Distribution and Origin of Boron in Fresh and Thermal Waters in Different Areas of Greece

World Health Organisation (WHO) guideline value for boron is 0.5 mg/l. The drinking-water standard of the European Community [11] (EC Directive, 1983) is twice the value recommended by WHO, but still boron concentrations in many ground-and surface waters in Greece exceed this value, rendering such water unacceptable according to the European standards. Boron is biologically an essential element, but at high concentrations is toxic to plants (above approximately 1 mg/l in irrigation water) and probably to humans. Because of this potential toxicity and the need of implementation of EU regulation on national level, the study of the boron levels in both ground- and surface water is of great significance for water management. In Greece, a significant number of thermal, mineral and superficial water springs, especially in Northern Greece and in islands, present high boron values. Nevertheless, such ground waters or borehole water with high temperature and high boron content are frequently used for irrigation and drinking purposes, and could therefore have an antagonistic effect on crop yield and health. In order to study the boron contamination and to elucidate the origin of B, we collected a number of hot and fresh waters all over Greece. The relatively high concentrations of boron in groundwater became a major problem in the study areas. Some million m(3) of groundwater are rendered unusable due to the high boron content. The need of significant quantities of high quality water is an important issue due to rapid urbanization and increasing touristic development of the study areas. Thus, the investigation of the boron problem is crucial, with regard to B spatial distribution and its possible sources. In all sampled waters, the boron concentration exceeds the limit of 0.5 mg/l, which is the former recommended WHO limit. Moreover, in the irrigation waters examined, the boron concentration exceeds the value of 0.75 mg/l, which is the limit for sensitive plants (for plants of moderate and high tolerance, these values vary between 0.75-3 mg/l and >3 mg/l respectively). In all cases, elevated boron and salinity could be attributed to geothermal activity, anthropogenic sources and/or seawater intrusion into the aquifers. This finding has important implications for water management: In a setting of high natural geochemical background values, control of the pollution source is not possible and water managers have to cope with a local to regional geochemical anomaly that implies boron specific water treatment or mixing with low-boron water resources to bring concentrations down.