Wood Preservation Site Research Articles

Effects of anaerobic incubation on the desorption of polycyclic aromatic hydrocarbons from contaminated soils

Incubation of field-contaminated soil under anaerobic conditions can lead to increased mobilization of polycyclic aromatic hydrocarbons (PAHs) into water. In the present study, we evaluated the effects of anaerobic incubation on the rate and extent of desorption of PAH from two field-contaminated soil samples. One was a highly contaminated soil from a former wood-preserving site that had not been subject to previous treatment; the other was a soil from a former manufactured-gas plant site that had been treated in an aerobic bioreactor. A two-site desorption model was applied to quantify the fast and slowly desorbing fractions of each PAH and the corresponding first-order rate constants for each fraction. For most of the PAHs, the total amount desorbed after 18 d from anaerobically incubated samples was significantly greater than that from their counterparts not subjected to anaerobic incubation, but the overall effect was modest. The rate constant corresponding to the slowly desorbing fraction (k(2)) was much higher for the samples incubated under active anaerobic conditions than that for the controls, implying anaerobic incubation had the greatest influence on the soil compartments controlling the slow release of PAHs. Anaerobic incubation had little to no effect on the rapidly desorbing fraction.

Genotoxicity Assessment of Wood-Preserving Waste–Contaminated Soil Undergoing Bioremediation

ABSTRACT Bioremediation represents one of the most cost-effective technologies for treatment of petroleum hydrocarbons in contaminated surface soils. A major concern for regulatory agencies when evaluating bioremediation is how to determine acceptable levels for residual organics in soil. Although guidelines have been developed for some organics in soil, limited information is available to define acceptable levels of the metabolites of biological degradation. The products of oxidative degradation are likely to be more water soluble and may also be more toxic. The purpose of the current study was to monitor changes in compound concentration and genotoxicity in soils undergoing bioremediation. The site selected for this study was a former wood-preserving site in the northwestern United States. Soil samples were collected over a 4-year period from two 6075-m2 land treatment units. Conditions for biodegradation were enhanced by the addition of water and nutrients, as well as by frequent tilling to add oxygen. Due to the location of the facility, the temperature was conducive to a more rapid rate of biodegradation for approximately 6 months per year. Soil samples were collected using a grid system and solvent extracted. Polycyclic aromatic hydrocarbons were quantified in soil extracts using gas chromatography–mass spectrometry (GC/MS), and genotoxicity measured using the Salmonella/microsome assay. After 2 years of treatment, concentrations of total and carcinogenic polycyclic aromatic hydrocarbons (PAHs) were reduced to approximately 10% the concentration in the untreated soil. However, the mean weighted activity of the untreated soil was 293 net revertants per g soil, whereas the extracts of soil collected after 2 years induced a mean weighted activity of 325 net revertants per g soil. Thus, although biodegradation clearly reduced the concentration of total and carcinogenic PAHs in the surface soils, the results from the genotoxicity bioassay indicate that there was a lag in the reduction of mutagenicity in treated soils.

Chemical-specific health consultation for chromated copper arsenate chemical mixture: port of Djibouti

Chemical-specific health consultation for chromated copper arsenate chemical mixture: port of Djibouti

Migration of viscous non-aqueous phase liquids (NAPLs) in alluvium, Fraser River lowlands, British Columbia

Coal tar, creosote, and similar viscous non-aqueous phase liquids (NAPLs) behave in alluvial soils in a manner significantly different from that of less viscous NAPLs, such as gasoline and chlorinated solvents. Their unique behavior is due to the interaction of their physical–chemical parameters: a density often greater than water, a viscosity significantly greater than water, and an interfacial tension that yields a positive initial spreading coefficient at air–water–NAPL interfaces. This results in slow, creeping flow that causes long-term contamination at former manufactured gas plants and wood-preserving sites and of their adjacent surface waters. Multiphase simulations of this creeping flow are shown for a site along the lower Fraser River near Vancouver, British Columbia, and the long-term consequences of the migration of viscous NAPLs in alluvium are discussed from the perspective of site characterization and brownfields redevelopment.Key words: creosote, coal tar, multiphase simulation, brownfields, NAPL.

Leaching of arsenic, chromium, and copper in a contaminated soil at a wood preserving site.

Leaching of arsenic, chromium, and copper in a contaminated soil at a wood preserving site.

Evaluation of white‐rot fungi for the remediation of creosote‐contaminated soil

AbstractApplication 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.

Metal contamination at a wood preservation site: characterisation and experimental studies on remediation

The aim of this investigation was to determine the occurrence of As, Cu, Cr and Zn in the soil at an abandoned wood preservation unit and to examine some possible extractants for the contaminants in the soil. The mean As content of the contaminated surface soils (0–10 cm) was 186 mg kg −1, where as the mean concentrations of Cu, Cr and Zn in soils from the contaminated area were 26, 29 and 91 mg kg −1, respectively. The elevated As content in the mineral soils is related to adsorption of inorganic As phases in the fine grained fractions, which are characterised by large surface area and high positive surface charge under the current acidic conditions. Cu and Cr were found to be rather mobile, which is reflected in their lower abundance in soils and significant accumulation in sediments in the drainage leaving the area. The fine fraction of the soil (<0.125 mm) has an average metal content increased by nearly 34% as compared to the <2-mm fraction conventionally used for the analysis and assessment of soil contamination. The <2-mm fraction constitutes approximately 65% of the total weight while the fine fraction (<0.125 mm) constitutes approximately 10%. These facts, taken together, are essential for the choice of remediation measures. Oxalate solutions have been tested as extractants for soil remediation. Dark acid oxalate extraction dissolves the amorphous Al- and Fe-oxides and hydroxides and mobilises the adsorbed inorganic As species. Oxalate also acts as a ligand for the cationic heavy metals, releasing them from exchangeable sites. With a three-step sequential leaching, up to 98–99% of the metals could be removed. At lower concentrations and higher pH, the leaching decreased to approximately 70%.

Effectiveness of an anaerobic granular activated carbon fluidized-bed bioreactor to treat soil wash fluids: a proposed strategy for remediating PCP/PAH contaminated soils

An integrated system has been developed to remediate soils contaminated with pentachlorophenol (PCP) and polycyclic aromatic hydrocarbons (PAHs). This system involves the coupling of two treatment technologies, soil-solvent washing and anaerobic biotreatment of the extract. Specifically, this study evaluated the effectiveness of a granular activated carbon (GAC) fluidized-bed reactor to treat a synthetic-waste stream of PCP and four PAHs (naphthalene, acenaphthene, pyrene, and benzo(b)fluoranthene) under anaerobic conditions. This waste stream was intended to simulate the wash fluids from a soil washing process treating soils from a wood-preserving site. The reactor achieved a removal efficiency of greater than 99.8% for PCP with conversion to its dechlorination intermediates averaging 46.5%. Effluent, carbon extraction, and isotherm data also indicate that naphthalene and acenaphthene were removed from the liquid phase with efficiencies of 86 and 93%, respectively. Effluent levels of pyrene and benzo(b)fluoranthene were extremely low due to the high-adsorptive capacity of GAC for these compounds. Experimental evidence does not suggest that the latter two compounds were biochemically transformed within the reactor.

Chromate reduction by a pseudomonad isolated from a site contaminated with chromated copper arsenate.

A pseudomonad (CRB5) isolated from a decommissioned wood preservation site reduced toxic chromate [Cr(VI)] to an insoluble Cr(III) precipitate under aerobic and anaerobic conditions. CRB5 tolerated up to 520 mg of Cr(VI) liter(-1) and reduced chromate in the presence of copper and arsenate. Under anaerobic conditions it also reduced Co(III) and U(VI), partially internalizing each metal. Metal precipitates were also found on the surface of the outer membrane and (sometimes) on a capsule. The results showed that chromate reduction by CRB5 was mediated by a soluble enzyme that was largely contained in the cytoplasm but also found outside of the cells. The crude reductase activity in the soluble fraction showed a K(m) of 23 mg liter(-1) (437 microM) and a V(max) of 0.98 mg of Cr h(-1) mg of protein(-1) (317 nmol min(-1) mg of protein(-1)). Minor membrane-associated Cr(VI) reduction under anaerobiosis may account for anaerobic reduction of chromate under nongrowth conditions with an organic electron donor present. Chromate reduction under both aerobic and anaerobic conditions may be a detoxification strategy for the bacterium which could be exploited to bioremediate chromate-contaminated or other toxic heavy metal-contaminated environments.

Episodic Release of Arsenic, Copper and Chromium from a Wood Preservation Site Monitored by Transplanted Aquatic Moss

Leaching from a wood preservation site in Norway, severely contaminated with copper (Cu), chromium (Cr) and arsenic (As), was investigated using aquatic moss. The objectives were three-fold: (i) study the release of trace metals into a river during a rainfall episode, (ii) determine whether aquatic moss can be used to detect leaching during episodic events when sampling is frequent, and (iii) determine whether aquatic moss can be used as a bioindicator in brackish water. Aquatic moss (Fontinalis antipyretica was transplanted into the river in eight moss-cages. Samples were collected during one episode of rainfall. Concentrations of As in the moss increased during the rainfall event. Cu and Cr concentrations in the moss increased during the beginning of the period, but tended to decrease because of dilution towards the end. Accumulation patterns of Cu, Cr and As in the moss varied probably because of differences in binding affinity to soil and to the moss. The use of F. antipyretica proved that leaching of trace metals do increase during a rainfall event. It was shown that aquatic moss can be used as an indicator to monitor leaching during rainfall events, however, timing of sampling is critical. Although the moss survived in brackish water, it is questioned whether ions in the water can cause competition and desorption of the metals in the moss.

Bioaerosols and Particle Release During Composting of Contaminated Sawmill Soil

Compost windrows for bioremediation of soil were built at a wood-preserving site contaminated with chlorophenols, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). Sampling of airborne particles during the mixing of the compost windrows found concentrations of PCDDs and PCDFs in different particle sizes. The congener distribution of PCDDs and PCDFs in the collected air particle fractions was similar to that in the compost windrows, and the level of PCDDs and PCDFs was 1000-fold higher than the atmospheric background values reported previously. Viable particle-sizing samplers and several selective growth media were used to enumerate bacteria and fungi in the airborne particles. From the collected air samples, 40 bacteria were isolated and identified. Among the isolated bacteria, 80% were Gram-positive and spore-forming. Two of the identified airborne bacteria, Pseudomonas aeruginosa and Bacillus cereus, may cause human disease and are classified in biological agent hazard group 2. The amounts of airborne fungi, molds, and yeasts were 1000 to 2000 colony-forming units (CFUs) per m3. The number of actinomycetes was up to 6-fold, and the number of bacteria was 2- to 20-fold compared to background values. The overall level of airborne bacteria (200 to 3500 CFUs per m3) was low compared to the level of bacteria (105 to 108 CFUs per m3) found when composting municipal waste.

Determination of Mercury Binding Forms in Contaminated Soils: Mercury Pyrolysis versus Sequential Extractions

Binding forms of mercury (Hg) in contaminated soils were studied by means of a pyrolysis method and a sequential leaching procedure (SEP). Changes of the Hg-binding forms occurring during the sequential extraction procedure were characterized by determination of the thermal mercury release characteristics after each extraction step. Soil samples were selected from the site of a former chloralkali plant, a wood preservation site, and two mining areas contaminated by metallic mercury (Hg0), mercury(II) chloride (HgCl2), or mercury sulfide (HgS), respectively. The results show that Hg0, matrix-bound Hg, and HgS occurring in the studied soils could be identified by their thermal release behavior. In contrast, results obtained from sequential leach ing did not allow the identification of any specific Hg compounds as in all samples most of the Hg is extracted in the nonspecific residual Hg fraction. Results of pyrolitic measurements after each extraction step demonstrated the insufficient selectivity of the used leachants, indicating that Hg found in the residual step can consist of Hg0, matrix-bound Hg, or mercury sulfide as well. Moreover, the effectiveness of the leachants is strongly influenced by the amount of soil organic matter or buffering carbonates, whereas the dissolution of the organic matter during SEP was concluded to be the critical step.

Bioassay-based risk assessment of complex mixtures

In order to compare a standard chemical-based risk assessment with in vitro genotoxicity assays, two complex environmental mixtures from a wood-preserving site were analyzed in the Salmonella/microsome and E. coli prophage induction assays. Using GC/MS, sample 003 was found to contain relatively low levels of polycyclic aromatic hydrocarbons (PAHs) and elevated levels of polychlorinated dibenzo- p-dioxins (PCDDs), while sample 005 had higher levels of PAHs and relatively low levels of PCDDs. The complex mixtures were sequentially extracted with methylene chloride and methanol for analysis in Salmonella, or extracted with a 1:1 hexane:acetone mixture for analysis in the E. coli prophage induction assay. At a dose of 1.0 mg/plate in Salmonella strain TA98 with metabolic activation, the methanol extract of sample 003 induced 197 net revertants, while sample 005 induced 436 net revertants. In the prophage induction assay, with activation, the hexane:acetone extract of sample 003 induced a genotoxic response that was slightly lower than that observed with sample 005. The estimated incremental carcinogenic risk for ingestion of PAHs was 1.5E – 3 for sample 003, while for sample 005 the estimated risk was 1.5E – 2. Thus, the sample which induced the maximum response in both bioassays also had the highest estimated cancer risk. However, the frequency of PAH-DNA adducts in both skin and liver tissues was appreciably higher with sample 003 than with sample 005. A combined testing protocol, using both biological and chemical analysis, therefore provides more accurate information from which to assess risk than the use of either method alone.

Screening of risk management options for abandoned wood-preserving plant sites in Alberta, Canada

Several abandoned wood-preserving sites have been identified in Alberta, Canada, which pose a potential threat to human health and the environment. The physiochemical, environmental, and toxicological properties of wood preservatives are discussed together with the predominant human exposure pathways for these chemicals in the environment. A Level II soil fugacity model is used to illustrate the comparative environmental fate of individual organic wood treatment chemicals following release to the soil environment. An evaluation of risk management options at five priority sites is used to illustrate problems associated with the treatment and disposal of mixed organic and inorganic contaminated soils, soil property limitations, and the predominance of organic contaminants within the residual oil phase. The latter reality dominates options for exposure reduction and risk management. Key words: contaminated soils, wood-preserving sites, remediation options, screening, fugacity model.

Polychlorinated dibenzo-p-dioxins and dibenzofurans associated with wood-preserving chemical sites: biomonitoring with pine needles

Gas chromatography-mass spectrometry (GC-MS) analysis of pine needle extracts from two pentachlorophenol wood-preserving sites detected relatively high overall concentrations of polychlorinated dibenzo-p-dioxins (PCDDs; 1798 and 935 ppt) and dibenzofurans (PCDFs; 310 and 141 ppt). The dominant congener was octachlorodibenzo-p-dioxin (Cl 8 DD), the ΣPCDDs>ΣPCDFs, and relatively low levels of the tetra- and pentachlorodibenzofurans (ΣCl 8 DFs and Cl 5 DFs) were detected

Application of Tradescantia Micronucleus Assay for In Situ Evaluation of Potential Genetic Hazards from Exposure to Chemicals at a Wood-Preserving Site

Insitu evaluation of biological hazards from wood preserving chemicals at a hazardous waste site using the Tradescantia micronucleus assay (Trad-MCN) is reported in this study. The chemical analysis of soil samples from the site showed high contamination with arsenic (1,292 mg/kg), chromium (1,444 mg/kg) and copper (924 mg/kg) on the surface of the drip area where wood was allowed to dry after the treatment. Exposure of Tradescantia plants grown within or adjacent to the drip area showed significantly (P=0.05) higher frequencies of micronuclei when compared to plants grown in nearby control plots. The results of Tradescantia plants treated with slurry of the soil samples from the test plots as well as the results from on site exposure showed significantly (P=0.05) higher frequencies of micronuclei as compared to the concurrent controls. After remediation, the levels of arsenic, chromium, and copper were substantially reduced and concomitantly no genotoxic activity was observed in plants grown on-site or in plants exposed in the laboratory to a slurry of soil samples from this site. The results from this pilot study show that simple plant assays such as Trad-MCN can be used as a sentinel for environmental contamination and to assess the efficacy of clean-up efforts.

Mobility of Polychlorinated Aromatic Compounds in Soils Contaminated With Wood-preserving Oil

Greater understanding of the mobility of polychlorinated aromatic compounds in soils is needed to investigate contamination and design suitable remediation strategies for sites contaminated with wood-preserving oil. The objectives of this study were (1) to develop a suitable aqueous batch extraction method for soil containing wood-preservative residues; (2) to determine partition coefficients for the primary contaminants [pentachlorophenol (PCP), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFS)] in oil, soil, and aqueous phases; and (3) to evaluate the potential soil migration of the primary contaminants. In a three-phase oil-soil-water mixture, PCP, PCDDs, and PCDFs were partitioned to the greatest extent in the oil phase. These results suggest that the migration of contaminants can occur in a saturated subsurface soil zone containing an oil phase at a wood-preserving site. In the absence of a free oil phase, PCDDs and PCDFs were highly partitioned onto soil and were considered non-leachable in the aqueous phase. However, PCP was considered highly leachable from contaminated soil containing only an aqueous liquid phase. Results from this study indicate that removal of any free oil phase present in subsurface soil should have highest priority during the cleanup of contaminated wood-preserving sites.