EFFECTS OF PH ON THE BIOCONCENTRATION OF PYRENE IN THE LARVAL MIDGE, CHIRONOMUS-RIPARIUS

Bioconcentration, depuration and biotransformation of the polycyclic a romatic hydrocarbon, pyrene, were studied at pH 4, 6 and 8 with larval stages of the chironomid midge, Chironomus riparius. C-14-labelled py rene was applied. The results revealed pH-dependant bioconcentration a nd depuration-kinetics as well as biotransformation of pyrene. At high er pH the bioconcentration rate (k(1)) was greater than at lower pH. H ereby the bioconcentration rate correlated with the accumulation poten tial of pyrene. That means at pH 8 the larvae accumulated pyrene stron gest, at pH 4 the bioconcentration of the larvae was lowest. Due to bi otransformation of pyrene the calculated bioconcentration factor (BCF) based on total C-14 found in the larvae. Depuration revealed a biphas ic kinetic. Data were fit with a two compartment model to calculate th e volume of each of the two compartments. To calculate for the depurat ion rate (k(2)), data were additionally fit with a one compartment mod el. The larvae displayed an intriguing pH-dependent behaviour: At pH 4 the Chironomus larvae started to increase mucus-production of the sal ivary glands and accelerated the built up of their tubes. The latter w ere of ''cocoon''-like structure. At pH 8 the composition of the tubes was more loose. It is hypothezised that this response to an acidified environment caused the reduced bioconcentration rate as well as the r educed biconcentration.