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10 páginas.- 2 figura.- 2 tablas.- 114 referencias, As is the case with many other industrial activities, the organic contaminants at military-impacted sites may pose significant hazards to the environment and human health. Given the expected increase in defense investments globally, there is a need to make society aware of the risks of emissions of organic contaminants generated by military activities and to advance risk minimization approaches. The most recent advances in environmental analytical chemistry, persistence, bioavailability and risk assessment of organic contaminants indicate that efficient risk reductions through biological means are possible. This review debates the organic contaminants of interest associated with military activities, the methodology used to extract and analyze these contaminants, and the nature-based remediation technologies available to recover these sites. In addition, we revise the military environmental regulatory frameworks designed to sustain such actions. Military activities that potentially release organic contaminants on land could be classified as infrastructure and base operations, training exercises and armed conflicts; additionally, chemicals may include potentially toxic compounds, energetic compounds, chemical warfare agents and military chemical compounds. Fuel components, PFASs, TNT, RDX and dyphenylcyanoarsine are examples of organic contaminants of environmental concern. Particularly in the case of potentially toxic and energetic compounds, bioremediation and phytoremediation are considered eco-friendly and low-cost technologies that can be used to remediate these contaminated sites. In addition, this article identifies implementing the bioavailability of organic contaminants as a justifiable approach to facilitate the application of these nature-based approaches and to reduce remediation costs. More realistic risk assessment in combination with new and economically feasible remediation methods that reduce risk by reducing bioavailability (instead of lowering the total contaminant concentration) will serve as an incentive for the military and regulators to accept nature-based approaches., We would like to thank the Spanish Ministry of Science and Innovation (PID2019-109700RB-C21) for supporting this work.

7 páginas.- 1 figura.- 3 tablas.- 47 referencias.- Supplementary data to this article can be found online athttps://doi.org/10.1016/j.scitotenv.2021.150025, There is a strong need for certified reference materials in the quality assurance of nonionic soil contaminant bioavailability estimations through physicochemical methods. We applied desorption extraction, a method recently standardized as ISO16751, to determine the bioavailable concentration of the most commonly regulated polycyclic aromatic hydrocarbon (PAH), benzo(a)pyrene (BaP), in the reference industrial soil BCR-524 with a certified BaP total concentration of 8.60 mg kg−1. This concentration represented BaP levels found in many PAH-polluted soils. The method, based on single-point extraction of the analyte desorbed into the aqueous phase by a receiving phase (Tenax or cyclodextrin), was applied ten times. The data fulfilled highly demanding quality criteria based on recovery and repeatability. The bioavailable BaP concentration detected through Tenax extraction, 1.82 mg kg−1, was comparable to bioavailable concentrations determined in field-contaminated soils and to environmental quality standards based on previously observed total BaP concentrations. There was good agreement (Student's t-test, P ≤ 0.05) with the bioavailable BaP concentration determined by cyclodextrin extraction (1.53 mg kg−1). The methods were extended to four other certified 4- and 5-ringed PAHs for comparative purposes. We suggest ways of improving of the ISO16751 standard related to further systematic assessment of the Tenax-to-soil ratio and incorporation of mass balances. Furthermore, BCR-524 is suitable for quality-assurance protocols with these methods when used in site-specific risk assessments of PAH-polluted environments., We would like to thank the Spanish Ministries of Economy and Competitiveness (CGL2016-77497-R) and Science and Innovation (PID2019-109700RB-C21) for supporting this work.

13 páginas.-- 6 figuras.- 1 tablas.- 43 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2020.143408, Partial transformation of pollutants and mobilization of the produced metabolites may contribute significantly to the risks resulting from biological treatment of soils polluted by hydrophobic chemicals such as polycyclic aromatic hydrocarbons (PAHs). Pyrene, a four-ringed PAH, was selected here as a model pollutant to study the effects of sunflower plants on the bacterial accessibility and cometabolism of this pollutant when located at a spatially distant source within soil. We compared the transformation of passively dosed 14C-labeled pyrene in soil slurries and planted pots that were inoculated with the bacterium Pseudomonas putida G7. This bacterium combines flagellar cell motility with the ability to cometabolically transform pyrene. Cometabolism of this PAH occurred immediately in the inoculated and shaken soil slurries, where the bacteria had full access to the passive dosing devices (silicone O-rings). Root exudates did not enhance the survival of P. putida G7 cells in soil slurries, but doubled their transport in column tests. In greenhouse-incubated soil pots with the same pyrene sources instead located centimeters from the soil surface, the inoculated bacteria transformed 14C-labeled pyrene only when the pots were planted with sunflowers. Bacterial inoculation caused mobilization of 14C-labeled pyrene metabolites into the leachates of the planted pots at concentrations of approximately 1 mg L−1, ten times greater than the water solubility of the parent compound. This mobilization resulted in a doubled specific root uptake rate of 14C-labeled pyrene equivalents and a significantly decreased root-to-fruit transfer rate. Our results show that the plants facilitated bacterial access to the distant pollutant source, possibly by increasing bacterial dispersal in the soil; this increased bacterial access was associated with cometabolism, which contributed to the risks of biodegradation. © 2020 Elsevier B.V., We thank the Spanish Ministries of Economy and Competitiveness ( CGL2016-77497-R ) and Science and Innovation ( PID2019-109700RB-C21 ) for supporting this work.

9 páginas.- 4 figuras.- 1 tabla.- referencias.-Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2020.137608, We studied how sunflower plants affect rhamnolipid biosurfactant mobilization of slowly desorbing fractions of polycyclic aromatic hydrocarbons (PAHs) in soil from a creosote-contaminated site. Desorption kinetics of 13 individual PAHs revealed that the soil contained initially up to 50% slowly desorbing fractions. A rhamnolipid biosurfactant was applied to the soil at the completion of the sunflower cycle (75 days in greenhouse conditions). After this period, the PAHs that remained in the soil were mainly present in a slowly desorbing form as a result of the efficient biodegradation of fast-desorbing PAHs by native microbial populations. The rhamnolipid enhanced the bioavailable fraction of the remaining PAHs by up to 30%, as evidenced by a standardized desorption extraction with Tenax, but the enhancement occurred with only planted soils. The enhanced bioavailability did not decrease residual PAH concentrations under greenhouse conditions, possibly due to ecophysiological limitations in the biodegradation process that were independent of the bioavailability. However, biodegradation was enhanced during slurry treatment of greenhouse planted soils that received the biosurfactant. The addition of rhamnolipids caused a dramatic shift in the soil bacterial community structure, which was magnified in the presence of sunflower plants. The stimulated groups were identified as fast-growing and catabolically versatile bacteria. This new rhizosphere microbial biomass possibly interacted with the biosurfactant to facilitate intra-aggregate diffusion of PAHs, thus enhancing the kinetics of slow desorption. Our results show that the usually limited biosurfactant efficiency with contaminated field soils can be significantly enhanced by integrating the sunflower ontogenetic cycle into the bioremediation design., We thank the Spanish Ministry of Economy, Industry and Competitiveness (CGL2016-77497-R), and the Andalusian Government (RNM2337). Joaquim Vila is a Serra Húnter Fellow (Generalitat de Catalunya). Sara N. Jiménez-Volkerink is recipient of a pre-doctoral fellowship from the Spanish Ministry of Science, Innovation and Universities (FPU15/06077).

8 páginas.- 6 figuras.- 40 referencias, The risks of pollution by polycyclic aromatic hydrocarbons (PAHs) may increase in bioremediated soils as a result of the formation of toxic byproducts and the mobilization of pollutants associated to suspended colloids. In this study, we used the motile and chemotactic bacterium Pseudomonas putida G7 as an experimental model for examining the potential role of bacterial motility in the cometabolism and biosorption of pyrene in a porous medium. For this purpose, we conducted batch and column transport experiments with 14C-labelled pyrene loaded on silicone O-rings, which acted as a passive dosing system. In the batch experiments, we observed concentrations of the 14C-pyrene equivalents well above the equilibrium concentration observed in abiotic controls. This mobilization was attributed to biosorption and cometabolism processes occurring in parallel. HPLC quantification revealed pyrene concentrations well below the 14C-based quantifications by liquid scintillation, indicating pyrene transformation into water-soluble polar metabolites. The results from transport experiments in sand columns revealed that cometabolic-active, motile cells were capable of accessing a distant source of sorbed pyrene. Using the same experimental system, we also determined that salicylate-mobilized cells, inhibited for pyrene cometabolism, but mobilized due to their tactic behavior, were able to sorb the compound and mobilize it by biosorption. Our results indicate that motile bacteria active in bioremediation may contribute, through cometabolism and biosorption, to the risk associated to pollutant mobilization in soils. This research could be the starting point for the development of more efficient, low-risk bioremediation strategies of poorly bioavailable contaminants in soils. © 2020 Elsevier B.V., We thank the Spanish Ministry of Economy, Industry and Competitiveness (CGL2016-77497-R), the Andalusian Government (RNM 2337), and the European Commission (LIFE15 ENV/IT/000396). Joaquim Vila is a Serra Húnter Fellow (Generalitat de Catalunya).

8 páginas.- 3 ilustraciones.- 4 tablas.- 72 referencias.- Supplementary data to this article can be found online a https://doi.org/10.1016/j.scitotenv.2021.14743, In this study we first measured the mineralization of pyrene on leaves of urban holm oak (Quercus ilex) by autochthonous microorganisms and an inoculated PAH degrading bacterium (i.e., Mycobacterium gilvum), selected as a model phyllosphere species, as well as the leaf-water (KLW) and leaf-air (KLA) partition coefficients for this chemical. Mineralization was investigated in two different experimental systems in terms of leaf and microorganism environment. Additionally, the influence on pyrene partitioning and mineralization when particulate matter (PM) was present on the leaf surface or removed was studied. Mineralization of 14C-labeled pyrene by autochthonous microorganisms was lower than 1% after approximately two weeks, while M. gilvum mineralized 5% to 17% of pyrene. These extents corresponded to mineralization half-lives that ranged between ~30 to ~200 days. We proposed that PM present at the leaf surface reduced the accumulation of pyrene by inner compartments (cuticle) distantly located from microbial cells and enhanced the bioaccessibility of pyrene, speeding up microbial activity and therefore mineralization. These results highlight that plant-phyllosphere microorganism interaction is more complex than currently established and deserves additional studies to further comprehend the air purification ecosystem service of phyllosphere microorganisms. © 2021 Elsevier B.V., We would like to acknowledge the Italian Society of Ecology (SItE) and the “Luigi and Francesca Brusarosco” Prize for supporting ET as visiting scientist at IRNAS, the University of Insubria for supporting the Post Doc salary of ET, and the Spanish Ministry of Science, Innovation and Universities (CGL2016-77497-R and PID2019-109700RBC21), for supporting the work of R. Posada-Baquero and J.J Ortega-Calvo.

7 páginas.-- 4 figuras.-- 6 tablas.-- 18 referencias.-- Supplementary data to this article can be found online at https://doi. org/10.1016/j.scitotenv.2019.03.056, The application of a rhamnolipid biosurfactant for enhanced solubilization and biodegradation of slowly desorbing polycyclic aromatic hydrocarbons (PAHs) in contaminated soils was determined in this study. The soil samples exhibited different levels of pollution and different bioremediation stages: the first soil originated from a creosote-polluted site, contained 4370 mg kg −1 of PAHs and had not been bioremediated; the second soil was the same as the first but had received bioremediation treatment with nutrient amendment in biopiles for a period of 5 months and contained 580 mg kg −1 of PAHs after this treatment; the third soil was treated by bioremediation for several years to reduce the concentration of PAHs to 275 mg kg −1 . The kinetics of PAH desorption were determined to assess the magnitude of the slowly desorbing fractions present in the polluted soil and to optimize the biosurfactant effectiveness in terms of biodegradation. The soils that had been treated by bioremediation were enriched in slowly desorbing PAHs. The rhamnolipid at a concentration above its critical micelle concentration enhanced biodegradation in the soils that had been bioremediated previously. The measurement of residual concentrations of native PAHs showed the promoting effect of the biosurfactant on the biodegradation of the slowly desorbing fractions. Interestingly, benzo(a)pyrene was biodegraded in the soil that had been bioremediated for a long time. Rhamnolipid can constitute a valid alternative to chemical surfactants in promoting the biodegradation of slow-desorption PAHs, which is one of the most important problems in bioremediation, but the efficiency depends strongly on the bioremediation stage in which the biosurfactant is applied, We thank the Spanish Ministry of Economy, Industry and Competitiveness (CGL2016-77497-R), the Andalusian Government (RNM 2337) and the European Commission (LIFE15 ENV/IT/000396) for supporting this work., 2021-06-10

10 páginas.- 7 figuras.- 96 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2020.139893., Urban trees provide important ecosystem services, including air quality improvement. Polycyclic aromatic hydrocarbons (PAHs) are among the most important pollutants in air, due to their elevated concentrations and toxicity. Plants can act as filters of PAHs and as "chemical reactors" for pollutant removal, therefore reducing air concentrations. Here, the first assessment of photo- vs. biodegradation of PAHs on leaves of urban trees is presented. A dynamic air-vegetation-soil model (SoilPlusVeg) was improved to simulate the fate of two representative PAHs with contrasting physico-chemical properties (phenanthrene and benzo[a]pyrene). Simulations were performed for two different environmental scenarios from Italy (Como and Naples), selected for their dissimilar meteorological parameters, plant species and emission levels. The effect of photo- and biodegradation on leaf concentrations and fluxes towards air and soil was investigated comparing deciduous (maple, cornet and hazelnut) and evergreen (holm oak) broadleaf woods. The results showed that biodegradation in the phyllosphere could not be neglected when evaluating the ecosystem services provided by urban trees, as this process contributed significantly to the reductions (up to 25% on average) in PAH leaf concentrations and fluxes to air and soil; however, the reductions revealed ample variations with time (up to more than two orders of magnitude) showing the dependence on meteorological parameters, air compartment structure, as well as type of woods. These findings permitted to improve the ecological realism of the simulations and obtain more accurate results when predicting organic contaminant uptake and release by plant leaves, including potential for food chain transfer and long-range transport. (C) 2020 Elsevier B.V. All rights reserved., the University of Insubria for supporting the Post Doc of ET and the Spanish Ministry of Science, Innovation and Universities (CGL2016-77497-R), for supporting the work of R. Posada-Baquero and J.J Ortega-Calvo.

7 páginas.- 4 figuras.- 3 tablas.- 23 referencias, We applied a standardized desorption extraction method (Tenax extraction), to assess the bioavailability of native polycyclic aromatic hydrocarbons (PAHs) present in contaminated soils. Single-time point Tenax extraction at 20 h has been recently proposed by the International Organization for Standardization as one of the chemical methods to measure environmental bioavailability of nonionic pollutants (ISO/TS 16751). This work is one of the first ones that use this ISO method systematically in the field of bioremediation, and shows its advantages when used in combination with total concentrations determined with conventional, exhaustive solvent extraction. This method has been applied to different PAHs contaminated soils which had a different level of total PAHs (66-4370 mg kg(-1)) and which were from different contaminated sites and dissimilar bioremediation approaches. Inmost samples the study was focused on phenanthrene and benzo(a)pyrene as representative pollutants, although the profile of total PAHs was also studied in some samples. The results from this study show that the pollutant fractions extracted with Tenax during 20 h (D20) decreased after traditional bioremediation (biostimulation and phytoremediation), but they often increased in bioavailability-oriented treatments involving either biosurfactants or bioaugmentation with specialized microbial inocula. Therefore, D20-based assessments provided information on the bioremediation performance, not directly evident through the measurement of total PAH concentrations. (C) 2019 Elsevier B.V. All rights reserved., We thank the Spanish Ministry of Economy, Industry and Competitiveness (CGL2016-77497-R), the Andalusian Government (RNM 2337) and the European Commission (LIFE15 ENV/IT/000396) for supporting this work. We also thank to Ilaria Re (Consorzio Italbiotec), from the LIFE BIOREST project, for the provision of the soil samples from Italy and France used in thiswork, to Fabrizio Beltrametti (Actygea SRL), for the inoculated consortia used in bioaugmentation experiments, as well as to M. Grifoll from University of Barcelona, for the provision of samples 1 and 2 from the creosote polluted site.

15 páginas.-- 2 figuras.-- 1 tabla.-- 73 referencias.--Proceeding of the third annual meeting of the COST Action FP1305 “Biolink” (www.bio-link.eu), held in Rome on 17–19 November, 2015, The bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil can be enhanced through a variety of microbial and plant functions, that can be incorporated into optimized bioremediation technologies. In this review, we examine the potential of (bio)surfactants, the chemotactic mobilization of pollutant-degrading bacteria, and the role of bacterial attachment, to enhance biodegradation of PAHs. Plants can also play an active role in enhancing bioavailability of PAHs through rhizosphere-related mechanisms associated to specific exudate components that affect bacterial chemotaxis, pollutant mobilization, and intra-aggregate bacterial growth., This study was supported by the Spanish Ministry of Science and Innovation (CGL2013-44554-R and CGL2016-77497-R), the Andalusian Government (RNM 2337), and the European Commission (LIFE15 ENV/IT/000396).

The microbial accessibility of native phenanthrene and pyrene was determined in soils representing background scenarios for pollution by polycyclic aromatic hydrocarbons (PAHs). The soils were selected to cover a wide range of concentrations of organic matter (1.7-10.0%) and total PAHs (85-952 μg/kg). The experiments included radiorespirometry determinations of biodegradation with 14C-labeled phenanthrene and pyrene and chemical analyses to determine the residual concentrations of the native compounds. Part of the tests relied on the spontaneous biodegradation of the chemicals by native microorganisms; another part also involved inoculation with PAH-degrading bacteria. The results showed the recalcitrance of PAHs already present in the soils. Even after extensive mineralization of the added 14C-PAHs, the concentrations of native phenanthrene and pyrene did not significantly decrease. We suggest that aging processes operating at background concentrations may contribute to recalcitrance and, therefore, to ubiquitous pollution by PAHs in soils., Support for this research was provided by the Spanish Junta de Andalucía (projects “Diagnóstico de la Situación Ambiental del Campo de Gibraltar” and PAI RNM 312), and the Spanish Ministry of Science and Innovation (CGL2007-64199 and CGL2010-22068-C02-01).

The phenylurea herbicide diuron [N-(3,4-dichlorophenyl)-N,N-dimethylurea] is widely used in a broad range of herbicide formulations and, consequently, it is frequently detected as a major soil and water contaminant in areas where there is extensive use. Diuron has the unfortunate combination of being strongly adsorbed by soil organic matter particles and, hence, slowly degraded in the environment due to its reduced bioavailability. N-Phenylurea herbicides seem to be biodegraded in soil, but it must be kept in mind that this biotic or abiotic degradation could lead to accumulation of very toxic derived compounds, such as 3,4-dichloroaniline. Research was conducted to find procedures that might result in an increase in the bioavailability of diuron in contaminated soils, through solubility enhancement. For this purpose a double system composed of hydroxypropyl-β-cyclodextrin (HPBCD), which is capable of forming inclusion complexes in solution, and a two-member bacterial consortium formed by the diuron-degrading Arthrobacter sulfonivorans (Arthrobacter sp. N2) and the linuron-degrading Variovorax soli (Variovorax sp. SRS16) was used. This consortium can achieve a complete biodegradation of diuron to CO 2 with regard to that observed in the absence of the CD solution, where only a 45% biodegradation was observed. The cyclodextrin-based bioremediation technology here described shows for the first time an almost complete mineralization of diuron in a soil system, in contrast to previous incomplete mineralization based on single or consortium bacterial degradation.

The aim of this work was to develop a method to assess the microbial accessibility of native phenanthrene present in soils and sediments. We developed an accelerated biodegradation assay, characterized by (a) inoculation with a sufficient number of phenanthrene-degrading microorganisms, (b) monitoring of the biodegradation activity through 14C-mineralization measurements, and (c) single-step chemical analysis of the native compound in the residue. The use of 14C-labeling allowed the determination of the time period needed for biodegradation of the bioaccessible fraction of the native chemical. The method was tested with environmental samples having a wide range of phenanthrene concentrations, i.e., from background levels (microg kg(-1)) originating in soil from atmospheric deposition, to acute concentrations (g kg(-1)) corresponding to industrial pollution of soils and sediments. The results showed a wide range of bioaccessibility (15-95% of the initial amount). The method can be used for the assessment of bioaccessibility involved in the management of polycyclic aromatic hydrocarbon (PAH) pollution.

Given the difficulties caused by low-permeable soils in bioremediation, a new electrokinetic technology is proposed, based on laboratory results with phenanthrene, to afford bioremediation of polycyclic aromatic hydrocarbons (PAH) in clay soils. Microbial activity in a clay soil historically polluted with creosote was promoted using a specially designed electrokinetic cell with a permanent anode-to-cathode flow and controlled pH. The rates of phenanthrene losses during treatment were tenfold higher in soil treated with an electric field than in the control cells without current or microbial activity. Results from experiments with Tenax-assisted desorption and mineralization of 14C-labeled phenanthrene indicated that phenanthrene biodegradation was limited by mass-transfer of the chemical. We suggest that the enhancement effect of the applied electric field on phenanthrene biodegradation resulted from mobilization of the PAH and nutrients dissolved in the soil fluids.

10 páginas.- 2 figuras.- 4 tablas.- referenicas.-Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2023.161600., The productive application of motile microorganisms for degrading hydrophobic contaminants in soil is one of the most promising processes in modern remediation due to its sustainability and low cost. However, the incomplete biodegradation of the contaminants and the formation of the intermediary metabolites in the process may increase the toxicity in soil during bioremediation, and motile inoculants may mobilize the pollutants through biosorption. Therefore, controlling these factors should be a fundamental part of soil remediation approaches. The aim of this study was to evaluate the sources of risk associated with the cometabolism-based transformation of 14C-labeled pyrene by inoculated Pseudomonas putida G7 and identify ways to minimize risk. Our model scenario examined the increase in bioaccessibility to a distant source of contamination facilitated by sunflower (Helianthus annuus L.) roots. A biochar trap for mobilized pollutant metabolites and bacteria has also been employed. The experimental design consisted of pots filled with a layer of sand with 14C-labeled pyrene (88 mg kg−1) as a contamination focus located several centimeters from the inoculation point. Half of the pots included a biochar layer at the bottom. The pots were incubated in a greenhouse with sunflower plants and P. putida G7 bacteria. Pots with sunflower plants showed a higher biodegradation of pyrene, its mobilization as metabolites through the percolate and the roots, and bacterial mobilization toward the source of contamination, also resulting in increased pyrene transformation. In addition, the biochar layer efficiently reduced the concentrations of pyrene metabolites collected in the leachates. Therefore, the combination of plants, motile bacteria and biochar safely reduced the risk caused by the biological transformation of pyrene., We would like to thank the Spanish Ministries of Economy and Competitiveness (CGL2016-77497-R) and Science and Innovation (PID2019-109700RB-C21 and PRIMA project PCI2020-111967) for supporting this work. We also acknowledge the European Union's Horizon 2020 research and innovation program (Marie Sklodowska-Curie grant agreement no. 895340; BIOTAC project)