Dynamics of cadmium and mercury compounds (inorganic mercury or methylmercury): uptake and depuration in Corbicula fluminea. Effects of temperature and pH

The kinetics of cadmium, inorganic mercury and methylmercury bioaccumulatio n and decontamination were studied in the Asiatic clam (Corbicula fluminea) . The contamination phase was studied over a 14-day period, and the deconta mination phase over 30 days. A further analysis of the decontamination kine tics of Cd and MeHg was carried out over a 120-day period. Combinations of two modalities, of temperature 12 and 24 degrees C, and of pH 6.0 and 8, en abled us to quantify the actions of these two abiotic factors and also thei r interactions on metal depuration. During the exposure period, the concent ration changes as a function of time clearly revealed a plateau tendency fo r the cadmium, and this was apparent as from time 4 days; in the case of th e Hg(II), however, the trend was almost linear. Against these two results, the methylmercury revealed no pronounced saturation phenomenon, despite ver y high mercury concentrations in the soft body parts. After 30 days of deco ntamination, no loss of Cd or Hg was observed in the molluscs previously co ntaminated with Cd or with MeHg. When this study was continued for 120 days , however, we observed decontamination rates of 25% for the Cd and 40% for the MeHg. For the inorganic mercury, the average decrease in burdens measur ed in the soft body parts was 30% after 30 days decontamination. The temper ature and pH factors had no significant effect on the decontamination proce sses at the organism or at the organs levels, despite the wide differences between the modalities of the two factors (12 and 24 degrees C, pH 6.0 and 8.0). (C) 1998 Elsevier Science B.V. All rights reserved.