an important air pollutant that affects human health, ecosystems, and climate. The contributions of O3 precursor emissions from different geographical source regions to the ...O3 concentration can help to quantify the effects of local versus remotely transported precursors on the O3 concentration in a certain area. This study presents a “tagging” approach within the WRF-Chem model that attributes O3 concentration in several European receptor regions to nitrogen oxide (NOx) emissions from within and outside of Europe during April–September 2010. We also examine the contribution of these different precursor sources to various O3 metrics and their exceedance events. Firstly, we show that the spatial distributions of simulated monthly mean MDA8 from tagged O3 source regions and types for late spring, summer, and early autumn 2010 varies with season. For summer conditions, O3 production is dominated by national and intra-European sources, while in the late spring and early autumn intercontinental transported O3 is an important contributor to the total O3 concentration. We have also identified shipping activities in the Mediterranean Sea as an important source of O3 for the Mediterranean countries, as well as the main contributor to high modelled MDA8 O3 concentration in the Mediterranean Basin itself. Secondly, to have a better understanding of the origin of MDA8 O3 exceedances, we compare modelled and observed values of MDA8 O3 concentration in the Po Valley and Germany–Benelux receptor regions, revealing that the contribution from local sources is about 41 % and 38 % of modelled MDA8 O3 during the exceedance days, respectively. By examining the relative contributions of remote NOx sources to modelled and observed O3 exceedance events, we determine that model underrepresentation of long-range O3 transport could be contributing to a general underestimation of modelled O3 exceedance events in the Germany–Benelux receptor region. Thirdly, we quantify the impact of local vs. non-local NOx precursors on O3 production for each European receptor region using different O3 metrics. The comparison between mean, MDA8 and 95th percentile O3 metrics accentuates the importance of large contributions from locally emitted NOx precursors to the high end of the O3 distribution. When we compare the vegetation and health metrics, we notice that the SOMO35 and AOT40 indexes exhibit rather similar behaviour, while the W126 index accentuates the importance of local emissions. Overall, this study highlights the importance of a tagging approach to quantify the contribution of local and remote sources to the MDA8 O3 concentration during several periods as well to different O3 metrics. Moreover, this method could be applied to assess different mitigation options.
Education is at or near the heart of policies for fostering greater social integration, social mobility and national competititveness and reducing social exclusion. Educational opportunity and ...attainment have for long been recognised to be class related, and in the US, there has been a strong racial dimension to issues of educational opportunity and attainment with major inequalities in educational attainment between Blacks and Whites. One question this article attempts to answer is why has education risen up the political agenda in many countries in recent years.
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BFBNIB, DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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