Dynamics of coastal groundwater and water radon content

The point dilutiont method with the use of radioactive tracers stands for the most reliable system to determine the flow velocity Vf in the Apulian calcareous aquifer. Moreover,knowing the velocity of filtracion is absolutely necessary to cope with pollution phenomena which, owing to the ever increasing exploitation groundwater is subject to. In order to reduce costs required by the use of radioactive tracers, an indirect and swift method,for Vf measurements through measures of water radon content, is being developed. Such a method is based on the consideraction that, where one can localise an area in which the aquifer is likely to be considered macroscopically homogenous, radon content variations are to be exclusively ascribed to Vf variations of waters. After defining, zone by zone. the relation between Rn content and Vf, it follows the possibility to determine Vf areal trend by means of the radon distribution map. The method, which was also tested on the field, yielded satisfactory results which let the researcher think that it could be successfully applied at least in those areas, such as the coastal ones, where Vf variations are such to affect radon content. In particular, experiments carried out at S. Cesarea Terme showed the considerable influence of temperature on radon content, above all in the ipothermal field. While investigations effected at T.re S. Isidoro evidenced a tight correlation, at least in a given lapse of time, between Vf values and radon content, and enabled also a possible interpretation on how radon concentration takes place in water. Moreover, the whole investigation carried out showed the considerable contribution that radon content measuraments and the consequent mapping of isoradons, offer within a systematic hydrogeological study. 131