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Periods of abnormally high concentrations of atmospheric pollutants, defined as air pollution episodes, can cause adverse health effects. Southern European countries experience high particulate matter (PM) levels originating from local and distant sources. In this study, we investigated the occurrence and nature of extreme PM10 (PM with an aerodynamic diameter =10 µm) pollution episodes in Greece. We examined PM10 concentration data from 18 monitoring stations located at five sites across the country: (1) an industrial area in northwestern Greece (Western Macedonia Lignite Area, WMLA), which includes sources such as lignite mining operations and lignite power plants that generate a high percentage of the energy in Greece; (2) the greater Athens area, the most populated area of the country; and (3) Thessaloniki, (4) Patra, and (5) Volos, three large cities in Greece. We defined extreme PM10 pollution episodes (EEs) as days during which PM10 concentrations at all five sites exceeded the European Union (EU) 24-hr PM10 standards. For each EE, we identified the corresponding prevailing synoptic and local meteorological conditions, including wind surface data, for the period from January 2009 through December 2011. We also analyzed data from remote sensing and model simulations. We recorded 14 EEs that occurred over 49 days and could be grouped into two categories: (1) Local Source Impact (LSI; 26 days, 53%) and (2) African Dust Impact (ADI; 23 days, 47%). Our analysis suggested that the contribution of local sources to ADI EEs was relatively small. LSI EEs were observed only in the cold season, whereas ADI EEs occurred throughout the year, with a higher frequency during the cold season. The EEs with the highest intensity were recorded during African dust intrusions. ADI episodes were found to contribute more than local sources in Greece, with ADI and LSI fraction contribution ranging from 1.1 to 3.10. The EE contribution during ADI fluctuated from 41 to 83 µg/m3, whereas during LSI it varied from 14 to 67 _g/m³. Implications: This paper examines the occurrence and nature of extreme PM10 pollution episodes (EEs) in Greece during a 3-yr period (2009-2011). Fourteen EEs were found of 49 days total duration, classified into two main categories: Local Source Impact (53%) and African Dust Impact (47%). All the above extreme PM10 air pollution episodes were the result of specific synoptic prevailing conditions. Specific information on the linkages between the synoptic weather patterns and PM10 concentrations could be used in the development of weather/health-warning system to alert the public that a synoptic episode is imminent. [ABSTRACT FROM AUTHOR]

The question to what extent primary and secondary air pollutants are relevant to atmospheric pollution and their effects on human health and the quality of the environment can be answered in a straight-forward manner: atmospheric processes, including oxidation procedures, particle formation and equilibria, determine the fate of primary emissions and, in most cases, the secondary products of these processes are the more important ones concerning their effects on human health and the quality of the environment. The formation of secondary products represents the critical property determining the establishment of certain air standards, rather than the actually emitted substance, although there are notable exceptions. In this paper, a review concerning transformation of primary pollutants as studied in the atmosphere of Athens is used to enlighten matters that may need further attention by the responsible authorities and stakeholders for the control and reduction of atmospheric pollution. [ABSTRACT FROM AUTHOR]

Abstract: Air Pollution control is of major concern for the Greater Athens Area (GAA) of Greece. High concentrations of Particulate Matter with diameter less than 10μm (PM10) have been observed and often reported to exceed the currently EU legislated 24-hour limit of 50μg/m3. Efforts therefore have been placed on understanding the PM10 concentration pattern in the area so that mitigation measures can be taken accordingly. The present paper presents a statistical methodology to discover causal relationships between daily PM10 exceedances at a monitoring site, with PM10 concentrations from existing stations from the monitoring network and associated weather patterns. The proposed approach utilised a dimension reduction algorithm, Positive Matrix Factorisation (PMF) algorithm, coupled with the k-means clustering algorithm to identify distinct groups of data. Then for each resulted cluster, the Granger Causality method aided by the Pearson correlation is applied to establish the causal relationships between the meteorological patterns and the observed PM10 exceedances. The study was conducted using 6-years of daily PM10 concentration data from the monitoring network in the GAA, complemented with meteorological data available from the National Centres for Environmental Prediction (NCEP) Global Forecasting System (GFS). The analysis yielded that the PM10 exceedances in the Athens area can be classified into 6 distinct types identified with varying spatial distribution characteristics and air pollution contributors. [Copyright &y& Elsevier]

An economic and quick methodology for performing a preliminary spatial assessment of a city air quality with the purpose to identify locations and zones susceptible to high pollution levels is proposed. A Patras case-study is selected, regarding the air pollutants of sulfur dioxide (SO2) and oxides of nitrogen (NOx). A total number of 451 samples of short duration, of which 225 were randomly picked in morning rush hours and 226 within evening rush hours, were collected from 50 locations of the major Patras area during a year period, when peaks of primary air pollutants usually occur. Concentration measurements at prescribed locations used to statistically calculate spatial average concentrations approximating 1-h mean values with mean probable errors less than 25.9% for SO2, NO and NOx and less than 15.5% for NO2. Then iso-concentration contour diagrams plotted indicate high pollution zones and possibly appropriate locations for continuous or random monitoring according to the European Community (EC) Directives. The 1-h mean concentrations were in good correlation to the corresponding traffic rates and useful relationships are given (0.54 ≤ r ≤ 0.63). In addition, comparisons with data available for other cities, as well as with the limit and guide values provided by the EC and the World Health Organization (WHO) were given. The present data could be useful for the design and optimization of a city network of stations for monitoring air quality, for environmental impact assessments, future reference and comparisons due to city development needs, as well as for validating dispersion models. [ABSTRACT FROM AUTHOR]