Mobility of Sludge‐borne 3,3′‐Dichlorobenzidine in Soil Columns

Abstract

AbstractFate of the carcinogen 3,3′‐dichlorobenzidine (DCB) in sludge‐amended soil was evaluated. Carbon‐14‐1abeled DCB was used as a tracer to examine mineralization and mobility of DCB present in sludge. Dichlorobenzidine was shown to be very persistent in soil and sludge‐amended soil with < 2% of the added [14C]DCB evolved as 14CO2 during a 182‐d incubation. Mobility of DCB was evaluated by using soil columns (5 by 45 cm) that were irrigated with 2.54 cm water d−1 for 84 d. The total 14C recovered in leachate water was from 0.16 to 0.063% of the total 14C added to the top 15 cm of the soil column at time zero. The strong binding of DCB to soil constituents rendered it highly immobile despite being placed in a sandy soil that was irrigated with large amounts of water. However, some finite, albeit small, quantity was apparently leached through the soil profile at a relatively constant rate. The immobilization of DCB presumably results from tbe formation of humus bound DCB residues and from its low water solubility.