Field sampling of soil pore water to evaluate the mobile fraction of trace elements in the Iglesiente area (SW Sardinia, Italy)

• We analysed major and trace elements in soil pore waters of the Iglesiente district.
• Waters contain environmentally significant amounts of Pb, Zn, Mn, Cd.
• The mobility of metals is mainly controlled by equilibrium with soil phases.
• Soil pore waters give realistic estimates of metal mobility and transfer to the biosphere.

Field soil pore water monitoring was applied in a highly heavy-metal contaminated area in SW Sardinia, Italy, as a direct, realistic measure of heavy metal mobility. The main chemistry of pore waters well reflects the local characteristics of soils, ranging from Ca–SO4 to (Ca)Mg–HCO3 to Ca(Na)–SO4(Cl), with a wide range of conductivity. The mobility of Zn and Pb is apparently controlled by equilibrium with minerals such as hydrozincite or smithsonite, and cerussite, respectively. These results allow a correct estimate of the actual environmental risk associated with the presence of heavy metals in soils, and may serve as a supporting tool for phytoremediation planning.