In order to reclaim a clay quarry, a topsoil material was mixed with gravel
ly spoil at different ratios and with various rates of sewage sludge. The i
nfluence of three spoil/topsoil ratios (1:1, 2:1 and 3:1) and three sludge
rates (40, 80 and 120 t ha(-1)) on chemical properties of the resulting mat
erial was investigated, with emphasis on heavy metal (Fe, Cu, Mn, Ni and Zn
) contents. The mixtures topsoil/spoil/sludge were water saturated and incu
bated for 15 or 30 days in a chamber under controlled conditions. The incub
ated samples were analysed for pH, total carbon and nitrogen, and total, av
ailable, exchangeable and soluble heavy metals. The addition of spoil to th
e topsoil increased the volume of material available, by utilizing an inert
material unsuitable by itself to grow plants. The addition of sewage sludg
e repaired the disadvantages of the spoil, increasing the pH and the organi
c matter contents. The total heavy metal contents in the mixtures followed
the sequence Fe much greater than Mn much greater than Zn, Cu > Ni. All exc
ept Cu were within the ranges allowed for agricultural lands. The available
heavy metals constituted a small fraction of total contents and decrease w
ith time due to complexation and immobilization processes. The exchangeable
and soluble fractions were almost negligible; only small amounts of Mn, Zn
and Cu were detected. Therefore, the risk of contamination by heavy metals
is insignificant in the conditions investigated. Copyright (C) 1999 John W
iley & Sons, Ltd.