INVESTIGATION OF THE TOXICOKINETICS OF PETROLEUM HYDROCARBON DISTILLATES WITH THE EARTHWORM EISENIA ANDREI

Abstract

The Canada-wide standards for petroleum hydrocarbons in soils regulate petroleum hydrocarbons based on four distillate ranges: F1 (C6-C10), F2 (>C10-C16), F3 (>C16-C34), and F4 (>C34). Previous toxicity tests with earthworms and F2, as well as two subfractions of F3, F3a (>C16-C23) and F3a (>C23-C34), indicate that test durations might not be sufficiently long to reach threshold effect concentrations, likely because of the differing toxicokinetics for each distillate. A study was conducted to determine the toxicokinetics of both aliphatic and aromatic fractions of F2, F3a, and F3b with the earthworm Eisenia andrei. Peak accumulation curves were observed for F2 aliphatics and aromatics and F3a aromatics, likely as a result of changes in exposure concentration over the test duration via loss or a decrease in the bioavailable fraction. Biota-soil accumulation factors were >1 for total F2 aliphatics and aromatics and F3a aromatics as well as for several individual polyaromatic hydrocarbons for each distillate. Aromatics were disproportionately accumulated over aliphatics and were the main contributors to toxicity; therefore, aromatics and aliphatics should be regulated separately. The toxicokinetics were used to interpret previous toxicity data. Higher molecular weight distillates need longer-than-standard test durations to determine toxicity, so toxicity test results from fixed, standard-duration tests are not strictly comparable for these petroleum distillates.

A User-Friendly Kinetic Model Incorporating Regression Models for Estimating Pesticide Accumulation in Diverse Earthworm Species Across Varied Soils

“…Inclusion of an earthworm property (SSAlipid) as an additional model input slightly improved the model fit for bulk soil-based elimination rate constants ( k out , R 2 = 0.88). The dependence of elimination rate constants on hydrophobicity (log K ow or TPSA) is consistent with previous studies, − which demonstrated that the strong binding of hydrophobic compounds to earthworm lipids may retard elimination. For example, Matscheko et al observed a strong negative correlation between elimination rate constants and log K ow (which itself is correlated negatively to TPSA) for polycyclic aromatic hydrocarbons and polychlorinated biphenyls.…”