Bioconcentration factors and kinetics of chlorobenzenes in a juvenile crab (Portunus pelagicus (L))

Abstract

The uptake- and depuration-rate constants (k₁ and k₂ respectively), according to first-order kinetics, were measured for a series of chlorobenzenes with juvenile crabs, Portunus pelagicus. These constants were found to be related to the lipophilicity of the chlorobenzenes as expressed by the octanol-water coefficient (log K_ow), giving relationships similar to those observed with fish. However, the actual magnitude of k₁ and k₂ on a lipid basis ranged from 720 to 5880 h^-1 and from 0.492 to 0.0102 h^-1 respectively, which is about ten times faster than those for fish. The bioconcentration factor (KB in wet weight units) obtained from these rate constants was related to K_ow, by the following expression.

log K_B=-2.88+1.09 log K_ow.

The empirical constants in this equation are similar to those observed with other aquatic organisms except that the value of -2.88 is lower than that reported with the other organisms. This is probably due to the relatively low lipid content of the crabs. It is suggested that the bioconcentration of essentially nonbiodegradable lipophilic compounds occurs as a result of partitioning between biota lipid and water.

Other physicochemical properties (molar volume and aqueous solubility) and two molecular descriptors (zero- and first-order Randik indices) exhibited good correlations with the bioconcentration characteristics described above.