Land Treatment of PAH-Contaminated Soil:  Performance Measured by Chemical and Toxicity Assays

Abstract

The performance of a soil remediation process can be determined by measuring the reduction in target soil contaminant concentrations and by assessing the treatment's ability to lower soil toxicity. Land treatment of polycyclic aromatic hydrocarbon (PAH)-contaminated soil from a former wood-treating site was simulated at pilot scale in temperature-controlled soil pans. Nineteen two- through six-ring PAHs were monitored with time (initial total PAHs = 2800 mg/kg). Twenty-five weeks of treatment yielded a final total PAH level of 1160 mg/kg. Statistically significant decreases in concentrations were seen in total, two-, three-, and four-ring PAHs. Carcinogenic and five- and six-ring PAHs showed no significant change in concentration. Land treatment resulted in significant toxicity reduction based on root elongation, Allium chromosomal aberration, and solid-phase Microtox bioassays. Acute toxicity, as measured by the earthworm survival assay, was significantly reduced and completely removed. The Ames spiral plate mutagenicity assay revealed that the untreated soil was slightly mutagenic and that treatment may have reduced mutagenicity. The variety of results generated from the chemical and toxicity assays emphasize the need for conducting a battery of such tests to fully understand soil remediation processes.

Multi-Species Ecotoxicity Assessment of Petroleum-Contaminated Soil

“…The lack of synchrony by different groups of organisms in response to the loss of hydrocarbons that we saw has been observed in other studies (Hund and Traunspurger, 1994;Salanitro et al, 1997;Sayles et al, 1999). In general, the inhibition of plant growth persisted longer than the effects on invertebrate viability or toxicity measured by Microtoxâ (Salanitro et al, 1997;Hund and Traunspurger, 1994).…”

Residues and source identification of persistent organic pollutants in farmland soils irrigated by effluents from biological treatment plants

“…Of combustion-derived PAHs, low molecular-weight parent PAHs are abundantly produced at low to moderated temperatures, while high-molecularweight parent PAHs are generated at high temperatures. Generally, HMW-PAHs, especially for 5-or 6-ring PAHs, are more recalcitrant to biodegradation or lose from soil through the physical -chemical processes, such as evaporation, deportation, leaching and dissolution etc and tend to absorb on the soils during irrigation since the hydrophobic properties of the PAHs (Manoli and Samara, 1999;Sayles et al, 1999;Mangas et al, 1998). Mo et al (2001) analyzed the final sludge from the biological process of SWTP studied, in which the ratio of domestic effluents/ industrial effluents was about 1:1.…”

“…Although adopted as the best available technology, biological treatment only removed part of a wide range of contaminants in wastewater. For example while low-molecular-weight (LMW-PAHs) with 2 or 3 rings are susceptible to biodegradation, HMW-PAHs with more than 4 rings that are highly mutagenic and carcinogenic remain recalcitrant (Manoli and Samara, 1999;Sayles et al, 1999;Mangas et al, 1998). Due to their mutagenic and carcinogenic property, persistence in the natural environment and discharging in significant quantity due to fossil fuel combustion in China, it is essential to study the accumulation of PAHs in soils and food chains in farmland whose irrigation regime has been mainly based on effluents from SWTP or industrial discharges.…”

Benefit of ecotoxicological bioassays in the evaluation of a biological treatment of PAHs polluted soil

“…5-ring PAHs showed a slight decrease in their content (14%), whereas the content of 6-ring PAHs remained almost constant. Sayles et al (1999) and Mendonça and Picado (2002), who followed a land treatment of PAH-contaminated soil, obtained similar results. This is in agreement with the results of different studies pointing out that biological processes only reduce low molecular weight PAHs (Bossert et al, 1984;Cerniglia, 1992).…”