The effect of temperature on uptake rate constants, depuration rate constants, and bioconcentration factors (BCF) for six organochlorines in the aquatic insect, Chironomus ripariu

Uptake rate constants, ku, depuration rate constants, kd, and bioconcentration factors, BCF, were determined for six organochlorine compounds (1,4-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, lindane, and DDE) at four temperatures (10$spcirc$C, 16$spcirc$C, 22$spcirc$C, and 30$spcirc$C) using the aquatic insect, Chironomus riparius. The rate constants were determined using the model equation, dCa/dt = kuCw $-$ kdCa (w = water; a = animal; t = time), from data generated in uptake experiments where midges were exposed up to eight hours to the chemical in a closed static system, and in depuration experiments where previously exposed midges were transferred to uncontaminated water in a flow-through system. BCF values were determined by the "kinetic approach" calculation, ku/kd, for all compounds and the "steady-state approach" calculation, Css/Cw, for 1,4-dichlorobenzene. The accumulation dynamics of the six organochlorines did not fit the model equation, dCa/dt = kuCw $-$ kdCa. The two uptake processes proposed to occur in 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, and lindane were described as ku$sb{rm fast}$ and ku$sb{rm slow}$. Both ku and kd generally increased with increases in temperature from 10$spcirc$C to 30$spcirc$C. Generally kd was more sensitive to temperature. BCF values for all six compounds were found to generally decline over the 10$spcirc$C to 30$spcirc$C temperature range which was consistent with the behavior of partition coefficients with temperature for similar hydrophobic chemicals reported in the literature. The midge ku and BCF values were found to be higher than ku and BCF values reported for fish in the literature. Correlations were made between rate constants and BCF values with octanol/water partition coefficients and aqueous solubilities. Octanol/water partition coefficients were found to be better correlated to the accumulation parameters. The highest correlation (r = 0.98) was found between BCF and octanol/water partition coefficients.;Acute toxicity experiments were conducted using four of the test chemicals (1,4-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, and lindane) with C. riparius at two temperatures (10$spcirc$C and room temperature). For dichlorobenzene and trichlorobenzene toxicity was greater at 10$spcirc$C. However, toxicity was greater at the warmer temperature for tetrachlorobenzene while lindane showed no significant difference in acute toxicity between the two temperatures.