Monitoring of extractable organic halogens (EOX) in chlorine bleached pulp and paper mill effluents using four species of transplanted aquatic mollusks

Four species of aquatic mollusks, three bivalves: Anodonta cygnea, Unio pictorum and Dreissena polymorpha, and one gastropod: Viviparus viviparus were collected in a lowly polluted area and transferred to three monitoring sites, one upstream and two downstream of a chlorine bleached pulp and paper mill effluent. During the 28 days of the experiment, water, sediment and mollusks were sampled at regular intervals and analyzed for organo-halogenated residues using the sum parameters AOX and EOX. AOX concentrations in the water of the downstream sites were subjected to daily fluctuations due to the mill activity, while they remained stable in the sediments. The EOX concentrations in the mollusks exposed at the upstream site remained steady during the 28 days of exposure. Downstream, the EOX concentrations at both sites increased regularly in the four species of mollusks.