Publications by authors named "Ulas Im"

Affected by both future anthropogenic emissions and climate change, future prediction of PM and its Oxidative Potential (OP) distribution is a significant challenge, especially in developing countries like China. To overcome this challenge, we estimated historical and future PM concentrations and associated OP using the Danish Eulerian Hemispheric Model (DEHM) system with meteorological input from WRF weather forecast model. Considering different future socio-economic pathways and emission scenario assumptions, we quantified how the contribution from various anthropogenic emission sectors will change under these scenarios.

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Background: Long-term air pollution is a risk factor for stroke. Which types and sources of air pollution contribute most to stroke in populations is unknown. We investigated whether risk of stroke differed by type and source of air pollution.

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Background: Air pollution is a well-recognized risk factor for cardiovascular disease. However, the mechanistic pathways underlying the association are not completely understood. Hence, further studies are required to shed light on potential mechanisms, through which air pollution may affect the development from subclinical to clinical cardiovascular disease.

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We used the EVAv6.0 system to estimate the present (2015) and future (2015-2050) global PM and O-related premature mortalities, using simulated surface concentrations from the GISS-E2.1-G Earth system model.

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Objective: Air pollution, road traffic noise and lack of greenness coexist in urban environments and have all been associated with type 2 diabetes. We aimed to investigate how these co-exposures were associated with type 2 diabetes in a multi-exposure perspective.

Methods: We estimated 5-year residential mean exposure to fine particles (PM), ultrafine particles (UFP), elemental carbon (EC), nitrogen dioxide (NO) and road traffic noise at the most (LdenMax) and least (LdenMin) exposed facade for all persons aged > 50 years living in Denmark in 2005 to 2017.

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The World Health Organization estimates that around 7 million people die every year from exposure to fine particles (PM) inpolluted air. Here, the number of premature deaths in Europe from different diseases associated to the ambient exposure to PM have here been studied both for present (1991-2010) and future periods (2031-2050, RCP8.5 scenario).

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Article Synopsis
  • Accurate simulations of aerosol absorption properties are essential for understanding their impact on meteorology and climate, with the mixing state of chemical species being a significant source of uncertainty.
  • This study compares aerosol optical property simulations in Europe and North America with one year of AERONET data to find a better representation of mixing states that fits observed data, focusing on black carbon's absorption enhancement.
  • Findings indicate that both external and core-shell mixing assumptions lead to biases in single scattering albedo, but using a combination (partial internal mixing) helps reduce these biases while highlighting issues with the spectral dependence of absorption.
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This study evaluates simulated vertical ozone profiles produced in the framework of the third phase of the Air Quality Model Evaluation International Initiative (AQMEII3) against ozonesonde observations in North America for the year 2010. Four research groups from the United States (US) and Europe have provided modeled ozone vertical profiles to conduct this analysis. Because some of the modeling systems differ in their meteorological drivers, wind speed and temperature are also included in the analysis.

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The evaluation and intercomparison of air quality models is key to reducing model errors and uncertainty. The projects AQMEII3 and EURODELTA-Trends, in the framework of the Task Force on Hemispheric Transport of Air Pollutants and the Task Force on Measurements and Modelling, respectively (both task forces under the UNECE Convention on the Long Range Transport of Air Pollution, LTRAP), have brought together various regional air quality models to analyze their performance in terms of air concentrations and wet deposition, as well as to address other specific objectives. This paper jointly examines the results from both project communities by intercomparing and evaluating the deposition estimates of reduced and oxidized nitrogen (N) and sulfur (S) in Europe simulated by 14 air quality model systems for the year 2010.

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Residential heating is one of the major sectors that contribute to emissions of harmful air pollutants in urban areas. In Istanbul, local sources are the main contributors of particulate matter levels. To quantify the contributions of residential heating sector to ambient particulate matter concentrations, we have developed an up to date spatially distributed high-resolution emissions inventory based on local activity data.

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Article Synopsis
  • The AQMEII3 initiative assesses the effects of a 20% reduction in anthropogenic emissions on air pollutant levels in 2010, focusing on Europe and North America.
  • Different regional air quality modeling groups utilize advanced chemistry and transport models to simulate these changes based on data from the global C-IFS model.
  • Results indicate a nearly linear correlation between reduced emissions and decreased concentrations of pollutants like NO, SO, and PM, with notable geographical variations in effects, particularly in emission hotspots.
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The impact of air pollution on human health and the associated external costs in Europe and the United States (US) for the year 2010 are modeled by a multi-model ensemble of regional models in the frame of the third phase of the Air Quality Modelling Evaluation International Initiative (AQMEII3). The modeled surface concentrations of O, CO, SO and PM are used as input to the Economic Valuation of Air Pollution (EVA) system to calculate the resulting health impacts and the associated external costs from each individual model. Along with a base case simulation, additional runs were performed introducing 20 % anthropogenic emission reductions both globally and regionally in Europe, North America and east Asia, as defined by the second phase of the Task Force on Hemispheric Transport of Air Pollution (TF-HTAP2).

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Ambient air pollution from ozone and fine particulate matter is associated with premature mortality. As emissions from one continent influence air quality over others, changes in emissions can also influence human health on other continents. We estimate global air pollution-related premature mortality from exposure to PM and ozone, and the avoided deaths from 20% anthropogenic emission reductions from six source regions, North America (NAM), Europe (EUR), South Asia (SAS), East Asia (EAS), Russia/Belarus/Ukraine (RBU) and the Middle East (MDE), three global emission sectors, Power and Industry (PIN), Ground Transportation (TRN) and Residential (RES) and one global domain (GLO), using an ensemble of global chemical transport model simulations coordinated by the second phase of the Task Force on Hemispheric Transport of Air Pollution (TF-HTAP2), and epidemiologically-derived concentration-response functions.

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Increasing emphasis has been placed on characterizing the contributions and the uncertainties of ozone imported from outside the US. In chemical transport models (CTMs), the ozone transported through lateral boundaries (referred to as LB ozone hereafter) undergoes a series of physical and chemical processes in CTMs, which are important sources of the uncertainty in estimating the impact of LB ozone on ozone levels at the surface. By implementing inert tracers for LB ozone, the study seeks to better understand how differing representations of physical processes in regional CTMs may lead to differences in the simulated LB ozone that eventually reaches the surface across the US.

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In this study we introduce a consisting of air quality models operating at both the global and regional scale. The work is motivated by the fact that these different types of models treat specific portions of the atmospheric spectrum with different levels of detail, and it is hypothesized that their combination can generate an ensemble that performs better than mono-scale ensembles. A detailed analysis of the hybrid ensemble is carried out in the attempt to investigate this hypothesis and determine the real benefit it produces compared to ensembles constructed from only global-scale or only regional-scale models.

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Article Synopsis
  • The study compares regional-scale chemistry transport models for air quality in Europe and North America to identify sources of modeling errors and areas needing further research.
  • It uses a framework known as AQMEII Phase 3 to assess model performance by comparing measurements with simulated data across multiple pollutants.
  • Key findings highlight the influence of model inputs like emissions, the importance of accurately representing the stable boundary layer, and the interconnectedness of meteorological and chemical variables in evaluating model bias.
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Black carbon (BC) is an important component of particulate matter due to its effects on human health and climate. In this study, we present the first BC concentrations measured in the Istanbul megacity (~15 million inhabitants). Two measurement campaigns have been conducted to measure BC and fine particulate matter (PM2.

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Ozone (O(3)) mixing ratios were measured at three different sites (urban/traffic, semi-rural and rural/island) in Istanbul from September 2007 to December 2009 in order to determine the diurnal, monthly and seasonal variations of O(3) and nitrogen oxides (NO(x)) and to study the local and regional impacts. This is the first study that evaluates the O(3) levels in semi-rural and rural sites in Istanbul in addition to the urban sites. The diurnal O(3) variations are generally characterized by afternoon maxima (64 ppb at the urban, 80 ppb at the semi-rural and 100 ppb at the rural site) and the nighttime minimum being more pronounced at the polluted urban site.

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Surface ozone concentrations at Istanbul during a summer episode in June 2008 were simulated using a high resolution and urban scale modeling system coupling MM5 and CMAQ models with a recently developed anthropogenic emission inventory for the region. Two sets of base runs were performed in order to investigate for the first time the impact of biogenic emissions on ozone concentrations in the Greater Istanbul Area (GIA). The first simulation was performed using only the anthropogenic emissions whereas the second simulation was performed using both anthropogenic and biogenic emissions.

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