Hellenic Karst Aquifers Vulnerability Approach Using Factor Analysis: The Example of the Louros Karst Aquifers

Temporal variations of spring hydrochemistry as clues to the karst system behaviour: an example of Louros Catchment

Effectively managing water resources in karst systems requires a thorough understanding of their general conduit network along with their seasonal dynamics. Their investigation has involved well construction or several advanced natural tracer data, most of which are not always available. Hence, this work showcases a pragmatic approach that makes use of basic hydrochemical variables of springs with coarse temporal resolution in characterising a karst system. In this study's example, physicochemical variables like major ion concentrations/ratios, Electrical Conductivity (EC), pH and water temperature (Tw) were measured on 20-day basis for a hydrological year at the Louros Catchment, Greece. We further performed the frequency distribution and variation analysis of EC and Tw, principal component analysis (PCA), scatter plots of carbonate ions vs sulphate and hydrochemographs to determine relevant hydrochemical processes and hydrogeological features. PCA and the scatter plots showed that the simple-type upper karst level is entirely dominated by carbonate dissolution, whereas the complex-type middle and lower levels also involve gypsum and dolomite dissolution. Presence of mixing between karst units was also detected. EC and Tw analyses revealed the degree of karstification of different units and relative depths of flow systems. Hydrochemographs reflected the seasonality of limestone and gypsum dissolution's contributions linked to the dominant flow type (conduit vs diffuse). This study thus was able to demonstrate the usefulness of such holistic hydrochemical analyses to better understand karst systems. Given their cost-effectiveness, they can be easily applied to any understudied karst system worldwide.

Hellenic karst waters: geogenic and anthropogenic processes affecting their geochemistry and quality

Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (< 100 mg L^-1) and high-chloride content (> 100 mg L^-1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L^-1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.).

Assessment of the Incidence of Human Adenovirus in Surface Waters of Southwest Greece: Vouraikos River as a Case Study

The purpose of this study is to assess the overall impact of different anthropogenic activities in the Vouraikos River basin (southwestern Greece, Natura 2000 area). Virological quality of river water samples was investigated. Positive samples for human adenoviruses were found occasionally, while porcine adenoviruses and bovine polyoma viruses were not detected. It is the first time that virological data are collected in the study area.