甜菜与牧草间作对多环芳烃污染土壤的修复作用

通过盆栽试验方法,选择经济作物甜菜和牧草类黑麦草、苏丹草、香根草为供试植物,研究了甜菜与3种牧草分别间作及各自单作对多环芳烃（PAHs）菲、荧蒽、芘和苯并[a]芘污染土壤修复作用。结果显示：经6个月连续两茬种植试验后,所有种植植物的处理中土壤PAHs的去除率均高于无植物种植组,间作种植土壤PAHs的去除率高于单作,黑麦草、苏丹草、香根草与甜菜间作对土壤PAHs的去除率分别达到84.85%、79.96%、84.11%;在土壤污染条件下,间作模式更有利于甜菜生长;种植植物增强了土壤中多酚氧化酶和过氧化氢酶的活性,间作模式下二者活性高于单作4.37%~43.07%,过氧化氢酶较多酚氧化酶对PAHs土壤污染更敏感,可作为关键酶用于评价土壤PAHs污染状况。在不影响农业生产的前提下,修复植物牧草和经济作物甜菜间作种植模式显著提高了土壤PAHs的降解率。     

多环芳烃在土壤中的环境行为研究进展

综述了土壤环境中多环芳烃(PAHs)来源及其进入环境后的行为和归宿,并提出多环芳烃污染土壤的修复对策。     

Milk--blood transfer of (14)C-tagged polycyclic aromatic hydrocarbons (PAHs) in pigs

Polycyclic aromatic hydrocarbons (PAHs) are lipophilic organic pollutants occurring widely in the terrestrial environment. To study the transfer of PAHs in the food chain, pigs have been fed with milk spiked either with [(14)C]phenanthrene or with [(14)C]benzo[a]pyrene. The analysis of blood radioactivity showed that both PAHs were absorbed with a maximum concentration at 5--6 h after milk ingestion, similar to fat metabolism. The blood radioactivity then decreased to reach background levels 24 h after milk ingestion. Furthermore, the blood radioactivity was higher for phenanthrene (even if the injected load was the lowest) than for benzo[a]pyrene, in agreement with their solubility difference. These findings suggest that milk fat and PAHs were absorbed during the same time period.     

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。     

Distribution of polycyclic aromatic hydrocarbons (PAHs) in floodplain soils of the Mosel and Saar River

Background, Aim and Scope  Polycyclic aromatic hydrocarbons (PAHs) have gained serious attention in the scientific community due to their persistence and toxic potential in the environment. PAHs may pose a risk to ecosystem health. Along the Mosel River/Germany, a tributary of the river Rhine, PAHs were found at significantly high concentrations (> 20 mg kg⁻¹, German national guideline value Z2, LAGA 1998). These high concentrations were detected during the construction of a storm water retention basin, in which the contaminated soils had to be removed and treated as hazardous waste. This resulted in higher construction costs for implementing flood prevention measures, but did not address the origin of these PAHs and its distribution along Mosel River. Hence, for future flood prevention projects, it is necessary to estimate the extent of PAH contamination along the Mosel River. The aim of the study is to determine the extent of PAH contamination in soils collected along Mosel and Saar River, and to obtain a first insight into the origin of the PAH contamination in this region. Materials and Methods  In total twenty seven sample sites were investigated. Forty two single samples were collected along a 167 km distance of Mosel River and six samples were collected along a 20 km distance of Saar River. Soil samples were collected at a depth of 0 to 2 m with a stainless steel corer (▫ 8 cm). Each 2 m sample was further separated into two sub-samples (0–1 m and 1–2 m). The sixteen EPA PAHs and three additional PAHs (1methylnaphthalene, 2methylnaphthalene and perylene) were analysed with gas chromatography mass spectrometry (GC-MS). For soil characterisation, total organic carbon (TOC), grain size, microscope and X-ray diffraction (XRD) analysis were performed. Results  Grain size for all soil samples was classified as a mixture of sand and silt. XRD analysis showed that all samples were dominated by quartz. Some clay minerals, such as illite and montmorillonite and feldspars, i.e. anorthoclase and orthoclase, were found in minor quantities. TOC ranged from 0.1% to 13%. Microscope analysis showed black coal particles in the majority of the soils collected from the Saar River and part of the Mosel River (downstream of the confluence of Saar and Mosel River). The black particles were not found further upstream along Mosel River. The sum of nineteen PAHs in the soil samples was up to 81 mg kg⁻¹ dry weight (dw). Most soil samples showed a relationship between the presence of coal particles and PAH concentrations. Discussion  Elevated PAH concentrations were found in all soil samples collected from Saar River and downstream Mosel River. Due to former coal mining activities in the Saarland, Germany, there is a strong evidence that the majority of the PAH contamination in the soils downstream Mosel River are linked to these mining activities. Upstream Mosel River coal particles were hardly found although PAH concentrations were high. Therefore another PAH source has to be responsible for these concentrations. PAH distribution patterns indicate a pyrogenic PAH input upstream Mosel River and a mixed input (petrogenic and pyrogenic) downstream Mosel River. Conclusions  Due to PAH distribution patterns, the contamination along the upstream of the Mosel River is probably linked to atmospheric depositions and other sources not linked to coal mining activities. Downstream Mosel River the PAH distribution patterns reflect former coal mining activities. We could corroborate for the first time that coal mining resulted in a serious problem of an extensive PAH contamination at Saar and Mosel River floodplain soils. Recommendations and Perspectives  Coal mining activities have a strong impact on the neighbouring regions (Johnson and Bustin 2006, Short et al. 1999, Stout et al. 2002). It is known that coals exhibit relative high PAH concentrations, especially in the low molecular weight PAHs (Chapman et al. 1996, Radke et al. 1990). However, PAHs in coals are hardly bioavailable (Chapman et al. 1996) and hence may have less adverse effects on exposed biota. They can act as sink for other hydrophobic contaminants. For the assessment of the environmental impact, a detailed study of the sorption and desorption behaviour of PAHs linked to coal particles should be carried out. ESS-Submission Editor: Dr. Ralph Portier (rportie@lsu.edu)     

Dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil microcosms amended with mushroom cultivation substrate

The potential of mushroom cultivation substrate (MCS) in bioremediation was examined in polycyclic aromatic hydrocarbon (PAH)-contaminated soil. After a 60-day incubation, 32.9% dissipation of the 15 studied PAHs was observed in MCS-amended microcosms, with anthracene, benzo(a)pyrene and benzo(a)anthracene being the most degradable PAHs. MCS significantly increased the abundance and changed the community compositions of bacteria, fungi and aromatic hydrocarbon degraders. Two species belonging to the Sordariomycetes of the Ascomycota were enriched in all MCS-treated soil samples, and coupled with the unique changes in the PAH profile, this implies the involvement of laccase-like enzymes. Limited improvement was observed after adding Pleurotus ostreatus, possibly because of its poor colonization of the soil. In addition, alfalfa appeared to antagonize the bioremediation effects of MCS. The results of this study suggest that MCS can be a cost-effective and green biostimulation agent, thereby providing support for the development of MCS-based biostimulation of PAH-contaminated soil.     

海洋细菌生物膜用于生物修复陆地生态系统中土壤多环芳烃污染

Polycyclic aromatic hydrocarbons(PAHs) in soil retain for a quite long period due to their hydrophobicity and aggregation properties. Biofilm-forming marine bacterial consortium(named as NCPR), composed of Stenotrophomonas acidaminiphila NCW702,Alcaligenes faecalis NCW402, Pseudomonas mendocina NR802, Pseudomonas aeruginosa N6P6, and Pseudomonas pseudoalcaligenes NP103, was used for the bioremediation of PAHs in a soil microcosm. Phenanthrene and pyrene were used as reference PAHs. Parameters that can affect PAH degradation, such as chemotaxis, solubility of PAHs in extracellular polymeric substances(EPS), and catechol2,3-dioxygenase(C23O) activity, were evaluated. P. aeruginosa N6P6 and P. pseudoalcaligenes NP103 showed chemotactic movement towards both the reference PAHs. The solubility of both the PAHs was increased with an increase in EPS concentration(extracted from all the 5 selected isolates). Significantly(P 0.001) high phenanthrene(70.29%) and pyrene(55.54%) degradation was observed in the bioaugmented soil microcosm. The C23O enzyme activity was significantly(P 0.05) higher in the bioaugmented soil microcosm with phenanthrene added at 173.26 ± 2.06 nmol min~(-1) mg~(-1) protein than with pyrene added at 61.80 ± 2.20 nmol min~(-1) mg~(-1) protein. The C23O activity and gas chromatography-mass spectrometer analyses indicated catechol pathway of phenanthrene metabolism. However, the metabolites obtained from the soil microcosm added with pyrene revealed both the catechol and phthalate pathways for pyrene degradation.     

In situ gradient distribution of polycyclic aromatic hydrocarbons (PAHs) in contaminated rhizosphere soil: a field study

Purpose

Little information is available heretofore on the gradient distribution of persistent organic pollutants in rhizosphere on a field scale. In this field study, we seek to explore the in situ distribution gradient of polycyclic aromatic hydrocarbons (PAHs) in rhizosphere soil proximal to the roots.

Materials and methods

Clover (Trifolium pratense L.) and hyssop (Hyssopus officinalis L.) grew in situ in the contaminated field soil near a petrochemical plant and were harvested when about 30 cm tall with mature roots. Rhizosphere soils of the plants were sampled including the rhizoplane, strongly adhering soil, and loosely adhering soil. Eleven EPA-priority PAHs were detected in each layer of rhizosphere soils in proximity to the root surface.

Results and discussion

The PAH concentrations followed the descending order of bulk soil, loosely adhering soil, strongly adhering soil, and rhizoplane soil in proximity to the root surface of clover and hyssop. The rhizosphere effect (R, in percent) on PAH distribution clearly decreased with increasing distance from the root, and a more significant decrease was observed for hyssop compared to clover. R values were generally lower for three- and four-ringed PAHs in the rhizosphere, which were more significant in loosely and strongly adhering rhizosphere layers.

Conclusions

Our field observations combined with previous potted studies demonstrated that PAH concentrations in rhizosphere soils increased with distance from the root. Results of this work provide new information on the fate of PAHs in rhizosphere.     

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...     

城市土壤多环芳烃的特征和来源解析研究进展

Polycyclic aromatic hydrocarbons (PAHs) are mainly produced by combustion processes and consist of a number of toxic compounds.They are always emitted as a mixture and have become a major type of pollutants in urban areas.The degree of soil contamination by PAHs is of special concern in areas immediately in proximity to cities with heavy traffic,factories,older buildings,and infrastructure.The accumulation of soil PAHs is also affected by non-anthropogenic factors,such as climate,vegetation,and soil property.This paper reviews three typical source identification techniques,including diagnostic ratios,positive matrix factorization,and principle conrponents analysis.The advantages or disadvantages of these techniques are analyzed.It is recommended that multiple identification techniques be used to determine the sources in order to minimize the weaknesses inherent in each method and thereby to strengthen the conclusions for PAH source identification.     

Potential role of polycyclic aromatic hydrocarbons (PAHs) oxidation by fungal laccase in the remediation of an aged contaminated soil

The transformation of PAHs by fungal laccases has been reported but there are no published studies on the direct application of free laccase in the remediation of PAHs-contaminated soil. Here we report a study in which the transformation of PAHs by a fungal laccase was studied both in reaction mixtures and in soil. Anthracene and benzo(a)pyrene were the most degradable of the 15 US Environmental Protection Agency (EPA) priority PAHs tested. Use of a redox mediator greatly enhanced the oxidation of several PAHs in reaction mixtures and the main intermediates were identified as anthraquinone for anthracene and benzo(a)pyrenyl acetate for benzo(a)pyrene as determined by GC–MS analysis. No significant correlation was found between oxidation and ionization potentials of individual PAHs. Soil microcosms were set up to test the potential of laccase to remediate an aged PAHs-contaminated soil. The laccase transformed the PAHs immediately after it was added to the soil and significant dissimilation of benzo(a)pyrene and toxic-equivalent concentration based on benzo(a)pyrene was observed after incubation for 14 days, indicating the potential of laccase to detoxify the soil. Moreover, extractable laccase activity was completely lost and the biomass of the indigenous microorganisms remained constant in the microcosms at the end of the incubation period, suggesting that the enzyme may have potential as an agent for the efficient and safe cleanup of soil contaminated with PAHs.     

Contamination of soils in the urbanized areas of Belarus with polycyclic aromatic hydrocarbons

The content of polycyclic aromatic hydrocarbons (PAHs) in the soils of urbanized areas, including the impact zones of Belarus, were studied. The concentrations of 16 PAHs in the soils were determined for individual and high-rise building zones, forests, and forest parks of Belarus. The levels of the PAH accumulation in the soils of different industrial enterprises and boiler stations were analyzed. Possible sources of soil contamination with PAHs were considered, and the structure of the PAHs in the soils was shown. The levels of the soil contamination were determined from the regulated parameters for individual compounds and the sum of 16 PAHs.     

Dissipation and sorption processes of polycyclic aromatic hydrocarbons (PAHs) to organic matter in soils amended by exogenous rich-carbon material

Purpose

The aim of the research was to assess the effect of biochar addition on aging, degradation, and sorption processes of polycyclic aromatic hydrocarbons (PAHs) to soil organic matter. The study was carried out as a sorption experiment in strictly controlled water and air conditions, which allowed for the accurate observation and prediction of PAH behavior in soils.

Materials and methods

Four soils were fortified with a PAH mixture (Fluorene-Flu, Anthracene-Ant, Phenanthrene-Phe, Pyrene-Pyr, Chrysene-Chry) at 20 mg kg^?1 of single-compound concentration level. The experiment was carried out in two trials: soils?+?5PAHs amended with biochar and soil?+?5PAHs without biochar addition with incubation times of 0, 1, 3, 6, and 9 months. After each interval time, the extractable (E-SOM) and stable organic matter (S-SOM) were measured as well as PAHs determined in two forms: total concentration (PAH-tot) and residual concentration (PAH-rest) after E-SOM extraction. The PAH loss and half-life times were estimated according to pseudo first-order kinetics equation.

Results and discussion

The amounts of PAH-tot in the soils without biochar decreased by an average of 92%, while in soil with biochar, this was 41% after 9 months of aging. The amount of PAHs-rest bounded with S-SOM after 9 months of incubation varied from 0.9 to 3.5% and 0.2 to 1.3% of the initial PAH concentration, respectively, for soils non-induced and induced by biochar. In soils without biochar, Flu, Ant, Phe, and Pyr exhibited similar T_1/2 (43–59 days), but Chry was characterized by a much higher and broader T_1/2 than other hydrocarbons (67–280 days). Biochar addition to the soils significantly influenced the half-life changes for all PAHs. The highest changes were noted for Phe (14-fold increase), and the lowest was for Flu (7-fold increase).

Conclusions

The addition of exogenous-rich carbon material such as biochar to the soil significantly changes the behavior and sorption potential of PAHs in the soil. Soils enriched with biochar are characterized by a higher persistence of PAHs, longer aging time, and lower affinity for sorption by native organic matter structures. Soils freshly polluted by PAH are mainly sorbed by E-SOM, which significantly increases their accessibility and reduces formation of bound-residues in the soil.

     

Hazard assessment of polycyclic aromatic hydrocarbons in water and sediment in the vicinity of coalmines

Purpose

Rivers feeding into the Loskop Dam, South Africa, pass through coal mining and heavily industrialised areas. Previous studies investigating mass mortalities of crocodile and fish in the river system, revealed the presence of organic compounds, including polycyclic aromatic hydrocarbons (PAHs), in their tissues.

Materials and methods

Samples were collected from nine sites within the dam in winter and summer. Liquid-liquid and microwave-assisted extraction was used for preconcentrating PAHs from water and sediment samples, respectively. Extracts were analysed by gas chromatography-mass spectrometry in the selected ion monitoring mode to determine the presence and levels of the 16 United States Environmental Protection Agency (US EPA)-priority PAHs.

Results and discussion

Significant levels of PAHs were found in both water and sediment samples. Concentrations were higher in sediments than in water, as well as in samples collected in winter. Levels of PAHs in sediments were generally higher than those reported by many researchers for other water bodies in industrialised areas. Zebrafish embryos were used to assess potential risks associated with the water and sediment, and to determine the effects of PAHs on aquatic life. Embryos, exposed to intact water and sediment samples, as well as to diluted sediment extracts, were monitored for 120 h post fertilisation. Sediment proved more toxic to zebrafish embryos than water, causing delayed embryo development and malformations.

Conclusions

These findings are alarming as they indicate that this water system is under stress. These findings can be typical of any water system situated in a coal mining and industrial region.

     

Influence of origin and properties of dissolved organic matter on the partition of polycyclic aromatic hydrocarbons (PAHs)

We investigated dissolved organic matter (DOM) from soil, sewage sludges, water from waste disposal sites, and composts as sorbents and potential carriers for hydrophobic polycyclic aromatic hydrocarbons (PAHs) in soil. Partition coefficients (expressed log K_DOC) for two 5-ring compounds were 4·8–4·9 for DOM from soil, 4·5–47 from composts, and 4·3–4·4 from sewage sludges. The DOM from compost and sewage sludge can influence the transport of non-ionic organic contaminants because of the large concentrations of dissolved organic carbon (DOC) released from these materials. Leachates from waste disposal sites did not sorb PAHs. The DOM from compost contained a large percentage of organic molecules > 14 000 Da (32–46%), whereas DOM from waste disposal leachates contained only 7-lo%, and so bound less PAHs. The percentage of total hydrophobic components, as characterized by XAD-8 chromatography, was 50 ± 9% for most of the DOM solutions and did not express the differences in affinity of the organic sorbents to PAHs in the same way as the K_DOC values. Isolated molecular-weight fractions of DOM from composts sorbed benzo(k)fluoranthene in each fraction. The log K_DOC values were 4·1–4·3 for both fractions, < 1000 and 1000–14 000 Da, and 4·8–5·0 for the fraction > 14 000 Da. The interaction of PAHs with DOM < 1000 Da cannot be explained by partitioning within intramolecular nonpolar environments of dissolved macromolecules; rather it seems to be due to the amphoteric properties of DOM. This type of interaction of PAHs with small DOM molecules might affect the mobility of hydrophobic organic chemicals in soils.     

Influence of different bulking agents on the disappearance of polycyclic aromatic hydrocarbons (PAHs) during sewage sludge composting

In order to improve properties of compost produced from sewage sludge, a wide range of additives is used. The aim of the present study has been to determine the influence of fly ash and sawdust on the range of losses of 16 PAHs (US EPA). Composting was carried out in containers in which there was sewage sludge (100%), sewage sludge with fly ash added (20 or 30% w/w) and sewage sludge with sawdust added (30% w/w). Composting was carried out for 353 days. Then the compost obtained was stored for another 300 days. The content of 16 PAHs was determined using the HPLC-UV method. After composting, in all the experimental treatments, ie, with sludge alone, and with the additions of 20% and 30% fly ash, and sawdust, decreases in the total PAH load of 87.5, 83.4, 82.9 and 88.1% respectively, were found. The content of the total PAH load was mainly determined by 3-ring compounds. In the case of these last PAHs the highest level of their disappearance (> 90%) was noted after composting. In all composts obtained, the content of PAHs was within allowable limits for biosolids that can be used for agricultural purposes. A significant lowering of total concentration of the 16 PAHs after storage period was noted only in the experimental variant with 20% of fly ash. However, the process of composts storage influenced individual PAHs.     

Evaluation of toxicity risk of polycyclic aromatic hydrocarbons (PAHs) in crops rhizosphere of contaminated field with sequential extraction

Purpose

The assessing bias of rhizosphere effect on polycyclic aromatic hydrocarbons (PAHs) degradation in soils would come out from formation of nonextractable PAHs and extractability difference of various solvents. The aim of this study was to evaluate the role of rhizosphere effect in long-term PAHs polluted soils by using sequential extraction approach.

Material and methods

The scheme of sequential extraction included methanol/water extractable PAHs, butanol extractable PAHs, DCM extractable PAHs, humic acid-bound PAHs, crude humin-bound PAHs, and organic-C enriched humin-bound PAHs. PAHs in plant tissues were extracted by dichloromethane after saponifying. The correlations between PAHs in plant tissues and sequentially extracted fractions were generated by partial least squares regression.

Results and discussion

The profiles of sequentially extracted PAHs varied with plant species. The discrepancy of toxicity equivalency concentrations between rhizosphere and bulk soils was much more significant than that of total PAHs concentrations. In partial least squares regression models, the concentration of PAHs in plant tissues was correlated with fractions strongly associated with soil.

Conclusions

The novelty of this study is the evaluation of concentration and toxicity equivalency concentration of PAHs in rhizosphere of crops sampled in a field polluted with PAHs for long term. This study has highlighted more significant role of rhizosphere in cleanup of cancerogenic toxicity of soil than amount of PAHs in polluted soils.     

Metabolism of polycyclic aromatic hydrocarbons by the wood-feeding termite Coptotermes formosanus (Shiraki)

Polycyclic aromatic hydrocarbons (PAHs) are among the most prevalent and persistent pollutants in the environment. In this study, the wood-feeding termite (WFT) Coptotermes formosanus (Shiraki) was studied regarding the potential ability to degrade two selected low-molecular-weight PAHs, phenanthrene and anthracene. Pyrolysis-gas chromatography/mass spectrometry was employed for analysis of in vivo PAH degradation by three gut segments (fore-, mid-, and hindgut) of the WFT. The results revealed the capability of lower termite for PAH metabolism, which started from the foregut and mainly occurred in the midgut region. Remediation of phenanthrene by the termite has been proposed to be initiated via hydroxylation at the C-10 position. Anthracene metabolism first occurred at the C-3, C-5, and C-12 positions with the addition of aldehyde and carbonyl groups. Ring hydroxylation, methoxylation, esterification, carboxylation, and methylation were detected on both the PAHs for ring fission, suggesting the existence of effective PAH modification activity in the alimentary canal of C. formosanus . This new PAH degradation system of the WFT provides new insights for potential technologies for bioremediation of PAH-contaminated soil and sediment based on the related lingolytic enzymes.