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The bioconcentration and toxicokinetics of atrazine in three different periphyton communities and in laboratory reared Daphnia magna were studied in natural and artificial waters with different dissolved organic carbon (DOC) concentrations and qualities. The exposure concentrations were similar to those short-lived peak concentrations found in contaminated waters. Atrazine uptake and elimination were very fast, and the bioconcentration was low both in periphyton and D. magna. The bioconcentration factors in D. magna were approx. 16% of those in periphyton. The uptake and elimination rates were also higher in periphyton than in Daphnia. The periphyton properties affected the bioconcentration of atrazine more than the DOC concentration and water quality. A steady state was reached within a few hours of uptake by the periphyton and within 24 h by D. magna. A residue of atrazine was left in the periphyton and D. magna after an 8-h biphasic depuration with clearly distinct fast and slow phases. In D. magna, atrazine may be eliminated during the normal life span of the organism. These results suggest that DOC has a minor influence on the toxicokinetics of atrazine.

Burbot (Lota lota) caught from Lake Päijänne, Central Finland, were exposed under laboratory conditions to four polychlorinated biphenyl (PCB) congeners delivered through diet, and accumulation of congeners to muscle, intestine, gonads, and liver were determined. The selected PCB congeners (PCB18, PCB44, PCB137, and PCB169) were added to intact dead vendace (Coregonus albula) and burbot were fed 5 or 10 contaminated meals (2- and 4-week experiment, respectively). Concentrations of fed congeners were different in the examined tissues. The highest concentrations of all the congeners were found in the livers of burbot. The mean retention efficiencies were 65.0% and 81.7% after 5 and 10 oral doses, respectively. The retention efficiency of the coplanar 169 was lower than those of the other fed congeners. The background organochlorine concentrations of the burbot of this study were compared with the PCB concentrations of burbot caught in the 1970s from Lake Päijänne. These concentrations were compared in order to clarify the PCB load and persistence in a boreal aquatic food web. The total PCB concentration in burbot has not declined during the last decades. The most abundant PCB congeners in the field were PCB138 and PCB153. Residual concentrations of pesticides were also found, especially the DDE, which is a metabolite of DDT.

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