Intercomparison of different tracers in the evaluation of groundwater dynamics in heterogeneous porous aquifers. A study in the alluvial plain of Venice

The paper deals with experiments carried out with artificial tracers on a site of the alluvial plain of Venice. The area has 13 boreholes 5-15 m in depth. The aquifer is very permeable and consists of gravel and coarse sand, the thickness of which reaches 450 m within the area. The experiments were made using 131I, 3H, NH4Cl, LiCl and Rhodamine WT. Because of the absence of fine matrix in the sediment, the tracer behaviour in the aquifer is nearly the same for all the tracers used; however the results are affected by the different detection methods and sensitivities. In practice 131I and 3H were detected at levels of 5 x 10-10 Ci·L-'1, while LiCl and NH4Cl were measured at levels of 10-8 and 10-6 kg·L-1. Rhodamine WT also gave good results; its detection limit was 10-9 L·L-1. (author). 7 refs, 8 figs, 1 tab