Organoclay adsorption of woodpreserving waste from groundwater: Analytical and toxicological evaluations
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abstract
Wood-preserving waste is a complex mixture composed primarily of polycyclic aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP), with trace concentrations of other halogenated aromatic hydrocarbons (HAHs). Although many of these compounds are slightly soluble in water, these substances have been detected in groundwater at high levels. Samples from the aquifers beneath a Superfund site in the northwestern United States were used to determine the efficacy of an organically modified clay adsorbent (CP/LPHM) for PAHs and PCP in the presence of background organics. Groundwater samples were treated with 0.5% (w/w) of CP/LPHM, and compared to samples which were not treated. Determination of the concentrations of the various PAHs was done by GC/MS. Naphthalene concentration, most abundant of all PAHs detected, was reduced by approximately 88% from 261 to 31 g/ml of the extract. Other PAHs, many of which are known to be genotoxic such as benzo[a]pyrene, were also substantially reduced following treatment with this organoclay. Pentachlorophenol concentration was reduced to nondetectable levels. A bioassay that is sensitive to the toxic effects of PAHs, the Chick Embryotoxicity Screening Test (CHEST), was performed with sample extracts to evaluate the relative toxicity of the samples before and after treatment with the organoclay. The groundwater, before treatment with the CP/LPHM, resulted in 88% mortality of the chick embryos. Following treatment, the mortality was decreased to 21%, which was not significantly different from solvent controls. These findings suggest that organoclays show potential for application in the treatment of contaminated groundwater as determined by both analytical and toxicological evaluations.
