Konstantinos Dimitriou

Three year study of tropospheric ozone with back trajectories at a metropolitan and a medium scale urban area in Greece

Three years of hourly O3 concentration measurements from a metropolitan and a medium scale urban area in Greece: Athens and Ioannina respectively, were analyzed in conjunction with hourly wind speed/direction data and air mass trajectories, aiming to reveal local and regional contributions respectively. Conditional Probability Function was used to indicate associations among distinct wind directions and extreme O3 episodes. Backward trajectory clusters were elaborated by Potential Source Contribution Function on a grid of a 0.5°×0.5° resolution, in order to localize potential exogenous sources of O3 and its precursors. In Athens, an increased likelihood of extreme O3 events at the Northern suburbs was associated with the influence of SSW-SW sea breeze from Saronikos Gulf, due to O3 transportation from the city center. In Ioannina, the impacts of O3 conveyance from the city center to the suburban monitoring site were weaker. Potential O3 transboundary sources for Athens were mainly localized over Balkan Peninsula, Greece and the Aegean Sea. Potential Source Contribution Function hotspots were isolated over the industrialized area of Ptolemaida basin and above the region of Thessaloniki. Potential regional O3 sources for Ioannina were indicated across northern Greece and Balkan Peninsula, whereas peak Potential Source Contribution Function values were particularly observed over the urban area of Sofia in Bulgaria. The implemented methods, revealed local and potential transboundary source areas of O3, influencing Athens and Ioannina. Differences among the two cities were highlighted and the role of topography was emerged. These findings can be used in order to reduce the emission of O3 precursors.

Local and regional sources of fine and coarse particulate matter based on traffic and background monitoring

The aim of this study was to identify local and exogenous sources affecting particulate matter (PM) levels in five major cities of Northern Europe namely: London, Paris, Hamburg, Copenhagen and Stockholm. Besides local emissions, PM profile at urban and suburban areas of the European Union (EU) is also influenced by regional PM sources due to atmospheric transport, thus geographical city distribution is of a great importance. At each city, PM10, PM2.5, NO2, SO2, CO and O3 air pollution data from two air pollution monitoring stations of the EU network were used. Different background characteristics of the selected two sampling sites at each city facilitated comparisons, providing a more exact analysis of PM sources. Four source apportionment methods: Pearson correlations among the levels of particulates and gaseous pollutants, characterisation of primal component analysis components, long-range transport analysis and extrapolation of PM size distribution ratios were applied. In general, fine (PM2.5) and coarse (PM10) particles were highly correlated, thus common sources are suggested. Combustion-originated gaseous pollutants (CO, NO2, SO2) were strongly associated to PM10 and PM2.5, primarily at areas severely affected by traffic. On the contrary, at background stations neighbouring important natural sources of particles or situated in suburban areas with rural background, natural emissions of aerosols were indicated. Series of daily PM2.5/PM10 ratios showed that minimum fraction values were detected during warm periods, due to higher volumes of airborne biogenic PM coarse, mainly at stations with important natural sources of particles in their vicinity. Hybrid single-particle Lagrangian integrated trajectory model was used, in order to extract 4-day backward air mass trajectories that arrived in the five cities which are under study during days with recorded PM10 exceedances. At all five cities, a significantly large fraction of those trajectories were classified in short- and medium-range clusters, thus transportation of particulates along with slow moving air masses was identified. A finding that supports the assumption of long-range transport is that, at background stations, long-range transportation effects were stronger, in comparison to traffic stations, due to less local particle emissions. Short-range trajectories associated to PM transport in Stockholm, Copenhagen and Hamburg were mainly of a continental origin. All three cities were approached by slow moving air masses originated from Poland and the Czech Republic, whereas Copenhagen and Stockholm were also influenced by short-range trajectories from Germany and France and from Jutland Peninsula and Scandinavian Peninsula, respectively. London and Paris are located to the north-west part of Europe. Trajectories of short and medium length arrived to these two megacities mainly through France, Germany, UK and North Atlantic.

The covariance of air quality conditions in six cities in Southern Germany - The role of meteorology

This paper analyzed air quality in six cities in Southern Germany (Ulm, Augsburg, Konstanz, Freiburg, Stuttgart and Munich), in conjunction with the prevailing synoptic conditions. Air quality was estimated through the calculation of a daily Air Stress Index (ASI) constituted by five independent components, each one expressing the contribution of one of the five main pollutants (PM10, O3, SO2, NO2 and CO) to the total air stress. As it was deduced from ASI components, PM10 from combustion sources and photochemically produced tropospheric O3 are the most hazardous pollutants at the studied sites, throughout cold and warm periods respectively, yet PM10 contribute substantially to the overall air stress during both seasons. The influence of anticyclonic high pressure systems, leading to atmospheric stagnation, was associated with increased ASI values, mainly due to the entrapment of PM10. Moderate air stress was generally estimated in all cities however a cleaner atmosphere was detected principally in Freiburg when North Europe was dominated by low pressure systems. Daily events of notably escalated ASI values were further analyzed with backward air mass trajectories. Throughout cold period, ASI episodes were commonly related to eastern airflows carrying exogenous PM10 originated from eastern continental Europe. During warm period, ASI episodes were connected to the arrival of regionally circulated air parcels reflecting lack of dispersion and accumulation of pollutants in accordance with the synoptic analysis.

Aerosol contributions at an urban background site in Eastern Mediterranean – Potential source regions of PAHs in PM10 mass

In this paper, two backward air mass trajectory-based models (Potential Source Contribution Function [PSCF] and Concentration Weighted Trajectory [CWT]) were combined, aiming to identify sources and factors defining the load of PM in the city of Limassol (Cyprus). The study also focused on the determination of atmospheric pathways enriching the aerosol phase of four carcinogenic Polycyclic Aromatic Hydrocarbons (PAHs): Benzo(a)pyrene (BaP), Benzo(a)anthracene (BaA), Benzo(b)fluoranthene (BbF) and Benzo(k)fluoranthene (BkF), in PM10 mass. The analysis was performed on a 0.5°·0.5° resolution grid for the two-year period 2011-2012. During cold seasons, regional airflows triggered the accumulation of locally produced PM2.5, while the impact of dust plumes originated from deserts in NE Africa, Syria and the Middle East, was apparent on PM2.5 and principally on PMCOARSE levels. On the contrary, within warm seasons, weaker dust PMCOARSE contributions were detected in Limassol from areas in Egypt and Libya. Raised particulate-phase PAH concentrations in Limassol were clearly related to air parcels reaching Cyprus via continental areas. The use of outdated technologies for heating and transportation in Turkey and Syria, and fire events in central Turkey, are possible sources of exogenous PAHs throughout cold and warm period respectively. The influence of clean marine air masses dropped the levels of PAH compounds in all seasons.

The influence of specific atmospheric circulation types on PM10-bound benzo(a)pyrene inhalation related lung cancer risk in Barcelona, Spain

Benzo(a)pyrene (BaP) is a Polycyclic Aromatic Hydrocarbon (PAH) well known for its carcinogenic effects. In this study, BaP levels in daily PM10 samples collected at 8 stations in Barcelona (Spain), during the years 2013-2015, were analyzed in relation to distinct atmospheric circulation patterns. Our objective was to estimate the BaP inhalation related Lung Cancer Risk (LCR) in connection with the prevailing synoptic conditions. Air masses were also analyzed in order to examine the possibility of transboundary BaP contributions. The influence of high pressure anticyclonic systems caused a sharp increase of PM10-bound BaP concentrations in all stations due to recirculation and accumulation of polluted air, whilst the calculated BaP inhalation related LCR values implied a potential health risk from BaP exposure and were not recommendable primarily at central heavily trafficked sites. However the LCR remained below the upper limit posed by United States Environmental Protection Agency (US EPA), even under the most stagnant atmospheric conditions. The elaboration of backward air mass trajectories with Concentration Weighted Trajectory (CWT) algorithm indicated that combustion emissions in Spain, France and the industrialized Northern coast of Algeria are potential contributors to the PM10-bound BaP concentrations measured in Barcelona.

Day by day evolution of a vigorous two wave Saharan dust storm – Thermal and air quality impacts

This paper conducts a day-by-day analysis of an intense Saharan dust storm that struck Athens (Greece) during April 2008 and consisted of two main dust waves (the first from 10/04/2008 to 14/04/2008 and the second from 19/04/2008 to 22/04/2008). Daily satellite data (1o × 1o resolution) of aerosol optical depth (AOD) were used, in order to follow the course of two dust plumes originated in North Africa through the eastern Mediterranean. Ground based measurements of particle concentrations (PM 10 and PM 2.5 ) and meteorological parameters (wind speed, air temperature, relative humidity and visibility) were also studied. The time intervals before and after each dust wave were taken under consideration, aiming to identify the atmospheric circulation that generated the dust storm and also the clearing mechanisms that removed the African dust from the Athenian atmosphere. Backward air mass trajectories isolated the source of the two dust plumes over Libya and Tunisia, where extreme daily AOD values were recorded. The transportation of dust in the Greek region, during both dust waves, was associated with south westerlies airflows attributed to the advent of low pressure systems from the Atlantic. The impact of both dust waves in Athens was interrupted by the prevalence of a strong north westerlies air stream, which carried the particles eastwards through Turkey, Cyprus and the Middle East. During this dust event, air quality in Athens was severely downgraded, but no thermal discomfort has occurred, according to the estimation of a Pollution Index (PI) and a Discomfort Index (DI), respectively. A drop in visibility was also reported.

Quantifying daily contributions of source regions to PM concentrations in Marseille based on the trails of incoming air masses

The hourly trails (trajectory points) of incoming air masses have been used in this study in order to compose independent variables for the quantification of regional PM10 and PM2.5 contributions in Marseille (Southern France), and also for the estimation of the atmospheric dispersion effect. These prediction variables were used as input for a Multiple Linear Regression Model (MLRM) in order to estimate daily PM10 and PM2.5 concentrations in Marseille. For a more exact localization of fine and coarse particle sources, during cold and warm period, our analysis was supplemented by the findings of Concentration Weighted Trajectory (CWT) algorithm on a 0.5°·0.5° resolution grid. A strong coherence was revealed among measured and estimated daily levels of PM10 and PM2.5; thus, the proposed MLRM can be a useful tool for assessing air quality in terms of atmospheric circulation. Increased PM contributions in Marseille from local and all-around emission sources were indicated by MLRM primarily within cold seasons. In addition, Northeast (NE) atmospheric circulation was associated by MLRM and CWT with extreme intrusions of exogenous particulate air pollution from Central Europe, during winter and early spring. Throughout warm period, the scarceness of NE airflows prevented the transportation of aerosols from continental Europe. Episodes of desert dust transportation from Northwest Africa (Algeria and Tunisia) had a clear footprint in the PMCOARSE (=PM10-PM2.5) fraction.