wAbstract
@Concentrations of total and dissolved elements were determined
in 35 water samples collected from rivers in Sardinia, a Mediterranean
island in Italy. The overall composition did not change for waters
sampled in both winter and summer (i.e. January at high-flow condition
and June at low-flow condition), but the salinity and concentrations
of the major ions increased in summer. Concentrations of elements
such as Li, B, Mn, Rb, Sr, Mo, Ba and U were higher in summer
with only small differences between total and dissolved (i.e.,
in the fraction 0.4Κm) concentrations. The fact that these elements
are mostly dissolved during low flow periods appears to be related
to the intensity of water-rock interaction processes that are
enhanced when the contribution of rainwater to the rivers is low,
that is during low-flow conditions. In contrast, the concentrations
of Al and Fe were higher in winter during high flow with total
concentrations significantly higher than dissolved concentrations,
indicating that the total amount depends on the amount of suspended
matter. In waters filtered through 0.015Κm pore-size filters,
the concentrations of Al and Fe were much lower than in waters
filtered through 0.4Κm pore-size filters, indicating that the
dissolved fraction comprises very fine particles or colloids.
also, Co, Ni, Cu, Zn, Cd and Pb were generally higher in waters
collected during the high-flow condition, with much lower concentrations
in 0.015Κm pore-size filtered waters; this suggests aqueous transport
via adsorption onto very fine particles. The rare earth elements
(REE) and Th dissolved in the river waters display a wide range
in concentrations (°REE: 0.1-23Κg/L; Th:0.005-0.58Κg/L). Higher
REE and Th concentrations occurred at high flow. The positive
correlation between °REE and Fe suggests that the REE are associated
with very fine particles (0.015 and 0.4Κm); the abundance of
these particles in the river controls the partitioning of REE
between solution and solid phases.
@Twenty percent of the water samples had dissolved Pb and total
Hg concentrations that exceeded the Italian guidelines for drinking
water (10Κg/L Pb and 1 Κg/L Hg). The highest concentrations
of these heavy metals were observed at high-flow conditions and
they were likely due to the weathering of mine wastes and to uncontrolled
urban wastes discharged into the rivers.x
1. Introduction
2. Study area
3. Sampling and analytical methods
4. Results and discussion
@4.1. Dissolved and total trace elements
@4.2. Rare earth elements and thorium
@4.3. Water quality
5. Conclusions
Acknowledgments
References