The Middle Valdarno Plain (Tuscany, Italy) is a densely urbanized and industrialized area. Aquifer vulnerability is generally high. On the basis of more than 1700 litostratigraphic records and a piezometric survey on 400 wells, a detailed reconstruction of geologic and hydrogeologic features of the alluvial sediments was conducted. In such a way it has been possible to map the degree of protection against pollution of the shallow aquifer. The analysis of water samples collected from 280 wells, located acording to a regular grid in the plain, has enabled us to define the fundamental geochemistry of the groundwater and to map the areas with contaminated groundwater by nitrogen compounds. The protective geology features have been compared to: a) the location of potential soruces of pollution; b) the area where groundwater is contaminated by nitrites, nitrates and organo-halogenated compounds. Nitrate occurrence with a concentration value greater than 50 mg/L are in a good spatial correlation with areas where aquifers are poorly protected. Because nitrate is a simple and conservative ion, spilled all around an urbanized area, the distribution of its contamination demonstrates that groundwater vulnerability mapping based on hydrogeological elements is reliable.
La qualitè des eaux souterraines en relation au degrè de protection contre la pollution des aquiferes. Un exemple en Toscane: la plaine de Florence
GARGINI, Alessandro;
1995
Abstract
The Middle Valdarno Plain (Tuscany, Italy) is a densely urbanized and industrialized area. Aquifer vulnerability is generally high. On the basis of more than 1700 litostratigraphic records and a piezometric survey on 400 wells, a detailed reconstruction of geologic and hydrogeologic features of the alluvial sediments was conducted. In such a way it has been possible to map the degree of protection against pollution of the shallow aquifer. The analysis of water samples collected from 280 wells, located acording to a regular grid in the plain, has enabled us to define the fundamental geochemistry of the groundwater and to map the areas with contaminated groundwater by nitrogen compounds. The protective geology features have been compared to: a) the location of potential soruces of pollution; b) the area where groundwater is contaminated by nitrites, nitrates and organo-halogenated compounds. Nitrate occurrence with a concentration value greater than 50 mg/L are in a good spatial correlation with areas where aquifers are poorly protected. Because nitrate is a simple and conservative ion, spilled all around an urbanized area, the distribution of its contamination demonstrates that groundwater vulnerability mapping based on hydrogeological elements is reliable.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
