Alper Unal | Istanbul Technical University (original) (raw)

Papers by Alper Unal

Atmospheric Environment, 2010

High winter-time PM 10 , sulfate, nitrate and ammonium levels in Istanbul were investigated using... more High winter-time PM 10 , sulfate, nitrate and ammonium levels in Istanbul were investigated using a high resolution WRF/CMAQ mesoscale model system. A model-ready anthropogenic emission inventory on 2 km spatial resolution was developed for the area and the present study is the first attempt to test these emissions. The results suggested that the system was capable of producing the magnitudes. PM 10 levels calculated by the model underestimated the observations with an average of 10 per cent at Bogazici University sampling station, whereas an overestimation of 12 per cent is calculated for all stations. High uncertainties, particularly in traffic and coal combustion, led to over estimations around emission hot spots. Base case results together with the sensitivity studies pointed significant contribution of local sources, pointing to the need of control strategies focusing on primary particulate emissions.

Atmospheric Chemistry and Physics, 2011

Changes in temperature due to variability in meteorology and climate change are expected to signi... more Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9 ± 3% K −1 . Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O 3 K −1 for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O 3 K −1 increase is calculated, which is about half of the domain-averaged increase of 0.9 ± 0.1 ppb O 3 K −1 . The computed changes in atmospheric processes are also linearly related with temperature changes.

Science of The Total Environment, 2011

Changes in temperature due to variability in meteorology and climate change are expected to signi... more Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9 ± 3% K −1 . Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O 3 K −1 for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O 3 K −1 increase is calculated, which is about half of the domain-averaged increase of 0.9 ± 0.1 ppb O 3 K −1 . The computed changes in atmospheric processes are also linearly related with temperature changes.

Atmospheric Environment, 2012

The impact of ambient temperature on the levels and chemical composition of aerosols over the Eas... more The impact of ambient temperature on the levels and chemical composition of aerosols over the Eastern Mediterranean in July 2004 is investigated using the WRF/CMAQ model system coupled with the MEGAN biogenic emissions model. CMAQ is able to capture the observed mean aerosol concentrations over the studied period. Non-sea-salt sulfate (nss-SO 4 2À ) is calculated to be the major aerosol component contributing by 63%, 16% and 40% to the fine (PM 2.5 ), coarse (PM 2.5e10 ) and total particulate matter mass (PM 10 ), respectively. PM 2.5 to PM 10 mass ratios reach more than 80% over the large urban agglomerations but decrease to 45% at downwind locations suggesting coagulation and condensation on coarse particles. Higher temperatures increase biogenic emissions, enhance spatially-averaged biogenic secondary organic aerosol (SOA, by 0.01 AE 0.00 mg m À3 K À1 ) and nitrate (NO 3 À ) aerosol concentrations (by 0.02 AE 0.02 mg m À3 K À1 ). They reduce nss-SO 4 2À (by À0.04 AE 0.07 mg m À3 K À1 ), induced by significant reduction in the cloud cover (90% K À1 ) and subsequent aqueous-phase production. The PM 2.5 concentrations show a very small positive response to temperature changes, increasing by 0.003 AE 0.042 mg m À3 K À1 (0.04% K À1 ) due to the compensation of organic carbon increases by nss-SO 4 2À reductions. Locally, larger changes are computed, with nss-SO 4 2À and NO 3 À in fine aerosols reduced by up to 0.62 mg m À3 K À1 and 0.80 mg m À3 K À1 , respectively. Increases as high as 0.097 mg m À3 K À1 and 0.034 mg m À3 K À1 are calculated for organic and elemental carbon, respectively. Results show that changes in temperature modify not only the aerosol mass but also its chemical composition.

While most regulation and research of air pollution episodes are focused on Europe, transport of ... more While most regulation and research of air pollution episodes are focused on Europe, transport of air pollutants from Europe to Northern and Western Turkey hasn't been studied sufficiently, although unusually high air pollution episodes occur in these regions. As an example during 05-12 of January, 2002, it has been identified from observational data that particulate matter levels were almost 4-5 times (364 μg/m3) higher than the World Health organization standards for Europe (70 μg/m3).

Abstract In a world where at least 50 percent of the population is living in urban environments, ... more Abstract In a world where at least 50 percent of the population is living in urban environments, air pollution and specifically particulate matter became one of the most critical issues. There have been many studies that focused on mass concentration measurements of PM10 and PM2. 5. Recent studies suggest that chemical composition is critical in understanding the effects of PM on health as well as climate.

This paper analyzes data obtained from international studies that compared natural gas, diesel, a... more This paper analyzes data obtained from international studies that compared natural gas, diesel, and hybrid technologies for buses to determine differences in particulate matter (PM 10), nitrogen oxides (NO x), nonmethane hydrocarbon (NMHC), carbon monoxide (CO), greenhouse gas, and air toxic emissions. The results presented here are for 90-passenger 12-m buses. Two types of comparisons were made: technology and fuel.

Abstract A good estimate of gas and aerosol anthropogenic emissions is crucial for estimating gas... more Abstract A good estimate of gas and aerosol anthropogenic emissions is crucial for estimating gases and aerosol concentrations in the atmosphere. Although high-resolution emission inventories covering the entire Europe exist and they have been applied in several studies, their quality has not been evaluated uniformly in all the European regions. Most of these existing studies analyzed mainly the North-Western European countries supported also by a large variety of observations.

Abstract Nuclear energy will continue to have an important role in the production of electricity ... more Abstract Nuclear energy will continue to have an important role in the production of electricity in the world as the need of energy grows up. But the safety of power plants will always be a question mark for people because of the accidents happened in the past. Chernobyl nuclear reactor accident which happened in 26 April 1986 was the biggest nuclear accident ever. Because of explosion and fire large quantities of radioactive material was released to the atmosphere.

Abstract Crustal thinning due to regional extensional tectonics played an important role in the p... more Abstract Crustal thinning due to regional extensional tectonics played an important role in the petrogenesis and chemical evolution of magmatism in western Anatolia starting in the Late Oligocene-Early Miocene. The study area is particularly critical because it contains various products of OligoMiocene magmatism whose geological and geochemical features indicate post-collisional setting. The magmatic rocks in this area are formed from two different groups of rocks, which display the close relationships in time and space.

Abstract This study provides valuable new insights into the key contributors to ambient air quali... more Abstract This study provides valuable new insights into the key contributors to ambient air quality in Istanbul, one of the largest mega-cities in Europe. The study builds on work in Europe that links air quality with national dynamics such as economical, vehicle activity and, meteorology in the long-term. Spatial and temporal analysis was performed on PM10 levels measured at 10 air quality monitoring sta-tions (AQMSs) in Istanbul from 1998 to 2008.

Emission inventories are a fundamental input to atmospheric chemical transport models(CTMs). As t... more Emission inventories are a fundamental input to atmospheric chemical transport models(CTMs). As the latter become increasingly demanding, modern inventories began to provide much more information(high spatial and temporal disaggregation, more chemical compounds etc).

Abstract In this study, we investigated the relationship between synoptic weather types and rainf... more Abstract In this study, we investigated the relationship between synoptic weather types and rainfall patterns in the Marmara region, northwestern part of Turkey. For this purpose, the automated Lamb weather type classification method was applied to the NCEP/NCAR reanalysis daily mean sea level pressure data for the period between 2001 and 2010. Ten synoptic weather types were found that represent the 90% of the synoptic patterns that affect the Marmara region.

Abstract Shipping is considered as one of the main emission sources worldwide. Recent studies sug... more Abstract Shipping is considered as one of the main emission sources worldwide. Recent studies suggest that, in the Mediterrenean, ship emissions are responsible for 10-50% of black carbon, 2-12% ozone in the surface layer and 5-20% for nitrogen dioxide atmospheric column burden (Marmer et al., 2009). It is, therefore, essential to have an accurate emissions estimation for ships. Marmara Sea, an inland sea connecting the Mediterrenean to the Black Sea, has significant marine activity.

Atmospheric Environment, 2010

High winter-time PM 10 , sulfate, nitrate and ammonium levels in Istanbul were investigated using... more High winter-time PM 10 , sulfate, nitrate and ammonium levels in Istanbul were investigated using a high resolution WRF/CMAQ mesoscale model system. A model-ready anthropogenic emission inventory on 2 km spatial resolution was developed for the area and the present study is the first attempt to test these emissions. The results suggested that the system was capable of producing the magnitudes. PM 10 levels calculated by the model underestimated the observations with an average of 10 per cent at Bogazici University sampling station, whereas an overestimation of 12 per cent is calculated for all stations. High uncertainties, particularly in traffic and coal combustion, led to over estimations around emission hot spots. Base case results together with the sensitivity studies pointed significant contribution of local sources, pointing to the need of control strategies focusing on primary particulate emissions.

Atmospheric Chemistry and Physics, 2011

Changes in temperature due to variability in meteorology and climate change are expected to signi... more Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9 ± 3% K −1 . Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O 3 K −1 for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O 3 K −1 increase is calculated, which is about half of the domain-averaged increase of 0.9 ± 0.1 ppb O 3 K −1 . The computed changes in atmospheric processes are also linearly related with temperature changes.

Science of The Total Environment, 2011

Changes in temperature due to variability in meteorology and climate change are expected to signi... more Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9 ± 3% K −1 . Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O 3 K −1 for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O 3 K −1 increase is calculated, which is about half of the domain-averaged increase of 0.9 ± 0.1 ppb O 3 K −1 . The computed changes in atmospheric processes are also linearly related with temperature changes.

Atmospheric Environment, 2012

The impact of ambient temperature on the levels and chemical composition of aerosols over the Eas... more The impact of ambient temperature on the levels and chemical composition of aerosols over the Eastern Mediterranean in July 2004 is investigated using the WRF/CMAQ model system coupled with the MEGAN biogenic emissions model. CMAQ is able to capture the observed mean aerosol concentrations over the studied period. Non-sea-salt sulfate (nss-SO 4 2À ) is calculated to be the major aerosol component contributing by 63%, 16% and 40% to the fine (PM 2.5 ), coarse (PM 2.5e10 ) and total particulate matter mass (PM 10 ), respectively. PM 2.5 to PM 10 mass ratios reach more than 80% over the large urban agglomerations but decrease to 45% at downwind locations suggesting coagulation and condensation on coarse particles. Higher temperatures increase biogenic emissions, enhance spatially-averaged biogenic secondary organic aerosol (SOA, by 0.01 AE 0.00 mg m À3 K À1 ) and nitrate (NO 3 À ) aerosol concentrations (by 0.02 AE 0.02 mg m À3 K À1 ). They reduce nss-SO 4 2À (by À0.04 AE 0.07 mg m À3 K À1 ), induced by significant reduction in the cloud cover (90% K À1 ) and subsequent aqueous-phase production. The PM 2.5 concentrations show a very small positive response to temperature changes, increasing by 0.003 AE 0.042 mg m À3 K À1 (0.04% K À1 ) due to the compensation of organic carbon increases by nss-SO 4 2À reductions. Locally, larger changes are computed, with nss-SO 4 2À and NO 3 À in fine aerosols reduced by up to 0.62 mg m À3 K À1 and 0.80 mg m À3 K À1 , respectively. Increases as high as 0.097 mg m À3 K À1 and 0.034 mg m À3 K À1 are calculated for organic and elemental carbon, respectively. Results show that changes in temperature modify not only the aerosol mass but also its chemical composition.

While most regulation and research of air pollution episodes are focused on Europe, transport of ... more While most regulation and research of air pollution episodes are focused on Europe, transport of air pollutants from Europe to Northern and Western Turkey hasn't been studied sufficiently, although unusually high air pollution episodes occur in these regions. As an example during 05-12 of January, 2002, it has been identified from observational data that particulate matter levels were almost 4-5 times (364 μg/m3) higher than the World Health organization standards for Europe (70 μg/m3).

Abstract In a world where at least 50 percent of the population is living in urban environments, ... more Abstract In a world where at least 50 percent of the population is living in urban environments, air pollution and specifically particulate matter became one of the most critical issues. There have been many studies that focused on mass concentration measurements of PM10 and PM2. 5. Recent studies suggest that chemical composition is critical in understanding the effects of PM on health as well as climate.

This paper analyzes data obtained from international studies that compared natural gas, diesel, a... more This paper analyzes data obtained from international studies that compared natural gas, diesel, and hybrid technologies for buses to determine differences in particulate matter (PM 10), nitrogen oxides (NO x), nonmethane hydrocarbon (NMHC), carbon monoxide (CO), greenhouse gas, and air toxic emissions. The results presented here are for 90-passenger 12-m buses. Two types of comparisons were made: technology and fuel.

Abstract A good estimate of gas and aerosol anthropogenic emissions is crucial for estimating gas... more Abstract A good estimate of gas and aerosol anthropogenic emissions is crucial for estimating gases and aerosol concentrations in the atmosphere. Although high-resolution emission inventories covering the entire Europe exist and they have been applied in several studies, their quality has not been evaluated uniformly in all the European regions. Most of these existing studies analyzed mainly the North-Western European countries supported also by a large variety of observations.

Abstract Nuclear energy will continue to have an important role in the production of electricity ... more Abstract Nuclear energy will continue to have an important role in the production of electricity in the world as the need of energy grows up. But the safety of power plants will always be a question mark for people because of the accidents happened in the past. Chernobyl nuclear reactor accident which happened in 26 April 1986 was the biggest nuclear accident ever. Because of explosion and fire large quantities of radioactive material was released to the atmosphere.

Abstract Crustal thinning due to regional extensional tectonics played an important role in the p... more Abstract Crustal thinning due to regional extensional tectonics played an important role in the petrogenesis and chemical evolution of magmatism in western Anatolia starting in the Late Oligocene-Early Miocene. The study area is particularly critical because it contains various products of OligoMiocene magmatism whose geological and geochemical features indicate post-collisional setting. The magmatic rocks in this area are formed from two different groups of rocks, which display the close relationships in time and space.

Abstract This study provides valuable new insights into the key contributors to ambient air quali... more Abstract This study provides valuable new insights into the key contributors to ambient air quality in Istanbul, one of the largest mega-cities in Europe. The study builds on work in Europe that links air quality with national dynamics such as economical, vehicle activity and, meteorology in the long-term. Spatial and temporal analysis was performed on PM10 levels measured at 10 air quality monitoring sta-tions (AQMSs) in Istanbul from 1998 to 2008.

Emission inventories are a fundamental input to atmospheric chemical transport models(CTMs). As t... more Emission inventories are a fundamental input to atmospheric chemical transport models(CTMs). As the latter become increasingly demanding, modern inventories began to provide much more information(high spatial and temporal disaggregation, more chemical compounds etc).

Abstract In this study, we investigated the relationship between synoptic weather types and rainf... more Abstract In this study, we investigated the relationship between synoptic weather types and rainfall patterns in the Marmara region, northwestern part of Turkey. For this purpose, the automated Lamb weather type classification method was applied to the NCEP/NCAR reanalysis daily mean sea level pressure data for the period between 2001 and 2010. Ten synoptic weather types were found that represent the 90% of the synoptic patterns that affect the Marmara region.

Abstract Shipping is considered as one of the main emission sources worldwide. Recent studies sug... more Abstract Shipping is considered as one of the main emission sources worldwide. Recent studies suggest that, in the Mediterrenean, ship emissions are responsible for 10-50% of black carbon, 2-12% ozone in the surface layer and 5-20% for nitrogen dioxide atmospheric column burden (Marmer et al., 2009). It is, therefore, essential to have an accurate emissions estimation for ships. Marmara Sea, an inland sea connecting the Mediterrenean to the Black Sea, has significant marine activity.