Contaminated soil

An experimental design approach, based on central composite design, has been used to investigate the dependence of accelerated solvent extraction operating variables (pressure, temperature, extraction time) on the recovery of 16 polycyclic aromatic hydrocarbons (PAHs) from native, contaminated soil. At the 95% confidence interval, no significance in terms of the three operating parameters was found when considering the total PAH recovery. However, when individual PAHs were consid-ered, some compounds were found to be dependent on operating variables. The most significant operating vari-able was extraction temperature. Low extraction temper-ature (40 °C) was found to be significant for naphthalene, chrysene, and benzo[b]fluoranthene. Using constant operating conditions (100 °C, 14 MPa and an extraction time of 5 min plus 5 min equilibriation time), the influence of extraction solvent was evaluated. No depen-dence on recovery was found when polar organic solvents, i.e., a dipole momen...

Bioremediation is a possible mechanism for clean-up of hydrocarbon-contaminated soils in the Antarctic. Microbes indigenous to the Antarctic are required that degrade the hydrocarbon contaminants found in the soil, and that are able to survive and maintain activity under in situ conditions. Alkane- degrading bacteria previously isolated from oil-contaminated soil from around Scott Base, Antarctica, grew on a number of n-alkanes from hexane (C6) through to eicosane (C20) and the branched alkane pristane. Mineralization of 14C-dodecane was demonstrated with four strains. Representative isolates were identified as Rhodococcus species using 16S rDNA sequence analysis. Rhodococcus spp. strains 5/14 and 7/1 grew at −2°C but numbers of viable cells declined when incubated at 37°C. Both strains appear to have the major cold-shock gene cspA. Partial nucleotide sequence analyses of the PCR-amplified cspA open reading frame from Rhodococcus spp. strains 5/14 and 7/1 were approximately 60% identical to cspA from Escherichia coli.

The efficacy of a new rhamnolipid biosurfactants mixture to enhance the removal of pyrene from a soil artificially contaminated was investigated. The molar solubilization ratio (MSR) and the partition coefficient between the micelles and water (log K(m)) were found to be 7.5 x 10(-3) and 5.7, respectively. From soil column studies, the pyrene removal increased linearly with the concentration of the injected biosurfactants solution above the effective critical micellar concentration (0.4 g L(-1)). Flushing with a 5.0 g L(-1) biosurfactants solution increased the pyrene concentration in the effluent by 178 times. At high biosurfactants' concentrations (2.5 and 5.0 g L(-1)), the cumulative pyrene recovery reached 70%. This pyrene remobilization takes place independently of the soil organic carbon solubilization. This study provides a combination of batch and column experiments in order to find the conditions for effective soil remediation using a new rhamnolipids mixture.

An innovative bioprocess method, Systematic Environmental Molecular Bioremediation Technology (SEMBT) that combines bioaugmentation and biostimulation with a molecular monitoring microarray biochip, was developed as an integrated bioremediation technology to treat S-and ...

Over440 yd,of radioactively contaminated soil containing toxic mercury was generated during a ComprehensiveEnvironmental Response, Compensation and Liability Act (CERCLA) removal action atBrookhaven,National Laboratory (BNL). The U.S. Department of Energy’s (DOE) Office of Scienceand,Technology Mixed Waste Focus Area (DOE MWFA) is sponsoring a comparison of severaltechnologies that may be used to treat these wastes and similar wastes at BNL and

Application of fungal-based bioaugmentation was evaluated for the remediation of creosote-contaminated soil at a wood-preserving site in West Virginia. Soil at the site contained creosote-range polycyclic aromatic hydrocarbons (PAHs) at concentrations in some areas that exceed industrial risk-based levels. Two white-rot fungi (Pleurotus ostreatus and Irpex lacteus) were evaluated for remediation effectiveness in a two-month bench-scale treatability test. Both fungi produced similar results, with up to 67.3 percent degradation of total PAHs in 56 days. Pilot-scale testing was performed at the site using Pleurotus ostreatus grown on two local substrate mixtures. During the 276-day field trial, total PAHs were degraded by up to 93.2 percent, with all individual PAHs except one achieving industrial risk-based concentrations. It was recommended that fungal-based remediation be applied to all contaminated soil at the site. © 2002 Wiley Periodicals, Inc.

Few studies have been done to evaluate the transfer of catabolic plasmids from an introduced donor strain to indigenous microbial populations as a means to remediate contaminated soils. In this work we determined the effect of the conjugative transfer of two 2,4-D degradative plasmids to indigenous soil bacterial populations on the rate of 2,4-D degradation in soil. We also assessed the influence of the presence of 2,4-D on the number of transconjugants formed. The two plasmids used, pEMT1k and pEMT3k, encode 2,4-D degradative genes (tfd) that differ in DNA sequence as well as gene organisation, and confer different growth rates to Ralstonia eutropha JMP228 when grown with 2,4-D as a sole carbon source. In an agricultural soil (Ardoyen) treated with 2,4-D (100 ppm) there were ca. 10(7) CFU of transconjugants per gram bearing pEMT1k as well as a high number of pEMT3k bearing transconjugants (ca 10(6) CFU/g). In this soil the formation of a high number of 2,4-D degrading transconjugan...

A total of 2454 samples were collected to evaluate the degree, extent, and distribution of Pb contaminated soil in Minnesota. Samples were collected primarily at locations where susceptible populations were concentrated. Soil Pb concentrations in chilldren's play areas, urban gardens, and at open sites were generally below 100 μg g −1 when Pb painted structures were absent. Street side and yard soils typically had Pb concentrations between 10 to 300 μg g−1, with samples collected near major highways or Pb painted structures exhibiting greater values. The most severely contaminated soils were found in localized areas around the foundations of private residences, where concentrations up to 20 136 μg g−1 were detected. Exterior Pb based house paint is the major Pb source in these soils, and its presence greatly influences the distribution of contaminated soil in individual yards. Contamination attributable to autoemissions is less concentrated but more widespread than contamination from paint. A higher proportion of soils exceeding 1000 wg g−1 Pb was found in large cities than elsewhere. However, a sufficient number were detected in small cities and rural areas to confirm that high soil Pb levels are not exclusively an urban phenomenon. By examining the degree, extent, and distribution of Pb contaminated soils in Minnesota, this study provides information useful in guiding response actions to reduce children's exposure to Pb by this pathway.

The present work describes a coke oven soil treatability study by landfarming, conducted on-site in a field scale facility covering 100 m2. The soil contamination was mainly due to high concentrations of polynuclear aromatic hydrocarbons (PAHs) up to 1140 mg/Kg dry weight (ΣEPA). Along the treatment process the soil was characterised at the chemical, microbiological and ecotoxicological levels. After 3 months a reduction of 63% in total PAHs concentration was observed, being detected a more pronounced reduction for PAHs with 2, 3 and 4 rings (79%). Concomitantly, a change in the composition of the microbial population was observed with a significant increase in the PAHs degrading and total heterotrophic colonies. Concerning the ecotoxicity and genotoxicity data no effect was detected in the treated soil samples eluates.