PUMA
Istituto di Geoscienze e Georisorse     
Bortolami G., Fontes J. C., Panichi C. Isotopes du milieu et circulation dans les acquiferes du sous-sol venetien. In: Earth and Planetary Science Letters, vol. 19 (2) pp. 154 - 167. Elsevier, 1973.
 
 
Abstract
(English)
The subsidence of the plain of Venice, which can be estimated to about 1 cm/yr under the historical site, is correlated with the overexploitation of the deep artesian aquifers. The classical hydrogeological studies are difficult because of the complexion of the aquifer layers composed of several hundred meters of both continental and marine quaternary deposits. The study of the characteristics of these aquifers has been undertaken by geochemical and isotopic techniques (oxygen 18, deuterium, tritium, carbon 13 and carbon 14). The contents in stable isotopes show the existence of two groups of deep waters both correlated to a cold climatic recharge (δ18O= −10 and −12). These waters are clearly different from those of the unconfined shallower aquifers (δ18O −8). The deep supplies can be respectively correlated to the basins of collection of the prealpine rivers Brenta and Piave (δ18O −10) from one hand, and from the other hand to the paleoriver of the alpine river Adige. The underground extension of the alpine waters is limited to the zone of the lagoon and to the southwestern part of the plain. The waters of prealpine type are located under the remaining, i.e., the main part of the plain. The determination of the flow rate depends about the validity of the transit times estimated by the mean of14C contents. The high13C contents of the alpine waters show obviously that the14C activities are not significant because of an isotopic exchange with the carbonates of the aquifer layers or because of an overcharge in old dissolved carbon. The waters coming from the prealpine area exhibit in the recharge zones relatively high tritium contents (85 to 120 TU) associated with rather low14C activities (60 to 70%). The13C contents indicate that the dissolved carbon has not undergone any significant exchange with solid carbonates. The discussion of the whole set of data suggests that the circulation is rapid in the recharge areas where the supply in waters of great altitude occurs by seepage coming from the hydrographic network or (and) from the karstic system of the Prealps. In the lower parts of the plain the flow velocities are low and decrease eastward and downward from 3m/yr to 1m/yr. It is possible that a drastic breakdown in these velocities occurs in the western part of the plain due to a major sedimentological discontinuity as for instance the western limit of the marine deposits.
URL: http://www.journals.elsevier.com/earth-and-planetary-science-letters
Subject Italy
Veneto region
aquifers
groundwaters circulaion
isotopes


Icona documento 1) Download Document PDF


Icona documento Open access Icona documento Restricted Icona documento Private

 


Per ulteriori informazioni, contattare: Librarian http://puma.isti.cnr.it

Valid HTML 4.0 Transitional