Biodegradation combined with ozone for the remediation of contaminated soils

The effectiveness of the SS-SBR (Soil Slurry – Sequencing Batch Reactor) process for the remediation of soils contaminated by several organic pollutants has been evaluated. Experimental tests have been performed on two different soils, a spiked one and an industrial aged soil. The spiked soil, artificially contaminated, has been prepared trying to simulate the pollution of an industrial aged soil in terms of number and kind of contaminants. PAHs (Polycyclic Aromatic Hydrocarbons) and phenols degradation has been particularly investigated because they are considered persistent and recalcitrant. Concerning the spiked soil, removal efficiencies higher than 95% in 6 to 9 weeks have been found for all the pollutants, except for five-rings PAHs; however, these compounds were partly removed in 11 to 13 weeks. Good results have been achieved also for the industrial aged soil with a maximum removal of about 80% in 7–8 weeks. To enhance the pollutants degradation, trying to obtain a faster remediation, the biological treatment has been combined with a chemical oxidation with ozone. The best degradation effectiveness of the combined process has been obtained applying the ozonation after few days of the biological treatment. Therefore, a combined biological and chemical treatment allowed to markedly improve the remediation of contaminated soils.     

Photochemical oxidation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in soils — a tool to assess their degradability?

To determine the degradability of PAHs and PCBs for soil remediation or ecotoxicological risk assessment, a simple method is needed. We tested the suitability of photocatalytic oxidation for this purpose. We determined the concentrations of 20 PAHs and 12 PCBs in four mineral topsoil horizons, six organic horizons, and four particle‐size fractions of each of three soils before and after UV irradiation with TiO₂ as a catalyst in suspension. Preliminary experiments showed that in dry soil no photooxidation occurred, but after 48 h of irradiation in suspension the PCB concentrations decreased by up to 40—50 %, while the PAH concentrations did not change significantly. In contrast to this, 95—100 % of PAH and PCB standards spiked on quartz sand were degraded within 8 h, indicating that sorption to organic matter limited degradation of PAHs and PCBs in soil suspensions. There was no difference in the degradation among different individual PAHs and PCBs, respectively, indicating that the degradation did not occur in dissolved state, but in association with soil organic matter. In all samples except one, the degradation of PCBs (10—80 % loss of initial concentrations) was higher than those of the PAHs (0—40 % loss). This suggests that the accessibility of PCBs for OH· radicals generated during irradiation was higher, or the oxidation of PAHs was limited by the properties of the sorbing organic matter. Thus, the tested method was not suitable to predict biodegradability, because it did not reflect the differences in degradability of individual compounds.     

Biochar reduces uptake and accumulation of polycyclic aromatic hydrocarbons (PAHs) in winter wheat on a PAH-contaminated soil

For years, biochar has been successfully used for the remediation of polycyclic aromatic hydrocarbons(PAHs) in contaminated soils, not only for improving their removal from soil but also for reducing their uptake by crops. However, the underlying mechanism of biochar application reducing PAH uptake and accumulation in winter wheat remains unclear. Pot trials were conducted on a PAH-contaminated soil amended with bamboo biochar, coconut shell biochar,and maize straw biochar(MSB) for an entire gro...     

锯末对生物修复荧蒽和芘污染土壤的强化作用及影响因素

通过土壤微宇宙培养试验,研究了锯末尺寸、添加量和种类等因素对荧蒽特效降解菌MC(Mycobacterium flavescens)修复污染土壤(潮土、红壤、黑土、黄棕壤和水稻土)的效果.结果表明:锯末联合降解菌MC修复荧蒽污染的黄棕壤效果较好,优化条件下25 d荧蒽降解率为42.63％ ±1.05％;该联合修复对黑土和...     

过一硫酸盐的化学氧化机理及在有机污染土壤修复中应用研究进展

基于过一硫酸盐(PMS)的高级氧化技术因反应快速高效、降解有机污染物效果优越,在环境修复领域拥有广阔的应用潜能。经过活化的PMS化学氧化技术在有机污染废水处理中被广泛应用,污染物的去除机制也在不断被发现并完善,其在有机污染土壤修复中也已得到应用。本文综述了PMS对有机污染物的化学氧化机制,分析了有机污染物降解的自由基和非自由基反应过程,探讨了不同活化方式(碱、过渡金属、碳基材料、辐射等)对PMS降解有机污染物的影响,阐述了PMS在有机污染土壤修复中的研究进展和存在问题,并进行了研究展望。     

Polyzyklische Aromatische Kohlenwasserstoffe (PAKs) in den Böden der Rieselfelder der Stadt Münster (Westfalen)

Polycyclic Aromatic Hydrocarbons (PAHs) in soils of the Münster (Westfalia) irrigation fields From 1901 to 1975 municipal sewage waters with a daily amount of finally about 40.000 m³ were seeped in the irrigation fields of the city of Münster (Westfalia). Soil samples of former seeped sites and non-seeped neighbour sites have been examined with regard to 6 polycyclic aromatic hydrocarbons (PAHs) of the German “drinking water regulation”. The irrigation caused an enrichment of PAH in the topsoils of the former irrigation basins up to an average concentration of 0,57 mg PAH/kg soil, while the topsoils outside of the irrigation fields show an average concentration of only 0,14 mg PAH/kg soil. Significant correlations between different soil properties, e.g. the organic matter content, and the concentration of PAHs are not evident. After termination the irrigation of sewage water, single irrigation bassins were filled with substratum, which is contaminated with scoriaceous materials. The average PAH concentration of such an area amounts to 7 mg PAH/kg topsoil. The PAH distribution in a soil profile shows a decreasing concentration by depth but a clear enrichment in oxidized gleyic horizons (Go) of different age. Probably the PAHs were leached under recent conditions by chemical bond to dissolved organic carbon (DOC) and finally adsorbed by Fe oxides. Since the end of irrigation Fluoranthene, the most mobile PAH compound, was leached down to 110 cm depth. A contamination of the superficial groundwater at such sites cannot be excluded.     

高锰酸钾氧化修复污染土壤中菲和芘的研究

利用人工污染土壤,研究了高锰酸钾对4种不同土壤中菲和芘的氧化修复效果。结果表明,当高锰酸钾浓度为33.33mmol·L^-1时,土壤中菲和芘的氧化去除率达到最大。高锰酸钾氧化去除率不仅与高锰酸钾浓度有关,还与土壤性质和老化时间有关。土壤有机质含量的增加会降低高锰酸钾对土壤中菲和芘的氧化去除率;随着老化时间的增加,高锰酸钾的氧化去除率逐渐降低。老化40d后,4种土壤中菲和芘的氧化去除率显著降低,菲的氧化去除率在14%～67%之间,芘的氧化去除率在61%～84%之间。高锰酸钾氧化前后,4种土壤中有机质含量下降范围为0.77%～9.21%。从土壤有机质含量来看,高锰酸钾氧化修复多环芳烃污染土壤对土壤质量影响较小,具有较好的应用前景。     

持久性有机污染场地土壤淋洗法修复研究进展

持久性有机污染场地土壤淋洗法是污染场地土壤物化修复方法中一种常用的技术。淋洗法是指运用特定淋洗剂对污染土壤进行深度洗涤,通过分离净化淋洗剂,实现回用集成,达到去除土壤中污染物的目的,并最终安全化处置污染物和修复土壤的过程。本文根据污染场地土壤处理位置、淋洗剂种类和淋洗剂施用方式的差异,将持久性有机污染场地土壤淋洗法划分为不同的种类;总结了为达到高效去除土壤中污染物质,可运用多级淋洗方式、超声方式、电动力方式和化学氧化等方式实现强化修复效率;阐述了污染场地土壤质地、污染物性质、淋洗剂性质、淋洗条件优化以及淋洗剂回用效率等因素对淋洗修复整体效用的显著影响;同时指出了目前持久性有机污染场地土壤淋洗法存在的问题和今后国内外研究和应用的方向。综合考虑土壤淋洗修复技术适用范围和成本因素,认为淋洗法是一种较符合我国持久性有机污染场地土壤实情的修复技术,具有较强的针对性和较广泛的运用前景。     

Enhanced bioremediation of PAH-contaminated soil by immobilized bacteria with plant residue and biochar as carriers

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are largely accumulated in soils in China. The immobilized-microorganism technique (IMT) is a potential approach for abating soil contamination with PAHs. However, few studies about the application of IMT to contaminated soil remediation were reported. Due to recalcitrance to decomposition, biochar application to soil may enhance soil carbon sequestration, but few studies on the application of biochars to remediation of contaminated soil were reported. In this study, we illustrated enhanced bioremediation of soil having a long history of PAH contamination by IMT using plant residues and biochars as carriers.

Materials and methods

Two PAH-degrading bacteria, Pseudomonas putida and an unidentified indigenous bacterium, were selected for IMT. The extractability and biodegradation of 15 PAHs in solution and an actual PAH-contaminated soil amended with immobilized-bacteria materials were investigated under different incubation periods. The effects of carriers and the molecular weight of PAHs on bioremediation efficiency were determined to illustrate their different bio-dissipation mechanisms of PAHs in soil.

Results and discussion

The IMT can considerably enhance the removal of PAHs. Carriers impose different effects on PAH bio-dissipation by amended soil with immobilized-bacteria, which can directly degrade the carrier-associated PAHs. The removal of PAHs from soil depended on PAH molecular weight and carrier types. Enhanced bio-dissipation by IMT was much stronger for 4- and 5-ring PAHs than for 3- and 6-ring ones in soil. Only P400 biochar-immobilized bacteria enhanced bio-dissipation of all PAHs in contaminated soil after a 90-day incubation.

Conclusions

Biochar can promote bioremediation of contaminated soil as microbial carriers of IMT. It is vital to select an appropriate biochar as an immobilized carrier to stimulate biodegradation. It is feasible to use adsorption carriers with high sorptive capabilities to concentrate PAHs as well as microorganisms and thereby enhance dissipation of PAHs and mitigate soil pollution.     

Predicting bioavailability of PAHs in soils to wheat roots with triolein-embedded cellulose acetate membranes and comparison with chemical extraction

Triolein-embedded cellulose acetate membrane (TECAM) was buried in 15 field-contaminated soils in parallel with the cultivation of wheat to predict bioavailability of naphthalene, phenanthrene, pyrene, and benzo[a]pyrene to wheat roots, and the method was compared with chemical extraction methods. Although a good linear relationship was found between PAH concentrations in chemical extractants and wheat roots, the percentage of PAH in soil removed by chemical extraction was much higher than the corresponding percentage removed by wheat roots. In contrast to chemical extraction, a nearly 1:1 relationship was found between the amount of each PAH taken up by TECAMs and wheat roots (r(2) = 0.798-0.925, P < 0.01). Furthermore, the uptake of PAHs by TECAMs and wheat roots had the same pathway of passive transport via the soil solution. Moreover, TECAM caused minimal disturbance to the soil and was easy to deploy. Therefore, TECAM is believed to be a useful tool to predict bioavailability of PAHs to wheat roots grown in contaminated soils.     

高级氧化技术修复萘污染土壤和地下水研究进展

多环芳烃是土壤和地下水中普遍存在的持久性有机污染物。其中，萘是结构最简单的多环芳烃，具有迁移性强的特点，可通过多种途径在土壤和地下水中富集，是焦化、化工等历史遗留地块重点关注的污染物之一。高级氧化技术高效、安全且经济，因此，基于高级氧化的萘污染土壤和地下水修复技术受到越来越多的关注。本文综述了芬顿和类芬顿氧化、臭氧氧化和过硫酸盐氧化的反应机理，重点阐述了二价铁、微纳级零价铁、铁矿物、铁螯合物等均相及非均相活化剂活化的氧化技术在修复萘污染土壤和地下水方面取得的研究进展，介绍了多种高级氧化技术联合修复以及高级氧化技术与生物降解技术协同修复的研究现状，指出了目前萘的高级氧化技术研究存在的问题，并对研究做出了展望。     

多环芳烃污染土壤表面活性剂清洗及生物柴油强化

针对某焦化厂内高浓度多环芳烃污染土壤,以烷基苷（APG）、十二烷基苯磺酸钠（SDBS）和曲拉通X-100（TX100）为表面活性剂代表物,采用静态平衡法和高效液相色谱分析,探索采用单一及混合表面活性剂清洗修复多环芳烃污染土壤,并考察生物柴油对多环芳烃去除效果的影响。结果表明,单一表面活性剂对土壤中多环芳烃去除率顺序为SDBS〉APG〉TX100。APG／SDBS混合处理及TX100/SDBS为9：1混合处理提高了土壤中多环芳烃去除率,而APG／TX100混合处理没能提高多环芳烃去除率。生物柴油对TX100及TX100／SDBS去除多环芳烃效果没有明显提高,对APG及APG/TX100去除多环芳烃略有提高。当APG／SDBS为9：1时,生物柴油可以使多环芳烃去除率从（63．3±2．0）％提高到（75．6±2．0）％。单一表面活性剂、混合表面活性剂、及表面活性剂-生物柴油乳液对多环芳烃各组分去除率比较类似,对菲的去除率最高,茚并[1,2,3-d]芘次之,其余相对较低。因此,建议采用APG／SDBS＋生物柴油的混合体系对高浓度多环芳烃污染土壤进行修复。     

某氮肥厂场地土壤PAHs污染特征研究

采用现场采样及室内测试方法对广州某氮肥厂原料车间和油库区土壤中16种优控多环芳烃（PAHs）的含量进行调查研究,分析了EPAHs含量及其组成特征和垂直分布特征,并在此基础上进行了源解析。结果表明,分析样品中∑PAHs范围在10-7795μg·kg,原料车间土壤中的∑PAHs小于油库区土壤中的,菲、芘、荧蒽、并（b）荧蒽、苯并（a）芘为主要污染物;油库土壤0-40cm的样品中16种PAHs均有检出,∑PAHs和单体分布基本一致;原料车间土壤∑PAHs和单体浓度随着地面深度的增加而减少。通过对单组分比值（菲／蒽,荧蒽／芘）的分析可以看出油库区土壤中PAHs来源于石油和燃烧源,而原料车间污染源主要为燃烧源。     

The Potential for Bioremediation of Soils Containing PAHs by Composting

? Environmental contamination by synthetic polynuclear aromatic hydrocarbons (PAHs) has become a major pollution problem. Plant tissues, lignin, soil humus constituents, some pesticides, and numerous commercial organic chemicals are also based upon aromatic building blocks. Many of these molecules are potentially toxic and carcinogenic. Some PAH compounds occur naturally at a low concentration in soils. Long exposure to naturally occurring hydrocarbons has enabled bacteria to evolve enzymes that degrade them.

Landfarming and incineration are the primary technologies used for removing PAH compounds from soils and groundwater. Recent data suggest that bioremediation by PAH composting can offer significant advantages to other treatment alternatives. Landfarming is a relatively uncontrolled method of reducing PAHs in residues. Composting is quicker, more controlled, and requires less space than landfarming. Although composting is slower and less complete than incineration, it is significantly more cost-effective.

This presentation deals with the feasibility of composting PAH contaminated soils and residues. Included will be methods for process evaluation and control, degradation potential of specific PAHs, and determining the application of composting to specific situations.     

Polycyclic aromatic hydrocarbons in green space soils in Shanghai: source,distribution, and risk assessment

Purpose

The purpose of this study is to study the major sources, concentrations, and distributions of polycyclic aromatic hydrocarbons (PAHs) in three different types of green space in Shanghai. In addition, we will quantitatively assess the burden of PAHs in the soil, as well as the potential carcinogenic risk of PAHs in humans. These results will provide valuable information for soil remediation and human health risk management.

Materials and methods

A total of 166 surface soil samples were collected in parks, greenbelts, and woodlands. Soils were extracted using accelerated solvent extraction (ASE). PAHs were analyzed by gas chromatography-mass spectrometry (GC-MS). The positive matrix factorization (PMF) model was used to identify major PAH emission sources and quantitatively assess their contributions to PAHs. The incremental lifetime cancer risk (ILCR) was used to quantify the potential health risk of PAHs.

Results and discussion

The average concentrations of ∑15 PAHs are 227?±?95 ng g^?1, 1632?±?251 ng g^?1, and 1888?±?552 ng g^?1 in the woodland, park, and greenbelt soils, respectively. The PMF results show that biomass (33%), coal (21%), vehicles (17%), natural gas (14%), oil (9%), and coke (7%) are the dominant sources of PAHs in the park soils. Diesel (40%), tire debris (30%), biomass (15%), gasoline (9%), and oil (5%) are the main sources in the greenbelt soils. Biomass (48%), vehicles (37%), and coal (15%) are the main sources in the woodland soils. The ILCRs of adults and children who are exposed to PAHs in soils range from 9.53?×?10^?8~1.42?×?10^?5.

Conclusion

In three types of green space in Shanghai, the dominant PAHs are high–molecular weight (HMW) compounds (≥?4 rings). This may be due to the proximity of the sampling site to emission sources. In addition, low–molecular weight (LMW) PAHs (with 2–3 rings) are relatively unstable, and these compounds are prone to volatilization and degradation. Source identification indicates that biomass combustion is the most dominant PAH source in the park and woodland soils, while vehicles are the dominant PAH source in the greenbelt soils. The ILCRs of adults and children indicate potential health risks, and children have a greater health risk than adults.

     

Evaluation of two bacterial delivery systems for in-situ remediation of PAH contaminated sediments

Intention, Goal and Background  Contaminated sediments represent a significant, worldwide environmental problem since they contain a mixture of different xenobiotics and heavy metals. The presence of mixed contamination presents a unique set of obstacles for remediation efforts. Often sediment remediation occurs as an ex-situ application (i.e., after dredging) in an attempt to minimize some of the problems. However, dredging poses it’s own issues. It does not address contaminated water and often material is not completely removed thereby leaving a long-term residual contamination source in the waterway. Objective  The potential of bio remediation to treat sediments contaminated with polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and heavy metals was addressed. The primary objective was to assess two delivery mechanisms for microbial inoculation to facilitate in-situ remediation of PAH contaminated sediments. Methods  Simulated river beds were constructed to mimic the Mahoning River. Contaminated sediment from the river was added to each reactor at a uniform depth, followed by the addition of river water. Fifteen inoculation points were used in each simulated river bed to ensure adequate microbial populations. One tank was inoculated with an acclimated bacteria solution as a free suspension. The other tank was inoculated with an attached growth biofilm system. Sediment samples were taken throughout the experiment and the percent PAH degradation determined. Water characteristics (DO, pH, bacterial activity, etc.) were also tracked as corroborating evidence. Results and Discussion  The monitoring sites indicated that an attached growth system was more effective, and achieved a 99% PAH degradation efficiency at some of the sampling sites. Tracking individual PAH compounds also indicated a higher overall microbial activity with the attached growth system. This activity was evident by the formation and subsequent biodegradation of lower molecular weight degradation byproducts. However, more of the sediment area was treated by the free suspension inoculum due to the ease of microbial migration. Conclusions  The applicability of using an aerobic microbial consortium composed ofMycobacterium sp., Pseudomonas aeruginosa, andPseudomonas flourescens to treat contaminated sediment was demonstrated. In addition, it was found that introducing the consortium as an attached growth was more effective than when delivered as a free suspension. Recommendation and Outlook  The results demonstrated that the consortium was effective at treating the PAHs present in the contaminated soil. An additional study to evaluate the consortium’s effectiveness at remediating the PCB present in the sediment is warranted. Optimization of the consortium-nutrient combination could enable a treatment approach to effective for all the organic contaminants present. Although this would not address the heavy metals present in the sediment, it would afford a great opportunity at remediating a severely contaminated sediment system.     

Characterization and Sources of PAHs and Potentially Toxic Metals in Urban Environments of Sevilla (Southern Spain)

The purpose of this study was to determine the degree of PAH contamination and the association of PAHs with metals in urban soil samples from Sevilla (Spain). Fifteen polycyclic aromatic hydrocarbons-PAHs (naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, indeno[1,2,3-c,d]pyrene) and seven metals (Cd, Cr, Cu, Mn, Ni, Pb, Zn) have been evaluated in representative urban soil samples. Forty-one top soils (0–10 cm) under different land use (garden, roadside, riverbank and agricultural allotment) were selected. PAHs from soil samples were extracted by sonication using dichloromethane. The simultaneous quantification of 15 different PAH compounds were carried out by HPLC using multiple wavelength shift in the fluorescence detector. For qualitative analysis a photo diode-array detector was used. Metal (pseudo-total) analysis was carried out by digestion of the soils with aqua regia in microwave oven. The mean concentration of each PAH in urban soils of Sevilla showed a wide range, they are not considered highly contaminated. The results of the sum of 15 PAHs in Sevilla soils are in the range 89.5–4004.2 μg kg^?1, but there seems not to be a correlation between the concentration of PAHs and the land use. Of the 15 PAHs examined, phenanthrene, fluoranthene and pyrene were present at the highest concentrations, being the sum of these PAHs about 40% of the total content. Although metal content were not especially high in most soils, there are significant hints of moderate pollution in some particular spots. Such spots are mainly related with some gardens within the historic quarters of the city. The associations among metals and PAHs content in the soil samples was checked by principal components analysis (PCA). The largest values both for ‘urban’ metals (Pb, Cu and Zn) and for PAHs were mainly found in sites close to the historic quarters of the city in which a heavy traffic of motor vehicles is suffered from years.     

土壤环境中多环芳烃的微生物降解及联合生物修复

研究土壤环境中持久性有机污染物的生物降解及其生物修复技术是当今国际环境修复科学技术前沿领域的重要课题。本文重点论述了土壤环境中持久性有机污染物多环芳烃的微生物降解机理及其在生物修复中的应用等,并结合当前研究进展,展望了基于多种修复措施相结合的多环芳烃污染土壤联合生物修复工程技术的开发与应用前景。     

Availability of polycyclic aromatic hydrocarbons in aging soils

Purpose  

The soil contamination by hydrophobic organic contaminants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), poses great threats to human health and ecological security and attracts worldwide concerns. The total HOC concentrations overestimate its available fraction to the soil biota. Increased understanding of the availabilities of PAHs in soil environment will have considerable benefits for their risk assessment and be very instructive to food safety and remediation strategies in contaminated sites. However, the availability of PAHs in aging soils and particularly the correlations of the availabilities with their forms in soils have yet to be elucidated. In this work, the availabilities of PAHs in aging soils were evaluated using a sequential mild extraction technique.     

Prediction of Polycyclic Aromatic Hydrocarbon Bioaccessibility to Earthworms in Spiked Soils by Composite Extraction with Hydroxypropyl-β-Cyclodextrin and Organic Acids

Traditional exhaustive extraction methods often overestimate the risk of polycyclic aromatic hydrocarbon(PAH) bioaccessibility to biota. Therefore, reliable assessment methods need to be established. In this study, a composite extraction with hydroxypropyl-β-cyclodextrin(HPCD) and three low-molecular-weight organic acids, oxalic acid(OA), malic acid(MA), and citric acid(CA), was used to predict the PAH bioaccessibility to earthworms, subjecting to two soils(red soil and yellow soil) spiked with selected PAHs,phenanthrene, pyrene, chrysene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene. For both soils,concentrations of PAHs by composite extraction using HPCD-OA(R~2= 0.89–0.92, slope = 1.89–2.03; n = 35), HPCD-MA(R~2=0.92–0.96, slope = 1.43–1.67; n = 35), and HPCD-CA(R~2= 0.92–0.96, slope = 1.26–1.56; n = 35) were significantly correlated with PAH accumulation in the Eisenia fetida earthworms. Moreover, the HPCD-CA-and HPCD-MA-extracted PAH concentrations were closer to the earthworm-accumulated PAH concentration than the extraction using just HPCD. The results indicated that the composite extraction could improve the prediction of PAH bioaccessibility, and therefore can serve as a reliable chemical method to predict PAH bioaccessibility to earthworms in contaminated soils.