多环芳烃长期污染土壤的微生物强化修复初步研究

本研究通过室内模拟试验,以急性毒性较强的菲(Phe)和遗传毒性较强的苯并[a]芘(B[a]P)为代表性多环芳烃(PAHs)污染物,以不同C源、通气状况和水分条件为调控因子,对PAHs长期污染土壤的土著微生物强化修复进行初步研究。结果表明,搅动处理使污染土壤中Phe和B[a]P的降解率分别达59.44%和26.14%,而淹水处理使两者降解率分别达46.48%和13.27%。添加C源(淀粉和葡萄糖)处理提高了土壤中PAHs的降解率,且随着C源的施用量而增加。同时也发现污染土壤中PAHs降解菌和微生物总量呈正相关,并随着PAHs降解菌数量的增加,土壤中PAHs降解率也随之提高。可见,土壤中PAHs降解速率主要决定于PAHs的降解菌数量。     

微生物降解石油源多环芳香烃的研究进展

石油源多环芳香烃是存在于石油中的一类致畸、致癌污染物,具有以低环(2~3环)为主且取代基比例明显高于其他来源PAHs的组分特征。石油泄露引发的PAHs污染,其降解主要依赖于微生物的活动。本文对能够降解PAHs的微生物种类、降解机理、代谢途径及编码基因进行了概述。从PAHs作为碳源的角度将微生物降解机理划分为能以PAHs为唯一碳源进行生长的降解机理和共代谢机理。对与PAHs有关的好氧和厌氧微生物降解途径及对应的编码基因簇进行了总结。自然界中细菌、放线菌、真菌及藻类都能够降解PAHs,由加氧酶催化的苯环羟基化和还原酶介导的苯环脱芳烃化是好氧和厌氧降解途径的关键步骤,与降解有关的pca,cat,paa,nah,nah-like和bcr基因簇则分别调控好氧和厌氧降解过程。这些进展有助于系统了解石油源PAHs的降解过程、微生物作用机理和分子遗传机制,为进一步利用微生物促进环境生物修复提供理论依据。     

混合菌降解土壤中多环芳烃的试验研究

PAHs生物降解程度受多种因素影响。通过筛选驯化PAHs降解菌,研究混合菌对土壤中菲、芘、苯并（a）蒽、苯并（b）荧蒽、苯并（k）荧蒽、茚并（1,2,3-cd）芘的生物降解性能,并考察污染时间对土壤中PAHs降解效果的影响。结果表明,筛选的混合菌具有很强的PAHs降解能力,缩短了PAHs生物降解的半衰期,且PAHs起始降解速率较快,之后趋于平缓。27d内土壤中的菲、芘、苯并（a）蒽、苯并（b）荧蒽、苯并（k）荧蒽、茚并（1,2,3-cd）芘的平均降解率分别为98.14%、89.97%、88.47%、63.55%、65.24%、60.49%,其中菲在5d之内的降解率高于93%。污染210d的土壤中各PAHs的起始降解速率高于污染50d的土壤,因此污染时间越长,PAHs生物降解的停滞期越短。     

三唑类农药的微生物降解研究进展

三唑类农药是一种广泛使用的防治植物病害的杀菌剂和植物生长调节剂,可通过抑制麦角甾醇的合成阻碍病原菌的细胞壁形成,从而起到防治作物病害的作用,也能抑制植物赤霉素合成延缓植物生长;但因大范围应用及其难以降解的特性,污染环境和影响人类健康。为给三唑类农药的微生物降解提供参考,基于文献研究,梳理总结了三唑类农药降解菌的种类、影响降解的环境因素和降解机理方面的研究进展,明确了微生物在不同环境中能有效降解三唑类农药,微生物降解技术有望应用于治理三唑类农药造成的环境污染。     

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。     

土壤中多环芳烃的微生物降解: 降解途径及其影响影子

Adverse effects on the environment and high persistence in the microbial degradation and environmental fate of polycyclic aromatic hydrocarbons (PAHs) are motivating interest. Many soil microorganisms can degrade PAHs and use various metabolic pathways to do so. However, both the physio-chemical characteristics of compounds as well as the physical, chemical, and biological properties of soils can drastically influence the degradation capacity of naturally occurring microorganisms for field bioremediation. Modern biological techniques have been widely used to promote the efficiency of microbial PAH-degradation and make the biodegradation metabolic pathways more clear. In this review microbial degradation of PAHs in soil is discussed, with emphasis placed on the main degradation pathways and the environmental factors affecting biodegradation.     

多环芳烃高效降解菌的筛选

以多环芳烃(PAHs)菲、蒽、芘、■和苯并(a)芘为供试物,对土著混合菌和引进菌同时进行筛选实验。结果表明,引进菌和土著混合菌经过驯化后对菲、蒽、芘、■和苯并(a)芘均具有一定的降解能力。其中,在pH=6时,混合菌U03在48h内对5种PAHs的降解率均相对较高,分别为:72.38%;64.46%;65.77%;66.49%和64.77%,并且其的降解速率在各菌剂中同样最快,通过SPSS数理统计分析软件对数据进行处理后得出,混合菌U03可在较短时间内达到较好的降解目的。室内模拟试验证明混合菌U03具有较强的降解PAHs的能力,混合菌的协同作用有利于污染土壤中PAHs的降解。     

微生物降解阿特拉津的研究进展

除草剂阿特拉津长期使用所造成环境污染问题的日益加重,受污染土壤、水体的生物降解、生态修复等诸多问题也受到人们的广泛关注,本文综述了降解阿特拉津的微生物类群、阿特拉津降解酶以及微生物对阿特拉津的作用方式和降解途径,并对其应用前景进行了展望。     

寒区降解多环芳烃耐冷菌株的分离鉴定及特性

多环芳烃（Polycyclic Aromatic Hydrocarbons,PAHs）是土壤中一种典型的持久性有机污染物。典型寒区东北地区因农业投入品不合理使用、污灌等造成农田土壤中含有大量致癌、致畸与致突变的多环芳烃,针对寒区气候特征致使农田中微生物降解多环芳烃效果不佳,难以改善农田土壤环境并降低食品风险的关键问题,基于目前常用商品化的降解微生物多来自于温暖地区,且难以适应寒区气候的特性,该研究以PAHs典型污染物-菲（PHE）为研究底物,驯化温度15 ℃,筛选分离出适应寒区低温环境的7株菌。经鉴定及降解性能研究,筛选了3株在温度20 ℃、接种量5%、pH值为8、底物浓度500 mg/L,以及外源物质腐殖酸的促进的条件下PHE降解率达到80%的高效降解耐冷菌。以上3株菌两两之间与三者组合均无拮抗关系。对菌株进行碳源的广谱性分析,菌株对2-5环多环芳烃降解率可达15%～85%之间,在将菌株应用至20 ℃土壤环境时,60 d可降解土壤中75%的PHE。该耐冷菌群适应条件符合寒区农田土壤实际环境,研究结果对黑土地区土壤多环芳烃污染的微生物修复提供了一定的基础资料。     

城市土壤多环芳烃污染研究进展

针对城市土壤特性,对土壤中多环芳烃(polycyclic aromatic hydrocarbons,PAHs)污染方面的研究进行了分析与综述,归纳总结了城市土壤PAHs的含量、分布、来源、影响因子及污染评价。结果表明城市土壤PAHs含量在地区、时间上存在较大差异,其来源主要是人为源,同时还受到气候、土壤理化性质、土壤微生物作用及地表植物种类的影响,目前许多城市土壤PAHs存在一定程度的污染,需要尽快建立PAHs数据库,为城市土壤PAHs的污染预警及防治提供数据支持。     

溶解性富里酸对土壤中多环芳烃迁移的影响

多数多环芳烃（PAHs）因其水溶性低,且易被土壤有机质固持,曾经被认为其迁移能力十分微弱。但土壤中溶解性有机质可能影响PAHs的溶解、吸附等环境过程,进而影响其迁移性。本文旨在研究富里酸提取的溶解性有机质（FDOM）对PAHs在土－水间迁移的影响及其可能机制。溶液化学稳定性研究结果显示,FDOM在溶液pH 2.0～7.0、CaCl₂浓度0～1 500 mmol L^-1范围内均能保持较好的分散性,未发生絮凝沉淀。室内土柱淋溶试验结果表明,FDOM在土壤中具有较强的迁移能力,在FDOM持续淋溶条件下,菲、芘以及苯并[a]芘在淋出液中的浓度明显提高,并有少量二苯并[a, h]蒽淋出。FDOM淋溶处理的土柱表层土壤中菲、芘、苯并[a]芘和二苯并[a, h]蒽的淋失率分别为92.06%、92.07%、84.52%和23.27%,显著高于对照组（p<0.05）。以上研究结果表明,FDOM可作为载体提高PAHs在土壤中的迁移性,增加PAHs向深层土壤和地下水迁移的可能性。     

生物表面活性剂强化微生物修复多环芳烃污染土壤的初探

通过温室盆栽实验,单独或联合接种多环芳烃专性降解菌(DB)和添加生物表面活性剂-鼠李糖脂(RH),研究了生物表面活性剂强化微生物修复多环芳烃(PAHs)长期污染土壤的效果。结果表明,添加RH和接种DB能明显促进土壤中PAHs总量和各组分PAHs的降解。经过90 d培养后,添加RH、DB和RH+DB处理的PAHs的降解率分别为21.3%、32.6%、36.0%,较对照分别提高了333.0%、563.3%、633.0%。此外,随着苯环数的增加,土壤中15种PAHs平均降解率逐渐降低。同时也发现DB、RH+DB处理土壤中脱氢酶活性、多酚氧化酶活性和PAHs降解菌数量显著高于CK、RH处理,但是CK与RH处理没有显著差异,说明DB、RH在促进土壤中PAHs的降解方面有不同的机制。     

多环芳烃污染土壤的植物-微生物联合修复初探

在温室盆栽条件下,通过种植紫花苜蓿单独或联合接种菌根真菌(Glomus caledonium L.)(AM)和多环芳烃专性降解菌(DB),研究了利用植物-微生物强化修复多环芳烃(PAHs)长期污染土壤的效果。试验结果表明,接种菌根真菌和PAHs专性降解菌能促进紫花苜蓿的生长和土壤中PAHs的降解。经过90天修复试验,种植紫花苜蓿接种AM、DB和DB+AM处理的PAHs的降解率分别为47.9%、49.6%、60.1%,均高于只种植紫花苜蓿的对照处理(CK)(21.7%)。另外,随着PAHs苯环数的增加,其平均降解率逐渐降低,但是接种PAHs专性降解菌能够提高4环和5环PAHs的降解率。同时也发现土壤中脱氢酶活性和PAHs降解菌数量越高的处理,土壤PAHs的降解率也越高,这也是种植紫花苜蓿接种微生物能够有效促进土壤PAHs降解的原因。     

丛枝菌根作用下土壤中多环芳烃的残留及形态研究

采用盆栽试验方法,以苊为多环芳烃(PAHs)代表物,研究了丛枝菌根(AM)作用下土壤中 PAHs 的残留及形态.供试污染土壤中苊的起始浓度为 35.0 mg/kg.结果表明,AM作用下土壤中苊总残留量明显降低;接种摩西球囊霉菌Glomus mosseae或幼套球囊霉菌Glomus etunicatum后,供试两个污染土样中苊总残留降解率达32.7%～45.2%,比未接种对照高 6.8%～9.8%.有机溶剂提取态是土壤中苊残留的主要部分,AM 作用促进了苊各形态之间的转化;接种AM后土壤 1、2 中苊可脱附态和有机溶剂提取态残留量分别比对照降低了17.0%～37.8% 和 5.4%～26.6%,而结合态残留量比对照增加了12.2%～89.5%.AM 作用能降低土壤中苊可提取态残留含量;但培养55 天后土壤中仍有 65.7%～81.7% 苊属于可提取态残留,对生物有毒害风险.     

Phytotoxicity of polycyclic aromatic hydrocarbons to willow trees

The toxicity of PAH to willow trees(Salix alba, S. viminalis, S. viminalis x schwerinii) was investigated. Willow cuttings were grown in PH-saturated hydroponic solution (naphthalene NAP, phenanthrene PHEN and benzo(a)pyrene BaP). Toxicity was related to aqueous solubility and was highest for NAP. PHEN did not show significant effects, except in one case. Exposure of trees to BaP showed no effect in two cases, but increased transpiration and growth in two others. High dosages of NAP were fatal for the trees, the lowest dosage significantly stimulated growth. Soil samples were taken from several PAH contaminated sites, among them gas works sites and a former sludge basin. The PAH contents ranged from 1.76 mg/kg to 1451 mg/kg. None of the soils was lethally toxic to the trees, and difference between growth in control soils and growth in PAH contaminated soils was not apparent. Growth and water use efficiency were positively, but not significantly correlated to the PAH content of the soils. Outdoor growth of willows and poplars on the former sludge basin in Valby was monitored, with willows growing faster than poplars(Fopulus trichocarpa). Phytotoxic effects could be observed at some willows at the Valby sludge basin, but it is not sure whether these effects can be contributed to PAH.     

Sorption of polycyclic aromatic hydrocarbons to mineral surfaces

Minerals contribute crucially to the retention of polycyclic aromatic hydrocarbons (PAHs) in subsurface environments. To investigate the sorption behaviour to mineral surfaces batch sorption experiments were conducted using three PAHs (phenanthrene, pyrene, benzo(a)pyrene) and three mineral sorbents that were representative of subsurface materials (quartz, goethite‐coated quartz, quartz‐montmorillonite mixture). Sorption kinetics showed an instantaneous, considerable PAH sorption to all minerals, except for phenanthrene sorption to quartz at small aqueous‐phase concentrations. Apparent sorption equilibrium was achieved after 4 hours of contact time. The sorption characteristics were fitted to six isotherm models by applying Monte Carlo simulation and nonlinear regression. Best‐fit models were obtained by a model discrimination approach. Phenanthrene and pyrene sorption were best described by the Freundlich isotherm model, with the exception of phenanthrene sorption to quartz (linear isotherm). Good fit results for quartz were also obtained for the combined linear‐Freundlich isotherm. Benzo(a)pyrene sorption to all minerals followed linear high‐affinity isotherms. In the case of phenanthrene and pyrene, the Monte Carlo simulations resulted in mean values with small standard deviations for the isotherm parameters, indicating a negligible influence of the experimental uncertainties on the accuracy of the fitted parameters. For phenanthrene, (i) linear isotherms to quartz and goethite‐coated quartz and (ii) a nonlinear concave‐shaped isotherm to quartz–montmorillonite, assuming a pore‐filling process to micropores formed by clay aggregates, were confirmed. For pyrene, nonlinear convex‐shaped isotherms to the mineral surfaces were assessed. A specific sorption affinity of pyrene to the goethite surface indicated a non‐covalent cation‐π interaction. Small sorption affinities to quartz–montmorillonite support an unfavourable partitioning into the adjacent water.     

Extraction of polycyclic aromatic hydrocarbons from spiked soil

A homogenization method was evaluated for extracting polycyclic aromatic hydrocarbons (PAHs) from soils. Fifteen PAHs were spiked and recovered from 2 soils at concentrations ranging from 1 to 1000 micrograms/g, using the homogenization method and a Soxhlet extraction method. Each extraction method performed well in removing the 15 PAHs from both soils over a broad range of concentrations. In general, Soxhlet extraction yielded slightly but significantly (P less than 0.05) higher recoveries than did the homogenization method. The homogenization method, however, was easy to use, and the extraction step turnaround time was less than 15 min/sample. The method should be suitable for other applications requiring the extraction of hydrophobic organic compounds from soils.     

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.