Stabilisation of trace element contaminated soil is a soil remediation method
used to reduce the mobile fraction of critical elements in the soil using
soil additives (amendments). The stabilisation of trace elements occurs
through i.e. sorption, co-precipitation or complex formation. In this work,
different amendments and combinations of amendments have been added to
chromate cupper arsenate (CCA) contaminated soil collected at a former wood
preservation site at Robertsfors works, Sweden. The amendments used in the
experiments were blast furnace slag (BFS), zerovalent iron (Fe0), blaster
sand (BS), coal fly ash (CFA) and peat. The changes in the element mobility
were tested performing standard compliance batch leaching tests at L/S
(liquid to solid ratio) 2 and 10.
The purpose of the investigation was to increase knowledge about the behavior
of the trace elements occurring in CCA contaminated soil when adding
different amendments. One goal was to identify an amendment or combination of
amendments that effectively stabilized the contaminants (reducing the
mobility of the contaminants). A second goal was to test how the
effectiveness of the selected amendment changed in different geochemical
environments. To vary the geochemical environment the parameters pH, amount
of water added to the soil and redox potential were controlled. The
evaluation of the results was based on the leaching of As, but the behavior
of the other trace elements e.g. chromium, copper was also considered.
All amendments added alone decreased the mobility of As, except for peat
which increased the amount of As in the leachate about 4 times. The most
effective amendment to decrease the leaching of As was Fe0 alone. Fe0 also
decreased the leaching of Cr, Cu and Zn. A combination of amendments that
effectively reduced the mobility of the trace elements was Fe0 and BFS
together. When more water was added to the soil (L/S 10) it was observed that
Fe0 alone worked more effectively than the combination of BFS and Fe0.
Further investigations were made for the soil treated with Fe0. The effect of
redox could not be evaluated because the treatment with nitrogen gas of the
samples during the leaching did not permit to reach low redox potential, i.e.
to reach oxygen ...
