Biological mobilization of arsenic in a pyrite cinders polluted soil

Bioavailability of arsenic (As) in soil is governed by chemical and biological factors, in particular the redox condition. The objective of this research was to study (1) the effect of plant material decomposition on arsenic mobilization in a contaminated soil under flooded and not flooded conditions; (2) arsenic uptake and translocation in willows (Salix purpurea L). The experimental soil was a mixture (1:1 w/w) of a unpolluted soil and pyrite cinders, contaminated by several metals and As. 1-year old cutlings of willow were transplanted in pots containing 1 kg of experimental soil amended with dry alfalfa. During two months of growth two environmental conditions were tested by maintaining soil in submersion or at 70% of the water holding capacity. Samples of soil solution were weekly collected by Rhyzon syringes and pH, redox potential, Fe, and As were determined. Leaves of salix were sampled at day 0 and day 56 and As and Fe concentrations were determined. The reductive conditions induced by organic matter decomposition in submersion resulted in a fast arsenic mobilization.