Phytoremediation of polycyclic aromatic hydrocarbons in soil: part I. Dissipation of target contaminants

Phytoremediation has been demonstrated to be a viable cleanup alternative for soils contaminated with petroleum products. This study evaluated the application of phytoremediation to soil from a manufactured gas plant (MGP) site with high concentrations of recalcitrant, polycyclic aromatic hydrocarbons (PAHs). Two greenhouse studies investigated the potential dissipation and plant translocation of PAHs by fescue (Festuca arundinacea) and switchgrass (Panicum virgatum) in the first experiment and zucchini (Curcubita pepo Raven) in the second. The MGP soil was highly hydrophobic and initially inhibited plant growth. Two unplanted controls were established with and without fertilization. In the first experiment, concentrations of PAHs decreased significantly in all treatments after 12 mo. Plant biomass and microbial numbers were statistically equivalent among plant species. PAH concentrations in plant biomass were negligible for fescue and switchgrass. In the second experiment, zucchini enhanced the dissipation of several PAHs after 90 d of treatment when compared to the unvegetated soil. Plant tissue concentrations of PAHs were not elevated in the zucchini roots and shoots, and PAHs were not detectable in the fruit.     

微生物降解多环芳烃(PAHs)的研究进展

从多环芳烃(PAHs)的降解菌株的筛选、降解机制以及PAHs污染的生物修复等方面介绍了微生物降解PAHs的最新研究进展。     

微生物降解多环芳烃的研究进展

多环芳烃(PAHs)是具有严重危害的环境污染物质。介绍PAHs的降解菌,降解机理和PAHs的生物修复方面的研究进展。土壤中PAHs的生物修复被认为是解决污染的有效方法,目前,菲的生物降解途径已经比较清楚,但对结构更为复杂的多环芳烃研究较少。文章还对消除环境中多环芳烃的相关生物技术提出展望。     

Biodegradation of selected UV-irradiated and non-irradiated polycyclic aromatic hydrocarbons (PAHs)

Biodegradation of UV-irradiated anthracene, pyrene,benz[a]anthracene,and dibenz[a,h]anthracene was comparedto that of the non-irradiated samples, individuallyand in synthetic mixtures with enrichment cultures.Combined treatment was repeated for individual anthraceneand for the PAH mixture with Sphingomonas sp.strain EPA 505 and Sphingomonas yanoikuyae.Enrichment culture studies were performed on the PAHmixtures in the presence of the main photoproduct ofanthracene, pure 9,10-anthracenedione. Photochemicallypretreated creosote solutions were also subjected tobiodegradation and the results were compared tothose of the non-irradiated solutions. The primaryinterest was on 16 polycyclic aromatic hydrocarbons(PAHs) listed as priority pollutants by European Union(EU) and the United States Environmental ProtectionAgency (USEPA). Irradiation accelerated thebiodegradation onset for anthracene, pyrene, andbenz[a]anthracene when they were treatedindividually. The biodegradation of irradiatedpyrene started with no lag phase andwas complete by 122 h whereas biodegradation of thenon-irradiated sample had a lag of 280 h andresulted in complete degradation by 720 h. Biodegradation ofPAHs was accelerated in synthetic mixtures, especiallyin the presence of pure 9,10-anthracenedione.In general, irradiation had no effect on the biodegradation of PAHsincubated in synthetic mixtures or with pure cultures. Undercurrent experimental conditions, the UV-irradiation invariablyreduced the biodegradation of PAHs in creosote. Based onthe results of the present and previous photochemical-biologicalstudies of PAHs, the influence of the photochemical pretreatmenton the biodegradation is highly dependent on the compoundsbeing treated and other process parameters.     

Multispecies and monoculture rhizoremediation of polycyclic aromatic hydrocarbons (PAHs) from the soil

In this study, we investigated the potential of multispecies rhizoremediation and monoculture rhizoremediation in decontaminating polycyclic aromatic hydrocarbon (PAH) contaminated soil Plant-mediated PAH dissipation was evaluated using monoplanted soil microcosms and soil microcosms vegetated with several different grass species (Brachiaria serrata and Eleusine corocana). The dissipation of naphthalene and fluorene was higher in the "multispecies" vegetated soil compared to the monoplanted and nonplanted control soil. The concentration of naphthalene was undetectable in the multispecies vegetated treatment compared to 96% removal efficiencies in the monoplanted treatments and 63% in the nonplanted control after 10 wk of incubation. Similar removal efficiencies were obtained for fluorene. However, there was no significant difference in the dissipation of pyrene in both the mono- and multispecies vegetated treatments. There also was no significant difference between the dissipation of PAHs in the monoplanted treatments with different grass species. Principle component analysis (PCA) and cluster analysis were used to evaluate functional diversity of the different treatments during phytoremediation of PAHs. Both PCA and cluster analysis revealed differences in the metabolic fingerprints of the PAH contaminated and noncontaminated soils. However, the differences in metabolic diversity between the multispecies vegetated and monoplanted treatments were not clearly revealed. The results suggest that multispecies rhizoremediation using tolerant plant species rather than monoculture rhizoremediation have the potential to enhance pollutant removal in moderately contaminated soils.     

Phytoremediation of polycyclic hydrocarbon contaminated soil: part II. Impact on ecotoxicity

Several biological assays were used to evaluate the toxic effects of contaminants in soil after phytoremediation. During the treatment process, significant decreases in overall toxicity were observed. Specifically, earthworm survivability and lettuce germination increased over the study period. Microbial respiration improved, but only in planted treatments. Toxicity and total polycyclic aromatic hydrocarbon concentrations showed some correlation, but the relationships generally were not significant. Soil moisture was less of a predictor for biological responses. The presence of plants did not provide a clear advantage for improving toxicity compared to unplanted treatments.     

Fate of polycyclic aromatic hydrocarbons (PAH) in the rhizosphere and mycorrhizosphere of ryegrass

Polycyclic aromatic hydrocarbons (PAH) can be degraded in the rhizosphere but may also interact with vegetation by accumulation in plant tissues or adsorption on root surface. Previous studies have shown that arbuscular mycorrhizal (AM) fungi contribute to the establishment and maintenance of plants in a PAH contaminated soil. We investigated the fate of PAH in the rhizosphere and mycorrhizosphere including biodegradation, uptake and adsorption. Experiments were conducted with ryegrass inoculated or not with Glomus mosseae P2 (BEG 69) and cultivated in pots filled with soil spiked with 5 g kg⁻¹ of anthracene or with 1 g kg⁻¹ of a mixture of 8 PAH in a growth chamber. PAH were extracted from root surfaces, root and shoot tissue and rhizosphere soil and were analysed by GC-MS. In both experiments, 0.006 – 0.11‰ of the initial extractable PAH concentration were adsorbed to roots, 0.003 – 0.16‰ were found in root tissue, 0.001‰ in shoot tissue and 36 – 66% were dissipated, suggesting that the major part of PAH dissipation in rhizosphere soil was due to biodegradation or biotransformation. With mycorrhizal plants, anthracene and PAH were less adsorbed to roots and shoot tissue concentrations were lower than with non mycorrhizal plants, which could contribute to explain the beneficial effect of AM fungi on plant survival in PAH contaminated soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Individual and combined effects of cadmium and polycyclic aromatic hydrocarbons on the phytoremediation potential of Xanthium sibiricum in co-contaminated soil

Soil contamination with heavy metals and organic pollutants continues to cause major ecological damage and human health problems. Phytoremediation offers a highly promising technology for the recovery of sites contaminated with mixed pollutants. In this study, we performed a greenhouse experiment to investigate the individual and combined effects of cadmium (Cd) and polycyclic aromatic hydrocarbon (PAH) contamination on the growth of Xanthium sibiricum, and also the ability of this species to accumulate and remove Cd and to reduce PAHs over a period of 75 days. Our results demonstrated that individual or combined contamination by Cd and PAHs showed no significant differences to the control treatment except in the high Cd treatment. The reduction of PAH concentration in the soil with the passage of time was similar in the presence or absence of plants. At higher levels of Cd, the removal of pyrene decreased in both planted and non-planted soils; however, this effect might be due to the higher Cd content. Soil dehydrogenase and polyphenol oxidase activities showed that soil contamination did not have a significant effect on the removal of PAHs. Overall, our results suggest that X. sibiricum might be a suitable species for use in the phytoremediation of contaminated soils.     

Removal of polycyclic aromatic hydrocarbons from oil-contaminated Kuwaiti soil

In the uncontaminated farm soil, more than 80% of the supplemented acenaphthene, fluoranthene, and pyrene (100 mg/100 g soil) decreased in 90 days, while ratio of removal was about 20%, 30%, and 0%, respectively, in the Kuwaiti oil-contaminated soil. Simultaneous addition of naphthalene, phenanthrene, and anthrathene (100 mg of each compound/100 g soil) led the acenaphthene to a decrease of about 20% to 45% but not of fluoranthene and pyrene. Addition of the farm soil to the Kuwaiti soil did not enhance the decrease of these three PAHs.     

Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in Taihu Lake sediments, China

Taihu Lake is one of the largest freshwater lakes in China. The lake is very shallow with a mean depth of 1.9 m and an area of 2428 km². This is the first time that polycyclic aromatic hydrocarbon concentrations in the surface sediments of Taihu Lake have been analyzed. A distinctive spatial distribution of PAHs was observed. Sediments from Lake Wulihu and Meiliang Bay (sites 1–5) had significantly higher PAH concentrations (858–5260 g kg^–1 dw) than any other area of Taihu Lake. These high PAH levels were associated with the input of untreated and partially treated domestic and industrial sewage from Wuxi, Changzhou, Wujin and other cities. Special PAH ratios, such as phenanthrene/anthracene and fluoranthene/pyrene, were calculated to evaluate the relative importance of different origins. The data confirmed a relatively high level of petrogenic contamination in sites 1–5 (mainly sewage discharge and the river runoff). The other samples were further from the sources of pollution and have relatively low PAH concentrations (410–768 g kg^–1 dw). The sources of PAHs in these sites (6–13) were characterized by combustion-derived PAH contamination associated with atmospheric deposition. In addition, effects range low (ERL) and effects range median (ERM) guidelines (Long et al., 1995) were used to estimate the potential of adverse effects resulting from PAH contamination in Taihu Lake sediments. The results indicated that some sites in the northern part of the lake had levels of PAH that exceeded the ERL value. This was interpreted to mean that acute biological effects may occasionally be expected to occur.     

微生物降解多环芳烃的研究进展

多环芳烃是一类长久存在于环境中,具有毒性、致突变与致癌等特性的环境优先污染物。本文对降解多环芳烃的微生物类群进行了阐述,介绍了在土壤与厌氧条件下细菌降解多环芳烃的研究情况,最后介绍了降解多环芳烃的相关酶类以及分子生物学的研究,并对消除环境中多环芳烃的相关生物技术提出展望。     

Degradation of straight-chain aliphatic and high-molecular-weight polycyclic aromatic hydrocarbons by a strain of Mycobacterium austroafricanum

AIMS: Our goal was to characterize a newly isolated strain of Mycobacterium austroafricanum, obtained from manufactured gas plant (MGP) site soil and designated GTI-23, with respect to its ability to degrade polycyclic aromatic hydrocarbons (PAHs). METHODS AND RESULTS: GTI-23 is capable of growth on phenanthrene, fluoranthene, or pyrene as a sole source of carbon and energy; it also extensively mineralizes the latter two in liquid culture and is capable of extensive degradation of fluorene and benzo[a]pyrene, although this does not lead in either of these cases to mineralization. Supplementation of benzo[a]pyrene-containing cultures with phenanthrene had no significant effect on benzo[a]pyrene degradation; however, this process was substantially inhibited by the addition of pyrene. Extensive and rapid mineralization of pyrene by GTI-23 was also observed in pyrene-amended soil. CONCLUSIONS: Strain GTI-23 shows considerable ability to mineralize a range of polycyclic aromatic hydrocarbons, both in liquid and soil environments. In this regard, GTI-23 differs markedly from the type strain of Myco. austroafricanum (ATCC 33464); the latter isolate displayed no (or very limited) mineralization of any tested PAH (phenanthrene, fluoranthene or pyrene). When grown in liquid culture, GTI-23 was also found to be capable of growing on and mineralizing two aliphatic hydrocarbons (dodecane and hexadecane). SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate that this isolate of Myco. austroafricanum may be useful for bioremediation of soils contaminated with complex mixtures of aromatic and aliphatic hydrocarbons.     

Biodegradation of polycyclic aromatic hydrocarbons in soil around Mathura oil refinery,India

Six polycyclic aromatic hydrocarbons [naphthalene, anthracene, phenanthrene, pyrene, chrysene and benzo(a)-pyrene] were detected in soil receiving effluents from an oil refinery. Biodegradation studies revealed a time-dependent disappearance of these polycyclic aromatic hydrocarbons when they were added to soil samples: naphthalene disappeared completely in 60 days, whereas phenanthrene, anthracene, pyrene, chrysene and benzo(a)pyrene decreased by 87%, 34%, 21%, 5% and 40%, respectively, in 120 days.B.T. Ashok and J. Musarrat were and S. Saxena is with the Interdisciplinary Biotechnology Unit, A.M.U., Aligarh-202002, Uttar Pradesh, India. K.P. Singh is with the Environmental Chemistry Section, Industrial Toxicology Research Centre, M.G. Road, Lucknow-226001, Uttar Pradesh, India. B.T. Ashok is now with the Department of Biochemistry, J.N. Medical College, A.M.U., Aligarh-202002, Uttar Pradesh, India. J. Musarrat is now with the Department of Radiology and Blochemistry Program. The Ohio State University, Columbus, OH 43210, USA.     

Physiological characterization of Mycobacterium sp. strain 1B isolated from a bacterial culture able to degrade high-molecular-weight polycyclic aromatic hydrocarbons

AIM: The aim of this study was to further characterize a bacterial culture (VUN 10,010) capable of benzo[a]pyrene cometabolism. METHODS AND RESULTS: The bacterial culture, previously characterized as a pure culture of Stenotrophomonas maltophilia (VUN 10,010), was found to also contain another bacterial species (Mycobacterium sp. strain 1B), capable of degrading a similar range of PAH substrates. Analysis of its 16S rRNA gene sequence and growth characteristics revealed the strain to be a fast-growing Mycobacterium sp., closely related to other previously isolated PAH and xenobiotic-degrading mycobacterial strains. Comparison of the PAH-degrading characteristics of Mycobacterium sp. strain 1B with those of S. maltophilia indicated some similarities (ability to degrade phenanthrene and pyrene), but some differences were also noted (S. maltophilia able to degrade fluorene, but not fluoranthene, whereas Mycobacterium sp. strain 1B can degrade fluoranthene, but not fluorene). Unlike the S. maltophilia culture, there was no evidence of benzo[a]pyrene degradation by Mycobacterium sp. strain 1B, even in the presence of other PAHs (ie pyrene) as co-metabolic substrates. Growth of Mycobacterium sp. strain 1B on other organic carbon sources was also limited compared with the S. maltophilia culture. CONCLUSIONS: This study isolated a Mycobacterium strain from a bacterial culture capable of benzo[a]pyrene cometabolism. The Mycobacterium strain displays different PAH-degrading characteristics to those described previously for the PAH-degrading bacterial culture. It is unclear what role the two bacterial strains play in benzo[a]pyrene cometabolism, as the Mycobacterium strain does not appear to have endogenous benzo[a]pyrene degrading ability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the isolation and characterization of a novel PAH-degrading Mycobacterium strain from a PAH-degrading culture. Further studies utilizing this strain alone, and in combination with other members of the consortium, will provide insight into the diverse roles different bacteria may play in PAH degradation in mixed cultures and in the environment.     

土壤－植物系统中多环芳烃和重金属的行为研究

对土壤中多环芳烃和重金属的行为研究表明,与对照相比,０—２０ｃｍ以上表土层存在多环芳烃和重金属积累,２０ｃｍ以下土层未发现积累;与春、秋两次采样结果相比,土壤中多环芳烃的含量有所下降,表明土壤微生物对多环芳烃有一定降解作用,且其降解程度与土壤－植物系统的生态结构有关．菲在地下水中检出浓度较高,表明这一污染物有向下迁移的可能性．此外,柳树对土壤中重金属Ｃｄ的积累有明显的削减与净化作用．本研究表明,严格限制污水中多环芳烃和重金属的污染负荷以及设计合理的生态结构是避免多环芳烃和重金属在土壤中积累的关键．     

Plant--rhizosphere-microflora association during phytoremediation of PAH-contaminated soil

The capability of plants to promote the microbial degradation of pollutants in rhizosphere soil is a principal mechanism of phytoremediation of PAH-contaminated soil. The formation of a specific rhizosphere microbocenosis with a high degradative potential toward contaminants is largely determined by plant species. The comparative PAH-degradation in unplanted soil and in soil planted with reed (Phragmites australis) and alfalfa (Medicago sativa) was studied in pot experiments during 2 years. Both alfalfa and reed successfully remediated contaminated soil by degrading 74.5 and 68.7% of PAHs, respectively. The study of the rhizosphere, rhizoplane, and unplanted-soil microflora in experimental pots showed that alfalfa stimulated the rhizosphere microflora of PAH-contaminated soil more effectively than did reed. Alfalfa clearly enhanced both the total number of microorganisms (1.3 times, according to fluorescence microscopy data) and the rate of the PAH-degrading population (almost seven times, according to plate counting). The degradative potential of its rhizosphere microflora toward PAHs was higher than the degradative activity of the reed rhizosphere. This study provides relevant information for the successful application of alfalfa to phytoremediate PAH-contaminated soil.     

Plant terpenes and lignin as natural cosubstrates in biodegradation of polyclorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs)

The objective of this minireview is to examine how cometabolic biodegradation of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) might be affected by plant terpenes and lignins as natural substrates abundant in nature. The topics covered, hence, are environmental significance of PCBs and PAHs, nature and distribution of plant terpenes and lignin, structural and metaoblic similarities of the natural compounds to PCBs and PAHs, and possible roles of the natural substrates in inducing the biodegradative pathways of PCBs and PAHs.     

Degradation of polycyclic aromatic hydrocarbons in soil by a two-step sequential treatment

The objectives of this work were to isolate the microorganisms responsible for a previously observed degradation of polycyclic aromatic hydrocarbons (PAH) in soil and to test a method for cleaning a PAH-contaminated soil. An efficient PAH degrader was isolated from an agricultural soil and designated as Mycobacterium LP1. In liquid culture, it degraded phenanthrene (58%), pyrene (24%), anthracene (21%) and benzo(a)pyrene (10%) present in mixture (initial concentration 50 μg ml⁻¹ each) and phenanthrene (92%) and pyrene (94%) as sole carbon sources after 14 days of incubation at 30°C. In soil, Mycobacterium LP1 mineralised ¹⁴C-phenanthrene (45%) and ¹⁴C-pyrene (65%) after 10 days. The good ability of this Mycobacterium was combined with the benzo(a)pyrene oxidation effect obtained by 1% w/w rapeseed oil in a sequential treatment of a PAH-spiked soil (total PAH concentration 200 mg kg⁻¹). The first step was incubation with the bacterium for 12 days and the second step was the addition of the rapeseed oil after this time and a further incubation of 22 days. Phenanthrene (99%), pyrene (95%) and anthracene (99%) were mainly degraded in the first 12 days and a total of 85% of benzo(a)pyrene was transformed during the whole process. The feasibility of the method is discussed.     

Influence of catclaw Mimosa monancistra on the dissipation of soil PAHs

Phytoremediation is a cost-effective biotechnology for decontamination of polycyclic aromatic hydrocarbons (PAHs)-polluted soils. A greenhouse experiment was conducted to determine the growth of Mimosa monancistra, a N2-fixing leguminous plants, and its capacity to remove phenanthrene, anthracene, and benzo(a)pyrene (BaP)from soil. The PAHs decreased shoot and root dry biomass of M. monancistra 2.7- and 3.9-fold, respectively, compared to uncontaminated soil and inhibited nodule formation. The removal of phenanthrene and anthracene was similar in vegetated and unvegetated soil, but the dissipation of BaP was significantly faster in vegetated soil as compared to unvegetated soil after 14, 56, 70, and 90 d. After 90 d, dissipation of BaP was 96% in vegetated soil and 87% in unvegetated soil. Nitrification and ammonification were not affected by the addition of PAHs as concentrations of NH4+, NO2-, and NO3- were similar in contaminated and uncontaminated vegetated soil. Growth of M. monancistra was inhibited by contamination with hydrocarbons, but removal of BaP was accelerated in the rhizosphere.     

Fungal metabolism of polycyclic aromatic hydrocarbons: past, present and future applications in bioremediation

This article examines the importance of non-ligninolytic and ligninolytic fungi in the bioremediation of polycyclic aromatic hydrocarbon contaminated wastes. The research from the initial studies in Dave Gibson’s laboratory to the present are discussed. Received 10 August 1997/ Accepted in revised form 15 August 1997