『Abstract
In the study area physical and chemical factors control the composition
of surface and groundwaters, which in turn determine the surface
and groundwaters, which in turn determine the water quality of
the “Biviere di Gela” lake. These factors combine to create diverse
water types which change their compositional character spatially
as rainfall infiltrates the soil zone, moves down a topographically
defined flow path, and interacts with bedrock minerals. Low-salinity
waters, which represent the initial stage of underground circulation,
start dissolving calcium carbonate from the local rocks. The progressive
increase in salinity, characterized by substantially higher Ca,
SO4, Na and Cl concentrations, suggests that
dissolution of CaSO4 and NaCl is an important
process during water-rock interactions. The “Biviere di Gela”
lake is often separated into two units (Lago Grande and Lago Piccolo).
“Lago Grande” water is generally of Na-SO4-Cl-type,
whereas “Lago Piccolo” water is of Na-Cl-SO4-type.
Their total content of dissolved salts varies with season, the
amount of rainfall, and inflow of ground and drainage water. Over
time, an increasing trend towards greater salinity and also sudden
changes in the relative abundances of Cl and SO4
have been recorded for the “Lago Grande.” The isotope composition
of the lake water appears to be affected by inflow of ground and
surface waters and also by evaporative loss. The nitrate content
of waters from the recharge basin is of particular concern because
it contributes to lake eutrophication. The trace element contents
do not evidence the presence of any significant metal contamination
of lake waters, although a future potential hazard of metals bioaccumulation
by the aquatic biota must be taken into consideration. Finally,
a water balance for the basin shows that a drop in precipitation
of about 20% might be critical for lake survival.
Keywords: wetland area; hydrogeochemistry; environmental geochemistry;
isotope geochemistry; water balance』
1 Introduction
2 Experiment
2.1 Site description
2.2 Geology and hydrogeology
2.3 Sampling and analytical methods
3 Results and discussion
3.1 Groundwater chemistry
3.2 Statistical treatment of data
3.3 Hydrogeochemical evolution of groundwaters along the flow
path
3.4 Isotope composition of local rainwaters and groundwaters
3.5 Geochemistry of the lake water
3.6 “Lago Grande” water budget
3.7 Trace elements in lake waters and bottom sediments
4 Conclusions
Acknowledgment
References