Groundwater aggressiveness assessment according to EN 206-1: data, methods and application on groundwater in the Horna Nitra basin, Slovakia

The history of groundwater aggressiveness evaluation procedures applied in the Slovak Republic is summarized and compared with the newly adopted European technical standard STN EN 206-1. The methodology of data acquiring and processing for groundwater aggressiveness evaluation was proposed. The procedure included basic principles of data mining, requested number of chemical analyses and ways of groundwater aggressiveness assessment. Ways of results interpretation and graphical visualization were proposed, too. The procedure was applied in the area of the Horna Nitra in Slovakia. A total number of 953 groundwater analyses were used to assess the groundwater aggressiveness. The resulting map of zoning comprised eight groundwater aggressiveness zones. Zones with the non-aggressive degree (X0) groundwater to moderately aggressive degree (XA2) were delineated. The aggressiveness was caused mainly by presence of aggressive carbon dioxide (depending on the rock type in the area) and by lowered pH values in association with increased sulfate contents in areas of brown coal mining activities and in heavy industrialized areas. The compilation of a locality map was proposed, where for each municipality type and degree of aggressiveness is assessed. It should serve to local authorities as background information within the decision-making process connected to the permission of construction work.