Flux measurements in the surface Marine Atmospheric Boundary Layer over the Aegean Sea, Greece.

Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air-sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from -60 to 40 W/m(2)) and it was found that they are affected by the limited spatial and temporal scales of the responding air-sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature.

Quantification of environmental tobacco smoke contribution on outdoor particulate aliphatic and polycyclic aromatic hydrocarbons.

The objective of this study was to identify and quantify the sources of fine particulate aliphatic and polycyclic aromatic hydrocarbons (PAHs) in an urban area in southeastern Europe. A total of 91 urban PM2.5 samples were analyzed by gas chromatography coupled with mass spectrometry for alkanes and PAHs. Exploratory statistical tools were applied to resolve a decreased number of components based on the variation of measurements. Molecular markers and diagnostic ratios were examined to assign retained components to specific sources. The contributions of the sources were estimated by multivariate linear regression. Sources of aliphatic and PAHs hydrocarbons included primary particles from traffic (3.9 ng/m(3) for alkanes and 240 pg/m(3) for PAHs), evaporative fugitive (4.0 ng/m(3) for alkanes and 93 pg/m(3) for PAHs), and unburnt fuels and oil residues (1.1 ng/m(3) for alkanes and 230 pg/m(3) for PAHs). For the first time, we quantified the contribution of environmental tobacco smoke (ETS), which accounted for 5.2 ng/m(3) of alkanes and 128 pg/m(3) of PAHs. The findings of this study underlined the persistence of ETS and possible exposures to significant quantities of tobacco residues outdoors. Tobacco smoke is known to induce adverse respiratory and cardiovascular illnesses and increased risk for cancer.

PM2.5 and volatile organic compounds (VOCs) in ambient air: a focus on the effect of meteorology.

PM(2.5) and VOCs (benzene, toluene, m-p-o-xylenes) concentrations were measured in an urban and a suburban site in Athens, Greece, during the period between April and November 2004. This period, which is considered to be the warmer period in Greece, is characterized by the development of sea-breeze over the Attica Basin. Additionally strong Northern, North-eastern winds called "The Etesians", predominate during the summer months (July-August), acting positively to the dispersion of pollutants. In this campaign, 24 days with sea-breeze development were observed, 15 days with northern winds, 6 days with southern winds while the rest of the days presented no specific wind profile. Maximum concentrations of PM(2.5), VOCs and nitrogen oxides, were detected during the days with sea-breeze, while minimum concentrations during the days with northern winds. Ozone was the only pollutant that appeared to have higher concentrations in the background site and not in the city centre, where benzene presented strong negative correlation with ozone, indicating the photochemical reaction of hydrocarbons that lead to the ozone formation. The BTX ratios were similar for both sites and wind profiles, indicating common sources for those pollutants. T/B ratio ranged in low levels, between 3-5 for site A and 2-5 for site B, suggesting vehicles emissions as the main sources of volatile compounds. Finally, the strong correlations of PM(2.5) and benzene concentrations, between the two sampling sites, indicate that both the city centre and the background site, are affected by the same sources, under common meteorological conditions (sea-breeze, northern winds).

Emissions of total volatile organic compounds and indoor environment assessment in dental clinics in Athens, Greece.

OBJECTIVE: To quantify the amount of Total Volatile Organic Compounds (TVOCs) emitted from five dental substances commonly used in a dental clinic. METHOD: An assessment of the indoor air quality in two clinics of the Athens University Dentistry Faculty was conducted. RESULTS: It was found that TVOC emissions from Kalocryl and Bacillol reached extremely high values affecting the air in the dental clinics at short and long distances from the source. Six pollutants TVOCs, CO2, PM10, PM2.5, SO2 and NO(x) were measured and indoor sources associated with dental activities were identified. Very high concentrations of TVOCs were found which exceeded the acceptable levels by a factor of 20, associated with the nature of the dental activities and the ventilation conditions. The CO2 concentration levels were high and the indoor conditions were considered unsatisfactory, associated with the number of occupants and the ventilation conditions. PM concentrations were high due to the nature of the dental activities and they exceeded the outdoor levels by a factor of 5 to 6. The concentrations of the gaseous pollutants NO(x) were low while the SO2 concentrations were hardly detectable.

Indoor air quality in a dentistry clinic.

The purpose of this work is to assess, both experimentally and theoretically the status of air quality in a dentistry clinic of the Athens University Dentistry Faculty with respect to chemical pollutants and identify the indoor sources associated with dental activities. Total VOCs, CO(2), PM(10), PM(2.5), NO(x) and SO(2) were measured over a period of approximately three months in a selected dentistry clinic. High pollution levels during the operation hours regarding CO(2), total VOCs and Particulate Matter were found, while in the non-working periods lower levels were recorded. On the contrary, NO(x) and SO(2) remained at low levels for the whole experimental period. These conditions were associated with the number of occupants, the nature of the dental clinical procedures, the materials used and the ventilation schemes, which lead to high concentrations, far above the limits that are set by international organizations and concern human exposure. The indoor environmental conditions were investigated using the Computational Fluid Dynamics (CFD) model PHOENICS for inert gases simulation. The results revealed diagonal temperature stratification and low air velocities leading to pollution stratification, accompanied by accumulation of inert gaseous species in certain areas of the room. Different schemes of natural ventilation were also applied in order to examine their effect on the indoor comfort conditions for the occupants, in terms of air renewal and double cross ventilation was found to be most effective. The relative contribution of the indoor sources, which are mainly associated with indoor activities, was assessed by application of the Multi Chamber Indoor Air Quality Model (MIAQ) to the experimental data. It was found that deposition onto indoor surfaces is an important removal mechanism while a great amount of particulate matter emitted in the Clinic burdened severely the indoor air quality. The natural ventilation of the room seemed to reduce the levels of the fine particles. The emission rates for the fine and coarse particulates were found to be almost equal, while the coarse particles were found susceptible to deposition onto indoor surfaces.

Lung deposition of fine and ultrafine particles outdoors and indoors during a cooking event and a no activity period.

UNLABELLED: Some indoor activities increase the number concentration of small particles and, hence, enhance the dose delivered to the lungs. The received particle dose indoors may exceed noticeably the dose from ambient air under routine in-house activities like cooking. In the present work, the internal dose by inhalation of ultrafine and fine particles is assessed, using an appropriate mechanistic model of lung deposition, accommodating aerosol, and inhalation dynamics. The analysis is based on size distribution measurements (10-350 nm) of indoor and outdoor aerosol number concentrations in a typical residence in Athens, Greece. Four different cases are examined, namely, a cooking event, a no activity period indoors and the equivalent time periods outdoors. When the cooking event (frying of bacon-eggs with a gas fire) occurred, the amount of deposited particles deep into the lung of an individual indoors exceeded by up to 10 times the amount received by an individual at the same time period outdoors. The fine particle deposition depends on the level of physical exertion and the hygroscopic properties of the inhaled aerosol. The dose is not found linearly dependant on the indoor/outdoor concentrations during the cooking event, whereas it is during the no activity period. PRACTICAL IMPLICATIONS: The necessity for determining the dose in specific regions of the human lung, as well as the non-linear relationship between aerosol concentration and internal dose makes the application of dosimetry models important. Lung dose of fine and ultrafine particles, during a cooking event, is compared with the dose at no indoor activity and the dose received under outdoor exposure conditions. The dose is expressed in terms of number or surface of deposited particles. This permits to address the dosimetry of very small particles, which are released by many indoor sources but represent a slight fraction of the particulate matter mass. The enhancement of the internal dose resulting from fine and ultrafine particles generated during the cooking event vs. the dose when no indoor source is active is assessed. The results for those cases are also compared with the dose calculated for the measured aerosol outdoors.

Gas-particle concentration and characterization of sources of PAHs in the atmosphere of a suburban area in Athens, Greece.

Atmospheric polycyclic aromatic hydrocarbons (PAH) were determined in two places in a suburban area of Athens greater area (AGA) during June and November 2003. Fourteen PAHs were quantified in the collected samples. The total concentration in the gas phase ranged between 6.89 and 124ngm(-3), while in the particulate phase between 0.44 and 13.2ngm(-3). Maximum concentrations of the total PAHs (gas and particulate phase) were observed during the cold period with an average of 40.7ngm(-3). PAHs were correlated with NO, NO(2) and O(3), wind speed, wind direction and temperature. Positive correlation was observed between PAHs and NO, NO(2), while negative correlation was detected between PAHs and O(3). The most abundant members were phenanthrene, anthracene, fluorene, fluoranthene and pyrene. Potential sources of PAHs in aerosols were investigated using molecular diagnostic ratios, which reflect sources such as diesel and gasoline engines, although other sources such as coal combustion and liquefied petroleum gas also contributed.

Temporal variations of PM2.5 in the ambient air of a suburban site in Athens, Greece.

Twenty-three hour measurements of PM(2.5) particulate matter have been carried out during the period between the 1st April and the 13th November 2003 in a suburban area of Athens. The monitoring site was located in the National Research Center "DEMOKRITOS", on the foot of Hemittos Mountain and about 12 km away from the center of Athens. The site covers an area of 600 acres in a forest of pine trees close enough to the newly constructed Hemittos Mountain peripheral highway. PM(2.5) samples were collected on 47 mm filters, with the use of low volume gravimetric samplers while a meteorological station recorded meteorological data 6 m above the ground, nearby the sampling instrumentation. The daily average PM(2.5) concentration reached 21.1 microg m(-3) and all measurements were below U.S. Environmental Pollution Agency daily limit (65 microg m(-3)). A regression analysis was used to investigate the relationship among PM(2.5) concentrations and meteorological parameters. Additionally, PM(2.5) mass concentrations were correlated with other inorganic gaseous pollutants (O(3), NO, NO(2), SO(2)) while weekly and seasonal PM(2.5) variations were also investigated.

Sodar mixing height estimates and air pollution characteristics over a Mediterranean big city.

Sodar systems are progressively used for quantitative and qualitative profile information on the atmospheric structure parameters. However, there is still a need for well-established relations between atmospheric physics parameters and air quality patterns, especially in urban environments. In this respect it is of importance to investigate the correlations among specific atmospheric quantities and air pollution patterns. It is the purpose of this paper to study correlations between the Sodar produced mixing height using the most recent and accurate methods, and O3, NOx and CO concentrations recorded by the Athens air quality monitoring network, during selected meteorological conditions. The continuous mixing height monitoring allows for deeper investigation of air pollution characteristics, especially during the transitional periods of the day. The obtained results indicate that there is good correlation between the pollutants concentrations and the mixing height especially during episode days. Furthermore, it is indicated that there is a strong dependence between the rate of increase of the mixing height and the concentration levels in the early morning hours as well as during the Atmospheric Boundary Layer (ABL) collapse in the afternoon. These results are of importance for urban air pollution modelling, which has recently attracted the attention of many research groups.