2. Materials and methods
2.1. Soil and amendments
About 5 kg of soil sample was collected at 5-20 cm depth from a
Portuguese abandoned mining complex. The collection site was constituted by a set of mines, where hydrothermal veins rich in Pb
and Zn were explored during the 19th and 20th centuries. The soil
sample was air dried and sieved through 2 mm mesh to remove
large particles.
The compost soil amendments that were tested were obtained
at laboratory scale by using self-heating reactors of 105 L with
forced aeration, as described by Soares et al. (2013). CES compost
was derived from industrial potato peel, grass clippings, rice husk
and industrial eggshell (ES) wastes in the proportions of 35.4%,
22.7%, 11.9% and 30% (w/w), respectively. CWES compost was prepared
in the same conditions as CES, without eggshell in the initial
mixture while keeping the relative proportions of the other
ingredients.