Microbial changes in rhizospheric soils contaminated with petroleum hydrocarbons after bioremediation

Effects of bioremediation on microbial communities in soils contaminated with petroleum hydrocarbons are a scientific problem to be solved. Changes in dominate microbial species and the total amount of microorganisms including bacteria and fungi in rhizospheric soils after bioremediation were thus evaluated using field bioremediation experiments. The results showed that there were changed dominant microorganisms including 11 bacterial strains which are mostly Gram positive bacteria and 6 fungal species which were identified. The total amount of microorganisms including bacteria and fungi increased after bioremediation of microbial agents combined with planting maize. On the contrary, fungi in rhizospheric soils were inhibited by adding microbial agents combined with planting soybean.

Laboratory Design Criteria for Monitoring Biostimulated Bioremediation of a Crude Oil Contaminated Soil in Niger Delta Using Total Petroleum Hydrocarbon

The remediation of crude oil-impacted soil has always been a challenge in different soil environments and climatic conditions. Bioremediation technology has offered a breakthrough in restoring crude oil-impacted soil/sediment in muddy, dry soil and wetlands. Though, there have been varied environmental conditions that have hampered the success of the bioremediation process. This study has evaluated the effectiveness of a biostimulated bioremediation of crude oil-impacted soil using some design criteria—nutrient amendment (NPK fertilizer) and moisture content. Soil sample sets—A, B, C, D, E, F, and G were impacted with crude oil at a ratio of 10 g/kg and amended with varying amounts of nutrient 30, 60, and 80 g of N.P.K fertilizer. The medium for the inoculation of the nutrient was water and the volume of water applied varied from 30% to 80% saturation. The soil sample sets were harvested at an interval of 3 months for 180 days to determine the concentration of total petroleum hydrocarbon left in the soil. The analysis of the total petroleum hydrocarbon was achieved using a GC-FID with a capillary column and autosampler. Soil samples were extracted with mixed solvent dichloromethane and acetone at a 1:1 ratio. The total petroleum hydrocarbon results show that biostimulated bioremediation achieved better results in soil sample sets with low moisture content (30% water saturation) and moderate nutrient amendment. The biodegradation of the sample sets with high water saturation and a high nutrient amendment was slow with a higher amount of total hydrocarbon content at the end of the 180 days. The variability in the hydrocarbon degradation pattern of contaminated soil shows that biostimulated bioremediation achieved better results in soils with low moisture content than in soil environments with high water content (saturation). More so, nutrient overdosing of the substrate hampered the effectiveness of the remediation process.

Application of bioremediation in oil contaminated soil

The long-term oil exploitation in oil fields has led to pollution of surrounding soil, creating a serious ecological problem. In order to promote and improve the application of microbial remediation in oil contaminated soil, experiment is carried out in polluted area in Zhongyuan Oilfield. In the experiment, indigenous microorganisms and other physical and chemical methods are employed, ryegrass is grown, and environmental factors in soil are regulated to degrade the oil and treat the polluted soil. Results show that when the average oil content in the soil is about 523.08 mg/kg, 65 days' remediation through plants and microorganisms could help bring the oil content down to 74.61 mg/kg, achieving a degradation rate of 85.74%; through salinity treatment, salt content in soil is reduced by 62.93-82.03% to 399-823 mg/kg from previous 2.22 g/kg. Through this experiment, the bioremediation method is improved and its effectiveness and feasibility are testified. The result has been applied in Zhongyuan Oilfield and has brought fair ecological and economic benefits, providing technical support to the treatment of contaminated soil of the same kind, and offering some insights to the treatment of soil contaminated by other organic pollutants.

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient(0-0.4043 g/g)in surface(5-10 cm)and subsurface(35-40 cm)petroleum-contaminated soil samples from the Dagang Oilfield,China.Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods,the bacterial diversity of the soil was studied.Subsequently,the environmental parameters were measured to analyze its relationship with the community variation.Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils,but no differences were observed in different depths of petroleum-contaminated soil.Meanwhile,many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties.Total petroleum hydrocarbon,total organic carbon,and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils.Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Reclamation of Smaller Volumes of Petroleum Hydrocarbon Contaminated Soil Using an Innovative Reactor System: A Case Study Evaluation of the Design

Petroleum products contamination is a world-wide problem that threatens polluting groundwater and surface water systems. However, the problem is not only large-scale in scope when viewed from a case-by-case basis. Many fueling, construction, agricultural, and industrial activities result in the problem of managing smaller quantities of these soils from an ecological safety perspective. Landfilling has been the disposal method of choice in the US;however, this option is becoming economically prohibitive and it does not really offer a true degradation fate for the pollutants. This study focused on the proving of an innovative biocell design that afforded a high level of petroleum degradation within a simple and cost effective design. Additionally, the design offered a remediation solution for sites not easily accessed. Soil contaminated with both diesel fuel and gasoline collected from a former filling station was used in this on-site remediation case study. Rapid biodegradation of the petroleum products were observed at the initiation of the study with rates leveling off as the study progressed with the final total petroleum hydrocarbon concentration being 10 mg/kg at Day 90. Oxygen uptake rates were monitored and found to nicely track both microbial activity and pollutant removal dynamics. The biocell design met all expectations by being effective, yet simple to build and operate.

In-situ remediation of deep petroleum-contaminated soil injection

A computational fluid dynamics(CFD)numerical simulation and field experiment were used to investigate optimal operating parameters of high-pressure jet grouting equipment and clarify the boundary law of the injection area in the remediation process.The response surface optimization design results show that the optimal injection pressure is 30 MPa,rotation speed is 23 r/min,commission speed is 30 cm/min,and the optimal injection diameter is 147.3 cm.Based on the CFD numerical simulation,the ratio of the injection core,turbulent zone,and seepage zone is approximately 1∶4∶2.The distribution law of jet core,turbulence zone and seepage zone at different cross-sections under 30 MPa operating conditions is as follows:The jet core radius is approximately 100 mm,the turbulence zone is mainly distributed at 100 to 500 mm,the seepage zone is mainly distributed at 500 to 700 mm,the seepage zone could be completed within 2 h,and the proportion of the three boundary zones in the injection zone is similar to that of the numerical simulation.This study provides theoretical parameters and practical reference for the remediation of deep pollution via in-situ chemical oxidation in the Loess Plateau soil environment.

Bioremediation of Total Polycyclic Aromatic Hydrocarbon Contaminated Soil Using Nitrified Sawdust and Pseudomonas auriginosa

Bioremediation involving bioaugmentation and biostimulation are eco-friendly existing methods for degrading polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. This study investigates the efficiency of Pseudomonas auriginosa and nutrient-enriched sawdust (SD) in biodegrading ∑PAHs in contaminated soil (CS). Four compost mixtures of CS/SD (1:0, 3:1, 1:1, 1:3) were applied for 2, 4, 6, 8-week bio-cleanup after inoculation. Results show ∑PAHs concentrations decreased with increasing time of treatment for all four compost in experimental and control setups. The removal efficiency of ∑PAHs was clearly associated with nutrient-enriched sawdust and Pseudomonas auriginosa, especially for 3:1, 1:1, and 1:3 ratios. Both factors had a significant effect (p = 0.05) on removal efficiency compared to the control setup. The highest (78.5%) and lowest (37.8%) ∑PAHs removal efficiency were observed for CS/SD ratios of 1:3 and 1:0 respectively after 8-week treatment. In this instance, this study recommends a CS/SD ratio of 1:3 at 8-week treatment to achieve maximum removal efficiency of ∑PAHs in contaminated soils.

The Bioremediation of Crude Oil Contaminated Soil

Alongwiththerapiddevelopmentofthepetroleumindustry,alotofsoiliscontaminatedbycrudeoil,andthusremedyingthecontaminatedsoilbecomesurgent.Therearemanyremediationmethodsforcrude-oilcontaminatedsoil,suchassolidification,thermaldesorption,washing,solventex...

Petroleum Hydrocarbon Degradation Potential of Soil Bacteria Native to the Yellow River Delta

The bioremediation potential of bacteria indigenous to soils of the Yellow River Delta in China was evaluated as a treatment option for soil remediation. Petroleum hydrocarbon degraders were isolated from contaminated soil samples from the Yellow River Delta. Four microbial communities and eight isolates were obtained. The optimal temperature, salinity, pH, and the ratios of C, N, and P (C:N:P) for the maximum biodegradation of diesel oil, crude oil, n-alkanes, and polyaromatic hydrocarbons by indigenous bacteria were determined, and the kinetics changes in microbial communities were monitored. In general, the mixed microbial consortia demonstrated wider catabolic versatility and faster overall rate of hydrocarbon degradation than individual isolates. Our experimental results demonstrated the feasibility of biodegradation of petroleum hydrocarbon by indigenous bacteria for soil remediation in the Yellow River Delta.

Characterization of recuperating talent of white-rot fungi cells to dye-contaminated soil/water

This study was purposed to explore the decolorization of dyes by fungi on either a soil or in a liquid medium and to determine the application through batch shaking system. Two commercial dyes were decolorized and studied with four fungal strains in three media. Fungal growth is the best in malt extract/glucose medium for all organisms. Decolorization of reactive blue 220 and methyl red was investigated in soil medium by Trametes versicolor. These dyes were removed 91% and 80% for methyl red and reactive blue 220 respectively(dye concentration; 100 mg·L^(-1)) by both organisms. Enzymatic activities were monitored. Laccase(Lac) and manganese peroxidase(Mn P) were detected. MnP enzyme had important role for the dye decolorization. This study demonstrates that it is possible to decolorize some synthetic dyes, which would be highly advanced for dye containing wastewater and soil. These applications could be used for dye bioremediation.

Effects of oil contamination and bioremediation on geotechnical properties of highly plastic clayey soil

Leakage of oil and its derivatives into the soil can change the engineering behavior of soil as well as cause environmental disasters.Also,recovering the contaminated sites into their natural condition and making contaminated materials as both environmentally and geotechnically suitable construction materials need the employment of remediation techniques.Bioremediation,as an efficient,low cost and environmentalfriendly approach,was used in the case of highly plastic clayey soils.To better understand the change in geotechnical properties of highly plastic fine-grained soil due to crude oil contamination and bioremediation,Atterberg limits,compaction,unconfined compression,direct shear,and consolidation tests were conducted on natural,contaminated,and bioremediated soil samples to investigate the effects of contamination and remediation on fine-grained soil properties.Oil contamination reduced maximum dry density(MDD),optimum moisture content(OMC),unconfined compressive strength(UCS),shear strength,swelling pressure,and coefficient of consolidation of soil.In addition,contamination increased the compression and swelling indices and compressibility of soil.Bioremediation reduced soil contamination by about 50%.Moreover,in comparison with contaminated soil,bioremediation reduced the MDD,UCS,swelling index,free swelling and swelling pressure of soil,and also increased OMC,shear strength,cohesion,internal friction angle,failure strain,porosity,compression index,and settlement.Microstructural analyses showed that oil contamination does not alter the soil structure in terms of chemical compounds,elements,and constituent minerals.While it decreased the specific surface area of the soil,and the bioremediation significantly increased the mentioned parameters.Bioremediation resulted in the formation of quasi-fibrous textures and porous and agglomerated structures.As a result,oil contamination affected the mechanical properties of soil negatively,but bioremediation improved these properties.

Heavy Metal Contamination in Farmland Soil and Bioremediation Measures: A Case Study of the Mining Area in Shaoguan

With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination in the mining area of Shaoguan and the causes of heavy metal contamination in recent years,brings forward the bioremediation measures to control soil heavy metal contamination,and points out the development direction of bioremediation in farmland soil heavy metal contamination in the mining area.

Qualitative and Quantitative Assessment of Petroleum Contaminants in Soils under Tropical Weather Conditions

GC-FID methods for the analysis of Petroleum hydrocarbons were developed and optimised. Contamination of soil from the Niger Delta was investigated about 40 days after crude oil spillage from the Shell Petroleum marginal well head. Soil samples and controls were collected at depths of 0 - 15 cm, 15 - 30 cm and 30 - 60 cm. Samples were analysed using gas chromatography fitted with a flame ionisation detector. Penetration and migration of C10-C26 and C26-C34 hydrocarbons through the soil layers were assessed by cluster analysis to determine the spatial distribution, penetration and similarity of these compounds over the contaminated area. The results also indicated elevated levels of total hydrocarbon contents when compared with the reference sites. Recommendations are made to carefully monitor and remediate the environment.

Biochar-based materials as remediation strategy in petroleum hydrocarbon-contaminated soil and water:Performances,mechanisms,and environmental impact

Petroleum contamination is considered as a major risk to the health of humans and environment.Biochars as low-cost and eco-friendly carbon materials,have been widely used for the removal of petroleum hydrocarbon in the environment.The purpose of this paper is to review the performance,mechanisms,and potential environmental toxicity of biochar,modified biochar and its integration use with other materials in petroleum contaminated soil and water.Specifically,the use of biochar in oil-contaminated water and soil as well as the factors that could influence the removal ability of biochar were systematically evaluated.In addition,the modification and integrated use of biochar for improving the removal efficiency were summarized from the aspects of sorption,biodegradation,chemical degradation,and reusability.Moreover,the functional impacts and associated ecotoxicity of pristine and modified biochars in various environments were demonstrated.Finally,some shortcoming of current approaches,and future research needs were provided for the future direction and challenges of modified biochar research.Overall,this paper gain insight into biochar application in petroleum remediation from the perspectives of performance enhancement and environmental sustainability.

Degradation of TCP in Soil Planted with Alfalfa(Medicago sativa L.)

[Objective] The research aimed to study the degradation of 2,4,6-trichlorophenol （TCP） in soil planted with alfalfa （Medicago sativa L.）,as well as to provide references for the Chlorophenols phytoremediation technology in the practical application.[Method] By the use of pot culture experiment in greenhouse,the phytoremediation effect of alfalfa on TCP-contaminated soil,the growth conditions of alfalfa,as well as the effect of TCP on the activity of soil polyphenol oxidase,dehydrogenase and catalase were studied.[Result] After the alfalfa was grown for 75 d,the TCP content in soil of three different concentrations treatments （low,middle and high） decreased dramatically within 15 d,and then the decreasing rate was gradually slow; on the 30^th d of cultivation,the fresh weight of treated alfalfa showed no significant difference with the control （P〈0.05）,indicating that TCP in soil had inhibition effect on the growth of alfalfa; alfalfa could significantly enhance the activities of polyphenol oxidase,dehydrogenase and catalase,thus raising the degradation capability of soil plants and microorganisms on pollutants in soil.[Conclusion] There results indicated that alfalfa could enhance the degradation rate of organics in the contaminated soil and enhance soil enzyme activity,so the alfalfa could be used for the bioremediation of TCP contaminated soil.

Assessing Earthworm Influence on Remediating Potentials of Soil Micro-Organisms, and Bioavailable Hydrocarbon Pollutant in the Niger Delta, Nigeria

In the Niger Delta region of Nigeria, oil explorations and exploitations abound, causing environmental pollution with serious consequences on soil ecosystem and its biodiversity. In spite of the relationship between microbes and fauna in soil ecosystem, such that both organisms can metabolize certain range of petroleum hydrocarbon substrates with the fauna influencing the remediation potentials of bacteria, yet soil fauna is still not fully considered in bioremediation. The influence of earthworm;Lumbricus terrestris on the remediating potentials of soil bacteria in petroleum hydrocarbon contaminated soils was investigated. Eighteen pots were filled with 700 g of soil each, with nine treated with mixture of 3 levels crude oil and remediated with earthworm, while the other nine had no earthworm. The total petroleum hydrocarbon (TPH), soil physical, nutrient compositions, and TPH degrading bacteria biodiversity were determined before contamination or commencement of study and thirty days after. The results showed a decrease in TPH concentration of 55.58%, 62.57% and 67.07% in 1 ml, 2 ml and 3 ml crude oil contaminated soil, respectively. Species richness and abundance of bacteria organisms increased with high relative abundance in soils remediated with earthworms, hydrocarbon utilizing bacteria increased from less than 0.1 cfu/g to 0.4 cfu/g, and total heterotrophic bacteria 1.6 cfu/g at the end of the study. Earthworms increased rate of remediation potentials of bacteria, such that within 30 days post remediation treatment, 34.14% of reduced concentration was achieved over soil samples without earthworms at 3 ml, and 25.14% at 2 ml concentration. Reduction in pH levels in remediated soils was between 6.39 to 6.17 and 6.74 to 6.72 in unremediated soils, while moisture content was 6.73% to 6.77% unremediated and 5.85% to 6.62% in earthworm remediated soils. Total organic carbon, nitrates in soils inoculated with earthworms were lower in concentration than those without earthworms. Reverse was the case with potassium, phosphate and phosphorous concentrations which were above those without earthworms. Results indicate statistically, significant difference between reduction in TPH in earthworm remediated soils and unremediated soils, pointing out that earthworm is a good candidate for facilitation of bacteria remediation-petroleum hydrocarbon contamination.

预氧化联合激活剂促进微生物长效降解土壤中烷烃的研究

微生物降解是一种修复石油污染土壤中烷烃的技术,但该技术易受环境条件影响,修复效率较低。为找到一种使土壤微生物能够长期有效降解烷烃的方法,进行了预氧化联合微生物激活剂降解土壤中烷烃的研究,其中利用芬顿反应进行预氧化,微生物激活剂由葡萄糖和乙酸共同组成。通过激活组(预氧化结合激活剂)、非激活组Ⅰ(仅添加激活剂,不进行预氧化)、非激活组Ⅱ(仅进行预氧化,不添加激活剂)和空白组4种不同处理方法,探究石油污染土壤微生物的数量、呼吸活性、种群变化对烷烃降解效果的影响。结果表明:激活组中烷烃半衰期只需64 d,比非激活组Ⅱ缩短了333 d,其烷烃降解率长期维持较高值,其中0~20 d、20~40 d和40~60 d的降解率分别为14.23%、17.93%和15.73%,且每20 d的烷烃降解量均维持在1500 mg/kg以上。然而其他3组的烷烃降解率随着时间推移而显著降低,40~60 d时烷烃降解率最高仅有5.50%。预氧化后土壤中类腐殖酸和类富里酸的荧光标准积分体积分别是土壤氧化前的2.80倍和3.82倍,预氧化促进了土壤微生物的快速增长。在添加乙酸和葡萄糖后土壤微生物被激活,激活剂的利用率分别达到88.06%和91.38%,其土壤微生物呼吸活性(以每kg土壤中微生物产生CO_(2)的物质的量计,下同)维持在5.00 mol/kg以上,而非激活组的土壤微生物呼吸活性在40~60 d时最高只达到2.12 mol/kg。此外,激活组的石油降解菌数量(以每g土壤中含有的石油降解菌数量计)在后期超过了9.00 lg(CFU/g),形成了芽孢杆菌属、不动杆菌属、微杆菌属、链霉菌属和水杆菌属5种优势菌属,而非激活组最多只形成了3种优势菌属。研究显示,微生物长效降解土壤中的烷烃主要由其呼吸活性、石油降解菌数量、优势菌属数和营养利用率驱动。研究结果为解决土壤石油污染问题提供了一种经济有效的方法。

基于CiteSpace的国内外土壤污染治理研究进展和发展动态分析

为全面了解国内外土壤污染防治的研究趋势和热点,利用CiteSpace可视化软件分析了近20年土壤污染治理研究相关文献的发文量、发文国家、发文机构、高被引文献和关键词等。结果表明,中英文发文量呈稳定增长趋势,中国于2010年发文量超过美国而成为该领域发文量最多的国家;中国科学院是发文量最多的机构,但国内机构间的合作较为稀疏;当前土壤污染治理中热点污染物主要侧重于重金属、多环芳烃、石油污染物和农药方面,修复技术则聚焦于生物修复和植物修复方面;学者们近几年更关注土壤污染的来源解析和健康风险评估等;结合基因组学的生物修复、生物炭钝化等高效绿色修复技术是当下和未来土壤污染修复的研究重点。