| 1. |
- Alfeus, Anna, et al.
(författare)
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PM2.5 in Cape Town, South Africa: Chemical characterization and source apportionment using dispersion-normalised positive matrix factorization
- 2024
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Ingår i: Atmospheric Pollution Research. - 1309-1042. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding fine particulate matter (PM2.5) composition and sources is beneficial to improving visibility, addressing climate change, and mitigating poor air quality and related public health effects. Source apportionment techniques have been instrumental in evaluating the impact of sources and secondary processes on the ambient PM2.5 concentrations in receptor areas. Positive Matrix Factorization (PMF) is now the most commonly used tool due to its ability to provide mixture resolution based on available PM2.5 compositional data. Sampling and analysis of PM2.5 was conducted in Cape Town, South Africa from April 2017 to April 2018. The resulting data were dispersion normalized to address the modifications of the source concentrations resulting from the varying dispersion conditions and thereby permit dispersion normalized PMF (DN-PMF) to be employed. DN-PMF quantified the 6 sources as 2-stroke vehicles/galvanizing industries (16.8%); soil/road dust (12.3%); sulphate/marine diesel (3.6%), traffic (15.7%), sea salt (21.8%), and heating/biomass burning/cooking (15.7%). In addition, air mass back trajectory analysis using the Hybrid Single Particle Lagrangian Trajectory (HYSPLIT) model identified long-range transport pathways to Cape Town. The HYSPLIT results showed air masses from the Atlantic SSW (6%), Atlantic SW (24%), Indian Ocean (31%), and Atlantic WSW (39%) influence air quality. The primary sources affected by the transport clusters were heating, 2-stroke vehicles/galvanizing, road and soil dust, and traffic emissions. These results show that reducing emissions from the local sources will improve air quality.
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| 2. |
- Baker, H. Kent, et al.
(författare)
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Payouts and stock ownership
- 2021
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Ingår i: Journal of Multinational Financial Management. - : Elsevier BV. - 1042-444X .- 1873-1309. ; 60
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Tidskriftsartikel (refereegranskat)abstract
- Using a unique Swedish database that records the ultimate stockholdings in public firms, we decompose stock ownership by domiciles using votes rather than cashflows. We then study the impact of variables related to the lifecycle theory of dividends and the catering theory of dividends. We also examine the propensity of firms to pay dividends and/or activate a stock buyback program. Univariate analysis reveals a positive association between a firm’s maturity and its likelihood to pay dividends. Logistic regression finds a positive relation between payouts and retained earnings to total assets. Foreign institutional investors are less likely to hold dividend-paying stocks than domestic institutional investors. The analysis finds no support for the catering theory of dividends. After controlling for stock ownership, our evidence is consistent with the lifecycle theory of dividends, which states that more mature firms are associated with dividends. It also supports the transaction cost hypothesis claiming that foreign investors face additional administrative costs when holding dividend-paying stocks.
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| 3. |
- Bergström, Clas, et al.
(författare)
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Price differentials between different classes of stocks: an empirical study on Chinese stock markets
- 2001
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Ingår i: Journal of multinational financial management. - : Elsevier B.V. - 1873-1309 .- 1042-444X. ; 11:4, s. 407-426
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the effect of strict segmentation on pricing in the context of the Chinese stock markets. The paper demonstrates that information asymmetry between foreign investors and domestic investors, liquidity effects, diversification effects, clientele bias, risk-free return differentials between foreign and domestic investors, and foreign exchange risks are significant factors in explaining discounts on shares that can only be owned by foreign investors.
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| 4. |
- Bidleman, Terry F, et al.
(författare)
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Chiral persistent organic pollutants as tracers of atmospheric sources and fate : review and prospects for investigating climate change influences
- 2012
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Ingår i: Atmospheric Pollution Research. - 1309-1042. ; 3:4, s. 371-382
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Tidskriftsartikel (refereegranskat)abstract
- Elimination of persistent organic pollutants (POPs) under national and international controls reduces “primary” emissions, but “secondary” emissions continue from residues deposited in soil, water, ice and vegetation during former years of high usage. Secondary sources are expected to dominate in the future, when POPs transport and accumulation will be controlled by air–surface exchange and the biogeochemical cycle of organic carbon. Climate change is likely to affect mobilization of POPs through, e.g., increased temperature, loss of ice cover in polar regions, melting glaciers and changes in soil and water microbiology which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their ability to distinguish racemic (newly released or protected from microbial attack) and nonracemic (microbially altered) sources. Here we explain the rationale for this approach and suggest applications where chiral POPs could aid investigation of climate–mediated exchange and degradation processes. Examples include distinguishing agricultural vs. non–agricultural and recently used vs. residual pesticides, degradation and sequestration processes in soil, historical vs. recent atmospheric deposition, sources in arctic air and influence of ice cover on volatilization.
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| 5. |
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| 6. |
- Fatehi, Hesameddin, et al.
(författare)
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Effect of buoyancy on dispersion of reactive pollutants in urban canyons
- 2022
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Ingår i: Atmospheric Pollution Research. - : Elsevier BV. - 1309-1042. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we aim to investigate the interplay between chemistry, flow dynamics and temperature using high fidelity computational fluid dynamics (CFD) models in an urban environment. A detailed numerical model based on large eddy simulation (LES) is developed considering the temperature and buoyancy effect and the non-equilibrium chemical processes. The model is used to study flow and reaction inside experimental and real-size street canyons. Street canyons are chosen for this study, as they represent the smallest unit of urban environments where detailed flow simulations combined with chemical reactions can be performed with high numerical accuracy. The effect of thermal driven flow is studied in reacting and non-reacting conditions to understand the role of buoyancy in accurately modeling pollutant reaction and dispersion. It is shown that buoyancy has a significant effect on the dynamics of the flow, by altering the main vortex structure inside the canyon and by increasing turbulent kinetic energy. It is also found that the chemical reactions strongly affect final concentrations of pollutants, which indicates the potential need for implementation of more advanced chemical models in future work. The importance of correct boundary conditions to accurately predict pollutant concentrations are discussed. Finally, by comparing the LES results with experimental field measurements in a real street canyon, the limitation of using periodic boundary conditions, as it is commonly used in the literature, is discussed. Moreover, it is shown that implementation of a variable photolysis rate is likely needed.
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| 7. |
- Graham, Michael, et al.
(författare)
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On Institutional Investors and Firm Performance : A Disaggregated View
- 2009
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Ingår i: Journal of Multinational Financial Management. - : Elsevier BV. - 1042-444X .- 1873-1309. ; 19:5, s. 370-394
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Tidskriftsartikel (refereegranskat)abstract
- We study the relationship between institutional ownership and firm performance in Finland. A systems approach is employed to investigate the potential two-way causality between firm performance and ownership structure. Three-stage least squares estimation technique is used to solve for the systems. The evidence suggests an endogeneity problem between firm performance and institutional ownership. However, the magnitude of the problem differs with respect to the concentration of ownership measure used. Our results show that a more equal distribution of the voting power among the largest institutional stakeholder may exert positive effects on firm performance. We also find a significant difference relating to firm performances and equity ownerships between the two classes of institutional investor. Consistent with the ownership structure in Finland, we find that a simple ownership concentration index does not influence firm performance.
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| 8. |
- Grundström, Maria, 1979, et al.
(författare)
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Influence of atmospheric circulation patterns on urban air quality during the winter
- 2015
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Ingår i: Atmospheric Pollution Research. - 1309-1042. ; 6:2, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- Relationships between urban nitrogen dioxide (NO2) and atmospheric circulation at two spatial scales were studied for Southern Sweden. Lamb Weather Types (LWT) describe the circulation (scale: thousands of kilometers) including non–directional (cyclonic and anticyclonic) and directional types depending on the wind direction. LWTs with low wind speeds (anticyclonic, NW and N) were associated with strongly elevated [NO2], between 46–52% of the daily averages of NO2 exceeded the 60 μg m–3 air quality standard (AQS) when occurring during these LWTs. The lowest fractions of exceedances of NO2 AQS were generally observed for LWTs E, S, SW and W. A larger scale circulation (several thousands of kilometers) was represented by the North Atlantic Oscillation (NAO) affecting meteorology over middle and high latitudes in the Northern Hemisphere. While a negative NAO index (NAOI) favors stagnant high pressure weather over Northern Europe, a positive NAOI is often associated with windy conditions. High [NO2] was found to be frequent under negative NAOI. Additionally, larger fractions of exceedances of NO2 AQS were observed for the majority of LWTs occurring at negative NAOI. It’s concluded that both LWTs and NAOI had partly independent effects on the urban air quality in a North European city. These circulation indices can be useful tools for air pollution risk assessment and forecasting.
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| 9. |
- Gusev, Alexey, et al.
(författare)
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Intercontinental transport of persistent organic pollutants : a review of key findings and recommendations of the task force on hemispheric transport of air pollutants and directions for future research
- 2012
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Ingår i: Atmospheric Pollution Research. - 1309-1042. ; 3:4, s. 463-465
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Tidskriftsartikel (refereegranskat)abstract
- The Task Force on Hemispheric Transport of Air Pollution (TF HTAP) was established under the Convention on Long-range Transboundary Air Pollution (CLRTAP) to improve scientific understanding of the intercontinental transport of air pollutants and to deliver policy-relevant information on this issue. The first comprehensive assessment of POP intercontinental transport made by the TF HTAP was compiled in 2010 and published in 2011. The HTAP assessment was made possible by the contributions of a large network of experts in various national and international organizations and is intended to support further development of international policy and regulation of POPs under the frameworks of the UN ECE CLRTAP and the Stockholm Convention on POPs. By summarizing the outcome of past studies on POPs, the assessment highlights the evidence of POP intercontinental transport and the associated threat to human health and the environment. It presents the current state of knowledge on levels of POPs in the environment, emission inventories and projections, modeling of long-range transport and fate in various compartments, interactions with climate change, as well as harmful effects on human health and ecosystems. Two important outcomes of the HTAP 2010 assessment are the summary of key scientific and policy-relevant findings, and the recommendations for further work which include the need to a more fully developed integrated approach to the pollution assessment. In its next phase, which extends to 2015, the Task Force is planning to cooperate across different thematic areas of scientific activity on intercontinental transport of pollution, and exploit synergies of effort in cases where particulate matter (PM), ozone, mercury, and POPs share common sources. It is recognized that a fully integrated approach for building a scientific understanding of POPs in the environment should encompass measurements, modeling results, and emission estimates, and in addition it should more explicitly include assessment of ecosystem effects. (C) Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License.
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