Pot and field trials were carried out using sediment dredged from the port of Bremen (Germany) and deposited in a settling basin near Bremen; the sediment is polluted with Cd and Zn. Five iron-bearing materials were added to the soil (1% pure Fe in soil dry matter) to immobilize the heavy metals: ‘Red mud from the aluminium industry, sludge from drinking-water treatment, bog iron ore, unused steel shot and steel shot waste. | Pergamon Wat. Set. Tech. Vol. 37 No. 6-7 pp. 379-386 1998. 1998IAWQ. Published by Elsevier Science Ltd Printed in Great Britain. PII S0273-1223 98 00221-2 0273-1223 98 1900 000 IMMOBILIZATION OF HEAVY METALS IN SEDIMENT DREDGED FROM A SEAPORT BY IRON BEARING MATERIALS I. Miiller and E. Pluquet Geological Survey of Lower Saxony Institute of Soil Technology Friedr. Missler Str. 46 50 28211 Bremen Germany ABSTRACT Pot and field trials were carried out using sediment dredged from the port of Bremen Germany and deposited in a settling basin near Bremen the sediment is polluted with Cd and Zn. Five iron-bearing materials were added to the soil 1 pure Fe in soil dry matter to immobilize the heavy metals Red mud from the aluminium industry sludge from drinking-water treatment bog iron ore unused steel shot and steel shot waste. The pH and CEC were little influenced by any of these treatments but the NH4NO3 and DTPA extractable amounts of Cd and Zn and particularly the uptake of Cd and Zn by plants were markedly reduced. It was demonstrated that red mud and precipitated Fe-bearing sludge were the most effective materials. They caused an increase in the adsorption capacity of the dredged sediment with respect to Cd of about 50 . In the pot trials NH4NO3 soluble amounts of Cd and Zn in samples of soil treated with these materials were reduced by 50 DTPA -20 while the uptake by plants was reduced by 20-50 . In the field trial Cd and Zn were immobilized in the soil to a certain extent but less effect was observed on the concentfations in plants and soil extracts compared with the pot trials. In practice red mud is unsuitable as it contains large amounts of Cr and Al3 ions. Therefore only sludge from drinking-water treatment as long as the As concentration in it is low remains as a useful material for immobilizing heavy metals in polluted sediment dredged from a seaport. 1998IAWQ. Published by Elsevier Science Ltd KEYWORDS Dredged sediments iron oxides heavy metals .
