Knowledge of behaviour of pharmaceuticals as contaminants in nature is essential for their mobility and toxicity in the soils and surface-and ground-water environments. Their migration ability and toxicity can be affected by their interactions with organic matter. In this contribution, sulfapyridine (a sulfanilamide drug used for antibacterial medication) is studied from the point of view of its transport in hydrogels containing humic substances. Agarose hydrogel was used as a model medium for

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... he transport experiments. Standard Elliot soil humic acid (4S102H) purchased from International Humic Substances Society was incorporated into the hydrogel as an active nanomaterial for interactions with drug and potential suppression of their migration and toxicity in soil systems. The method of diffusion couple was applied on the diffusion experiments. Donor part was saturated by sulfapyridine and acceptor part was free of drug. After connecting of both parts, the time development of concentration profiles in the couple was monitored. The effective diffusion coefficients for the transport of sulfapyridine in hydrogel enriched by humic acids and pure agarose hydrogel were determined and compared. It was found that the transport of drug is influenced by interactions with humic acids which can immobilize partially sulfapyridine in humic structure. Simultaneously, sorption/desorption experiments were realized. Their results confirmed high degree of drug immobilization (60 -90 % in the dependence on drug concentration).