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Polycyclic aromatic hydrocarbons (PAHs) are hazardous organic compounds with mutagenic, genotoxic and carcinogenic properties. Although PAHs in soil can cause toxicity to microorganisms, the microbial community is able to degrade these compounds. For this reason, it is important to study acute and short-term effects of PAH contamination on soil microbial community, also to shed light on its possible exploitation in soil restoration. The effects of acute PAH contamination on the structure and metabolic activity of microbial communities in three forest (beech, holm oak, black pine) soils were studied. The soils were spiked with phenanthrene, pyrene or benzo[a]pyrene and incubated in experimental mesocosms, under controlled conditions. Enzymatic activities (laccase, total peroxidase and hydrolase), as well as microbial biomass and community structure (through phospholipid fatty acid and ergosterol analyses), were evaluated in the three soil systems 4 days after contamination and compared to no-spiked soils. In soil under holm oak, there was a stimulation of Gram+ bacteria after contamination with all the 3 PAHs, whereas in soil under pine, pyrene and phenanthrene additions mainly stimulated fungi and actinomycetes., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Microbial degradation is the main responsible for polycyclic aromatic hydrocarbons (PAHs) removal from contaminated soils, and the understanding of this process is pivotal to define effective bioremediation approaches. To evaluate the contribution of several microbial groups in soil anthracene and benzo[a]pyrene degradation, the analysis of phospholipid fatty acid (PLFA) profiles and machine learning techniques were employed. To this end, PLFAs and PAH concentrations were analysed, along 274 days of incubation in mesocosms, in soils artificially contaminated with anthracene and benzo[a]pyrene, subjected to different treatments: untreated soil and soils treated with biowaste compost or fungal consortium. Random forest models, figuring anthracene or benzo[a]pyrene concentrations as dependent variables and PLFAs as predictors, were then built to evaluate the contribution of each variable in PAH degradation. PLFA profiles varied substantially among soil treatments and along time, with the increase of Actinomycetes in soils added with fungi and other Gram+ bacteria in compost amended soils. The former, together with fungi, are primarily responsible for anthracene and benzo[a]pyrene degradation in both treated soils, a process in which also metanotrophs and other Gram+ and Gram- bacteria participate. In untreated soil, the cooperation of a multitude of different microorganisms was, instead, responsible for PAH removal, a process with lower efficiency in respect to treated soils., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Concentrations of four heavy metals (HMs) (Cd, Cr, Fe, Pb) and four polycyclic aromatic hydrocarbons (PAHs) (fluoranthene, phenanthrene, chrysene, benzo[a]pyrene) in Quercus ilex L. leaves collected at the Campania Region (Southern Italy) in previous air biomonitoring studies were employed to (1) test the correspondence with an a priori site subdivision (remote, periurban, and urban) and (2) evaluate long temporal trends of HM (approximately 20 years) and PAH (approximately 10 years) air contaminations. Overall, Q. ilex leaf HM and PAH concentrations resulted along the gradient: remote < periurban < urban sites, reflecting the a priori subdivision based on human management. Over a long time, although a clear decrease of leaf Pb, chrysene, fluoranthene, and phenanthrene concentrations occurred at the urban sites, a high contamination level persists.

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) were analysed in topsoil and in Quercus ilex L. leaves from holm oak woodlands located along urbanization gradients (urban, periurban and extraurban sites) in two Italian regions (Campania and Tuscany). In each sampling site, the metal bioavailability factors (MBFs) and the pollutant bioaccumulation factors (BAFs) were calculated to estimate the fraction of each total metal concentration in soil potentially available to root uptake and to know the fate of both HMs and PAHs in the plant-soil system. In general, the results indicated a low atmospheric deposition of pollutants and, in some cases, leaves and soils accumulated higher HM and PAH concentrations in the most urbanized areas. Correlation analyses showed that in each sampling site topsoil and leaves were exposed to the same atmospheric inputs of HMs and PAHs, although to a different extent. Notwithstanding the MBFs and BAFs differed between the two regions for the most HMs, they did not show a clear pattern in relation to the urbanization gradient. However, some information could be deduced by these ratios: the high BAF calculated for Mn shows that the foliar uptake plays an important role in accumulation of this metal. Moreover, for PAHs the different values of BAFs among low and high molecular weight compounds suggest their different fate, the first accumulated in leaves by stomata and the latter preferentially deposited on topsoil., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

For the first time until now, the results from a prediction model (Atmospheric Dispersion Modelling System (ADMS)-Road) of pollutant dispersion in a street canyon were compared to the results obtained from biomonitors. In particular, the instrumental monitoring of particulate matter (PM10) and the biomonitoring of 14 polycyclic aromatic hydrocarbons (PAHs) and 11 metals by Quercus ilex leaves and Hypnum cupressiforme moss bags, acting as long- and short-term accumulators, respectively, were carried out. For both PAHs and metals, similar bioaccumulation trends were observed, with higher concentrations in biomonitors exposed at the leeward canyon side, affected by primary air vortex. The major pollutant accumulation at the leeward side was also predicted by the ADMS-Road model, on the basis of the prevailing wind direction that determines different exposure of the street canyon sides to pollutants emitted by vehicular traffic. A clear vertical (3, 6 and 9 m) distribution gradient of pollutants was not observed, so that both the model and biomonitoring results suggested that local air turbulences in the street canyon could contribute to uniform pollutant distribution at different heights.

Soil microbial community plays a major role in removal of polycyclic aromatic hydrocarbons (PAHs) from soil, and bioremediation potentially offers an attractive and economic approach to the clean-up of polluted areas. To evaluate the contribution of different microbial groups in soil PAH degradation, enzymatic activity and phospholipid fatty acids (PLFAs) were analysed in a mesocosm trial in three different soils (two natural and one industrial) artificially contaminated with 3- and 5-rings PAHs. The Metabolic Activity Index (MAI) was applied to investigate the microbial community stability, in terms of resistance and resilience. Gram+ and Gram- bacteria were the predominant microbial groups in all soil types. In the first stage of incubation, fungi were predominant in the industrial soil, followed by mycorrhizae and actinomycetes, indicating their stimulation after PAH addition. In the two natural soils, several groups were predominant: actinomycetes in one, fungi and mycorrhizae in the other, indicating a different response of the two natural soils to PAH contamination. Regarding MAI calculated on the enzymatic activities, one natural soil showed a microbial community neither resistant nor resilient in respect to the other and to the industrial soil. Our results highlight that the microbial community changes its composition and then physiological functions according to the land use as a result of PAH addition. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) due to "long‐range atmospheric transport" can reach forest soil in areas far from anthropogenic activities. Information on microorganisms able to metabolize different PAHs helps in developing bioremediation strategies. We focused on the degradation of different molecular weight PAHs (phenanthrene, pyrene, and benzo[a]pyrene) in a biological natural attenuation process. Data on microbial biomass, growth, and enzyme activities, monitored along 360 days in mesocosms with forest soils (holm oak, black pine, and beech) artificially contaminated with the three PAHs, were analyzed by machine learning techniques, a powerful and novel approach in soil microbial ecology, still scantly employed. Nonlinear statistical learning methods (random forests) and linear‐based classifiers (linear discriminant analysis) were applied to identify which variables were able to separate distinct groups, independently from time. Random forest was also applied to evaluate the importance of each variable in determining the PAH degradation. Nonlinear statistical learning methods more accurately found patterns related to PAH exposure in soil microbial community than the linear‐based classifier. The role of fungi and their related enzymatic activities, laccase in holm oak and peroxidase in beech soil, in phenanthrene and pyrene degradation has been identified, suggesting the importance of myco‐remediation in contaminated‐site restoration. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are worldwide contaminants that, due to their long-range transport, can accumulate far from the emission sources, e.g. in forest soils. Since changes in soil microbial community can have an impact on ecosystem processes (e.g. nutrient cycling, decomposition, stress stability), studies on the succession of indigenous microbial community following exposure to PAHs are important. Most of these studies are limited to soils aged contaminated with PAHs, since our aim was to fill the knowledge gap on recent PAH contamination. To this aim, soils from three forest systems (holm oak, black pine and beech) were spiked with 3 PAHs (phenanthrene, pyrene and benzo[ a ]pyrene) and incubated under controlled conditions in mesocosm. During the first year after incubation, changes in the activity and biomass of the soil microbial community were estimated by analysing phospholipid fatty acids (PLFA), fungal biomass (ergosterol content), and fungal and bacterial growth. Findings demonstrated that PAHs affected the soil microbial community structure. Actinomycetes, fungi and Gram+-bacteria were initially resistant to PAH contamination in all the forest systems, whereas for fungi a recovery was observed at the end of incubation, such as ergosterol and growth, in holm oak and beech soils. PAH spikes seemed to have an overall negative effect on bacteria and Gram- groups in all the soils at the beginning of incubation. Considering the values of metabolic activity index (MAI), the composition of the microbial community did not seem to be resistant to the addition of PAHs. However, the soil under beech showed a slightly better resistance to contamination. Furthermore, the community structure did not appear to change in relation to the PAH considered. Overall, in the microbial community of holm oak and beech soils, different groups were able to quickly recover from the new soil conditions. • The native microbial community of forest soils is not resistant to PAH addition. • Community under holm oak and beech select taxa capable of recovering to contamination. • Holm oak and beech forests highly preserve soil ecological functions. [ABSTRACT FROM AUTHOR]

We determined genetic variation and metal and polycyclic aromatic hydrocarbon concentrations in Leptodon smithii moss collected in holm oak stands at cities, outskirts and remote areas of Campania and Tuscany (Italy) to investigate if anthropogenic pressure (pollutant emissions and land use change) affects moss genetic richness. In both regions, metal and polycyclic aromatic hydrocarbon concentrations reflected the trend urban > outskirts > remote areas, excepting Tuscany remote site. In both regions, the moss gene diversity increased from urban to remote areas. The findings suggest the extent and the fragmentation of urban green areas, as drivers of moss genetic richness. [ABSTRACT FROM AUTHOR]