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The maritime sector poses significant challenges in controlling the emission of harmful pollutants, such as particulate matter, and reducing their impact on coastal areas and the atmospheric environment. Efforts to regulate the sector necessitate new knowledge and methods to characterise the evolution and physicochemical transformation of maritime particle emissions dispersing in port areas. An experimental campaign at the Port of Rafina, Greece, was conducted with this in mind. In this paper, we report on the first multi-characteristic particle measurements, including particle number (PN), lung deposited surface area (LDSA), and black carbon (BC), performed at both land and sea using a novel instrument set-up mounted on an unmanned aerial vehicle (UAV). Land-based measurements showed that LDSA averages, which are influenced by particle number and size, increase up to 20 times above background levels as an emission plume progresses downwind, whereas BC concentrations, which are dominated by mass, are ∼12 times higher than the background concentration. Ground and UAV-based particle comparisons showed that PN and LDSA measurements exhibit greater differences than BC relative to the plume's location. Ground-based sensors had ∼50% lower LDSA and PN concentrations, whereas BC was about equal. The experimental observations are further substantiated by coupling a Gaussian plume dispersion model and a new computationally attractive approach, known as the Incompletely Stirred Reactor Network (ISRN) method, to predict the three-dimensional evolution of particle characteristics considering the effects of dilution, segregation, and physicochemical transformations, such as coagulation. Based on simplifying assumptions for the particle size distribution sources within the port area, the ISRN estimates suggest that the discrepancy between various metrics can be partly explained by coagulation, responsible for a non-linear increase in particle size, depending on the local level of dilution and mixing intensity, leading up to a ∼25% decrease in PN and LDSA compared to BC. Combined, measurements and modelling highlight the effect of the sampling location and the importance of monitoring more than one particle metric to characterise particle evolution. [Display omitted] • Measurement of multiple particle characteristics for in-use maritime vessels using a UAV. • Evaluation of particle mass and LDSA evolution in maritime plume dispersion. • Application of ISRN method to real-world maritime plume dispersion. • Vertical stratification of multiple particle characteristics replicated by ISRN estimates. • Coagulation may lead to an in-plume decrease of PN and LDSA by up to ∼25%. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents results derived from ultra-fine particle observations conducted in urban and semi-rural areas of the Athens basin in Greece. Aerosol particle size spectra were collected at 2.5-min time resolution with a Scanning Mobility Particle Sizer for approximately two months, along with standard meteorological, NO, NO2 and O3 measurements. The results obtained showed that a 10-fold less maximum number concentration of the mean spectrum was noticed at the semi-rural site compared with that at the urban site. The corresponding maximum for the median spectrum of urban site was only 20% less, indicating that extreme cases had little effect, at least in maximum mean concentration of 9.8 nm particles. The largest number concentration maximum in the mean size distribution spectrum for each area occurred at a modal diameter ≤9.8 nm. For particles ≥13.4 nm, the mean spectrum for Patision contained prominent accumulation particle populations at number median diameters of 13.4, 29.7, and 43.7 nm. In contrast, the major features of the accumulation region of the mean semi-rural spectrum were fit with 5 distribution functions of nearly the same amplitude. The most dominant feature occurred at a number median diameter of 70.1 nm, and thus substantially greater than the 43.7 nm most-dominant in the mean urban spectrum. High ultra-fine particle concentrations at the urban site generally coincided with periods of high NO concentrations and were well correlated with benzene, signifying emissions from motor vehicles. [Copyright &y& Elsevier]

Abstract: This paper examines the contribution of primary and secondary NO2 production in NOx concentrations and offers a comprehensive analysis of the long-term trends of NOx, NO2 and O3 concentrations, as well as of the NO2/NOx ratio, in the Athens urban conurbation. Long-term pollutant concentration time series show that NO2 concentrations in Athens have decreased since 1987 but at a slower rate than those of NOx, resulting to an increasing NO2/NOx concentration ratio. However, this increasing trend is much smaller than those observed in urban areas of other European countries. The possible causes of this trend are examined and especially the interaction with ozone and the amount of direct NO2 traffic emissions. The results indicate that the increasing NO2/NOx ratio in the Athens area is mainly attributable to an increased secondary formation of NO2 through photochemical reactions in the atmosphere. More specifically, two different empirical methodologies were applied to examine the primary NO2 concentration fraction in Athens, using ambient monitoring data from a kerbside station. Both methods indicate that the primary NO2 concentration share has not altered significantly between 1998 and 2006. This is mainly attributed to the fact that in the Athens area diesel passenger cars are not allowed and after-treatment technologies such as particle filters and oxidation catalysts are not yet applied in Greece. A probable future penetration of diesel passenger cars in Athens should be combined with inventories of primary NO2 emissions and with the development of appropriate policies to reduce ambient NO2 concentrations below the EU limit values. [Copyright &y& Elsevier]

Abstract: Managing urban air pollution necessitates a feasible and efficient abatement strategy which is characterised as a defined set of specific control measures. In practice, hard budget constraints are present in any decision-making process and therefore available alternatives need to be hierarchised in a fast but still reliable manner. Moreover, realistic strategies require adequate information on the available control measures, taking also into account the area’s special characteristics. The selection of the most applicable bundle of measures rests in achieving stakeholders’ consensus, while taking into consideration mutually conflicting views and criteria. A preliminary qualitative comparison of alternative control measures would be most handy for decision-makers, forming the grounds for an in-depth analysis of the most promising ones. This paper presents an easy-to-follow multicriteria methodological approach in order to include and synthesise multi-disciplinary knowledge from various stakeholders so as to result into a priority list of abatement options, achieve consensus and secure the adoption of the resulting optimal solution. The approach relies on the active involvement of public authorities and local stakeholders in order to incorporate their environmental, economic and social preferences. The methodological scheme is implemented for the case of Thessaloniki, Greece, an area considered among the most polluted cities within Europe, especially with respect to airborne particles. Intense police control, natural gas penetration in buildings and metro construction equally result into the most “promising” alternatives in order to control air pollution in the GTA. The three optimal alternatives belong to different thematic areas, namely road transport, thermal heating and infrastructure. Thus, it is obvious that efforts should spread throughout all thematic areas. Natural gas penetration in industrial units, intense monitoring of environmental standards and regular maintenance of heavy oil burners are ranked as 4th, 5th and 6th optimal alternatives, respectively. [Copyright &y& Elsevier]

Abstract: State of the art epidemiological research has found consistent associations between traffic-related air pollution and various outcomes, such as respiratory symptoms and premature mortality. However, many urban areas are characterised by the absence of the necessary monitoring infrastructure, especially for benzene (C6H6), which is a known human carcinogen. The use of environmental statistics combined with air quality modelling can be of vital importance in order to assess air quality levels of traffic-related pollutants in an urban area in the case where there are no available measurements. This paper aims at developing and presenting a reliable approach, in order to forecast C6H6 levels in urban environments, demonstrated for Thessaloniki, Greece. Multiple stepwise regression analysis is used and a strong statistical relationship is detected between C6H6 and CO. The adopted regression model is validated in order to depict its applicability and representativeness. The presented results demonstrate that the adopted approach is capable of capturing C6H6 concentration trends and should be considered as complementary to air quality monitoring. [Copyright &y& Elsevier]

Abstract: The paper introduces a new methodology for the prediction of daily PM10 concentrations, in line with the regulatory framework introduced through the EU Directive 2008/50/EC. The proposed approach is based on the efficient utilisation of the data collected over short time intervals (hourly) rather than the daily values used to derive the daily regulatory threshold. It is sufficiently simple and easily applicable in operational forecasting systems with the ability to accept as inputs both historical data and exogenous paraeters, such as meteorological variables. The application of the proposed methodology is demonstrated using data from five monitoring stations of air pollutants located in Athens, over a five year period (2000–2004) as well as compatible meteorological data from the NCEP (National Centers for Environmental Protection). A set of different models have been tested at the same time to reveal the effectiveness of the proposed approach, both univariate and multivariate, and linear and non-linear models. The analysis of all examined datasets has shown conclusive evidence that the introduction of the newly developed procedure which utilises data collected over a shorter horizon can significantly increase the forecasting ability of any developed model using daily historic PM10 data, under all examined metrics. [Copyright &y& Elsevier]

Abstract: The existing and emerging international and European policy framework for the reduction of ship exhaust emissions dictates the need to produce reliable national, regional and global inventories in order to monitor emission trends and consequently provide the necessary support for future policy making. Furthermore, the inventories of ship exhaust emissions constitute the basis upon which their external costs are estimated in an attempt to highlight the economic burden they impose upon the society and facilitate the cost–benefit analysis of the proposed emission abatement technologies, operational measures and market-based instruments prior to their implementation. The case of Greece is of particular interest mainly because the dense ship traffic within the Greek seas directly imposes the impact of its exhaust emission pollutants (NOx, SO2 and PM) upon the highly populated, physically sensitive and culturally precious Greek coastline, as well as upon the land and seas of Greece in general, whereas the contribution of Greece in the global CO2 inventory at a time of climatic change awareness cannot be ignored. In this context, this paper presents the contribution of Greece in ship exhaust emissions of CO2, NOx, SO2 and PM from domestic and international shipping over the last 25 years (1984–2008), utilizing the fuel-based (fuel sales) emission methodology. Furthermore, the ship exhaust emissions generated within the Greek seas and their externalities are estimated for the year 2008, through utilizing the fuel-based (fuel sales) approach for domestic shipping and the activity-based (ship traffic) approach for international shipping. On this basis, it was found that during the 1984 to 2008 period the fuel-based (fuel sales) ship emission inventory for Greece increased at an average annual rate of 2.85%. In 2008, the CO2, NOx, SO2 and PM emissions reached 12.9 million tons (of which 12.4 million tons of CO2) and their externalities were found to be around 3.1 billion euro. With regard to shipping within the Greek seas, the utilization of the fuel-based (fuel sales) analysis for domestic shipping and the activity-based (ship traffic) analysis for international shipping shows that the ship-generated emissions reached 7.4 million tons (of which 7 million tons of CO2) and their externalities were estimated at 2.95 billion euro. Finally, the internalization of external costs for domestic shipping was found to produce an increase of 12.96 and 2.71 euro per passenger and transported ton, respectively. [Copyright &y& Elsevier]

Springtime constitutes the most favorable period for Sahara dust outbreaks and transport over Eastern Mediterranean. This study investigates the aerosol properties during April 2005 using remote-sensing and ground-based measurements. Three dust events with high aerosol optical depth (AOD) values have been observed during the measuring period, with duration of two days, i.e. 11–12, 16–17 and 25–26 April 2005. In this paper we mainly focus on the intense dust event of 16–17 April 2005, when a thick dust layer transported from Libya affected the whole Greek territory. Very high AOD values obtained from Aqua-MODIS sensor were observed over Greece (mean 2.42±1.25) on 17 April, while the respective mean April value was 0.31±0.09. The AOD at 550 nm (AOD550) values over Crete were even larger, reaching ∼4.0. As a consequence, the PM10 concentrations over Athens dramatically increased reaching up to 200μgm−3. On the other hand, the fine-mode fraction values obtained from Terra-MODIS showed a substantial decrease in the whole Greek area on 17 April with values below 0.2 in the Southern regions. The intense dust layer showed a complex behavior concerning its spatial and temporal evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport routes due to the mixing processes with other aerosol types. The results from different measurements (ground-based and remote-sensing) did not contradict each other and, therefore, are adequate for monitoring of dust load over the Eastern Mediterranean. [Copyright &y& Elsevier]

Recent risk assessment studies have shown that high outdoor NO2 levels observed in residential areas contribute to increased respiratory and cardiovascular diseases and mortality. Detailed information on present NO2 levels as well as predictions of NO2 concentrations corresponding to reduced NO x levels in urban areas are very useful to decision and policy makers in order to protect the public health. In the present paper, monitoring stations of the Athens network are initially classified into two main groups, traffic affected and urban background, using effectively a criterion based on the ratio of annual mean NO:NO2 concentrations. Two empirical methodologies are then considered and compared for assessing the effect of different NO x levels on the attainment of the annual NO2 air quality standard at urban-background locations in the Athens area. An interesting finding is that these two methodologies, one more general and one both year and site dependent, give similar results for the specific study area and can be applied alternatively based on the length of available concentration time series. The results show that in order to meet the EU annual mean NO2 objective at all the urban-background locations of the Athens area, annual NO x concentrations should be reduced to approximately 60μgm−3, requiring NO x emission reductions of up to 30%. An analysis of the health implications of the currently observed NO2 levels is conducted, based on a dose–response relationship, and is coupled with available health-related data for the Athens area. This analysis suggests that if NO2 concentrations were reduced to the levels of the annual EU air quality standard, then a decrease of hospital admissions of up to 2.6% would be observed, depending on the levels of NO2 measured at different monitoring sites of the Athens conurbation. [Copyright &y& Elsevier]

Abstract: In this paper, the OSPM model is employed for the calculation of the PM10 concentration levels in the historical centre of the city of Thessaloniki (Greece). Although measurements of the background concentration are available at a suburban station, and a few measurements of PM10 concentrations do exist at particular areas inside the historical city centre, further assumptions had to be made (e.g., for the traffic load) in order to implement OSPM. To validate this approach, NO x and NO2 measurements were employed in addition to data for PM10. The good agreement observed allowed the prediction of PM10 concentrations in all streets in the historical city centre. The very high PM10 concentration levels obtained in almost all streets are indicative of the city''s situation today. Finally, developments in vehicle''s technology are invoked to model possible future scenarios. [Copyright &y& Elsevier]

Abstract: As part of the European project SUB-AERO, comprehensive aerosol and gaseous pollutant measurement campaigns were performed at the Finokalia station (July 2000 and January 2001) on the island of Crete (Greece) in combination with boat measurements in the eastern part of the Mediterranean area. The measurements were performed with the participation of nine European research institutions. The objective of the measurement campaigns was to evaluate and assess the spatial and temporal variability of photochemical pollutants and fine particles. The current overview paper presents the framework and main results of the measurements and modelling studies performed during the project. Extensive measurements of gaseous and atmospheric-aerosol physical, chemical and optical characteristics were performed during the measurement campaigns in conjunction with detailed chemical analyses of the aerosol species. Along with the experimental work mesoscale modelling, using a combination of the UAM-AERO air quality model together with the RAMS prognostic meteorological model, was used to reveal the dynamics of particulate matter and photo-oxidants. Furthermore, regional chemistry transport models were applied to determine the background and initial conditions for the mesoscale modelling. [Copyright &y& Elsevier]