Use of municipal solid waste compost to reclaim limestone quarries mine spoils as soil amendments: Effects on Cd and Ni

The use of composted municipal solid waste (MSWC) in restoration of quarries in Mediterranean environments was checked in order to evaluate the mobility of Cd and Ni in a technosol. The experiment was done simulating a topsoil (0-30 cm) formed by limestone outcrops and the addition in the 0-15 cm of MSWC. The availability for plants of these heavy metals in the soil and their presence in the leachates were checked. The availability for plants was low in these conditions for both. Cd and Ni presented a different behavior where the main different was that Ni was easily lixiviated and its mobility seems to be more important than Cd in the calcareous soil profile. In general, the retention of Cd in this limestone material seemed to be more important. The environmental risk due to the presence of both heavy metals in the compost used in this technosol was very low even though in the beginning of the experiment the availability for plants and the presence in the leachates were very reduced in these conditions.