The problem of arsenic in drinking water of volcanic areas: hydrogeological knowledge as a prerequisite for sustainable choices

In the volcanic areas of central and southern Italy the presence of arsenic in groundwater has been documented for about 30 years. Content of arsenic in groundwater above 10 micro g/L poses problems in the drinking water supply of many municipalities of the volcanic areas that have installed or will install treatment plants. These plants have considerable building and management costs. This study examines one of the volcanic systems where there are problems for drinking water supply. Specifically we have investigated the role of the groundwater flows at high elevation in the Cimino volcano (Central Italy) and the possible use of this resource as a source for drinking water. Groundwater flow at high altitude gives rise to several springs located at the edge of the lava domes of Cimino volcano. The origins of these springs can be related to dome-impounded groundwater or perched aquifers. For a groundwater basin extended for about 26 km2, a total groundwater flow rate of about 50 L/s was estimated. Chemical analyses of these waters highlight low concentration of arsenic (less than 10 micro g/L) and salinity (electrical conductivity between 100 and 300 micro S/cm) that makes them suitable for use as drinking water. At present this water resource is not completely and effectively tapped. Considering a daily supply of drinking water of 250 L/d per person, more than 15,000 people can be served, which constitutes more than three quarters of the residents in countries and villages located at the foot of the Cimino volcano. We must consider that the tapping of these groundwater can occur by gravity drainage, so without the cost of electricity for water lifting system. Moreover most of the recharge area falls in a nature reserve, therefore there is a reduced possibility of anthropogenic impacts on the water quality. Comparing this solution with the programmed treatment plants a significant reduction in costs results which makes the option of tapping the waters at high altitude surely in line with the concept of sustainability.