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10 páginas.- 4 figuras.- 4 tablas.- 45 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.2c03149, Recent research has demonstrated that chemotactic bacteria can disperse inside microsized pores while traveling toward favorable conditions. Microbe–microbe cotransport might enable nonmotile bacteria to be carried with motile partners to enhance their dispersion and reduce their deposition in porous systems. The aim of this study was to demonstrate the enhancement in the dispersion of nonmotile bacteria (Mycobacterium gilvum VM552, a polycyclic aromatic hydrocarbon-degrader, and Sphingobium sp. D4, a hexachlorocyclohexane-degrader, through micrometer-sized pores near the exclusion-cell-size limit, in the presence of motile Pseudomonas putida G7 cells. For this purpose, we used bioreactors equipped with two chambers that were separated with membrane filters with 3, 5, and 12 μm pore sizes and capillary polydimethylsiloxane (PDMS) microarrays (20 μm × 35 μm × 2.2 mm). The cotransport of nonmotile bacteria occurred exclusively in the presence of a chemoattractant concentration gradient, and therefore, a directed flow of motile cells. This cotransport was more intense in the presence of larger pores (12 μm) and strong chemoeffectors (γ-aminobutyric acid). The mechanism that governed cotransport at the cell scale involved mechanical pushing and hydrodynamic interactions. Chemotaxis-mediated cotransport of bacterial degraders and its implications in pore accessibility opens new avenues for the enhancement of bacterial dispersion in porous media and the biodegradation of heterogeneously contaminated scenarios., This research was funded by European Union's Horizon 2020 research and innovation program under the Marie Sklodowska- Curie grant agreement no. 895340 (BIOTAC project) and by the Spanish Ministry of Science and Innovation (PID2019- 109700RB-C21) .

34 páginas.- 2 figuras.- 3 tablas.- 225 referencias, The evaluation of a chemical substance's persistence is key to understanding its environmental fate, exposure concentration, and, ultimately, environmental risk. Traditional biodegradation test methods were developed many years ago for soluble, nonvolatile, single-constituent test substances, which do not represent the wide range of manufactured chemical substances. In addition, the Organisation for Economic Co-operation and Development (OECD) screening and simulation test methods do not fully reflect the environmental conditions into which substances are released and, therefore, estimates of chemical degradation half-lives can be very uncertain and may misrepresent real environmental processes. In this paper, we address the challenges and limitations facing current test methods and the scientific advances that are helping to both understand and provide solutions to them. Some of these advancements include the following: (1) robust methods that provide a deeper understanding of microbial composition, diversity, and abundance to ensure consistency and/or interpret variability between tests; (2) benchmarking tools and reference substances that aid in persistence evaluations through comparison against substances with well-quantified degradation profiles; (3) analytical methods that allow quantification for parent and metabolites at environmentally relevant concentrations, and inform on test substance bioavailability, biochemical pathways, rates of primary versus overall degradation, and rates of metabolite formation and decay; (4) modeling tools that predict the likelihood of microbial biotransformation, as well as biochemical pathways; and (5) modeling approaches that allow for derivation of more generally applicable biotransformation rate constants, by accounting for physical and/or chemical processes and test system design when evaluating test data. We also identify that, while such advancements could improve the certainty and accuracy of persistence assessments, the mechanisms and processes by which they are translated into regulatory practice and development of new OECD test guidelines need improving and accelerating. Where uncertainty remains, holistic weight of evidence approaches may be required to accurately assess the persistence of chemicals. Integr Environ Assess Manag 2022;1–34. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

10 páginas.- 6 figuras.- 1 tabla.- referencias .- . Supplementary data Figures showing the FIB-SEM images of the membrane bioreactor experiments, the tactic response of Pseudomonas putida G7 under sonication conditions in transport assays and capillary test and bioreactor transport experiments with different concentrations of the chemoeffectors. Tables showing the experimental growth control with chemical effectors and bacterial accessibility to the different porous fractions of contaminated soil. Supplementary data to this article can be found online at: doi.org/10.1016/j.scitotenv.2022.154938, A major cause of high bioremediation endpoints is the limited bioaccessibility to residual contaminants resting in soil pores with diameters close to the size exclusion limit of bacterial cells. Under nongrowing conditions and in the absence of hydraulic flow, we examined how the tactic behavior of motile, contaminant-degrading Pseudomonas putida G7 cells (2 × 1 μm) influenced passage through membranes with pores ranging in size from 1 μm to 12 μm. The bacteria were spontaneously retained by the membranes - even those with the largest pore size. However, the cells were mobilized through 5 μm and 12 μm pores after the application of an attractant (salicylate). Mobilization also occurred by attraction to the common root exudate constituents γ-aminobutyric acid and citrate and repellence (or negative taxis) to zero-valent iron nanoparticles. The observed pore size threshold for tactic mobilization (5 μm) and unaltered cell fluxes and effective cell diffusion against different chemoeffector strengths and concentrations suggest that there is a physical constraint on the gradient sensing mechanism at the pores that drives the tactic response. Our results indicate that chemically mediated, small-scale tactic reactions of motile bacteria may become relevant to enhance the bioaccessibility of the residual contaminants present in micrometer-sized soil pores., We would like to thank the Spanish Ministries of Economy and Competitiveness (CGL2016-77497-R) and Science and Innovation (BES-2017-079905 and PID2019-109700RB-C21) for supporting this work

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.

2 páginas.- 6 referencias.- Free Accessr.- This is a letter to Waring et al., https://doi.org/10.1111/gcb.15850, In an article published recently, Waring et al. (2020) introduced a conceptual framework, named PROMISE, to explore controls on belowground carbon cycling. This “fundamentally novel approach to measuring and modeling critical carbon cycle processes” represents soil pore space as an array of possible particle locations belonging to one of three pore size classes. Several aspects of this conceptual framework raise questions about its adequacy to describe the fate of carbon in heterogeneous soils. More than a decade ago already, Kuka et al. (2007) advocated the significance of the size of pores when modeling carbon turnover in soils and proposed a model, called CIPS (“Carbon Turnover in Pore Space”), which is not mentioned by Waring et al. (2020) even though in several respects, CIPS is very similar to PROMISE, and shares the same aims and approach. In CIPS, pores are also divided into three classes according to their size. Like PROMISE, CIPS does not assume any spatial arrangement, distance, or differences in connectivity among the three classes of pores.

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.

8 páginas.- 5 tablas.- 58 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.soilbio.2020.107722, The interaction between root exudates and soil microbes has been hypothesised as the primary mechanism for the biodegradation of organic pollutants in the rhizosphere. However, the mechanisms governing this loss process are not completely understood. This study aimed to investigate the effect of two important compounds within root exudates (citric and malic acid) on 14C-phenanthrene desorption and bioaccessibility in soil. Overall results showed that the presence of both citric and malic acid (>100 mmol l−1) enhanced the desorption of 14C-phenanthrene; this appeared to be concentration dependant. Increases in extractability were not reflected in a higher bioaccessibility. Despite enhancing the desorption of 14C-phenanthrene in soil, there is no direct evidence indicating that citric or malic acid have the ability to promote the biodegradation of 14C-phenanthrene from soil. Results from this study provide a novel understanding of the role that substrates, typically found within the rhizosphere due to root exudation, play in the bioaccessibility and biodegradation of hydrocarbons in contaminated soil., GVC would like to thank the Mexican National Council for Science and Technology (CONACyT) for their financial support through a scholarship (No. 313807 ) to pursue postgraduate studies at the Lancaster Environment Centre, Lancaster University.

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).

4 páginas.- 2 referencias, The bioavailability of potentially hazardous organic chemicals (persistent organic pollutants, pesticides, biocides, pharmaceuticals, and others) in soil and sediment has a major impact on the environmental and human health risks of these chemicals and is an important area of scientific research. However, this area remains only partially recognized by regulators. Based on the positive experiences from the previous implementation for metals, regulatory frameworks have recently started to include bioavailability within retrospective risk assessment (rRA) and remediation for organic chemicals. In this regard, realistic decision-making in terms of hazard definition and priority setting will ensure the protection of environmental and public health, in contrast to the established approach of using total extractable concentrations, which has been shown to be inappropriate. Moreover, by addressing bioavailability reduction instead of only pollutant removal as a paradigm shift, new remediation strategies become possible. However, the implementation of bioavailability for rRA remains difficult because scientific developments on bioavailability do not always translate into practical approaches for regulators, thus requiring specific measures. For the same reason, bioavailability remains largely unexplored within prospective regulatory frameworks (e.g., REACH, pesticide RA) that address the approval and regulation of organic chemicals.

Biodegradable chemicals may become persistent due to reductions in their bioavailability thereby impacting on the rate and extent of biodegradation in soils and sediments. This chapter examines this – commonly neglected – contradictory face of persistence assessments from the light of the latest advancements in bioavailability science. They include the microbial influences on bioavailability, the different sorption capacities of carbonaceous components of soils and sediments, and the dissimilar bioavailability shown by chemicals when they are present as non-extractable residues. We also discuss possible pathways to improve the realism in persistence assessments from standardized biodegradation tests by incorporating new bioavailability-based approaches. Innovations of the standard tests are possible through the modified chemical application of enhanced dispersion and passive dosing. In addition, we offer a proposal for integrating bioavailability measurements into standard simulation tests with soils and sediments, by using desorption extraction and passive sampling methods to assess the removal of the bioavailable fractions, in addition to the total extractable concentration of the chemical., We thank the Spanish Ministry of Science, Innovation and Universities (CGL2016-77497-R), for supporting the work of J.J Ortega-Calvo.

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).

10 páginas.-- 5 figuras.-- 2 tablas.-- 53 referencias.-- Supplementary data to this article can be found online at https://doi.org/10.1016/j.impact.2018.08.001., Previous reports on how carbon nanomaterials (CNMs) affect the biodegradation and mineralization of organic contaminants are mainly limited to pure culture studies, but little is known about the mineralization process by more complex and environmentally-relevant microbial communities. This study investigated the impact of fullerenes C60 and two multi-walled carbon nanotubes (outer diameter 50 nm: M50) at 300 and 3000 mg/kg on the mineralization kinetics of 14C-phenanthrene (18.5 mg/kg) by indigenous microorganisms in a natural soil for 120 days. Phenanthrene mineralization kinetics fitted well with the logistic growth equation regardless of the CNMs present (R2 = 0.965–0.985). The maximum mineralization rates and the total mineralization fraction were positively correlated with the initial phenanthrene bioavailability, assessed via β-HPCD extraction. Phenanthrene exposure induced significant responses of the catabolic gene biomarker nidA, fungi and bacteria communities by 275, 30, and 5 times, respectively, indicating a non-neglectable role of the fungal communities in phenanthrene mineralization. CNMs exerted a sorption- and level-dependent suppression (7.4–47.2%) on the total phenanthrene mineralization fractions at 120 d. Carbon nanotubes (300, 3000 mg/kg) caused significant adverse effects on the biomass of bacterial (47.8–60.7%), fungal (31.4–71.6%) and nidA-carrying degraders (25.7–59.9%) in the absence or presence of phenanthrene, which contributed to the inhibition of the total mineralization fractions at 120 d. Bacterial community structure was not significantly impacted by CNMs alone or co-exposure of CNM-phenanthrene. However, the fungal community showed a significant shift upon exposure to carbon nanotubes, especially M8, with the relative abundance of potential PAH degraders repressed (8.5–40.3%) at both levels of M8 tested. This corroborates the higher sensitivity of fungal communities. The findings from this study are important to inform how the released CNMs affect soil microbial communities that play a key role in the fate and remediation of organic contaminants in soil., This study was supported by the National Science Fund for Distinguished Young Scientist ( 41525005 ), the 973 Program ( 2014CB441104 ), National Natural Science Foundation of China ( 41390240 and 41629101 ), and the 111 Program ( B14001 ).

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.

Comunicación oral presentada en el 11º Congreso Ibérico y 8º Iberoamericano de Contaminación y Toxicología Ambiental los días 11, 12 y 13 de julio de 2018, Polycyclic aromatic hydrocarbons (PAHs) are the best representatives of chemicals for which specific limitations in bioremediation exist due to low bioavailability. The residual concentrations of the PAHs after bioremediation are crucial because they may limit the use of the area after treatment, or land use might not even be possible if the residual concentrations do not meet the legal requirements. For this reason bioavailability should be incorporated into soil bioremediation and a very important question is how should it be measured. One of the chemical methods which has been proposed to measure bioavailability of PAHs is the desorption extraction with Tenax during 20 h (ISO 17402) (Environ. Sci. & Technol. 49, 10255-10264, 2015; Environ Toxicol Chem 20:706¿711, 2001; Integr Environ Assess Manag, 11:208¿220, 2015). We have used this method in a greenhouse experiment in which different strategies have been used (use of microorganisms, plants and (bio)surfactants) in a PAHs contaminated soil, oriented to decrease the fraction of bioavailable pollutants. These agents have been shown previously in our group to act as bioavailability-promoting agents (Environ. Technol. 21, 1099-1110, 2000; Soil Biology and Biochemistry, 57, 830-840, 2013; Environ. Sci. & Technol. 45, 3019-3026, 2011). The greenhouse experiment was carried out with a creosote polluted soil with a total concentration of PAHs of 500 mg/kg. For this study, we used sunflower plants and a rhamnolipid biosurfactant (R90). There were four different treatments: contaminated soil (used as control); contaminated soil with rhamnolipid; planted contaminated soil; and planted contaminated soil with rhamnolipid. After certain time intervals, the soil was sampled in the different treatments. The rhamnolipid was applied to the soil after 75 days of treatment. The total concentration of PAHs was determined by Soxhlet extraction and HPLC analysis; the bioavailable concentration was determined by Tenax extraction. In addition, separate biodegradation experiments were designed in soil slurries to test the disappearance of the chemicals in these greenhouse samples under laboratory conditions (using an excess of nutrients, radiorespirometry determinations with 14C-pyrene and analysis of residual concentrations of native PAHs). These analytical methodologies have been previously used in our laboratory (Environ. Sci. Technol 45, 3019-3026, 2011). The most relevant result in this study was that bioavailability increases in planted soils receiving rhamnolipids, as evidenced by Tenax extraction and it was accompanied by an increased biodegradation in soil slurries. In conclusion, Tenax extraction during 20 h has resulted a reliable and robust method to determine bioavailable concentrations in a wide set of operational conditions ranging from a different time scale to dissimilar treatments (planting, biosurfactant application, etc.).

Resumen de la comunicación presentada en el 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water (New Orleans), LA 18-22, march 2018

Poster presentado en el 28th Annual Meeting of the Society of Environmental Toxicology and Chemistry- Europe (SETAC Europe), Rome, (Italy) 13 – 17 May 2018, Regulators are starting to consider bioavailability within retrospective risk assessment frameworks for organic chemicals, however, implementation is not straightforward because the developments of bioavailability science have not always been translated into ready-to-use approaches for regulators. Possible pathways for translating bioavailability science into regulation of organic chemicals have recently been identified (Environ. Sci. Technol. 49:10255-10264, 2015). A simplified approach was proposed in which the assessments of soil/sediment and the target chemicals should be based on two measurable values: the total extractable concentration and the bioavailable concentration as measured with robust and reproducible chemical and/or biological methods. One of the chemical methods which has been proposed to measure bioavailability of hydrophobic chemicals (HOCs) such as PAHs is the desorption extraction with Tenax during 20 h (ISO 17402) (Environ. Toxicol. Chem. 20:706–711, 2001; Integr Environ Assess Manag, 11:208–220, 2015). Understanding the role of bioavailability in the biodegradation of chemicals is relevant not only for retrospective contaminated land management but also prospective risk assessment applied in the approval and regulation of organic chemicals. With the aim of providing pathways for implementation into regulatory contexts, we carrying out desorption extraction measurements with Tenax in a greenhouse experiment in which different strategies (use of microorganisms, plants and (bio)surfactants) in a PAHs contaminated soil, oriented to decrease the fraction of bioavailable pollutants. The most relevant result in this study was that bioavailability increases in planted soils receiving rhamnolipids, as evidenced by Tenax extraction and it was accompanied by an increased biodegradation in soil slurries. In conclusion, tenax extraction during 20 h resulted a reliable and robust method to determine bioavailable concentrations in a wide set of operational conditions ranging from a different time scale to dissimilar treatments (planting, biosurfactant application, etc.).

7 páginas.-- 2 figuras.-- 1 tabla.-- 25 referencias.-- The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b02370., Chemoeffector-mediated bacterial motility and tactic swimming are major drivers for contaminant accessibility and biodegradation at submillimeter scales. In sand-filled percolated columns we tested how and to what degree chemoeffectors influenced bacterial transport and thereby promoted accessibility and degradation of distantly located 14C-naphthalene (NAH) at the centimeter scale. Sunflower root exudates and silver nanoparticles (AgNPs) were used as chemoeffectors to stimulate opposing effects of motility and tactic swimming of NAH-degrading Pseudomonas putida G7. Sunflower exudates prompted smooth bacterial movement and positive taxis, while AgNPs induced tortuous movement and repellent responses. Compared to chemoeffector-free controls exudates reduced deposition and stimulated bacterial transport during percolation experiments. AgNPs, however, provoked bacterial deposition and concomitant saturation of the collector surfaces (filter blocking) that led to progressively increased percolation of cells. Despite mechanistic differences, both motility patterns supported bacterial transport and promoted mineralization rates of NAH desorbing from a source placed at the column outlet. Observed mineralization rates in the presence of the chemoeffectors were 5-fold higher than those in their absence and similar to NAH-mineralization in well-stirred batch assays. Our results indicate that chemically mediated, small-scale bacterial motility patterns may become relevant for long-distance bacterial transport and the biodegradation of patchy contaminants at higher scales, respectively, We thank the Spanish Ministry of Economy, Industry, and Competitiveness (CGL2013-44554-R and CGL2016-77497- R), the Andalusian Government (RNM 2337) and the European Commission (LIFE15 ENV/IT/000396). This study contributes to the research topic Chemicals in the Environment (CITE) within the research program Terrestrial Environment of the Helmholtz Association.