Content Of Polycyclic Aromatic Hydrocarbons In Soils Research Articles

Spatiotemporal distribution, sources, and ecological risk of soil polycyclic aromatic hydrocarbons in Chinese urban agglomerations from 2000 to 2020

To investigate the spatial and temporal distribution, sources, and ecological risk of soil polycyclic aromatic hydrocarbons (PAHs) in China’s urban agglomerations from 2000 to 2020, a comprehensive search strategy was employed using the keywords “soil”, “PAHs”, and “city”. A total of 122 relevant studies that provided information on individual PAH content during the specified time period were collected. These studies encompassed 20 urban agglomerations in China, which were further categorized into two distinct periods: 2000 to 2010 and 2011 to 2020. The diagnostic ratio method and principal component analysis were employed to identify the sources of PAHs, and a risk quotient model was used to evaluate the soil ecological risk. The results revealed the average PAH content in the 20 urban agglomerations in China from 2011 to 2020 was 2,439 ± 4,633 ng·g-1, which exceeded the severe pollution level cut-off (> 1,000 ng·g-1). The soil PAH content in the period from 2011 to 2020 decreased by 28% compared to the soil PAH content in the period from 2000 to 2010. Soil PAH pollution was more severe in the northern urban agglomerations than in the southern urban agglomerations. Diagnostic ratios and principal component analysis demonstrated that the principal sources in most urban agglomerations in China were traffic and coal combustion. GeoDetector found that coal and fuel oil consumption were the main factors affecting the spatial differentiation of PAHs. The ecological risk quotient showed that approximately 80% of the urban agglomerations were at a medium-high ecological risk from 2000 to 2010, compared with 72% from 2011 to 2020. Thus, it is necessary to deepen energy structure reform to alleviate the threat of serious pollution caused by coal and fuel oil in urban agglomerations.

Prediction of PAHs Content in Soil Around Gas Stations in Beijing Based on BP Neural Network

With the rapid development of urbanization in China, the number of gas stations in cities is increasing. The composition of oil products in gas stations is complex and diverse, and a series of pollutants will be generated in the process of oil diffusion. Polycyclic aromatic hydrocarbons (PAHs) produced by gas stations can pollute the nearby soil and affect human health. In this study, soil samples (0-20 cm) near 117 gas stations in Beijing were collected, and the contents of seven PAHs were analyzed. Based on the BP neural network model, the contents of PAHs in soil of Beijing gas stations in 2025 and 2030 were predicted. The results showed that the total concentrations of the seven PAHs were 0.01-3.53 mg·kg-1. The concentrations of PAHs were lower than the soil environmental quality risk control standard for soil contamination of development land (Trial) GB 36600-2018. At the same time, the toxic equivalent concentrations (TEQ) of the above seven PAHs were lower than the standard value (1 mg·kg-1) of the World Health Organization (WHO), which they indicate a lower risk to human health. The prediction results showed that the rapid development of urbanization had a positive correlation with the increase in soil PAHs content. By 2030, the content of PAHs in Beijing gas station soil will continue to grow. The predicted concentrations of PAHs in the soil of Beijing gas stations in 2025 and 2030 were 0.085-4.077 mg·kg-1and 0.132-4.412 mg·kg-1, respectively. The contents of seven PAHs were lower than the soil pollution risk screening value of GB 36600-2018; however, the concentration of PAHs increased over time.The contents of PAHs in Chaoyang, Fengtai, and Haidian were relatively higher, which requires further attention.

Assessment of PAH content in soil and aboveground parts of Lolium perenne L. next to the communication arteries of the urban agglomeration

The research on the content of polycyclic aromatic hydrocarbons (PAHs) in soil and grass ( Lolium perenne L.) was carried out on samples collected in the city of Białystok, in north-eastern Poland. The test samples came from green belts in the vicinity of communication routes, differentiated in terms of the surrounding buildings and infrastructure and characterized by a different car traffic intensity. The highest total concentration of all sixteen PAHs in soil and grass samples was found near a large intersection at Nicholas Copernicus Street, one of the most important communication routes connecting two parts of the city. In the aboveground parts of the studied grass samples, benzo[a]pyrene was the most abundant, its content ranging from 53.8 μg/kg DM up to 91.7 μg/kg DM. On the other hand, in soil samples, much higher benzo[a]pyrene content was found, and the dominance of this compound was observed in almost every measurement location. Based on the obtained results, it was found that car traffic is a significant source of PAH emissions to the urban soil environment and urban greenery. The squares and green belts located along communication routes and intersections are the most exposed to pollution.

Concentration, source apportionment and potential carcinogenic risks of polycyclic aromatic hydrocarbons (PAHs) in roadside soils

PAHs are organic pollutants that have carcinogenic and mutagenic impacts on human health and are a subject of great concern. The soil-bound polycyclic aromatic hydrocarbons (PAHs) in the urban areas can be very lethal to human health. The concentrations, sources, and possible cancer risks of 15 PAHs were analysed by collecting roadside soil samples in Lucknow, India. The range of ∑15PAHs was found to be 478.94 ng/g to 8164.07 ng/g with a mean concentration of 3748.23 ng/g. The highest contribution (32.5%) was found to be from four-ring PAHs, followed by six-ring (24.5%) and five-ring (16.7%) PAHs. The source apportionment through diagnostic ratios ANT/(ANT + PHE) against FL-2/(FL-2+PYR) highlighted the dominance of petroleum, wood, coal, and grass combustion as sources of PAHs in the study area. Source apportionment was also done through positive matrix factorization, confirming the dominance of ‘vehicular emissions’ (49%), followed by ‘coal and biomass combustion’ (∼39%), and ‘leakages, volatilization and petroleum combustion’ (∼12%) as potential sources. The results from lifetime cancer risks (ILCR) varied in the range of 7.5 × 10−4 and 1.3 × 10 × −2 illustrating ‘high cancer risk’. The total cancer risk susceptibility of children was found to be 31% more than that of adults. The highest risk associated with toxic equivalent concentration (TEQ) was found at site S8 highlighting the impact of the presence of an international airport, and huge traffic load. The present study will prove to be useful for information related to human exposure to PAHs content in soil in the study area and as baseline study for policy makers, stakeholders, and researchers.

Reduced plant uptake of PAHs from soil amended with sunflower husk biochar

Biochar effect on the polycyclic aromatic hydrocarbons (PAHs) uptake by spring barley (Hordeum Sativum) was studied in model experiment conditions with Haplic Chernozem spiked by the high doses of benzo[a]pyrene (BaP) (400, 800 and 1200 µg kg-1), as the main marker of PAHs contamination. The relevance of the study is due to the BaP stability in natural environments and its carcinogenicity in relation to all living organisms. The express method of subcritical water extraction was used for BaP extraction from samples. The soil contamination by BaP contributed to the PAHs accumulation in soil and plants uptake from the polluted soil. It was found the 1% biochar application dose in the variant with 400 µg kg-1 contamination decreased the alone BaP and total PAHs content in soil and spring barley up to 50% compared to the contaminated variant. In soil contaminated with 800 µg kg-1 the 5% of biochar application led to the BaP content decreasing in the soil up to 56% and in the plants to 40-60%. Application of 5% biochar in the soil polluted with 1200 µg kg-1 led to the BaP and total PAHs content decreasing in soil up to 47% and 30%, respectively, plants the BaP content decreased up to 37-48%. Biochar 5% amendment effectiveness has been shown on the plants grown on the highly toxic variant contaminated with 1200 µg kg-1 BaP. The earing phase was inhibited in the spring barley plants growth at the most contaminated soil of the model experiment, whereas biochar application into the soil promoted the successful formation of the corn. The used biochar showed a high sorption capacity and its effectiveness under the soil remediation contaminated with BaP.

Content and source apportionment of polycyclic aromatic hydrocarbons in soil profile (0–100 Cm) of Urumqi petrochemical wastewater irrigation area, China

ABSTRACT For studying the level of pollution by polycyclic aromatic hydrocarbons (PAHs) in the Xinjiang Urumqi petrochemical wastewater irrigation area of farmland soil profiles, 60 soil samples were collected from the wastewater irrigation area and 3 different land-use types (cultivated land, wasteland, and forest land) were included. To investigate the distributions of PAHs in soil, the source analysis is performed using the method of characteristic ratio and the total index method. The results show that the PAHs content in the surface soil of the sewage irrigation area is 237.3–2028.6 µg/kg, with an average value of 911 µg/kg. The PAHs contents in the soil of different land-use types are in the following order: woodland > cultivated land > wasteland. In the soil profile of the polluted irrigated area, 0–40 cm is the main polluted layer, the dominant component being the 2–3-ring PAHs. The monomer concentration and the total PAHs concentration both decrease with increasing soil depth. According to the characteristic ratio and the total index method, the irrigation of petrochemical wastewater is considered the main contributor to PAHs pollution in the soil of different land types in the sewage irrigation area. In addition, there is the problem of automobile exhaust emissions and the influence of incomplete combustion.

Analysis of Migration of Polycyclic Aromatic Hydrocarbons from Sewage Sludge Used for Fertilization to Soils, Surface Waters, and Plants

In this paper, we discuss the effect sewage sludge (SS) application has on the contamination of polycyclic aromatic hydrocarbons in fertilized soils and groundwater. Morver, the contents of these compounds in plant biomass was analyzed. For six months, composted sewage sludge was introduced into sandy soil. The research was conducted under lysimetric experiment conditions with the possibility of collecting soil leachate in natural conditions. The following doses of sewage sludge were used: 0, 10, 20, 30, and 40 t/ha calculated per experimental object containing 10 kg of sandy soil. The examinations were carried out within a three-year time frame. Dactylis glomerata grass was grown on the fertilized soils. Every year, the content of polycyclic aromatic hydrocarbons (PAHs) was collected from fertilized objects and analyzed in soil leachate, which can contaminate surface water. The following six polycylic aromatic hydrocarbons defined by Polish standards were determined: benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, and benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene. Further, the content of PAHs in soils and the bioaccumulation of these compounds in cultivated plants were evaluated after each year. The results of the study showed that the increase in the dose of sewage sludge used for soil fertilization led to the rise in the amount of polycyclic aromatic hydrocarbons analyzed in the soil. The compounds migrated to cultivated plants. This phenomenon was observed especially in the first year following soil fertilization with sewage sludge. Excessive accumulation of PAHs (especially benzo(a)pyrene) was observed in plant biomass in the first year of a lysimetric experiment after sewage sludge fertilization with doses greater than 10 t/ha. The increase in bioaccumulation of this compound in plant biomass compared to control objects was 138%, 288%, and 505% after application of 20, 30, and 40 t/ha, respectively. Fertilization with sewage sludge did not cause contamination with PAHs in water leachates from the soils.

A PAH-degrading bacterial community enriched with contaminated agricultural soil and its utility for microbial bioremediation

A bacterial community was enriched with polycyclic aromatic hydrocarbons (PAHs) polluted soil to better study PAH degradation by indigenous soil bacteria. The consortium degraded more than 52% of low molecular weight and 35% of high molecular weight (HMW) PAHs during 16 days in a soil leachate medium. 16S rRNA gene high-throughput sequencing and quantitative polymerase chain reaction analyses for alpha subunit genes of ring-hydroxylating-dioxygenase (RHDα) suggested that Proteobacteria and Actinobacteria at the phylum level, Pseudomonas, Methylobacillus, Nocardioides, Methylophilaceae, Achromobacter, Pseudoxanthomonas, and Caulobacter at the generic level were involved in PAH degradation and might have the ability to carry RHDα genes (nidA and nahAc). The community was selected and collected according to biomass and RHDα gene contents, and added back to the PAH-polluted soil. The 16 EPA priority PAHs decreased from 95.23 to 23.41 mg kg−1 over 35 days. Compared with soil without the introduction of this bacterial community, adding the community with RHDα genes significantly decreased soil PAH contents, particularly HMW PAHs. The metabolic rate of PAHs in soil was positively correlated with nidA and nahAc gene contents. These results indicate that adding an indigenous bacterial consortium containing RHDα genes to contaminated soil may be a feasible and environmentally friendly method to clean up PAHs in agricultural soil.

Особенности аккумуляции и трансформации бенз(а)пирена в почве при искусственном загрязнении чернозема обыкновенного

The aim of the study. The aim of the study was to evaluate the benzo[a]pyrene (BaP) accumulation and transformation rate and pathways in soil under the model experiment conditions with artificial pollution. Location of the study. The work was carried out in the Academy of Biology and Biotechnology, Department of Soil Science and Land Resources Assessment, Southern Federal University (Rostov-on-Don), and in the Botanical Garden, Southern Federal University (Rostov-on-Don, Russia). Methodology. Extraction of BaP from the soil was carried out by the saponification method. The qualitative and quantitative determination of BaP and other polycyclic aromatic hydrocarbons (PAHs) was performed by High Performance Liquid Chromatography with fluorescence detection. Main results. The study showed that BaP accumulation in ordinary chernozem depended on the rate of pollutant addition. The first year of the experiment showed 11-40% decrease in  the soil BaP concentration, and two years later soil BaP concentration was found to decrease down to  15-44% from the initial soil BaP content. The relative soil BaP concentration decrease was found to increase with increasing rate of xenobiotic addition, and to decrease in the second year of the experiment. The increased rate of BaP addition into the soil of the model experiment led to the increase in other high molecular mass polyarenes, which indicated a fairly rapid BaP transformation in the Chernozem Ordinary. The soil PAHs content in the first year of the model experiment could be ranked as: pyrene> chrysene> fluoranthene> phenanthrene, with their bulked content exceeding 20% of the total soil PAHs content. In the second year of the experiment, a different rank pattern was observed in priiority PAHs: pyrene> chrysene> phenanthrene> fluoranthene, with their bulked content exceeding 20% of the total soil PAH content. Conclusion. The content of all PAHs, mostly of high molecular mass polyarenes, in the artificially polluted soil of the model experiment, increased with the increased rate of pollutant application, indicating a rather high degree of xenobiotics accumulation by Chernozem Ordinary. The PAHs accumulation and transformation in soil under artificial pollution showed the degradation of polycyclic PAHs into polyarenes with less number of rings (2-4 rings). During the two years of the model experiment, the concentration of BaP in the soil decreased up to 9–44%, indicating high potential of chernozemic soils for benzpyrene decomposition.

An environmentally friendly method for the determination of polycyclic aromatic hydrocarbons in different soil typologies

Environmental contextPolycyclic aromatic hydrocarbons (PAHs) are widespread organic pollutants that tend to accumulate in soil. We developed an environmentally friendly analytical method for PAHs to evaluate human health risks associated with their presence in soils. The method is feasible for the analysis of soils with widely varying PAH contamination levels, and is well suited to environmental monitoring studies of relevance to human health. AbstractA microwave-assisted extraction, with a dispersive solid-phase purification step followed by programmed temperature vaporisation–gas chromatography–tandem mass spectrometry, is proposed as an environmentally friendly, simple and cheap analytical method for polycyclic aromatic hydrocarbons (PAHs) in soil. Different extraction and clean-up operating variables were tested to achieve satisfactory analytical performances: trueness from 92 to 114%, limit of quantification (LOQ) from 0.4 to 2µgkg−1 for most PAHs and intermediate precision, calculated as relative standard deviation (RSD), below 10%. The method was validated using both Certified Reference Material and real soil samples collected at sites subjected to different human activities. PAH contents ranged from 0.11 (in holm oak forest soil) to 1mgkg−1 d.w. (in an industrial soil) according to the anthropic gradient. The soil PAH contents measured were used to estimate the risk to human health, which suggested the exposure to the PAHs in soil as a potential risk for human health, especially at the industrial site. The feasibility of the method for soils with different PAH contamination degrees makes it relevant in monitoring programs.

Comparing the removal of polycyclic aromatic hydrocarbons in soil after different bioremediation approaches in relationto the extracellular enzyme activities

A 120-day experiment was conducted to compare the removal of polycyclic aromatic hydrocarbons (PAHs) from agricultural soil after natural attenuation (NA), phytoremediation (P), mycoremediation (M), and plant-assisted mycoremediation (PAM) approaches in relation to the extracellular enzyme activities in soil. The NA treatment removed the total soil PAH content negligibly. The P treatment using maize (Zea mays) enhanced only the removal of low and medium molecular PAHs. The Pleurotus ostreatus cultivated on 30-50 mm wood chip substrate used in M treatment was the most successful in the removal of majority PAHs. Therefore, significantly (p < 0.05) highest total PAH removal by 541.4 μg/kg dw (dry weight) (36%) from all tested M treatments was observed. When using the same fungal substrate together with maize in PAM treatment, the total PAH removal was not statistically different from the previous M treatment. However, the maize-assisted mycoremediation treatment significantly boosted fungal biomass, microbial and manganese peroxidase activity in soil which strongly correlated with the removal of total PAHs. The higher PAH removal in that PAM treatment could be reflected in the following post-harvest time. Our suggested M and PAM approaches could be promising in situ bioremediation strategies for PAH-contaminated soils.

Effects of PAHs Pollution on the Community Structure of Denitrifiers in a Typical Oilfield

Agricultural soils in the oilfields have the potential risk of PAHs (polycyclic aromatic hydrocarbons) pollution, and the denitrification process with nitrate as the terminal electron acceptor might be important for soil PAHs elimination under anaerobic condition. In this study, 9 soil samples listed as JH-1 to JH-9 were collected from the JiangHan oilfield with a history of more than 50 years. Using the functional genes (nirK: Cu-nitrite reductase gene; nirS: cd1-nitrite reductase gene) involved in denitrification as biomarkers, the community structure of soil denitrifiers was investigated by quantitative-PCR and T-RFLP (terminal-restriction fragment length polymorphism) combined with clone library, and the relationship between soil properties and community structure of soil denitrifers was discussed. The result indicated that the copy numbers of nirK were higher than those of nirS in all soil samples, and the lowest copy numbers of nirK and nirS were both detected in the JH-4 with the highest PAHs content. Meanwhile, the correlation analysis also showed a negative correlation between the copy numbers of those functional genes and soil PAHs content (nirK: R2=0.54, P<0.05; nirS: R2=0.58, P<0.05). Furthermore, the result of T-RFLP indicated that the nirK community structures in different soil samples varied significantly, which was obviously unique in the sample (JH-4) with the highest PAHs content. The subsequent RDA (redundancy analysis) also demonstrated that soil PAHs content as well as the available nitrogen and phosphorus belonged to the most important factors affecting the nirK community structure in this oilfield soil. Compared with nirK, little variation was shown about the nirS community structure among the soil samples. However, the abundance of nirS-harboring pseudomonas had a remarkably positive relation with the soil PAHs content, which indicated that pseudomonas, a well known bacterial genus with strong ability to degrade organic pollutants, might be an essential driver for PAHs degradation via denitrification process in this oilfield soil.

The concentration and changes in freely dissolved polycyclic aromatic hydrocarbons in biochar-amended soil

The presence of polycyclic aromatic hydrocarbons (PAHs) in biochars hinders their environmental use. The aim of this study was to determine the freely dissolved (Cfree) PAH content in soil amended with biochar in a long-term (851 days) field experiment. Biochar was added to the soil at a rate of 30 and 45 t/ha. The addition of biochar to the soil resulted in a decrease in Σ13 Cfree PAHs by 25 and 22%, in the soil with the addition of biochar at the rate of 30 and 45 t/ha, respectively. As far as individual PAHs are concerned, in most cases a reduction in Cfree was also observed (from 3.6 to 66%, depending on the biochar rate). During the first 105 days of the experiment, the content of Σ13 Cfree in the biochar-amended soil significantly decreased by 26% (30 t/ha) and 36% (45 t/ha). After this period of time until the end of the experiment, no significant changes in Cfree were observed, regardless of the biochar rate. However, the behavior of individual PAH groups differed depending on the number of rings and experimental treatment. Ultimately, after 851 days of the experiment the content of Σ13 Cfree PAHs was lower by 29% (30 t/ha) and 35% (45 t/ha) compared to the beginning of the study as well as lower by 40% (30 t/ha) and 42% (45 t/ha) than in the control soil. The log KTOC coefficients calculated for the biochar-amended soils were higher immediately after adding biochar and subsequently they gradually decreased, indicating the reduced strength of the interaction between biochar and the studied PAHs. The obtained results show that the addition of biochar to soil does not create a risk in terms of the content of Cfree PAHs.

Distribution and risks of polycyclic aromatic hydrocarbons in suburban and rural soils of Beijing with various land uses.

We investigated the sources, distribution, and health risks of polycyclic aromatic hydrocarbons (PAHs) in soils of peri-urban Beijing. The mean concentrations of total 16 PAHs in suburban and rural soils of Beijing were 321.8 ± 408.2 and 219.2 ± 233.5ng/g, respectively. The PAH concentrations decreased along the urban-suburban-rural gradient and varied with land use categories. The industrial areas had the highest soil PAH concentrations followed by the living areas, roadsides, green areas, and agricultural areas. The major sources of PAHs in these soils were coal and biomass combustion. Traffic emission was not the dominant source of PAHs in peri-urban Beijing. At a few sites, high soil PAH contents were caused by point sources such as iron and steel plants and a wood preservative factory. The incremental lifetime cancer risks (ILCRs) of adults and children exposed to PAHs in the soils were acceptable. However, cautions should be paid to the abandoned industrial sites, which might be converted to residential area during the urbanization process.

Spatial Distribution of Polycyclic Aromatic Hydrocarbons in Soils around the Coal Waste Rock Dumps

We select a large coal waste rock dumps in Guangxi Heshan , study the characteristics of the distribution of polycyclic aromatic hydrocarbons (PAHs) in its surrounding soil and carry on a soil quality evaluation. Soil samples were collected in different distance and different depth from the dumps. After drying and filtrating the samples, we use the gas chromatography - mass spectrometry (GC - MS) technology for quantitative analysis of 16 kinds of priority pollutions of PAHs. The results show that in the plane, from the near to the distant, the content of PAHs in soil is from much to little. In vertical, from shallow to deep, the content of PAHs degressive changes. And the trend of change is from fast to slow in vertical and level. The plane distribution of PAHs in soil is mainly controlled by wind direction and slope, vertical distribution is controlled by its solubility in water and soil properties.Many kinds of PAHs in soils out of limit, which is poor soil.The 6 kinds of heavy ring PAHs which is carcinogenic is distributed in 5~15 cm of the topsoil.

PAHs in decaying Quercus ilex leaf litter: Mutual effects on litter decomposition and PAH dynamics

The investigation of the relationships between litter decomposition and polycyclic aromatic hydrocarbons (PAHs) is important to shed light not only on the effects of these pollutants on fundamental ecosystem processes, such as litter decomposition, but also on the degradation of these pollutants by soil microbial community. This allows to understand the effect of atmospheric PAH contamination on soil PAH content via litterfall. At this aim, we studied mass and PAH dynamics of Quercus ilex leaf litters collected from urban, industrial and remote sites, incubated in mesocosms under controlled conditions for 361d. The results highlighted a litter decomposition rate of leaves sampled in urban>industrial>remote sites; the faster decomposition of litter of the urban site is also related to the low C/N ratio of the leaves. The PAHs showed concentrations at the beginning of the incubation of 887, 650 and 143ngg−1d.w., respectively in leaf litters from urban, industrial and remote sites. The PAHs in litter decreased along the time, with the same trend observed for mass litter, showing the highest decrease at 361d for the urban leaf litter. Anyway, PAH dynamics in all the litters exhibited two phases of loss, separated by a PAH increase observed at 246d and mainly linked to benzo[e]pyrene.

Multi-factors influencing the spatial distribution of polycyclic aromatic hydrocarbons in soils surrounding drinking water protection zone

We selected the Guanting Reservoir in Beijing, China as a case where an industrial area locates on the upwind corner to study the influence of human activities and natural processes on the distribution of polycyclic aromatic hydrocarbons (PAHs) in soils. Soil PAH concentrations in the study area follow a log-normal probability distribution function, suggesting that distribution of PAH in soils was affected by human activities. Distribution of PAHs in soils was significantly affected by the point source that high PAH concentrations were observed in near industrial area with an obvious declining trend from the northwest to the southeast which was the prevailing wind direction in this area. Away from the influence of point source, distribution of PAHs in soils was found to significantly correlate with total organic carbon content, while the influences of agricultural land uses and type of soil texture on the total soil PAHs contents and ring compositions were quite limited. The results can provide some evidences and data on the pollutant accumulation in drink water protection area influenced by natural processes and human activities.

Content of polycyclic aromatic hydrocarbons in soils polluted with petrol and diesel oil after emediation with plants and various substances

The study was undertaken to determine the influence of compost, bentonite and calcium oxide on the content of polycyclic aromatic hydrocarbons (PAHs) in soils polluted with petrol and diesel oil, using plants as phytoremediators. Contamination of soil with petrol and diesel oil caused an increase in the total PAHs in soil. The effect of diesel oil on the content of PAHs in soil was stronger than that of petrol in the treatments with spring barley and yellow lupine &amp;ndash; maize, in reverse to spring rape &amp;ndash; oat. Pollution of soil with petroleum substances led to the increased contribution of naphthalene to the total PAHs at the expense of other hydrocarbons. Bentonite and CaO produced an evidently stronger effect on soil properties than compost, in general causing a decline in the content of PAHs in soil. The phytoremediatory effect of plants was the most beneficial in the treatment with spring rape and oat, but the weakest in trials with yellow lupine and maize. Plants were particularly effective in soil polluted with petrol.

Assessing the Potential of Rhizobacteria to Survive under Phenanthrene Pollution

Rhizobacteria possess a wide variety of qualities governing their pollutant-catabolic and rhizospheric competences. We investigated how the abilities to degrade phenanthrene and other polycyclic aromatic hydrocarbons (PAHs), to synthesize surfactants and the phytohormone indole-3-acetic acid (IAA), to be motile, and to perform chemotaxis toward phenanthrene and some potential root-exudate components were manifested in rhizobacteria isolated from oil-polluted sites. We observed that most of the examined rhizobacteria had the abilities under consideration and that in some strains, these were strongly affected by the bacterial environment. Only one strain—Sinorhizobium meliloti P221—exhibited increased PAH-degrading, surfactant-producing, and IAA-synthesizing activities, as well as distinct behavioral responses. We conclude that S. meliloti P221 can be used as a model to assess the contributions of all these activities to plant-inoculation-induced reduction in the soil PAH contents. This strain also may be useful for phytoremediation applications.

The concentrations, distribution and sources of PAHs in agricultural soils and vegetables from Shunde, Guangdong, China

The concentrations, distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in 30 agricultural soil and 16 vegetable samples collected from subtropical Shunde area, an important manufacturing center in China. The total PAHs ranged from 33.7 to 350 microg/kg in soils, and 82 to 1,258 microg/kg in vegetables. The most abundant individual PAHs are phenanthrene, fluoranthene, chrysene, pyrene and benzo(b)fluoranthene for soil samples, and anthracene, naphthalene, phenanthrene, pyrene and chrysene for vegetable samples. Average vegetable-soil ratios of total PAHs were 2.20 for leafy vegetables and 1.27 for fruity vegetables. Total PAHs in vegetable samples are not significantly correlated to those in corresponding soil samples. Principal component analyses were conducted to distinguish samples on basis of their distribution in each town, soil type and vegetable specie. Relatively abundant soil PAHs were found in town Jun'an, Beijiao, Chencun, Lecong and Ronggui, while abundant vegetable PAHs were observed in town Jun'an, Lecong, Xingtan, Daliang and Chenchun. The highest level of total PAHs were found in vegetable soil, followed by pond sediment and "stacked soil" on pond banks. The PAHs contents in leafy vegetables are higher than those in fruity vegetables. Some PAH compound ratios suggest the PAHs derived from incomplete combustion of petroleum, coal and refuse from power generation and ceramic manufacturing, and paint spraying on furniture, as well as sewage irrigation from textile industries. Soil PAHs contents have significant logarithmic correlation with total organic carbon, which demonstrates the importance of soil organic matter as sorbent to prevent losses of PAHs.