Search

Quantification of risks to the ecosystem is necessary for cost-effective remediation strategies. Contaminant endpoints need to be established that consider the bioavailability of toxicants in soil. The challenge is to develop methods that assign risk to the bioavailable toxic contaminants, thereby protecting ecosystems, while balancing remediation costs. Our objective was to evaluate changes in bioavailability of creosote constituents in soils to earthworms. An acute ecotoxicological investigation of three weathered creosote-contaminated and two slurry-phase-biotreated soils was conducted using a 14-d earthworm (Eisenia fetida) survival bioassay. Soil characterization (physical and chemical) and contaminant concentration data (polycyclic aromatic hydrocarbons [PAH] and total dichloromethane extractable organics [DEO]) were also determined. The toxicity of the soils could not always be predicted based on chemical concentrations alone. Soils having a low PAH:DEO ratio had higher cumulative earthworm survival times as measured by earthworm-days. We propose that the DEO fraction may regulate toxicity by altering bioavailability of toxicants. [ABSTRACT FROM AUTHOR]

The sorptive behavior of two surfactants (Triton X-100(R) and Dowfax(R) 8390) with two surface soil samples, a subsurface soil sample, a weathered black shale containing large amounts of aged organic matter, an aeolian sand, and two clay minerals (montmorillonite and kaolinite) was examined. Dowfax 8390 (dianionic surfactant) sorption was notdetected with any of the samples. In contrast, Triton X-100, an ethoxylated nonionic surfactant, sorbed to all the samples. The mole surfactant sorbed/g sorbent (mol surf/g sorbent) was greater for samples containing large amounts of smectite minerals and nonlinearity of theTriton X-100 isotherm increased in samples low in organic carbon. The X-ray diffraction analysis concluded that the ethoxylate group of Triton X-100 intercalates with montmorillonite. The weathered black shale sample also has a high mol surf/g sorbent value when reacted withTriton X-100 but contains less smectite clay. We suggest that TritonX-100 may be reacting via hydrophobic groups (branched alkyl chain) with the shale sample. Consequently, sorption of alcohol ethoxylate surfactants cannot be predicted solely on the basis of soil attributessuch as clay or organic matter content, for it appears that the organic matter-clay organization may predominate in these types of interactions. [ABSTRACT FROM AUTHOR]