Improving Mathematical Model in Biodegradation of PAHs Contaminated Soil Using Gram-Positive Bacteria

In published literature there are limited studies on the estimation of kinetic parameters of polycyclic aromatic hydrocarbons (PAHs) in soil. In addition, neither the kinetic studies were performed with Gram-positive bacteria nor conducted under non-indigenous condition in order to understand their removal performance. Thus, a mathematical model describing biodegradation of phenanthrene-contaminated soil by Corynebacterium urealyticum, bacterium isolated from municipal sludge, was developed in this study. The model includes three kinetic parameters that were determined using TableCurve 2D software, namely qmax (maximum substrate utilization rate per unit mass of bacteria), X (biomass concentration) and Ks (substrate concentration at one half the maximum substrate utilization rate). These parameters were evaluated and verified in five different initial phenanthrene concentrations. Highest degradation rate was determined to be 79.24 mg kg^?1 day^?1 at 500 mg kg^?1 initial phenanthrene concentrations. This high concentration shows that bacteria perform better in contaminated sand compared to liquid media. High r² values, ranging from 0.92 to 0.99, were obtained excluding 1000 mg/kg phenanthrene. The kinetic parameters, i.e., qmax and Ks, increased with the phenanthrene concentration and thus suggest that bacteria degrade at a higher degradation rate. This model successfully described the biodegradation profiles observed at different initial phenanthrene concentrations. The established model can be used to simulate the duration of phenanthrene degradation using only the value of the initial PAHs concentration.     

生物反应器法处理油泥污染土壤的研究

采油过程产生的油泥是整个石油烃污染源的重点。在陆地生态环境中 ,烃类的大量存在往往对植物的生物学质量产生不利影响 ,更重要的是石油中的一些多环芳烃是致癌和致突变物质 ,这些致癌和致突变的有机污染物进入农田生态系统后 ,在动植物体内逐渐富集 ,进而威胁人类的生存和健康[1 ,1 1 ] 。大量的废弃油泥 ,不仅污染农田 ,同时也给石油行业带来巨大的经济损失。污染土壤的治理主要有物理、化学和生物 (生物修复 )方法 ,生物修复方法被认为最有生命力。污染土壤生物修复技术主要有 3种 ,即原位处理、挖掘堆置处理和反应器处理。反应器处理是…     

中国水青冈分布,生长和更新特点

中国水青冈分布、生长和更新特点吴刚（中国科学院生态环境研究中心,北京１０００８５）Ｄｉｓｔｒｉｂｕｔｉｏｎ,ＧｒｏｗｔｈａｎｄＲｅｖｅｇｅｔａｔｉｏｎａｌＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＦａｇｕｓｉｎＣｈｉｎａ．ＷｕＧａｎｇ（ＲｅｓｅａｒｃｈＣｅｎ...     

污染土壤的植物修复

污染土壤的植物修复沈德中（中国农业大学资源与环境学院,北京１０００９４）ＰｈｙｔｏｒｅｍｅｄｉａｔｉｏｎｏｆＣｏｎｔａｍｉｎａｔｅｄＳｏｉｌ．ＳｈｅｎＤｅｚｈｏｎｇ（ＣｏｌｅｇｅｏｆＲｅｓｏｕｒｃｅｓａｎｄＥｎｖｉｒｏｎｍｅｎｔ,ＣｈｉｎａＡｇｒｉｃ...     

Effects of carbon substrate enrichment and DOC concentration on biodegradation of PAHs in soil

AIMS: Two common reasons to explain slow environmental biodegradation of polycyclic aromatic hydrocarbons (PAHs), namely lack of appropriate carbon sources for microbial growth and limited bioavailability of PAHs, were tested in a laboratory bioassay using a creosote-contaminated soil. METHODS AND RESULTS: The soil, containing a total of 8 mg g-1 of 16 PAHs, was sieved and incubated in bottles for 45 days. The first explanation was tested by enrichment with the analogue anthracene and the non-analogue myristic acid, and both failed to stimulate degradation of all PAHs except anthracene. The second explanation was tested by addition of different concentrations of dissolved organic carbon (DOC), with effects depending on the DOC concentration and the molecular size of the PAH. The degradation was enhanced from 10 to 35% for 12 PAHs when the soil was saturated. The degraded amounts of individual PAHs were proportional to their concentration in the soil. CONCLUSIONS: The slow in situ degradation of PAHs was enhanced by more than three times by adding water as a solvent. Addition of DOC facilitated the degradation of four- to six-ring PAHs. SIGNIFICANCE AND IMPACT OF STUDY: Bioremediation of PAH-contaminated sites may be facilitated by creating water-saturated conditions but retarded by addition of other carbon substrates, such as analogue compounds.     

石油污染土壤的生物修复技术

1　前　言在石油生产、贮运、炼制加工及使用过程中 ,由于事故 ,不正常操作及检修等原因 ,都会有石油烃类的溢出和排放。例如 ,油田开发过程中的井喷事故 ;输油管线和贮油罐的泄漏事故 ;油槽车和油轮的泄漏事故 ;油井清蜡和油田地面设备检修 ;炼油和石油化工生产装置检修等。石油烃类大量溢出 ,应当尽可能予以回收 ,但有的情况下回收很困难 ,即使尽力回收 ,仍会残留一部分 ,对环境 (土壤、地面和地下水 )造成污染。其进入土壤后 ,会破坏土壤结构 ,分散土粒 ,使土壤的透水性降低。其富含的反应基能与无机氮、磷结合并限制硝化作用和脱磷酸作…     

石油污染土壤生物降解生态条件研究

生物治理是石油污染土壤主要的有效的治理方法。微生物、污染物及环境等方面的因素都影响着生物降解效率。通过最佳生物降解条件的研究,提出了提高生物降解效率的措施。     

Growth of Tomato Plants in Soil Contaminated with Kuwait Crude Oil

This laboratory study measured growth of one plant species, Lycopersicon esculentum Big Girl (tomato), that is sensitive to the presence of soil contamination, in Kuwait soil amended with crude-oil-contaminated soil. Germinated tomato seeds were placed in containers with soil containing 0, 0.12, 0.24, 0.36, 0.48, 0.60, 1.2, and 2.4% crude oil and were grown in an indoor growth chamber. Plants grew in Kuwait soil containing up to 0.36% crude oil; however, growth and fruit production were compromised at crude oil concentrations greater than 0.12% when compared with control plants. Plants did not grow in Kuwait soil amended with 0.48% crude oil or higher.     

Biodegradation of Hopane Prevents Use as Conservative Biomarker During Bioremediation of PAHs in Petroleum Contaminated Soils

The pentacyclic triterpane C₃₀ 17α (H), 21β (H)-hopane, a biomarker commonly used in hydrocarbon bioremediation laboratory experiments and field studies, was found to be completely removed without the formation of the demethylated intermediate nor-hopane in a crude oil-contaminated soil undergoing slurry biotreatment, while PAHs such as benzo(e)pyrene were recalcitrant. The partial or complete biodegradation of hopane has also been previously reported in a few bioremediation studies and has been explored by petroleum geochemists in an effort to characterize crude oil deposits. It is currently not clear what conditions induce hopane biodegradation or biotransformation, although the use of microbial enrichment cultures appears to speed up the process. Considering that hopane is not necessarily conserved during a bioremediation study, the uncritical normalization of hydrocarbon concentrations using this biomarker can lead to incorrect estimates of biodegradation rates and extents. If hopane is found to be unstable in a particular case, other potential biomarkers such as pentahopane, oleanane, or vanadium may be used instead.     

有机污染土壤生物修复的生物反应器技术研究进展

人类广泛的工农业生产活动常常导致土壤污染。常见的土壤污染有重金属污染和有机污染。近年来 ,世界各国开始重视污染土壤的治理。处理方式主要包括热处理 (焚烧法 )、物理及物理化学处理(洗涤 )和生物处理 (生物修复技术 )。其中生物修复技术被认为最有生命力[1,7] 。目前 ,国外采用的土壤生物修复技术有原位处理、场上处理和生物反应器。生物反应器技术能够有效地发挥生物法的特长 ,是污染土壤生物修复技术中最有效的处理工艺 ,但该技术尚处于实验室研究阶段 ,未广泛应用于现场处理。本文就国外使用生物反应器治理有机污染土壤的研究进展…     

Removal of Heavy Metals from Contaminated Soil and Sediments Using the Biosurfactant Surfactin

The feasibility of using a biodegradable surfactant, surfactin from Bacillus subtilis, for the removal of heavy metals from a contaminated soil (890?mg/kg zinc, 420?mg/kg copper, 12.6% oil and grease) and sediments (110?mg/kg copper, 3300?mg/kg zinc) was evaluated. Results showed that after one and five batch washings of the soil, 25 and 70% of the copper, 6 and 25% of the zinc, and 5 and 15% of the cadmium could be removed by 0.1% surfactin with 1% NaOH, respectively. From the sediment, 15% of the copper and 6% of the zinc could be removed after a single washing with 0.25% surfactin/1% NaOH. The geochemical speciation of the heavy metals among the exchangeable, oxide, carbonate, organic, and residual fractions was determined by selective sequential extraction procedure. For both matrices, the exchangeable fractions were minimal, while the carbonate and the oxide fractions accounted for over 90% of the zinc present and the organic fraction constituted over 70% of the copper. Results after washing indicated that surfactin with NaOH could remove copper from the organic fraction, zinc from the oxide, and cadmium from the carbonate fractions. The residual fraction remained untouched. These experiments indicate that the sequential extraction studies could be useful in designing soil-washing procedures.     

Biodegradation of PAHs in Aggregates of a Low Permeability Soil

In the bioremediation of low-permeability soils, pollutant and, especially, the oxygen bioavailability are often the rate limiting steps. In cases when a biopile treatment can represent an applicable technique, pretreatment of the excavated soil is often necessary to attain an adequate air-filled porosity in the soil and to avoid the presence of large soil aggregates. The present work was performed to evaluate the influence of soil aggregate size in the bioremediation of a silt-clay type soil contaminated by PAHs. Microcosms were arranged with spherical soil aggregates of different diameter in near water-saturation conditions. Concentration of two and three aromatic ring PAHs, total biom-ass, and respiration rates were monitored. PAH concentration profiles inside the particles were also obtained. A simple and quick way to estimate the critical dimension of the soil aggregates was developed based on the evaluation of an oxygen penetration depth, that is, the distance from the external surface to the aggregate core beyond which oxygen concentration is practically zero. A very different time course of PAHs consumption was found in the external layer and the inner core of the aggregates as well as in aggregates of different dimensions. The results suggest that only the 3 mm external layer of the sphere is not limited by oxygen diffusion.     

Phytoremediation and natural attenuation of sulfentrazone: mineralogy influence of three highly weathered soils

Abstract

This study evaluated remediation of the herbicide sulfentrazone in soils with three different mineralogies (kaolinite, hematite, and gibbsite) and three remediation sulfentrazone treatments (Canavalia ensiformis L., Crotalaria juncea L., and natural attenuation). This study was conducted in a factorial scheme, in triplicate with randomized block design. Sulfentrazone was applied at 0 and 400?g ha^?1. We analyzed sulfentrazone residue in the soils by high-performance liquid chromatography and confirmed the results with bioassays of Pennisetum glaucum. Herbicide movement was greater in the kaolinitic soil without plant species. The retention of herbicide in the kaolinitic soil occurred in larger quantities in the 0–12?cm layer, with higher levels found in the treatments with plants. In the hematitic soil with C. juncea, all applied herbicides were concentrated in the 0–12?cm layer. In the other hematitic soil treatments, sulfentrazone was not detected by chemical analysis at any soil depth, although in many treatments, it was detected in the bioassay. Phytoremediation was more efficient with C. ensiformis grown in gibbsitic soil, reducing the sulfentrazone load by approximately 27%. Natural attenuation was more efficient than phytoremediation in oxidic soils due to soil pH and texture soils favored microbial degradation of the compound.

• Highlights

• The influence of soil mineralogy of herbicide sulfentrazone retention was evaluated.

• Canavalia ensiformis and Crotalaria juncea were evaluated as phytoremediation plants.

• Kaolinite soils presented great movement of sulfentrazone in the soil.

• Natural attenuation is more efficient in oxide soils than phytoremediation.

     

Enhanced Degradation of n-Hexadecane in Diesel Fuel Contaminated Soil by the Addition of Fermented Whey

The objective of this work has been to investigate the possibility of using fermented whey as an organic growth supplement in order to enhance the aerobic degradation of n-hexadecane in soil. Fermented whey was added at different dosages to nutrient amended soil microcosms contaminated with 5000 mg diesel fuel kg^?1 dry weight (dw). The target substance was ¹⁴C-labeled n-hexadecane, and the biodegradation was monitored by analysis of evolved ¹⁴CO₂. Biodegradation curves were fitted to a three-half-order kinetics model. Enhanced biodegradation was observed in sand at 7 and 22°C and in loamy sand at 22°C but the effect was most pronounced in the sand soil at 22°C. The addition of 6 or 60 ml fermented whey kg^{? 1} soil dw increased the degree of n-hexadecane biodegradation at the end of the experiment, 167 days, from 49% in the untreated sand to 60 or 67%, respectively. This increase in biodegradation was characterized by an increase in the amount of substrate biodegradation by first-order kinetics despite a decrease in the first order rate constant, k₁. The highest concentration of fermented whey, 60 ml kg^?1, gave rise to substrate competition, diauxie, which resulted in an extended lag phase.     

Reducing Copper Availability in Contaminated Soils Using Drinking Water Treatment Residuals

Copper mobility and availability in soil environments is largely controlled by Cu sorption reactions as well as its chemical forms. In this study, equilibrium, kinetic batch experiments, and a chemical fractionation scheme were carried out to evaluate effects of drinking water treatment residual (DWTR) application on sorption and bioavailability of Cu in three arid zone soils having different properties. Distinct differences in the amounts of Cu sorbed among the different soils were observed where highest sorption was associated with clay, OM, and CEC contents. The quantity of Cu sorbed on the three studied soils drastically increased as a result of increasing rates of DWTR application from 2% to 12% (w/w). Freundlich distribution coefficient (K_f) values indicate that Cu sorption affinities for the studied soils followed the trend Typic torrifluvent (TF) > Typic calciorthids (CO) > Typic torripsamment (TP) soils. The sorption of Cu was initially fast with 95, 92, and 73% of Cu sorbed on TF and CO and TP unamended soils, respectively, in the first 60 min. Following the initial fast reaction, the sorption reaction continued for 63 h, after which only a small amount of additional sorption occurred (2–6%). The parabolic diffusion law and the power function models described Cu sorption kinetics in all the sorbents studied equally well as the R² values were quite high and SE values were low. Addition of DWTR drastically reduced non-residual (NORS) Cu and simultaneously increased residual (RS) Cu fractions. At 12% application rate, DWTR decreased NORS-Cu in nonamended soils from 10.9 to 4.2, from 50.2 to 21.5, and from 78.6 to 33.3% in TF, CO, and TP soils, respectively. Our results suggest that as the application rate of DWTR to Cu-contaminated soils increased, more Cu was associated with the residual fractions, which decreased potential Cu mobility and bioavailability in these soils.     

Degradation and Detoxification of Nicosulfuron by a Pseudomonas Strain Isolated from a Contaminated Cornfield Soil

ABSTRACT

The dissipation and detoxification of nicosulfuron (NS) by Pseudomonas aeruginosa B9 isolated from a cornfield soil was investigated. The fastest decline of NS occurred at 40 µg ml^?1 in liquid media with 0.25% glucose plus 0.05% yeast extract (DT₅₀ = 4 days) with a notable pH reduction (pH ? 5). Bioassay tests showed considerable phytotoxicity of NS for Cress (Lepidium sativum L.) with 50% shoot growth inhibition (SGI) at 40 µg ml^?1. The dissipation of NS (40 µg ml^?1) by the B9 isolate reduced the SGI significantly (SGI: up to 45 ± 3%) compared to the non-inoculated media (SGI: up to 58 ± 4%). In soils with the B9 isolate, NS dissipation, especially at 0.3 µg g^?1, was faster with a more significant SGI reduction (k = 0.08 ± 0.00 day^?1; SGI = 2 ± 1%) compared to non-inoculated samples (k = 0.03 ± 0.00 day^?1; SGI = 8 ± 1%). NS initially inhibited soil respiration, microbial biomass carbon, and dehydrogenase activity. The effect was however transient, and these parameters recovered within 10 days, especially in the presence of the isolate. Overall, this study proves Pseudomonas aeruginosa B9 as a suitable candidate for bioremediation of NS in contaminated sites.     

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.     

Influence of Short-Chain Aliphatic Acids on the Phenanthrene Desorption and Mobilization from Contaminated Soil

This study was performed to investigate the influence of short-chain aliphatic acids (SCAAs) on the desorption of phenanthrene from artificially contaminated soils with this polycyclic aromatic hydrocarbon. Five SCAAs examined, including acetic acid, oxalic acid, malic acid, tartaric acid and citric acid, were related to the increase of phenanthrene desorption from two kinds of soil. Citric acid and oxalic acid enhanced phenanthrene desorption to a more significant extent than other organic acids. The effects of pH, SCAA concentration, and ionic strength were further evaluated. The phenanthrene desorption was enhanced as the pH increased. An increase in desorbed phenanthrene from pH 3 to pH 8 was observed, but that was followed by a slight decrease above pH 8 for most SCAAs. The phenanthrene desorption performance showed increments with increasing organic acid concentrations. However, the increase of phenanthrene desorption became less remarkable when SCAA concentrations were above 100 mmol/L. Moreover the results suggested that high ionic strength hindered the desorption of phenanthrene in the presence of SCAAs.     

Washing of Cadmium(II) from a Contaminated Soil Column

The washing of cadmium (from CdO_(s)) from a soil column employing either an acid solution or EDTA (a strong metal chelator) was examined. For Cd(II) levels of 50 to 1000 mg/kg, the fraction removed was essentially independent of the initial Cd(II) concentration. The most efficient washing of cadmium was achieved using an acid wash solution at pH 2.5. Lower Cd(II) removals were found at lower pH, apparently due to inhibition of CdO_(s) dissolution by constituents released from the soil under highly acidic conditions. EDTA wash solutions were employed at EDTA:cadmium molar ratios ranging from 1:1 to 10:1. Up to 90% removal of total Cd(II) was achieved at the 10:1 ratio after the passage of the first 50?PV of wash solution. Although higher chelate levels enhanced Cd(II) removal, the utilization efficiency of EDTA for cadmium decreased.     

Bioreduction of Hexavalent Chromium from Soil Column Leachate by Pseudomonas stutzeri

Bioreduction of Cr(VI) to less toxic Cr(III) by chromate-reducing bacteria has offered an ecological and economical option for chromate detoxification. The present study reports isolation of chromate-resistant bacterial strain Cr8 from chromium slag, identified as Pseudomonas stutzeri, based on 16S rRNA gene sequencing and their potential use in Cr(VI) reduction. The reduced product associated with bacterial cell was characterized by scanning electron microscopy–energy-dispersive x-ray spectroscopy (SEM-EDS) and x-ray diffraction (XRD) analyses. At initial concentrations of 100 and 200 mg L^?1 Cr(VI), P. stutzeri Cr8 reduced Cr(VI) completely within 24 h, whereas it reduced almost 1000 mg L^?1 Cr(VI) at the end of 120 h. Further, soil column leaching experiments were performed and found that bacterial cells reduced Cr(VI) leachate at faster rate that almost disappeared at the end of 168 h. The leachate precipitates also revealed efficient chromate bioreduction. The remediation process utilizing P. stutzeri could be considered as a viable alternative to reduce Cr(VI) contamination, especially emanating from the overburden dumps of chromite ores and mine drainage.