BIOCONCENTRATION OF PYRETHROID INSECTICIDES AND DDT BY RAINBOW-TROUT - UPTAKE, DEPURATION, AND EFFECT OF DISSOLVED ORGANIC-CARBON

The influence of dissolved (DOC) and particulate organic carbon (POC) on the uptake and bioconcentration of four synthetic pyrethroid insecticides, cypermethrin, deltamethrin, fenvalerate and permethrin, and p,p'-DDT, by rainbow trout (Oncorhynchus mykiss) was studied using filtered lake water, simulated (synthetic) water, and filtered and unfiltered Aldrich humic acid (AHA) solutions. Partition coefficients (K(DOC)) for the four pyrethroids in lake water ranged from 6.57 x 10(3) for cypermethrin to 2.18 x 10(4) for fenvalerate, and were consistent with results for other hydrophobic compounds. Uptake rate constants (k1; L kg-1 h-1) and bioconcentration factors (BCFs) for all compounds were lower in unfiltered AHA exposures because the combined absorption of pyrethroids by POC and DOC served to reduced dissolved concentrations. But consistent differences between k1 values in synthetic, lake and filtered AHA, all of which had low POC concentrations, were not observed for the pyrethroids indicating that the small fraction bound to DOC (2-15%) had little influence on overall bioaccumulation. Highest equilibrium BCFs were observed for pp'-DDT (3.37-9.10 x 10(4)) and fenvalerate (I 70-700), and lowest for deltamethrin (43-320). The low BCFs for the pyrethroids were primarily due to their rapid depuration: 25 to 50-fold more rapid than DDT. Half-lives of the pyrethroids in rainbow trout ranged from 37 +/- 4 h for permethrin to 78 +/- 22 h for cypermethrin.