scholarly journals The changing role of organic nitrates in the removal and transport of NO<sub><i>x</i></sub>

2020 ◽  
Vol 20 (1) ◽  
pp. 267-279 ◽  
Author(s):  
Paul S. Romer Present ◽  
Azimeh Zare ◽  
Ronald C. Cohen
Keyword(s):  
Air Pollution ◽  
The United States ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Nox Emissions ◽  
Direct Formation ◽  
In Situ Observations ◽  
Changing Role

Abstract. A better understanding of the chemistry of nitrogen oxides (NOx) is crucial to effectively reducing air pollution and predicting future air quality. The response of NOx lifetime to perturbations in emissions or in the climate system is set in large part by whether NOx loss occurs primarily by the direct formation of HNO3 or through the formation of alkyl and multifunctional nitrates (RONO2). Using 15 years of detailed in situ observations, we show that in the summer daytime continental boundary layer the relative importance of these two pathways can be well approximated by the relative likelihood that OH will react with NO2 or instead with a volatile organic compound (VOC). Over the past decades, changes in anthropogenic emissions of both NOx and VOCs have led to a significant increase in the overall importance of RONO2 chemistry to NOx loss. We find that this shift is associated with a decreased effectiveness of NOx emissions reductions on ozone production in polluted areas and increased transport of NOx from source to receptor regions. This change in chemistry, combined with changes in the spatial pattern of NOx emissions, is observed to be leading to a flatter distribution of NO2 across the United States, potentially transforming ozone air pollution from a local issue into a regional one.

scholarly journals The changing role of organic nitrates in the removal and transport of NO<sub>x</sub>

2019 ◽  
Author(s):  
Paul S. Romer Present ◽  
Azimeh Zare ◽  
Ronald C. Cohen
Keyword(s):  
Air Pollution ◽  
The United States ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Volatile Organic ◽  
Direct Formation ◽  
In Situ Observations ◽  
Changing Role

Abstract. A better understanding of the chemistry of nitrogen oxides (NONOx) is crucial to effectively reducing air pollution and predicting future air quality. The response of NOx lifetime to perturbations in emissions or in the climate system is set in large part by whether NOx loss occurs primarily by the direct formation of HNO3 or through the formation of alkyl and multifunctional nitrates (RONO2). Using 15 years of detailed in situ observations, we show that in the summertime continental boundary layer the relative importance of these two pathways can be well approximated by the relative likelihood that OH will react with NO2 or instead with a volatile organic compound (VOC). Over the past decades, changes in anthropogenic emissions of both NONOx and VOCs have led to a significant increase in the overall importance of RONO2 chemistry to NONOx loss. We find that this shift is associated with a decreased effectiveness of NONOx emissions reductions on ozone production in polluted areas and increased transport of NONOx from source to receptor regions. This change in chemistry, combined with changes in the spatial pattern of NONOx emissions, is observed to be leading to a flatter distribution of NO2 across the United States, potentially transforming ozone air pollution from a local issue into a regional one.

scholarly journals International Arctic Systems for Observing the Atmosphere: An International Polar Year Legacy Consortium

2016 ◽  
Vol 97 (6) ◽  
pp. 1033-1056 ◽  
Author(s):  
Taneil Uttal ◽  
Sandra Starkweather ◽  
James R. Drummond ◽  
Timo Vihma ◽  
Alexander P. Makshtas ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Satellite Observations ◽  
The Arctic ◽  
International Polar Year ◽  
Network Measurements ◽  
International Polar ◽  
In Situ Observations ◽  
Arctic Atmosphere

Abstract International Arctic Systems for Observing the Atmosphere (IASOA) activities and partnerships were initiated as a part of the 2007–09 International Polar Year (IPY) and are expected to continue for many decades as a legacy program. The IASOA focus is on coordinating intensive measurements of the Arctic atmosphere collected in the United States, Canada, Russia, Norway, Finland, and Greenland to create synthesis science that leads to an understanding of why and not just how the Arctic atmosphere is evolving. The IASOA premise is that there are limitations with Arctic modeling and satellite observations that can only be addressed with boots-on-the-ground, in situ observations and that the potential of combining individual station and network measurements into an integrated observing system is tremendous. The IASOA vision is that by further integrating with other network observing programs focusing on hydrology, glaciology, oceanography, terrestrial, and biological systems it will be possible to understand the mechanisms of the entire Arctic system, perhaps well enough for humans to mitigate undesirable variations and adapt to inevitable change.

scholarly journals Central role of nitric oxide in ozone production in the upper tropical troposphere over the Atlantic Ocean and western Africa

2021 ◽  
Vol 21 (10) ◽  
pp. 8195-8211
Author(s):  
Ivan Tadic ◽  
Clara M. Nussbaumer ◽  
Birger Bohn ◽  
Hartwig Harder ◽  
Daniel Marno ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Atlantic Ocean ◽  
General Circulation ◽  
Simulated Data ◽  
Ozone Production ◽  
Mixing Ratios ◽  
Western Africa ◽  
Tropical Troposphere

Abstract. Mechanisms of tropospheric ozone (O3) formation are generally well understood. However, studies reporting on net ozone production rates (NOPRs) directly derived from in situ observations are challenging and are sparse in number. To analyze the role of nitric oxide (NO) in net ozone production in the upper tropical troposphere above the Atlantic Ocean and western Africa, we present in situ trace gas observations obtained during the CAFE-Africa (Chemistry of the Atmosphere: Field Experiment in Africa) campaign in August and September 2018. The vertical profile of in situ measured NO along the flight tracks reveals lowest NO mixing ratios of less than 20 pptv between 2 and 8 km altitude and highest mixing ratios of 0.15–0.2 ppbv above 12 km altitude. Spatial distribution of tropospheric NO above 12 km altitude shows that the sporadically enhanced local mixing ratios (>0.4 ppbv) occur over western Africa, which we attribute to episodic lightning events. Measured O3 shows little variability in mixing ratios at 60–70 ppbv, with slightly decreasing and increasing tendencies towards the boundary layer and stratosphere, respectively. Concurrent measurements of CO, CH4, OH, HO2 and H2O enable calculations of NOPRs along the flight tracks and reveal net ozone destruction at −0.6 to −0.2 ppbv h−1 below 6 km altitude and balance of production and destruction around 7–8 km altitude. We report vertical average NOPRs of 0.2–0.4 ppbv h−1 above 12 km altitude with NOPRs occasionally larger than 0.5 ppbv h−1 over western Africa coincident with enhanced NO. We compare the observational results to simulated data retrieved from the general circulation model ECHAM/MESSy Atmospheric Chemistry (EMAC). Although the comparison of mean vertical profiles of NO and O3 indicates good agreement, local deviations between measured and modeled NO are substantial. The vertical tendencies in NOPRs calculated from simulated data largely reproduce those from in situ experimental data. However, the simulation results do not agree well with NOPRs over western Africa. Both measurements and simulations indicate that ozone formation in the upper tropical troposphere is NOx limited.

Language Tests, Language Policy, and Citizenship

2018 ◽  
Author(s):  
Kellie Frost ◽  
Tim McNamara
Keyword(s):  
Immigration Policy ◽  
The United States ◽  
Language Test ◽  
Immigrant Communities ◽  
Language Tests ◽  
Highly Skilled Migrants ◽  
The Impact ◽  
Changing Role ◽  
Significant Attention

The role of language tests in immigration policy has attracted significant attention in recent years as the disruptive effects of globalisation are felt. Much of the research has focused on the situation in Europe, where societies that were traditionally not countries of immigration now have significant and increasing immigrant communities. Less attention has been paid to countries of immigration such as Australia, Canada, New Zealand, and the United States, which have sometimes encouraged immigration and have found it easier to embrace various forms of multiculturalism, despite some inevitable tensions. This chapter provides an account of the complex and rapidly changing role that language test scores have played in immigration policies favouring highly skilled migrants in Australia, and draws on Foucault’s discussion of the function of examinations to explore the impact of these changes on the lives of individuals subjected to the policies.

Aquatic Stewardship Education in Theory and Practice

2007 ◽  
Keyword(s):  
Air Pollution ◽  
The United States ◽  
Theory And Practice ◽  
Marine Debris ◽  
Direct Link ◽  
Government Programs ◽  
And Behavior ◽  
Sewage Discharges ◽  
Over Time

Abstract.—In 2003, more than 69 million people participated in recreational boating in the United States. The tenet that boating activity leads to higher aquatic stewardship ethics is often assumed since heightened environmental sensitivity has been correlated with significant positive contact with the outdoors. However, a direct link between boating and stewardship has not been substantiated. A review of current outreach efforts suggests that measures of boating-related stewardship could include preventing petroleum-based pollution, reducing marine debris, reducing sewage discharges, reducing air pollution, reducing habitat disturbance and physical destruction, and utilizing less harmful chemicals for boating activities. Measures of positive stewardship could also include boater’s involvement in, and support of, government programs and funding that promote these on-the-water behaviors. While these behaviors could be considered outward signs of good stewardship ethics, the motivation behind them would be more difficult to assess, thereby complicating the distinction between actual stewardship and behavior motivated by other forces. However, to the natural resources manager, motivation may not be as important as the resulting behavior, as long as the desired behaviors are sustained over time. A review of behaviors being promoted by the boating community (and applied examples), their utility as measures of aquatic stewardship, and the role of motivations are discussed.

scholarly journals Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

2019 ◽  
Vol 19 (7) ◽  
pp. 5235-5249 ◽  
Author(s):  
Kuangyou Yu ◽  
Qiao Zhu ◽  
Ke Du ◽  
Xiao-Feng Huang
Keyword(s):  
High Resolution ◽  
Organic Aerosol ◽  
The United States ◽  
Ozone Production ◽  
Urban Site ◽  
Organic Nitrate ◽  
High Time Resolution ◽  
Organic Nitrates ◽  
Aerosol Mass

Abstract. Organic nitrates are important atmospheric species that significantly affect the cycling of NOx and ozone production. However, characterization of particulate organic nitrates and their sources in polluted atmosphere is a big challenge and has not been comprehensively studied in Asia. In this study, an aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at an urban site in China from 2015 to 2016 to characterize particulate organic nitrates in total nitrates with a high time resolution. Based on the cross-validation of two different data processing methods, organic nitrates were effectively quantified to contribute a notable fraction of organic aerosol (OA), namely 9 %–21 % in spring, 11 %–25 % in summer, and 9 %–20 % in autumn, while contributing a very small fraction in winter. The good correlation between organic nitrates and fresh secondary organic aerosol (SOA) at night, as well as the diurnal trend of size distribution of organic nitrates, indicated a key role of nighttime local secondary formation of organic nitrates. Furthermore, theoretical calculations of nighttime SOA production of NO3 reactions with volatile organic compounds (VOCs) measured during the spring campaign were performed, resulting in three biogenic VOCs (α-pinene, limonene, and camphene) and one anthropogenic VOC (styrene) identified as the possible key VOC precursors to particulate organic nitrates. The comparison with similar studies in the literature implied that nighttime particulate organic nitrate formation is highly relevant to NOx levels. This study proposes that unlike the documented cases in the United States and Europe, modeling nighttime particulate organic nitrate formation in China should incorporate not only biogenic VOCs but also anthropogenic VOCs for urban air pollution, which needs the support of relevant smog chamber studies in the future.

scholarly journals Characterization of ozone production in San Antonio, Texas, using measurements of total peroxy radicals

2019 ◽  
Vol 19 (5) ◽  
pp. 2845-2860 ◽  
Author(s):  
Daniel C. Anderson ◽  
Jessica Pavelec ◽  
Conner Daube ◽  
Scott C. Herndon ◽  
Walter B. Knighton ◽  
...  
Keyword(s):  
San Antonio ◽  
Peroxy Radical ◽  
Ozone Production ◽  
Peroxy Radicals ◽  
Entire Region ◽  
Volatile Organic ◽  
In Situ Observations ◽  
Study Sites

Abstract. Observations of total peroxy radical concentrations ([XO2] ≡ [RO2] + [HO2]) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made on board the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas, region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv h−1, a factor of 2 higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv h−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO2, suggest that the region was predominantly NOx-limited. Only approximately 20 % of observations were in the VOC-limited regime, predominantly before 11:00 EST, when ozone production was low. Biogenic volatile organic compounds (VOCs) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

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