In the present study the involvement of human activities is assessed in the revalorization of groundwater quality. The groundwater quality was assessed on the basis of physical and chemical analysis (electric conductivity, pH, total dissolved solids (TDS), total hardness, NO3 -, NO2 -, SO4 -2, Fe, Mn, Zn, Cu, B, residual sodium absorption (RSC) and sodium absorption ratio (SAR) for the period 2000-2004. From the analysis of results, it emerges that there are significant differences on the quality of water among the sample areas studied. The degradation of groundwater quality is mainly due to the pollution caused by the rural use of land, as well as its intensive exploitation. The salination and toxicity are potential problems of groundwater quality, especially in some areas, indicating that there is a need to take direct actions for the purpose of the optimum management of water resources in the Region of Thessaly. Β© 2007 Elsevier B.V. All rights reserved.

The paper studies changes in daily precipitation records at the National Observatory, Athens, during the period 1891-2004. This is the longest available time series of precipitation for Greece. The results show that both the shape and scale parameter of a fitted two parameter gamma distribution for the last two decades do show a significant difference of these parameters, when compared to any previous period from the 1890s through the 1970s. Also important changes are observed in daily precipitation totals exceeding various thresholds such as 10, 20, 30 and 50 mm. More specifically, a negative trend in the number of wet days (remarkable after 1968) and a positive trend in extreme daily precipitation are evident. The changes of heavy and extreme precipitation events in this part of SE Europe have significant environmental consequences which cause considerable damage and loss of life.

The goal of this study is to determine the chemical composition of rain, in the wider region of Athens, Greece for the time period 1st September 2001 to 31st August 2002. Two model automatic rain samplers were installed in the Meteorological Station of Laboratory of Climatology (latitude: 37Β° 58β€² N, longitude: 23Β° 47β€² E) inside the Athens University Campus and in a site at Heraklio Attica, a northern suburb of Athens (latitude: 38Β° 03β€² N, longitude: 23Β° 45β€² E). The concentrations (ΞΌeq l -1) of the major cations (H +, Na +, K +, Ca 2+ and Mg 2+) and anions (Cl -, NO 3 -, HCO 3 - ΞΊΞ±ΞΉ SO 4 2-, as well as pH and conductivity of rain in 39 total samples were determined. The figures of pH range from 6.4 to 8.4 and conductivity from 8 to 207 ΞΌS cm -1. The analysis showed that Ca 2+ ions are abundant within all examined samples, while HCO 3 - and SO 4 2- present the highest concentrations from the anions. In order to find out the origin of the air masses, the air mass back trajectories were calculated. Five sectors of the origin of air masses were revealed: the North, the South, the Local, the West and the East sector. Multivariate methods included Factor Analysis and Discriminant Analysis were applied to the examined ion concentrations and three main factors were extracted, which discriminated the ions according to their origin. The first group of ions is interpreted as the result of the anthropogenic activity, the second group represents the acidity-alkalinity independently of their source and the third one the marine influence. Β© 2007 Springer Science+Business Media B.V.

A long-term (2000-2005) monitoring of aerosol data from the moderate resolution imaging spectroradiometer (MODIS) is analyzed focusing on the Greater Athens Area (GAA) in the Eastern Mediterranean region. The MODIS aerosol optical depth standard product (AOD at 550 nm) and its respective ratio attributed to fine-mode (FM) particles are employed to evaluate the seasonal variability of the aerosol properties over Athens. The climatological trend of both parameters in the period 2000-2005 is nearly absent, while remarkable year-to-year variability can be observed. The seasonal analysis reveals a significant AOD variability over Athens, with minimum values in winter (AOD550 ∼ 0.2), and maximum in summer (AOD550 ∼ 0.45). Regarding the FM fraction, maximum values are present in spring and minimum in summer, thus revealing the dominance of FM and coarse-mode particles, respectively. For the whole data set, a method is implemented to distinguish the main aerosol types (urban/industrial (hereafter UI), clean maritime (hereafter CM type) and desert dust (hereafter DD) over Athens, based on both AOD and FM values. Because of the mixing processes in the atmosphere the majority of the cases (46.6%) belong to a mixed (hereafter MT) aerosol type. The UI aerosols are more frequent in spring (41.2%) and less in winter (9.1%), while the coarse particles, probably DD, more frequent in summer (35.8%) and less in winter (3.5%). In contrast, the clean atmospheric conditions are more frequent in winter (23.9%), when the mixing processes are also well established (63.5%). For each aerosol type, the mean AOD550 and FM values are also computed. Their seasonal variability exhibits a clear summer maximum for UI, CM and MT aerosols, while the DD exhibits maximum in spring. As regards the FM values of the different aerosol types they exhibit a rather constant variation with small fluctuations from season to season. © 2007 Elsevier Ltd. All rights reserved.