Variations of Metal Availability and Bio-accessibility in Water-Logged Soils with Various Metal Contents: In Vitro Experiments

Reducing conditions of submerged soils were simulated in laboratory experiments by keeping various soil samples from urban areas under an aqueous solution in sealed flasks for several lengths of time. A polluted soil from a different origin was also included for comparison. Metals dissolved at various times were determined, and availability and bio-accessibility of metals present in the solid phase were estimated. Although significant amounts of Fe and Mn were dissolved, other metals were released to the solution to a much lesser extent. This effect is attributed to the greater solubility of reduced forms of Fe and Mn, and the small amounts of other metals dissolved during water-logging were related with metals retained by, or occluded in, the reduced Fe or Mn compounds. The amounts of available and bio-accessible metals remaining in the solid phase were significantly increased by water-logging, particularly the latter form. Such increase of metal mobility is likely to favour metal leaching to the water table as well as the transfer of potentially toxic elements to humans during recreational activities.