scholarly journals Halogen activation via interactions with environmental ice and snow

2012 ◽  
Vol 12 (4) ◽  
pp. 8677-8769
Author(s):  
J. P. D. Abbatt ◽  
J. L. Thomas ◽  
K. Abrahamsson ◽  
C. Boxe ◽  
A. Granfors ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Regional Scale ◽  
Multiphase Reactions ◽  
Current State ◽  
Field Evidence ◽  
Halogen Chemistry ◽  
Activation Mechanisms ◽  
Global Impacts ◽  
Rapid Pace ◽  
Halogen Activation

Abstract. The role of ice in the formation of chemically active halogens in the environment requires a full understanding because of its role in atmospheric chemistry, including controlling the oxidizing capacity of the atmosphere. In particular, ice and snow are important for facilitating multiphase oxidative chemistry and as media upon which marine algae live. This paper reviews the nature of environmental ice substrates that participate in halogen chemistry, describes the multiphase reactions that occur on such substrates, presents the field evidence for ice-mediated halogen activation, summarizes our best understanding of ice-halogen activation mechanisms, and describes the current state of modeling these processes at different scales. Given the rapid pace of developments in the field, this paper largely addresses advances made in the past five years, with emphasis given to the polar boundary layer. The integrative nature of this field is highlighted in the presentation of work from the molecular to the regional scale, with a focus on understanding fundamental processes. This is essential for developing realistic parameterizations and descriptions of these processes for inclusion in larger scale models that are used to determine their regional and global impacts.

scholarly journals Halogen activation via interactions with environmental ice and snow in the polar lower troposphere and other regions

2012 ◽  
Vol 12 (14) ◽  
pp. 6237-6271 ◽  
Author(s):  
J. P. D. Abbatt ◽  
J. L. Thomas ◽  
K. Abrahamsson ◽  
C. Boxe ◽  
A. Granfors ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Regional Scale ◽  
Lower Troposphere ◽  
Current State ◽  
Field Evidence ◽  
Halogen Chemistry ◽  
Activation Mechanisms ◽  
Global Impacts ◽  
Rapid Pace ◽  
Halogen Activation

Abstract. The role of ice in the formation of chemically active halogens in the environment requires a full understanding because of its role in atmospheric chemistry, including controlling the regional atmospheric oxidizing capacity in specific situations. In particular, ice and snow are important for facilitating multiphase oxidative chemistry and as media upon which marine algae live. This paper reviews the nature of environmental ice substrates that participate in halogen chemistry, describes the reactions that occur on such substrates, presents the field evidence for ice-mediated halogen activation, summarizes our best understanding of ice-halogen activation mechanisms, and describes the current state of modeling these processes at different scales. Given the rapid pace of developments in the field, this paper largely addresses advances made in the past five years, with emphasis given to the polar boundary layer. The integrative nature of this field is highlighted in the presentation of work from the molecular to the regional scale, with a focus on understanding fundamental processes. This is essential for developing realistic parameterizations and descriptions of these processes for inclusion in larger scale models that are used to determine their regional and global impacts.

scholarly journals Tropospheric Ozone Assessment Report: Present-day tropospheric ozone distribution and trends relevant to vegetation

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Gina Mills ◽  
Håkan Pleijel ◽  
Christopher S. Malley ◽  
Baerbel Sinha ◽  
Owen R. Cooper ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Regional Scale ◽  
Mean Values ◽  
Assessment Report ◽  
North West ◽  
Northern India ◽  
Current State ◽  
Field Evidence ◽  
The Usa ◽  
The Republic

This Tropospheric Ozone Assessment Report (TOAR) on the current state of knowledge of ozone metrics of relevance to vegetation (TOAR-Vegetation) reports on present-day global distribution of ozone at over 3300 vegetated sites and the long-term trends at nearly 1200 sites. TOAR-Vegetation focusses on three metrics over vegetation-relevant time-periods across major world climatic zones: M12, the mean ozone during 08:00–19:59; AOT40, the accumulation of hourly mean ozone values over 40 ppb during daylight hours, and W126 with stronger weighting to higher hourly mean values, accumulated during 08:00–19:59. Although the density of measurement stations is highly variable across regions, in general, the highest ozone values (mean, 2010–14) are in mid-latitudes of the northern hemisphere, including southern USA, the Mediterranean basin, northern India, north, north-west and east China, the Republic of Korea and Japan. The lowest metric values reported are in Australia, New Zealand, southern parts of South America and some northern parts of Europe, Canada and the USA. Regional-scale assessments showed, for example, significantly higher AOT40 and W126 values in East Asia (EAS) than Europe (EUR) in wheat growing areas (p < 0.05), but not in rice growing areas. In NAM, the dominant trend during 1995–2014 was a significant decrease in ozone, whilst in EUR it was no change and in EAS it was a significant increase. TOAR-Vegetation provides recommendations to facilitate a more complete global assessment of ozone impacts on vegetation in the future, including: an increase in monitoring of ozone and collation of field evidence of the damaging effects on vegetation; an investigation of the effects on peri-urban agriculture and in mountain/upland areas; inclusion of additional pollutant, meteorological and inlet height data in the TOAR dataset; where not already in existence, establishing new region-specific thresholds for vegetation damage and an innovative integration of observations and modelling including stomatal uptake of the pollutant.

scholarly journals The global impacts of COVID-19 lockdowns on urban air pollution

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Georgios I. Gkatzelis ◽  
Jessica B. Gilman ◽  
Steven S. Brown ◽  
Henk Eskes ◽  
A. Rita Gomes ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Air Pollution ◽  
Future Research ◽  
Specific Method ◽  
Data Sets ◽  
Atmospheric Pollutant ◽  
Government Interventions ◽  
Pollutant Concentrations ◽  
Global Impacts ◽  
The Government

The coronavirus-19 (COVID-19) pandemic led to government interventions to limit the spread of the disease which are unprecedented in recent history; for example, stay at home orders led to sudden decreases in atmospheric emissions from the transportation sector. In this review article, the current understanding of the influence of emission reductions on atmospheric pollutant concentrations and air quality is summarized for nitrogen dioxide (NO2), particulate matter (PM2.5), ozone (O3), ammonia, sulfur dioxide, black carbon, volatile organic compounds, and carbon monoxide (CO). In the first 7 months following the onset of the pandemic, more than 200 papers were accepted by peer-reviewed journals utilizing observations from ground-based and satellite instruments. Only about one-third of this literature incorporates a specific method for meteorological correction or normalization for comparing data from the lockdown period with prior reference observations despite the importance of doing so on the interpretation of results. We use the government stringency index (SI) as an indicator for the severity of lockdown measures and show how key air pollutants change as the SI increases. The observed decrease of NO2 with increasing SI is in general agreement with emission inventories that account for the lockdown. Other compounds such as O3, PM2.5, and CO are also broadly covered. Due to the importance of atmospheric chemistry on O3 and PM2.5 concentrations, their responses may not be linear with respect to primary pollutants. At most sites, we found O3 increased, whereas PM2.5 decreased slightly, with increasing SI. Changes of other compounds are found to be understudied. We highlight future research needs for utilizing the emerging data sets as a preview of a future state of the atmosphere in a world with targeted permanent reductions of emissions. Finally, we emphasize the need to account for the effects of meteorology, emission trends, and atmospheric chemistry when determining the lockdown effects on pollutant concentrations.

Surface-Promoted Redox Reactions Occurs Spontaneously on Solvating Salt Surfaces

2021 ◽  
Author(s):  
Xiangrui Kong ◽  
Ivan Gladich ◽  
Dimitri Castarede ◽  
Erik Thomson ◽  
Anthony Boucly ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Species Abundance ◽  
Ammonium Oxidation ◽  
Gas Uptake ◽  
Sulfate Reducing ◽  
Interfacial Processes ◽  
Key Species ◽  
Halogen Chemistry

<p>Gas-particle interfaces play essential roles in the atmosphere and directly influence many atmospheric processes, including gas uptake, halogen chemistry, ozone depletion, and heterogeneous ice nucleation. However, because interfacial processes take place on molecular scales, classical bulk thermodynamic theories are often insufficient to describe interfaces. Also, interfacial processes are challenging to characterize and are often overlooked in current atmospheric chemistry.</p><p>For this study, ambient pressure X-ray photoelectron spectroscopy (APXPS) experiments were performed. A surface-promoted sulfate-reducing ammonium oxidation reaction is discovered to spontaneously take place on common inorganic aerosol surfaces undergoing solvation. Several key intermediate species including, S<sup>0</sup>, HS<sup>-</sup>, HONO, and NH<sub>3(aq)</sub> are identified as reaction components associated with the solvation process. Depth profiles of relative species abundance show the surface propensity of key species. The species assignments and depth profile features are supported by classical and first-principle molecular dynamics calculations. A detailed mechanism is proposed to describe the processes that lead to unexpected products during salt solvation. This discovery reveals novel chemistry that is uniquely linked to a solvating surface and has great potential to illuminate current puzzles within heterogeneous chemistry. Lastly, natural salts sampled from saline lakes and playas are examined for this behavior, and provide further evidence of the important roles this surface-promoted redox mechanism may play in nature.</p>

scholarly journals e-HRM in a Cloud Environment

2019 ◽  
Vol 10 (4) ◽  
pp. 16-40
Author(s):  
Robert-Christian Ziebell ◽  
Jose Albors-Garrigos ◽  
Klaus-Peter Schoeneberg ◽  
Maria Rosario Perello Marin
Keyword(s):  
Technology Implementation ◽  
Cloud Environment ◽  
Resources Management ◽  
Functional Changes ◽  
Current State ◽  
Use Of Technology ◽  
Rapid Pace ◽  
Different Dimensions ◽  
State Of Research ◽  
Technical Basis

As the digitization of HR processes in companies continues to increase, at the same time, the underlying technical basis is also developing at a rapid pace. Electronic human resources (e-HRM) solutions are used to map a variety of HR processes. However, the introduction of such systems has various consequences, which are not only technical but also imply organizational and functional changes within the organization. Additionally, the cloud environment contributes to enhancing e-HRM capabilities and introduces new factors in its adoption. A systematic review of the available literature on the different dimensions of electronic resources management was conducted to assess the current state of research in this field. This review includes topics such as the evolution of e-HRM, its practical application, use of technology, implementation as well as HR analytics. By identifying and reviewing articles under e-HRM, IT technology, and HR journals, it was possible to identify relevant controversial themes and gaps as well as limitations.

In Search of the True Faith: the Appearance of Orthodox Old Believers in Uganda and Spiritual Anti-globalism in Contemporary Africa

Exchange ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 127-155 ◽  
Author(s):  
Dmitri M. Bondarenko
Keyword(s):  
Ethnic Groups ◽  
Present Article ◽  
Old Believers ◽  
Religious Context ◽  
Current State ◽  
Field Evidence

Abstract The present article, based on field evidence collected in 2017, deals with a very recent phenomenon — the Orthodox Old Believers in Uganda. This faith originated in Russia, however in Uganda all its adherents belong to African ethnic groups. We describe the short by now history and current state of the Old-Believer communities in Uganda and then concentrate on their members’ motivation for converting to Old Believers vs. knowledge of this religion. We show that what brings them to Old Believers is the search for the true faith associated with the original and hence correct way of performing Christian rites. In this we see an intricate interplay of the features typical for authentic African cultures and acquired by them in the course of interaction with the wider world. Basing on our case study, we discuss how globalist and anti-globalist trends manifest themselves in the religious context in contemporary Africa.

scholarly journals IMIA Accreditation of Biomedical and Health Informatics Education: Current State and Future Directions

2017 ◽  
Vol 26 (01) ◽  
pp. 252-256
Author(s):  
M. W. Jaspers ◽  
J. Mantas ◽  
E. Borycki ◽  
A. Hasman
Keyword(s):  
Quality Assurance ◽  
Health Informatics ◽  
Academic Programs ◽  
Global Perspective ◽  
Future Directions ◽  
Current State ◽  
Adequate Information ◽  
Global Impacts ◽  
Quality Assurance Standards ◽  
Single Set

Summary Objectives: The educational activities initiated by the International Medical Informatics Association (IMIA) have had global impacts and influenced national societies and local academic programs in the field of Biomedical and Health Informatics (BMHI). After the successful publication and dissemination of its educational recommendations, IMIA launched an accreditation procedure for educational programs in BMHI. The accreditation procedure was pilot tested by several BMHI academic programs in different countries and continents to obtain a global perspective. Methods: This paper presents an overview of IMIA quality assurance and accreditation procedures along with feedback on issues and problems which emerged during the pilot. Results: It appears that IMIA quality assurance and procedures worked quite well in different countries of Europe, the Middle East, South America, and Asia. These first experiences provided adequate information for adapting, modifying, and optimizing the procedures and finally for the planning of future activities. Conclusions: IMIA accreditation framework comprises a single set of standards that apply at various levels to both academic and professional BMHI programs. The pilot phase confirmed the robustness and generalizability of quality assurance standards and associated procedures on which IMIA accreditation is based at an international level.

scholarly journals The contribution of marine organics to the air quality of the western United States

2010 ◽  
Vol 10 (15) ◽  
pp. 7415-7423 ◽  
Author(s):  
B. Gantt ◽  
N. Meskhidze ◽  
A. G. Carlton
Keyword(s):  
United States ◽  
Air Quality ◽  
San Francisco ◽  
Atmospheric Chemistry ◽  
Environmental Protection Agency ◽  
Regional Scale ◽  
The United States ◽  
Coastal Areas ◽  
Western United States ◽  
The Us

Abstract. The contribution of marine organic emissions to the air quality in coastal areas of the western United States is studied using the latest version of the US Environmental Protection Agency (EPA) regional-scale Community Multiscale Air Quality (CMAQv4.7) modeling system. Emissions of marine isoprene, monoterpenes, and primary organic matter (POM) from the ocean are implemented into the model to provide a comprehensive view of the connection between ocean biology and atmospheric chemistry and air pollution. Model simulations show that marine organics can increase the concentration of PM2.5 by 0.1–0.3 μg m−3 (up to 5%) in some coastal cities such as San Francisco, CA. This increase in the PM2.5 concentration is primarily attributed to the POM emissions, with small contributions from the marine isoprene and monoterpenes. When marine organic emissions are included, organic carbon (OC) concentrations over the remote ocean are increased by up to 50% (25% in coastal areas), values consistent with recent observational findings. This study is the first to quantify the air quality impacts from marine POM and monoterpenes for the United States, and it highlights the need for inclusion of marine organic emissions in air quality models.

scholarly journals Active and widespread halogen chemistry in the tropical and subtropical free troposphere

2015 ◽  
Vol 112 (30) ◽  
pp. 9281-9286 ◽  
Author(s):  
Siyuan Wang ◽  
Johan A. Schmidt ◽  
Sunil Baidar ◽  
Sean Coburn ◽  
Barbara Dix ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Oxidative Capacity ◽  
Free Troposphere ◽  
Mercury Deposition ◽  
Tropical Eastern Pacific ◽  
Ice Clouds ◽  
Bromine Oxide ◽  
Halogen Chemistry ◽  
Model Predictions ◽  
Wet Scavenging

Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10°N to 40°S), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (∼3.4 pptv at 13.5 km), and are 2–4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5–6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

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