Issue 5

This paper studies the characteristics of the heat waves that were observed in Athens, Greece since 1951. A heat wave is detected when two temperature criteria are fulfilled at the city centre: the daily maximum temperature value is at least 37 ^oC and the daily average temperature value is at least 31 ^oC. Information about the intensity, duration, timing in season and annual frequency of occurrence of heat waves were extracted. The slope of the linear fit of the annual number of heat wave days indicated that 1.30 more heat wave days per year were observed after 1992. The intensity and the duration of heat waves have also increased since 90s, while heat wave days have been detected during the whole summer since then, even during the first days of September. Additionally, air quality at the centre and at a suburb of Athens during the heat wave days that were identified during the last decade is examined. The daily average value of PM₁₀ concentration exceeded 50 μg m^-3 in 65% and 59% of the heat wave days at the urban and the suburban site, respectively, while the information and the alert O₃ threshold were exceeded in 17% and 5% of the heat wave days, respectively, at the suburban site. The degradation of air quality during heat wave days is also verified by the means of the common air quality index. Moreover, it was found that O₃ levels decrease when heat waves last more than 6 days. 

Present investigation is an exertion to explore safe means of water for the community in the water scare region. In order to accomplish such goal origin of springs as well as chemical analyses of groundwater samples from different locations were carried out. Four zones are discovered on the basis of nature of water points, rock types and water chemistry. These zones are Hard Rocks Springs (HRS), Valley Springs (VS), Recharge Areas Aquifers (RAA) and Central Valley Aquifers (CVA). HRS are originated from thick successions of limestone (Kirthar Limestone) and thick packages of channelized sandstone and conglomerates of the Siwalik Group. It is recommended that Chiltan, Parh, Kirthar, Dhok Pathan and Soan formations may be focused for future needs of safe water supply in the Quetta valley. This study includes the analysis of different physico-chemical parameters such as Total dissolved solids (TDS), pH, turbidity, Electrical conductivity (EC), hydrochemical facies, Sodium Adsorption Ration (SAR), Sodium Percent (Na%), Kelleys Index (KI), Permeability Index (PI), major cation and anions to assess the quality of groundwater sources. The outcomes of groundwater analyses were equated with various drinking water standards e.g., NSDWQ-Pak, USEPA, and EU. The results are plotted for determination of lateral variations and to empathize the reasons of these variations. The affects of rock types, geological structures as well as anthropogenic causes on origin and results are discussed systematically. The hydrochemical facies identified show that the alkaline earth exceeds alkalies, strong acids exceeds weak acids, mixed type (no cation, anion exceeds 50%), no dominant cation and anion types but water of VS is calcium chloride and sulfate type. The water is classified as C2-S1 (HRS), C3-S1 (CVA & RAA) and C3-S2 (VS) based on SAR and EC values, which intend that most water samples can be used for irrigation safely except water samples collected from VS. Based on the Na% the water samples are categorized as excellent to good and good to permissible limits. The water is suitable for irrigation as all samples bear KI less than 1. The PI values in the water samples studied (less than 40) also contemplate that the water is desirable for irrigation use, although caution is needed of VS water.

The aim of this research is to study the behavior of different forest species in accordance with their ability to retain heavy metals on their leaves in order to select the most suitable species for urban and peri-urban use, which will contribute to the reduction of the continuously growing atmospheric pollution in the cities. Five species were studied: Cupressus arizonica, Albizia julibrissin, Platanus orientalis, Celtis australis and Ligustrum japonicum. 360 leaf samples were collected and two treatments (non-washed and washed sheets) were applied on them. The determinative estimation of the concentration of metals in the clear filtrate was carried out with the use of ICP-OES inductively coupled plasma optical emission spectrometry. In order to correlate the concentration of heavy metals in leaves with the silvicultural characteristics of species, the following characteristics were measured in 20 individuals per species: diameter at breast height, total height of tree, crown beginning height and crown’s diameters. Statistically significant differences between the studied species were found for all metals. In addition, not a single species was found to retain the highest concentration of all. Metal concentration on leaves’ surface in declining order was: (Mn) > (Cu) > (Zn) > (Pb) > (Cr) > (Ni) > (Cd). The factor of height is significant both in the upper and lower layer of the crown. Broadleaves’ species as Albizia julibrissin with compound leaves capture significant heavy metals as conifer species. 

The aim of the study is to investigate the spatial and seasonal variation of precipitation in Greece using multi-temporal data analysis techniques. Mean monthly precipitation grids of 1 km² resolution of the period 1950-2000 were used in the analysis. Cross correlation quantified spatio-temporal patterns which are summarized as follows a) the absolute correlations of precipitation versus elevation and longitude are minimized during the winter period, b) the latitude dependency of precipitation presents a seasonal shift where winter precipitation tends to be higher in northern Greece, while summer precipitation tends to be higher in southern Greece. Principal components analysis indicated that the first two components account for the 92.8% of variance in the spatio-temporal variability of precipitation in Greece. Cluster analysis segmented the terrain to 27 regions with distinct seasonal variability of precipitation. The majority of irrigated agricultural land (plains of Macedonia, Thessaly and Thrace) belong to clusters which present the lowest values of annual precipitation (<600 mm year^-1). The derivation of precipitation signatures for each region of Greece using the proposed terrain segmentation approach can support environmental decision and agricultural planning at a regional (country) scale in relation to water resources management.