The simulation of a contamination event has been explored performing an artificial tracer test in the Supramonte massif, a karst aquifer hosted in a remote area in Central East Sardinia (Italy). The experiment was carried out in July 2014 by injection of a small amount of Na-fluorescein in the lake of the Dorgheddie Cave, a shaft that opens within the fluviokarstic canyon of Gorropu, at the eastern side of the Supramonte aquifer. For its detection, charcoal bags were places in the two main accessible outflows of the karst aquifer: Gorrupu and Su Gologone springs, few hundred metres and 10 km from the cave, respectively. In winter 2015, six months later from dye injection and after few days of intense rainstorms following a very dry summer and fall, the fluorescein was detected at the Su Gologone spring. Even after several weeks of sampling, no fluorescent tracer was detected in the charcoal bags at the Gorropu spring. The tracer test has reveals a threshold in the karst aquifer that hydrogeologically controls the response of the Central-Eastern part of the karst system at least during low flow conditions as those of the hydrologic year 2014-2015. This functioning involves great challenges to the prediction of a hypothetic contaminant transport that would be detect at the spring with very long delay.
Gli autori descrivono l'esperimento di una simulazione di contaminazione eseguito mediante un test di tracciamento artificiale nell'area centro - orientale della Sardegna, test costituito dall'immissione di Na-fluorescina nella grotta di Dorgheddie ubicata nel canyon di Gorropu - lato orientale dell'acquifero del Supramonte. I punti di captazione sono stati collocati nelle due principali sorgenti carsiche accessibili: Gorropu e Su Gologone, ubicate rispettivamente poche centinaia di metri ed una decina di chilometri dal punto di iniezione del tracciante. A distanza di sei mesi caratterizzati da siccità e dopo alcuni giorni di intense piogge, la fluorescina è stata nettamente individuata nell'acqua di Su Gologone mentre, anche a seguito di più campionamenti, nessuna traccia è stata rilevata nelle acque di Gorropu. Il tracciamento ha permesso di rilevare la presenza di una netta differenziazione idrogeologica all'interno dell'acquifero carsico. Una situazione questa che consente di prevedere, per questa area, provenienza, trasporto e tempi di percorrenza di ipotetici agenti inquinanti.
Threshold behavior of the Supramonte karst aquifer (Sardinia, Italy) inferred from tracer test: implication for groundwater protection
Laura Sanna;
2019
Abstract
The simulation of a contamination event has been explored performing an artificial tracer test in the Supramonte massif, a karst aquifer hosted in a remote area in Central East Sardinia (Italy). The experiment was carried out in July 2014 by injection of a small amount of Na-fluorescein in the lake of the Dorgheddie Cave, a shaft that opens within the fluviokarstic canyon of Gorropu, at the eastern side of the Supramonte aquifer. For its detection, charcoal bags were places in the two main accessible outflows of the karst aquifer: Gorrupu and Su Gologone springs, few hundred metres and 10 km from the cave, respectively. In winter 2015, six months later from dye injection and after few days of intense rainstorms following a very dry summer and fall, the fluorescein was detected at the Su Gologone spring. Even after several weeks of sampling, no fluorescent tracer was detected in the charcoal bags at the Gorropu spring. The tracer test has reveals a threshold in the karst aquifer that hydrogeologically controls the response of the Central-Eastern part of the karst system at least during low flow conditions as those of the hydrologic year 2014-2015. This functioning involves great challenges to the prediction of a hypothetic contaminant transport that would be detect at the spring with very long delay.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
