Kinetics and biotransformation of benzo(a)pyrene in Chironomus riparius.

Uptake and depuration kinetics for benzo(a)pyrene (B(a)P) were determined for the midge Chironomus riparius (Diptera) with one and two compartment models. Nonfeeding animals were exposed to nominal 1.0 microgram.L-1 14C- B(a)P for eight hr. Depuration over eight hr was determined in animals with and without substrate. The uptake rate constant was 214 +/- 20 hr-1 (X +/- SE, n = 3), while elimination rate constants for the first four hr were 0.22 hr-1 (with substrate) and 0.06 hr-1 (without substrate). Biphasic depuration was observed with an initial rapid phase that lasted several hr. Approximately 10% of accumulated 14C was associated with exoskeleton. As much as 50% of the accumulated B(a)P was transformed into polar compounds after one hr. Based on steady state 14C concentration, an apparent bioconcentration factor of 650 was determined. The bioconcentration value based on B(a)P analysis was 200.