In this study, we determined the limits and extent of hydrocarbon biodegradation, earthworm and plant toxicity, and waste leachability of crude oil-containing soils. Three oils (heavy, medium, and light of API gravity 14, 30, and 55, respectively) were mixed into silty loamy soils containing low (0.3%) or high (4.7%) organic carbon at 4000−27 000 mg/kg TPH. Hydrocarbon bioremediation in these artificially weathered oily soils usually followed first-order removal rates in which 50−75% and 10−90% of the total petroleum hydrocarbons (TPH) were degraded in 3−4 months for the low and high organic soils, respectively. Gas chromatographic profiles (simulated boiling point distillation of saturates and aromatic compounds) showed that, after bioremediation, hydrocarbons in oily soils decreased from 70 to 90%, from 40 to 60%, and from 35 to 60% for those carbon number species in the range of C11−C22, C23−C32, and C35−C44, respectively. Most oily soils were initially toxic to earthworms in which few animals survived 14-day bioassays. In a solid phase Microtox test, most oily soils had EC50 values that were ≤50%. Seed germination and plant growth (21-day test, wheat and oat but not corn) were also significantly reduced (0−25% of controls) in untreated soils containing the medium and light crude oils but not the heavy oil. Bioremediated soils were neither toxic to earthworms, inhibitory in the Microtox assay, nor inhibited seed germination after 5 (high organic soil) or 10−12 (low organic soil) months of treatment. Water-soluble hydrocarbons (e.g., O&G and BTEX) could leach from pretreated soils (medium and light crude oily soils) in column or batch extraction experiments. However, after bioremediation, most of the aromatic compounds were no longer leachable from the soils. These data demonstrate that treated oily soils lose their toxicity and potential to leach significant amounts of BTEX. These nontoxic soils contain 1000−8600 mg/kg residual hydrocarbons as TPH. Furthermore, these data suggest that the remaining petroleum compounds may be bound or unavailable in that they are not (a) biodegraded further, (b) toxic to soil-dwelling species (earthworms and plants), and (c) susceptible to leaching and subsequent impact to groundwater. These findings provide a basis for a framework in which petroleum hydrocarbon-containing soils can be evaluated by ecological assessment methods such as biodegradability, ecotoxicity, and leaching potential of regulated substances.

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Abstract-Ecotoxicological assessments of contaminated soil aim to understand the effect of introduced chemicals on the soil flora and fauna. Ecotoxicity test methods were developed and conducted on hydrocarbon-contaminated soils (Ͻ5,000-30,000 mg/kg total petroleum hydrocarbon) and on adjacent uncontaminated control soils from eight field locations. Tests included 7-d, 14-d, and chronic survival tests and reproduction assays for the earthworm (Eisenia fetida) and seed germination, root length, and plant growth assays for corn, lettuce, mustard, and wheat. Species-specific responses were observed with no-observed effect concentrations (NOECs) ranging from Ͻ1 to 100% contaminated soil. The 14-d earthworm survival NOEC was equal to or greater than the reproduction NOEC values for numbers of cocoons and juveniles, which were similar to one another. Cocoon and juvenile production varied among the control soils. Germination and root length NOECs for mustard and lettuce were less than NOECs for corn and wheat. Root length NOECs were similar to or less than seed germination NOECs. Statistically significant correlations (p Ͻ 0.05) for earthworm survival and seed germination as a function of hydrocarbon measurements were found. The 14-d earthworm survival and the seed germination tests are recommended for use in the context of a risk-based framework for the ecological assessment of contaminated sites.

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This paper brings together over 250 published and unpublished studies on the environmental properties, fate, and toxicity of the four major, high-volume surfactant classes and relevant feedstocks. The surfactants and feedstocks covered include alcohol sulfate or alcohol sulfate (AS), alcohol ethoxysulfate (AES), linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and long-chain alcohol (LCOH). These chemicals are used in a wide range of personal care and cleaning products. To date, this is the most comprehensive report on these substance's chemical structures, use, and volume information, physical/chemical properties, environmental fate properties such as biodegradation and sorption, monitoring studies through sewers, wastewater treatment plants and eventual release to the environment, aquatic and sediment toxicity, and bioaccumulation information. These data are used to illustrate the process for conducting both prospective and retrospective risk assessments for large-volume chemicals and categories of chemicals with wide dispersive use. Prospective risk assessments of AS, AES, AE, LAS, and LCOH demonstrate that these substances, although used in very high volume and widely released to the aquatic environment, have no adverse impact on the aquatic or sediment environments at current levels of use. The retrospective risk assessments of these same substances have clearly demonstrated that the conclusions of the prospective risk assessments are valid and confirm that these substances do not pose a risk to the aquatic or sediment environments. This paper also highlights the many years of research that the surfactant and cleaning products industry has supported, as part of their environmental sustainability commitment, to improve environmental tools, approaches, and develop innovative methods appropriate to address environmental properties of personal care and cleaning product chemicals, many of which have become approved international standard methods.