Summary:
This thesis aims to study and assess the water quality status of the Alfeios river and the broader hydrological network of the lignite basin in Megalopolis. Specifically, the chemical composition of the rivers in the area was examined in terms of both natural and anthropogenic activities. The study area is defined as the Alfeios river's hydrological basin in the Arcadia Megalopolis region. The main activity in the area, from 1969 until recent years, has been the operation of lignite-fired steam-electric power stations. The exploitation and jurisdiction of the land in the area belong to the Public Power Corporation (DEI). In recent years, in compliance with European Union regulations, Greece has been phasing out its last lignite-fired units, with Megalopolis set to withdraw by the end of 2024. Large-scale projects have been planned in this area, such as pumped storage projects and photovoltaic parks. Part of the land will be given to the public to create new activities, such as agriculture and industrial installations.
From a geological point of view, the basin is mainly built by the unity of Pindos (carbonates and radiolarites), the Tripolis unit (carbonates), and to a lesser extent, the Arna unit in the northeastern part (schists and quartzites). According to international studies, lignite extraction, transportation, and combustion affect the environment, especially during the deposition of by-products (gypsum and fly ash) and the disposal of mining waste. Additionally, the presence of biological treatment plants and industrial waste requires special attention to the water quality in the area. This thesis aims to investigate the water quality in the area and the possible correlation with the geological structure and rocks of the area and industrial activity.
For this investigation, 24 samples from surface waters were collected during the wet season in early March 2024. The rivers and streams examined are located within the DEI area and flow either directly or indirectly into the Alfeios River. Sampling of the Alfeios River was conducted before, during, and after its passage through the lignite mines. During sampling, physicochemical parameters such as pH, TDS (total dissolved solids), Eh (oxidation-reduction potential), DO (dissolved oxygen), and EC (electrical conductivity) were determined in situ using a pre-calibrated portable multiparameter meter. All chemical analyses of major ions and trace elements were performed using ICP-MS, ICP-OES, IC chromatography, and an HACH spectrophotometer at the accredited PPC Innovation Hub Material and Environmental Chemistry Laboratory, according to ISO 17020 and ISO 17025 standards. HCO3- measurements were conducted at the Laboratory of Economic Geology and Geochemistry of the Department of Geology and Geoenvironment.
The research results indicate that the most significant environmental concerns in the area are the chemical parameters NH4+, SO42-, Mn, and Mo. These chemical parameters exceed the legislative limits for drinking water (FEK 3525B_20023 & WHO, 2022) and the Environmental Quality Standards (EQS) limits for certain pollutants and priority substances in surface waters, according to the Greek legislation (FEK 69B_2016 & FEK 1909B_2010). The highest concentrations of these chemical parameters are found in isolated samples. The quality status of Alfeios does not seem to be strongly affected by mining activity, except for small burdens on some of the above parameters due to natural and possibly anthropogenic factors.
Keywords:
Megalopolis basin, Alfeios river, Lignite mining, Surface water quality
