Sorption and metabolism of selected herbicides in river biofilm communities

In the present study, biofilms were grown in rotating annular bioreactors w ith river water as inoculum and sole source of nutrients. The herbicides at razine and diclofop methyl were applied to the bioreactors, while an identi cal reactor acted as a control. Biofilm structure was visualized using spec ific fluorescent probes in conjunction with confocal laser scanning microsc opy. The concentration of both herbicides in the bulk water phase followed the pattern of application. Atrazine and metabolites were detected in biofi lm samples using direct insertion probe tandem mass spectrometry (DIP-MS/MS ) and only trace levels were detected after the addition phase. Monoclonal antibody (MAb) studies indicated that sorption of atrazine was associated w ith a unique microcolony type. In contrast, diclofop and metabolites reache d a maximum level in the biofilm at the end of the addition phase and persi sted in the biofilm. Experiments with C-14-labeled atrazine and diclofop me thyl indicated that mineralization of these compounds to CO2 (<1%) occurred in the river biofilms. Thus, both herbicides were sorbed and metabolized b y the river biofilm community and detected in biofilms when they were not d etected in the bulk water phase. These results indicate that biofilms and s pecific community members may act as a sink for herbicides, and that this s hould be taken into account in terms of both sampling and studies of the en vironmental chemodynamics of contaminants.