Changes in copper, lead and zinc concentrations in plants from paper mill sludge-treated soils.

Effects of paper mill sludge addition on the availability of metals were studied on different soils both laboratory and naturally polluted; copper, lead and zinc concentrations were determined in Hordeum Distichum plants grown on the untreated and on sludge-treated soils. In some case a decrease of metal concentration is observed on sludge-treated soils; these results are consistent with the reduction of metal mobile forms in the soil, before plant growth. The decrease of metal availability in sludge-treated soils may be related with the pH value of the soil after sludge addition.