The experiment was carried out in containers (70 cm
long!60 cm wide!40 cm deep) that were placed outdoors
and filled with the first 20 cm of the contaminated soil
(1.32 g cmK3 bulk density). Containers were arranged
according to a complete randomised block design with
seven treatments (four organic treatments, one inorganic
treatment and two control treatments) and four replicatesper treatment. The organic amendments were: a municipal
waste compost (MWC) from a city refuse treatment plant; a
biosolid compost (BC) made of wastewater sludge from a
water treatment plant mixed with vegetative waste from
parks and gardens; a litter (LIT) collected from a deciduous
forest; and a leonardite (LEO), a low rank coal between peat
and sub-bituminous rich in humic acids. Furthermore, an
inorganic amendment, sugar beet lime (SL), a residual
material from the sugar manufacturing process with 70–
80% of CaCO3 (dry basis) was also tested, because of its
common use in regulating the pH in acid and contaminated
soils (Chlopecka and Adriano, 1996). These amendments
were chosen because they constitute low-cost, representative
amendment materials for land treating extensive areas.
The characteristics of the amendments are shown in Table 2.
Trace element content of all amendments was below the
limits established by the European Union (CEC, 1986) for
sewage sludge application on agricultural soils. The
amendments were applied on a fresh basis (20–25%
moisture content) and mixed with the topsoil (10 cm) in
the containers. Within the 18 months of the study two doses
of each amendment were applied: the first one at the
beginning of the experiment (100 Mg haK1) and the second
one (50 Mg haK1) 12 months later.
The containers were sown with Agrostis stolonifera L.
(167 kg haK1) twice: the first 1 month after the initial
amendment addition and the second 2 weeks after the
second amendment application. Agrostis stolonifera L. was
selected because of its tolerance to HM (Siedlecka et al.,
2001). Two control treatments without amendments were
also established: control with plant (CTRP) and control
without plant (CTR). Containers were also watered
regularly to ensure water supply to the plant.