Chemical and microbiological characterization of an aged PCB-contaminated soil

Enhanced dechlorination and degradation of Aroclor 1260 by resuscitation-promoting factor under alternating anaerobic-aerobic conditions: Superior performance and associated microbial populations

The combined processes of dechlorination and degradation are essential for the effective bioremediation of environments contaminated with complex polychlorinated biphenyl (PCB) mixtures. Although resuscitation-promoting factor (Rpf) has been reported to enhance anaerobic dechlorination and aerobic degradation of PCBs by microorganisms, its impact on microbial populations during alternating anaerobic-aerobic treatments remains unexplored. This study investigated the dechlorination and degradation of Aroclor 1260 under anaerobic (AN), aerobic (AE), and alternating anaerobic-aerobic (AA) conditions, both with and without Rpf supplementation. The results demonstrated that Rpf significantly promoted Aroclor 1260 dechlorination under AN conditions, enhanced degradation under AE conditions, and markedly improved both processes under AA conditions, achieving nearly twice the degradation efficiency compared to AE alone. Furthermore, Rpf supplementation significantly increased the abundance of dechlorination-associated microbial taxa, including members of Firmicutes, Chloroflexi, Bacteroidota, and Desulfobacterota under AN conditions, as well as degradation-associated genera such as Pseudomonas and Sphingomonas under AE and AA conditions. Rpf also strengthened microbial interactions by enhancing positive correlations among functional populations and increasing network complexity. These findings establish Rpf as a powerful enhancer of PCB dechlorination and degradation, which provide valuable insights into its superior efficiency in PCB removal under AA conditions.

Microbial Diversity Drives Decomposition More than Advantage of Home Environment-Evidence from a Manipulation Experiment with Leaf Litter

Microbial diversity plays a crucial role in litter decomposition. However, the relationships between microbial diversity and substrate successional stage are the drivers of this decomposition. In this study, we experimentally manipulated microbial diversity and succession in post-mining soil. We used leaf litter samples from two forests of a post-mining site near Sokolov, Czech Republic: one alder plantation and one mixed forest with birch aspen and willow. Litter from each site was decomposed in the field for 3 and 12 months. The litter was X-ray sterilized and part of the litter was kept unsterilized to produce inoculum. Leaf litter samples of two different ages (3 and 12 months) from each site were each inoculated with litter of two different ages (3 and 12 months), using less and more diluted inoculum, producing two levels of microbial diversity. In each of these eight treatments, the bacterial community was then characterized by amplicon sequencing of the 16S rRNA gene and microbial respiration was used to assess the rate of decomposition. A significantly higher respiration (p < 0.05) was found for the litter inoculated with the higher level of microbial diversity. Higher respiration was also found for the younger litter compared to the older litter and both litter origins. This shows a reduction in microbial respiration with substrate age and inoculation diversity, suggesting that microbial diversity supports the decomposition of soil organic matter.

Investigating PCB degradation by indigenous fungal strains isolated from the transformer oil-contaminated site: degradation kinetics, Bayesian network, artificial neural networks, QSAR with DFT, molecular docking, and molecular dynamics simulation

The widespread prevalence of polychlorinated biphenyls (PCBs) in the environment has raised major concerns due to the associated risks to human health, wildlife, and ecological systems. Here, we investigated the degradation kinetics, Bayesian network (BN), quantitative structure-activity relationship-density functional theory (QSAR-DFT), artificial neural network (ANN), molecular docking (MD), and molecular dynamics stimulation (MS) of PCB biodegradation, i.e., PCB-10, PCB-28, PCB-52, PCB-138, PCB-153, and PCB-180 in the soil system using fungi isolated from the transformer oil-contaminated sites. Results revealed that the efficacy of PCB biodegradation best fits the first-order kinetics (R2 ≥ 0.93). The consortium treatment (29.44-74.49%) exhibited more efficient degradation of PCBs than those of Aspergillus tamarii sp. MN69 (27.09-71.25%), Corynespora cassiicola sp. MN69 (23.76-57.37%), and Corynespora cassiicola sp. MN70 (23.09-54.98%). 3'-Methoxy-2, 4, 4'-trichloro-biphenyl as an intermediate derivative was detected in the fungal consortium treatment. The BN analysis predicted that the biodegradation efficiency of PCBs ranged from 11.6 to 72.9%. The ANN approach showed the importance of chemical descriptors in decreasing order, i.e., LUMO > MW > IP > polarity no. > no. of chlorine > Wiener index > Zagreb index > HOMU > Pogliani index > APE in PCB removal. Furthermore, the QSAR-DFT model between the chemical descriptors and rate constant (log K) exhibited a high fit and good robustness of R2 = 99.12% in predicting ability. The MD and MS analyses showed the lowest binding energy through normal mode analysis (NMA), implying stability in the interactions of the docked complexes. These findings provide crucial insights for devising strategies focused on natural attenuation, holding substantial potential for mitigating PCB contamination within the environment.

Effects of different organic substrate compositions on the decontamination of aged PAH-polluted soils through outdoor co-composting

The effects of different organic substrate compositions on the efficiency of outdoor co-composting as a bioremediation technology for decontaminating soil polluted by polycyclic aromatic hydrocarbons (PAHs) were investigated. Four different substrate mixtures and two different aged PAH-contaminated soils were used in a semi-pilot-scale experiment that lasted nearly 700 days. The two soils (A and B) differed concerning both the initial concentrations of the Ʃ16 US EPA PAHs (5926 vs. 369 mg kg-1, respectively) and the type of predominant PAH group by molecular weight. The experiments revealed that while the composition of the organic substrate had an impact on the rate of PAH degradation, it did not significantly influence the final extent of PAH degradation. Notably, the organic substrate consisting of green waste and wood chips (GW) was found to facilitate the most rapid rate of PAH degradation (first-order rate constant k = 0.033 ± 0.000 d-1 with soil A over the initial 42 days of the experiment and k = 0.036 ± 0.000 d-1 with soil B over the initial 56 days). Despite the differences in organic substrate compositions and types of soil being treated, PAH degradation levels exceeded at least 95% in all the treatments after more than 680 days of co-composting. Regardless of the composition, the removal of low- and medium- molecular-weight (2-4 rings) PAHs was nearly complete by the end of the experiment. Furthermore, high-molecular-weight PAHs (5 rings and more) were significantly degraded during co-composting, with reductions ranging from 54% to 79% in soil A and from 59% to 68% in soil B. All composts were dominated by Proteobacteria, Firmicutes, and Actinobacteria, with significant differences in abundance between soils. Genera with PAH degradation potentials were detected in all samples. The results of a battery of toxicity tests showed that there was almost no toxicity associated with the final composts.

Nano zerovalent Fe did not reduce metal(loid) leaching and ecotoxicity further than conventional Fe grit in contrasting smelter impacted soils: A 1-year field study

The majority of the studies on nanoscale zero-valent iron (nZVI) are conducted at a laboratory-scale, while field-scale evidence is scarce. The objective of this study was to compare the metal(loid) immobilization efficiency of selected Fe-based materials under field conditions for a period of one year. Two contrasting metal(loid) (As, Cd, Pb, Zn) enriched soils from a smelter-contaminated area were amended with sulfidized nZVI (S-nZVI) solely or combined with thermally stabilized sewage sludge and compared to amendment with microscale iron grit. In the soil with higher pH (7.5) and organic matter content (TOC = 12.7 %), the application of amendments resulted in a moderate increase in pH and reduced As, Cd, Pb, and Zn leaching after 1-year, with S-nZVI and sludge combined being the most efficient, followed by iron grit and S-nZVI alone. However, the amendments had adverse impacts on microbial biomass quantity, S-nZVI being the least damaging. In the soil with a lower pH (6.0) and organic matter content (TOC = 2.3 %), the results were mixed; 0.01 M CaCl2 extraction data showed only S-nZVI with sludge as remaining effective in reducing extractable concentrations of metals; on the other hand, Cd and Zn concentrations were increased in the extracted soil pore water solutions, in contrast to the two conventional amendments. Despite that, S-nZVI with sludge enhanced the quantity of microbial biomass in this soil. Additional earthworm avoidance data indicated that they generally avoided soil treated with all Fe-based materials, but the presence of sludge impacted their preferences somewhat. In summary, no significant differences between S-nZVI and iron grit were observed for metal(loid) immobilization, though sludge significantly improved the performance of S-nZVI in terms of soil health indicators. Therefore, this study indicates that S-nZVI amendment of soils alone should be avoided, though further field evidence from a broader range of soils is now required.

Endogenous biohydrogen from a rhizobium-legume association drives microbial biodegradation of polychlorinated biphenyl in contaminated soil

Endogenous hydrogen (H₂) is produced through rhizobium-legume associations in terrestrial ecosystems worldwide through dinitrogen fixation. In turn, this gas may alter rhizosphere microbial community structure and modulate biogeochemical cycles. However, very little is understood about the role that this H₂ leaking to the rhizosphere plays in shaping the persistent organic pollutants degrading microbes in contaminated soils. Here, we combined DNA-stable isotope probing (DNA-SIP) with metagenomics to explore how endogenous H₂ from the symbiotic rhizobium-alfalfa association drives the microbial biodegradation of tetrachlorobiphenyl PCB 77 in a contaminated soil. The results showed that PCB77 biodegradation efficiency increased significantly in soils treated with endogenous H₂. Based on metagenomes of ¹³C-enriched DNA fractions, endogenous H₂ selected bacteria harboring PCB degradation genes. Functional gene annotation allowed the reconstruction of several complete pathways for PCB catabolism, with different taxa conducting successive metabolic steps of PCB metabolism. The enrichment through endogenous H₂ of hydrogenotrophic Pseudomonas and Magnetospirillum encoding biphenyl oxidation genes drove PCB biodegradation. This study proves that endogenous H₂ is a significant energy source for active PCB-degrading communities and suggests that elevated H₂ can influence the microbial ecology and biogeochemistry of the legume rhizosphere.

A novel strategy for enhancing bioremediation of polychlorinated biphenyl-contaminated soil with resuscitation promoting factor and resuscitated strain

PCBs bioremediation is largely impeded by the reduced metabolic activity and degradation ability of indigenous and exogenous microorganisms. Resuscitation promoting factor (Rpf) of Micrococcus luteus, has been reported to resuscitate and stimulate the growth of PCB-degrading bacterial populations, and the resuscitated strains exhibited excellent PCB-degrading performances. Therefore, this study was conducted to assess the feasibility of supplementing Rpf (SR) or resuscitated strain LS1 (SL), or both (SRL) for enhanced bioremediation of PCB-contaminated soil. The results indicated that Rpf and/or LS1 amended soil microcosms achieved more rapid PCBs degradation, which were 1.1-3.2 times faster than control microcosms. Although soil-inoculated LS1 maintained the PCB-degrading activity, higher PCBs degradation was observed in Rpf-amended soil microcosms compared with SL. The order of enhancement effect on PCBs bioremediation was SRL > SR > SL. PCBs degradation in soil microcosms was via HOPDA-benzoate-catechol/protocatechuate pathways. The improved PCBs degradation in Rpf-amended soil microcosms was attributed to the enhanced abundances of PCB-degrading populations which were mainly belonged to Proteobacteria and Actinobacteria. These results suggest that Rpf and resuscitated strains serve as effective additive and bio-inoculant for enhanced bioremediation, providing new approaches to realizing large scale applications of in situ bioremediation.

Interactions of microplastics with contaminants in freshwater systems: a review of characteristics, bioaccessibility, and environmental factors affecting sorption

Microplastics (MPs), plastic particles of 1 nm to <5 mm, have been identified in the atmosphere, soil, and aquatic environments across the globe. MPs may act as vectors to transport environmental contaminants to sensitive receptors, including humans. In this review, the capability of MPs to sorb persistent organic pollutants (POPs) and metals is investigated, along with how sorption is affected by factors, such as pH, salinity, and temperature. Sensitive receptors may take up MPs through incidental ingestion. In the gastrointestinal tract (GIT), contaminants may desorb from MPs, and this desorbed portion is then considered bioaccessible. Understanding the sorption and bioaccessibility of such contaminants is important in determining potential risks of exposure to MPs. Thus, a review is presented on the bioaccessibility of contaminants sorbed to MPs in the human and avian GIT s. The current state of knowledge on MP-contaminant interactions in freshwater systems is limited; these interactions can differ considerably from those in marine environments. The bioaccessibility of contaminants sorbed to MPs can vary significantly, from near zero to 100%, depending on MP type, contaminant characteristics, and the digestive phase. Further research is needed to characterize the bioaccessibility and the potential risks, especially for POPs associated with MPs.

Myco- and phyco-remediation of polychlorinated biphenyls in the environment: a review

Polychlorinated biphenyls (PCBs) are toxic organic compounds and pose serious threats to environment and public health. PCBs still exist in different environments such as air, water, soil, and sediments even on ban. This review summarizes the phyco- and myco-remediation technologies developed to detoxify the PCB-polluted sites. It was found that algae mostly use bioaccumulation to biodegradation strategies to reclaim the environment. As bio-accumulator, Ulva rigida C. Agardh has been best at 25 ng/g dry wt to remove PCBs. Evidently, Anabaena PD-1 is the only known PCB degrading alga and efficiently degrade Aroclor 1254 and dioxin-like PCBs up to 84.4% and 37.4% to 68.4%, respectively. The review suggested that factors such as choice of algal strains, response of microalgae, biomass, the rate of growth, and cost-effective cultivation conditions significantly influence the remediation of PCBs. Furthermore, the Anabaena sp. linA gene of Pseudomonas paucimobilis Holmes UT26 showed enhanced efficiency. Pleurotus ostreatus (Jacq.) P. Kumm is the most efficient PCB degrading fungus, degrading up to 98.4% and 99.6% of PCB in complex and mineral media, respectively. Combine metabolic activities of bacteria and yeast led to the higher detoxification of PCBs. Fungi-algae consortia would be a promising approach in remediation of PCBs. A critical analysis on potentials and limits of PCB treatment through fungal and algal biosystems have been reviewed, and thus, new insights have emerged for possible bioremediation, bioaccumulation, and biodegradation of PCBs.

Moss biocrust accelerates the recovery and resilience of soil microbial communities in fire-affected semi-arid Mediterranean soils

After wildfires in Mediterranean ecosystems, ruderal mosses are pioneer species, stabilizing the soil surface previous to the establishment of vascular vegetation. However, little is known about the implication of pioneer moss biocrusts for the recovery and resilience of soils in early post-fire stages in semi-arid areas. Therefore, we studied the effects of the burgeoning biocrust on soil physicochemical and biochemical properties and the diversity and composition of microbial communities after a moderate-to-high wildfire severity. Seven months after the wildfire, the biocrust softened the strong impact of the fire in soils, affecting the diversity and composition of bacteria and fungi community compared to the uncrusted soils exposed to unfavourable environmental stress. Soil moisture, phosphorous, and enzyme activities representing the altered biogeochemical cycles after the fire, were the main explanatory variables for biocrust microbial community composition under the semi-arid conditions. High bacterial diversity was found in soils under mosses, while long-lasting legacies are expected in the fungal community, which showed greater sensitivity to the fire. The composition of bacterial and fungal communities at several taxonomical levels was profoundly altered by the presence of the moss biocrust, showing a rapid successional transition toward the unburned soil community. Pioneer moss biocrust play an important role improving the resilience of soil microbial communities. In the context of increasing fire intensity, studying the moss biocrust effects on the recovery of soils microbiome is essential to understanding the resistance and resilience of Mediterranean forests to wildfires.

Community reassemblies of eukaryotes, prokaryotes, and viruses in the hexabromocyclododecanes-contaminated microcosms

The microbial community in seriously contaminated environment were not well known. This research investigated the community reassemblies in microcosms made of two distinct mangrove sediments amended with high levels of hexabromocyclododecanes (HBCDs). After eight months of contamination, the transformation of HBCDs yielded various lower brominated products and resulted in acidification (pH ~2). Therefore, the degraders and dehalogenase homologous genes involved in transformation of HBCDs only presented in low abundance to avoid further deterioration of the habitats. Moreover, in these deteriorated habitats, 1344 bacterial, 969 archaeal, 599 eukaryotic (excluded fungi), 187 fungal OTUs, and 10 viral genera, were reduced compared with controls. Specifically, in two groups of microcosms, Zetaproteobacteria, Deinococcus-Thermus, Spirochaetes, Bacteroidetes, Euryarchaeota, and Ascomycota, were positively responding taxa to HBCDs. Caloneis (Bacillariophyta) and Ascomycota turned to the dominant eukaryotic and fungal taxa. Most of predominant taxa were related to the contamination of brominated flame retardants (BFRs). Microbial communities were reassembled in divergent and sediment-dependent manner. The long-term contamination of HBCDs leaded to the change of relations between many taxa, included some of the environmental viruses and their known hosts. This research highlight the importance of monitoring the ecological effects around plants producing or processing halogenated compounds.

Asymmetric Interaction Between Two Mycorrhizal Fungal Guilds and Consequences for the Establishment of Their Host Plants

Arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) are the most abundant and widespread types of mycorrhizal symbiosis, but there is little and sometimes conflicting information regarding the interaction between AM fungi (AMF) and EcM fungi (EcMF) in soils. Their competition for resources can be particularly relevant in successional ecosystems, which usually present a transition from AM-forming herbaceous vegetation to EcM-forming woody species. The aims of this study were to describe the interaction between mycorrhizal fungal communities associated with AM and EcM hosts naturally coexisting during primary succession on spoil banks and to evaluate how this interaction affects growth and mycorrhizal colonization of seedlings of both species. We conducted a greenhouse microcosm experiment with Betula pendula and Hieracium caespitosum as EcM and AM hosts, respectively. They were cultivated in three-compartment rhizoboxes. Two lateral compartments contained different combinations of both host plants as sources of fungal mycelia colonizing the middle compartment, where fungal biomass, diversity, and community composition as well as the growth of each host plant species' seedlings were analyzed. The study's main finding was an asymmetric outcome of the interaction between the two plant species: while H. caespitosum and associated AMF reduced the abundance of EcMF in soil, modified the composition of EcMF communities, and also tended to decrease growth and mycorrhizal colonization of B. pendula seedlings, the EcM host did not have such effects on AM plants and associated AMF. In the context of primary succession, these findings suggest that ruderal AM hosts could hinder the development of EcM tree seedlings, thus slowing the transition from AM-dominated to EcM-dominated vegetation in early successional stages.

Recent advances in PCB removal from historically contaminated environmental matrices

Despite being drastically restricted in the 1970s, polychlorinated biphenyls (PCBs) still belong among the most hazardous contaminants. The chemical stability and dielectric properties of PCBs made them suitable for a number of applications, which then lead to their ubiquitous presence in the environment. PCBs are highly bioaccumulative and persistent, and their teratogenic, carcinogenic, and endocrine-disrupting features have been widely reported in the literature. This review discusses recent advances in different techniques and approaches to remediate historically contaminated matrices, which are one of the most problematic in regard to decontamination feasibility and efficiency. The current knowledge published in the literature shows that PCBs are not sufficiently removed from the environment by natural processes, and thus, the suitability of some approaches (e.g., natural attenuation) is limited. Physicochemical processes are still the most effective; however, their extensive use is constrained by their high cost and often their destructiveness toward the matrices. Despite their limited reliability, biological methods and their application in combinations with other techniques could be promising. The literature reviewed in this paper documents that a combination of techniques differing in their principles should be a future research direction. Other aspects discussed in this work include the incompleteness of some studies. More attention should be given to the evaluation of toxicity during these processes, particularly in terms of monitoring different modes of toxic action. In addition, decomposition mechanisms and products need to be sufficiently clarified before combined, tailor-made approaches can be employed.

Phytoremediation of PCB: contaminated Algerian soils using native agronomics plants

Pot cultivation experiments were conducted to assess the phytoremediation potential of two local agronomic plants, namely Avena sativa and Vicia sativa. Several soils with long-standing contamination and different levels of Polychlorinated biphenyl (PCB) contamination were used for this study. The soil samples came from different regions of Algeria and had different physico-chemical parameters. We studied the influence of these parameters on remediation potential of the two tested plants. The removal rate of the seven PCBs (PCB 28, 52, 101, 138, 153, 156 and 180) was examined after 40 and 90 days. The results showed that the presence of the plants reduced significantly the overall PCB content, ranging initially from 1.33-127.9 mg kg¹. After 90 days, the forage plant Vicia sativa allowed us to reach an excess dissipation rate of 56.7% compared to the unplanted control for the most polluted soil. An average dissipation rate of 50% was obtained in the moderately polluted soil. The less contaminated soil had an excess dissipation rate of about 24% for both plants and a predominant dissipation of the low chlorinated PCBs.

Conversion of spent coffee grounds into vermicompost

The present study was focused on vermicomposting of spent coffee grounds (SCG) and its mixtures with straw pellets. The process was evaluated in terms of biological and physico-chemical properties. The greatest number and biomass of earthworms was found in the treatment with 25% vol. SCG + 75% vol. straw pellets. In this treatment, the upper youngest layer exhibited 1.6-fold and 4.5-fold greater earthworm number and biomass, respectively, than the bottom oldest layer. Earthworm weight decreased in direct proportion to the layer age. The oldest treatment layer was characterized by lesser contents of fungi and six hydrolytic enzymes, compared to the younger layers. Further, the oldest treatment layer had suitable agrochemical properties. Earthworms were able to substantially reduce the caffeine stimulant content, which is considered the most representative pharmaceutically active compound.

Response of soil enzyme activity and soil bacterial community to PCB dissipation across different soils

Soils are a repository for polychlorinated biphenyls (PCBs). A pot incubation experiment was performed with four soils (black soil, paddy soil, oasis soil, and fluvo-aquic soil) treated with Aroclor 1242 to achieve PCB concentrations of 5 mg kg^-1. The soil enzyme activities of protease, phosphatase, catalase, dehydrogenase, and laccase were determined by spectrophotometry. The soil bacterial communities were investigated using Illumina sequencing analysis. The results showed that the characteristics of the test soils varied among the soil types. The fluvo-aquic soil had the greatest PCB dissipation rate (86.41%), followed by the oasis (79.31%), paddy (56.09%), and black (50.65%) soils. The soil pH, cation exchange capacity, soil organic matter content, and particle diameter played significant roles in PCB dissipation from soils. The soil type had a greater influence than PCB contamination on the soil enzyme activities and bacterial communities (alpha diversity, community structure, and composition). Among the four soils, the bacterial communities of the fluvo-aquic soil were the most susceptible to PCB contamination. However, the bacterial communities of the black soil were not changed by PCB contamination.

Discovering the potential of an nZVI-biochar composite as a material for the nanobioremediation of chlorinated solvents in groundwater: Degradation efficiency and effect on resident microorganisms

Abiotic and biotic remediation of chlorinated ethenes (CEs) in groundwater from a real contaminated site was studied using biochar-based composites containing nanoscale zero-valent iron (nZVI/BC) and natural resident microbes/specific CE degraders supported by a whey addition. The material represented by the biochar matrix decorated by isolated iron nanoparticles or their aggregates, along with the added whey, was capable of a stepwise dechlorination of CEs. The tested materials (nZVI/BC and BC) were able to decrease the original TCE concentration by 99% in 30 days. Nevertheless, regarding the transformation products, it was clear that biotic as well as abiotic transformation mechanisms were involved in the transformation process when nonchlorinated volatiles (i.e., methane, ethane, ethene, and acetylene) were detected after the application of nZVI/BC and nZVI/BC with whey. The whey addition caused a massive increase in bacterial biomass in the groundwater samples (monitored by 16S rRNA sequencing and qPCR) that corresponded with the transformation of trichloro- and dichloro-CEs, and this process was accompanied by the formation of less chlorinated products. Moreover, the biostimulation step also eliminated the adverse effect caused by nZVI/BC (decrease in microbial biomass after nZVI/BC addition). The nZVI/BC material or its aging products, and probably together with vinyl chloride-respiring bacteria, were able to continue the further reductive dechlorination of dichlorinated CEs into nonhalogenated volatiles. Overall, the results of the present study demonstrate the potential, feasibility, and environmental safety of this nanobioremediation approach.

Potentiality of Native Ascomycete Strains in Bioremediation of Highly Polychlorinated Biphenyl Contaminated Soils

Polychlorinated biphenyls (PCBs) are organic pollutants that are harmful to environment and toxic to humans. Numerous studies, based on basidiomycete strains, have reported unsatisfactory results in the mycoremediation of PCB-contaminated soils mainly due to the non-telluric origin of these strains. The abilities of a five-Ascomycete-strain consortium in the mycoremediation of PCB-polluted soils and its performance to restore their sound functioning were investigated using mesocosm experiments associated with chromatography gas analysis and enzymatic activity assays. With the soil H containing 850 ppm PCB from which the strains had been isolated, a significant PCB depletion of 29% after three months of treatment was obtained. This led to an important decrease of PCBs from 850 to 604 ppm. With the soil L containing 36 ppm PCB, biodegradation did not occur. In both soils, the fungal biomass quantified by the ergosterol assay, did not increase at the end of the treatment. Biodegradation evidenced in the soil H resulted in a significantly improved stoichiometry of N and P acquiring enzymatic activities. This unprecedented study demonstrates that the native Ascomycetes display remarkable properties for remediation and restoration of functioning of the soil they originated from paving the way for greater consideration of these strains in mycoremediation.

Municipal waste landfill as a source of polychlorinated biphenyls releases to the environment

This study aimed to investigate the impact of municipal waste landfill on polychlorinated biphenyls (PCBs) release to the environment concerning groundwater flow directions. The contents of polychlorinated biphenyls in soils, plants and water were analysed at various distances from the landfill. Thanks to low solubility PCBs in water groundwater flow direction, under the landfill, have an influence on PCBs concentration in groundwater. Strong PCBs' sorption to organic matter caused that no affect groundwater flow directions on PCB content in soils and plants' tissues was observed. The largest PCBs deposition zone was located 50 m from the contamination source (landfill). Tri-CB and tetra-CB homologues were capable of migration deep into the soil profile, which could be related to the geological material from which the soils under study were developed, as well as to the properties of the PCB homologues.

Effect of pyrolysis temperature on removal of organic pollutants present in anaerobically stabilized sewage sludge

Sewage sludge was excluded from the list of component materials for the production of EU fertilizing products and it was banned as feedstock to produce pyrolysis & gasification materials in European Commission's technical proposals for selected new fertilizing materials under the Regulation 2019/1009 (STRUBIAS report). This exclusion of pyrolysis as a viable way to treat sewage sludge was mainly due to the lack of data on the fate of organic pollutants at pyrolysis conditions. In this work, we are addressing this knowledge gap. We studied slow pyrolysis as a potential process to efficiently treat organic pollutants present in stabilized sewage sludge. Sewage sludge was pyrolyzed in a quartz fixed bed reactor at temperatures of 400-800 °C for 2 h and the sludge and resulting sludge-chars were analyzed for the presence of four groups of organic pollutants, namely (i) polychlorinated biphenyls (PCBs), (ii) polycyclic aromatic hydrocarbons (PAHs), (iii) pharmaceuticals, and (iv) endocrine-disrupting and hormonal compounds. Pyrolysis at ≥ 400 °C effectively removed pharmaceuticals (group iii) to below detection limits, whereas pyrolysis at temperatures higher than 600 °C was required to remove more than 99.8% of the compounds from groups i, ii and iv. Based on these findings, we propose, that high temperature (>600 °C) slow pyrolysis can satisfactory remove organic pollutants from the resulting sludge-char, which could be safely applied as soil improver.

Enhancement of polychlorinated biphenyl biodegradation by resuscitation promoting factor (Rpf) and Rpf-responsive bacterial community

The activities of indigenous bacterial communities in polychlorinated biphenyls (PCBs) contaminated environments is closely related to the efficiency of bioremediation processes. Using resuscitation promoting factor (Rpf) from Micrococcus luteus is a promising method for resuscitation and stimulation of functional bacterial populations under stressful conditions. This study aims to use the Rpf to accelerate the biodegradation of Aroclor 1242, and explore putative PCB degraders which were resuscitated by Rpf addition. The Rpf-responsive bacterial populations were investigated using culture-dependent and culture-independent approaches, respectively. The results confirm that Rpf was capable of enhancing PCB degradation of enriched cultures from PCB-contaminated soils, and improving the activities of cultures with low tolerance to PCBs. High-throughput 16S rRNA analysis displays that the Rpf greatly altered the composition and abundance of bacterial populations in the phylum Proteobacteria. Identification of the resuscitated strains further suggests that the Rpf-responsive population was mostly represented by Sphingomonas and Pseudomonas, which are most likely the key PCB-degraders for enhanced biodegradation of PCBs.

Vermicomposting of sludge from a malt house

Malting sludge is waste that could be used as a good soil conditioner after proper treatment. In the current study, the feasibility of vermicomposting malting sludge and its mixtures with straw pellets on the basis of physico-chemical and biological properties was verified. A vermicomposting system with continuous feeding of earthworms Eisenia andrei was used. The greatest number and biomass of earthworms was found in the variant with 25% malt house sludge + 75% straw pellets (on average of all layers: 320 earthworms/kg and 35 g/kg, respectively), followed by a variant with 50% malt house sludge + 50% straw pellets (on average of all layers: 47 earthworms/kg and 13 g/kg, respectively), indicating that a minimum of 50% (vol.) straw pellets is necessary for successful vermicomposting of malting sludge. Most earthworms lived in the youngest upper layer (42% and 52% of total number and earthworm biomass, respectively). On the contrary, the oldest bottom layers (final vermicomposts) after 180 days of vermicomposting were characterized by maturity, indicating lesser contents of microorganisms and enzyme activity. These vermicomposts had favorable agrochemical properties (pH = 7.8, EC = 1.2 mS cm^-1, C/N = 11, P_tot = 1.23%, K_tot = 2.55%, Mg_tot = 0.42%). The proportion of the available contents in the total contents were 10%, 59%, and 19% for P, K, and Mg, respectively.

Soil metabolome correlates with bacterial diversity and co-occurrence patterns in root-associated soils on the Tibetan Plateau

Metabolites in root-zone soils mediate microbe-to-microbe interactions and govern the overall microbial community. However, how chemicals relate to diversity and co-occurrence patterns of bacterial communities in root-associated soils is still poorly understood. Here, we studied the relationships of soil metabolome with bacterial community diversity and co-occurrence patterns in root-associated soils across different land types on the Tibetan Plateau. The soil metabolome mainly encompassed a range of organic acids, and sugars and sugar derivatives, which were widely negatively correlated with bacterial alpha-diversity. Compared to the investigated environmental variables, metabolites accounted more for the variations in the Shannon diversity and bacterial community compositions. Compared to sugars, organic acids accounted more for bacterial community compositions at high taxonomic ranks, while reversed at genus and species levels. The relative abundances of some bacterial genera and metabolites were closely linked to soil types and plant genotypes. The differential compounds were significantly correlated with the distinctive bacterial taxa across land types and plant genotypes. Keystone species in co-occurrence network, such as Bradyrhizobium, Bryobacter, and Microvirga were significantly correlated with sugars and organic acids. Structural equation modeling revealed that sugar metabolism can play a crucial role in altering the bacterial community diversity. This study provides new insights into the ecological mechanism that maintains bacterial community in the root-associated soils on the Tibetan Plateau.

Combined Effects of Compost and Medicago Sativa in Recovery a PCB Contaminated Soil

The effectiveness of adding compost and the plant Medicago sativa in improving the quality of a soil historically contaminated by polychlorinated biphenyls (PCBs) was tested in greenhouse microcosms. Plant pots, containing soil samples from an area contaminated by PCBs, were treated with the compost and the plant, separately or together. Moreover, un-treated and un-planted microcosms were used as controls. At fixed times (1, 133 and 224 days), PCBs were analysed and the structure (cell abundance, phylogenetic characterization) and functioning (cell viability, dehydrogenase activity) of the natural microbial community were also measured. The results showed the effectiveness of the compost and plant in increasing the microbial activity, cell viability, and bacteria/fungi ratio, and in decreasing the amount of higher-chlorinated PCBs. Moreover, a higher number of α-Proteobacteria, one of the main bacterial groups involved in the degradation of PCBs, was found in the compost and plant co-presence.

Biodegradation of PCBs in contaminated water using spent oyster mushroom substrate and a trickle-bed bioreactor

Due to their persistence, polychlorinated biphenyls (PCBs) represent a group of important environmental pollutants, but conventional physicochemical decontamination techniques for their removal are usually expensive. The main aim of this work was to develop a cost-effective method for PCB bioremediation, focusing on contaminated water and utilizing the well-known degradation capability of Pleurotus ostreatus (the oyster mushroom). For this purpose, the conditions of several laboratory-scale reactors (working volume 1 L) were optimized. Spent oyster mushroom substrate obtained from a commercial farm was used as a fungal inoculum and growth substrate. The highest degradation efficiency (87%) was recorded with a continuous low-flow setup, which was subsequently scaled up (working volume 500 L) and used for the treatment of 4000 L of real contaminated groundwater containing 0.1-1 μg/L of PCBs. This trickle-bed pilot-scale bioreactor was able to remove 82, 80, 65, and 30-50% of di-, tri-, tetra- and pentachlorinated PCB congeners, respectively. No degradation was observed for hexa- or heptachlorinated congeners. Multiple mono- and dichlorobenzoic acids (CBAs) were identified as transformation products by mass spectrometry, confirming the role of biodegradation in PCB removal. A Vibrio fischeri bioluminescence inhibition test revealed slight ecotoxicity of the primary reactor effluent (sampling after 24 h), which was quickly suppressed once the effluent passed through the reactor for the second time. Moreover, no other effluent exhibited toxicity for the rest of the experiment (71 days in total). Microbial analyses (phospholipid fatty acid analysis and next-generation sequencing) showed that P. ostreatus was able to degrade PCBs in the presence of an abundance of other fungal species as well as aerobic and anaerobic bacteria. Overall, this study proved the suitability of the use of spent oyster mushroom substrate in a bioremediation practice, even for pollutants as recalcitrant as PCBs.

Aerobic degradation of 3,3',4,4'-tetrachlorobiphenyl by a resuscitated strain Castellaniella sp. SPC4: Kinetics model and pathway for biodegradation

Resuscitated strains which were obtained by addition of resuscitation promoting factor (Rpf) could provide a vast majority of microbial source for obtaining highly efficient polychlorinated biphenyl (PCB)-degrading bacteria. In this study, the Castellaniella sp. strain SPC4 which was resuscitated by Rpf addition showed the highest efficiency in degradation of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) among the resuscitated and non-resuscitated isolates. Further investigations on the PCB 77 degradation capability of the resuscitated strain SPC4 showed that SPC4 could efficiently degrade PCB 77 with maximum degradation rate (q_max) of 0.066/h at about 20 mg/L of PCB 77. The maximum growth rate on PCB 77 was 2.663 × 10⁷ CFU/(mL·h) (0.024/h). The most suitable model of Edward demonstrated that the SPC4 could achieve q_max of 0.9315/h, with substrate-affinity of 11.33 mg/L and substrate-inhibition constants of 11.41 mg/L. Meanwhile, the presence of bphA gene expression and chlorine ions release, together with the identification of metabolites, confirmed that the bph-encoded biphenyl pathway was involved in PCB 77 mineralization by SPC4. This report is the first to demonstrate aerobic degradation of PCB 77 by the resuscitated strain Castellaniella sp. SPC4, indicating excellent potential for PCB bioremediation.

Mycoremediation of PCBs by Pleurotus ostreatus: Possibilities and Prospects

With the rising awareness on environmental issues and the increasing risks through industrial development, clean up remediation measures have become the need of the hour. Bioremediation has become increasingly popular owing to its environmentally friendly approaches and cost effectiveness. Polychlorinated biphenyls (PCBs) are an alarming threat to human welfare as well as the environment. They top the list of hazardous xenobiotics. The multiple effects these compounds render to the niche is not unassessed. Bioremediation does appear promising, with myco remediation having a clear edge over bacterial remediation. In the following review, the inputs of white-rot fungi in PCB remediation are examined and the lacunae in the practical application of this versatile technology highlighted. The unique abilities of Pleurotus ostreatus and its deliverables with respect to removal of PCBs are presented. The need for improvising P. ostreatus-mediated remediation is emphasized.

Identification of Sulfonated and Hydroxy-Sulfonated Polychlorinated Biphenyl (PCB) Metabolites in Soil: New Classes of Intermediate Products of PCB Degradation?

In this paper we describe the identification of two classes of contaminants: sulfonated-PCBs and hydroxy-sulfonated-PCBs. This is the first published report of the detection of these chemicals in soil. They were found, along with hydroxy-PCBs, in soil samples coming from a site historically contaminated by the industrial production of PCBs and in background soils. Sulfonated-PCB levels were approximately 0.4-0.8% of the native PCB levels in soils and about twice the levels of hydroxy-sulfonated-PCBs and hydroxy-PCBs. The identification of sulfonated-PCBs was confirmed by the chemical synthesis of reference standards, obtained through the sulfonation of an industrial mixture of PCBs. We then reviewed the literature to investigate for the potential agents responsible for the sulfonation. Furthermore, we predicted their physicochemical properties and indicate that, given the low pK_a of sulfonated- and hydroxy-sulfonated-PCBs, they possess negligible volatility, supporting the case for in situ formation from PCBs. This study shows the need of understanding their origin, their role in the degradation path of PCBs, and their fate, as well as their (still unknown) toxicological and ecotoxicological properties.

Identification and characterization of a meta-cleavage product hydrolase involved in biphenyl degradation from Arthrobacter sp. YC-RL1

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants (POPs) widely existing in the environment. Arthrobacter sp. YC-RL1 is a biphenyl-degrading bacterium that shows metabolic versatility towards aromatic compounds. A 2-hydroxy-6-oxo-6-phenylhexa-2, 4-dienoate (HOPDA) hydrolase (BphD) gene involved in the biodegradation of biphenyl was cloned from strain YC-RL1 and heterologously expressed in Escherichia coli BL21 (DE3). The recombinant BphD_YC-RL1 was purified and characterized. BphD_YC-RL1 showed the highest activity at 45 °C and pH 7. It was stable under a wide range of temperature (20-50 °C). The enzyme had a K_m value of 0.14 mM, K_cat of 11.61 s^-1, and V_max of 0.027 U/mg. Temperature dependence catalysis exhibited a biphasic Arrhenius Plot with a transition at 20 °C. BphD_YC-RL1 was inactivated by SDS, Tween 20, Tween 80, Trition X-100, DTT, CHAPS, NBS, PMSF, and DEPC, but insensitive to EDTA. Site-directed mutagenesis of the active-site residues revealed that the catalytic triad residues (Ser115, His275, and Asp247) of BphD_YC-RL1 were necessary for its activity. The investigation of BphD_YC-RL1 not only provides new potential enzyme resource for the biodegradation of biphenyl but also helps deepen our understanding on the catalytic process and mechanism.

Stimulation of earthworms (Eisenia fetida) on soil microbial communities to promote metolachlor degradation

Degradation of metolachlor in surface soil is extremely important to its potential mobility and overall persistence. In this study, the effects of earthworms (Eisenia fetida) on the degradation of metolachlor at two concentration levels (5 and 20 mg kg^-1) in soil were investigated via the column experiment. The degradation kinetics of metolachlor indicate that addition of earthworms enhances metolachlor degradation significantly (P < 0.05), with the enhanced degradation rate of 30% and 63% in the low and high concentration treatments at the 15th day, respectively. Fungi rather than bacteria are primarily responsible for metolachlor degradation in soil, and earthworms stimulate metolachlor degradation mainly by stimulating the metolachlor-degrading functional microorganisms and improving fungal community structure. Earthworms prefer to promote the possible fungal degraders like order Sordariales, Microascales, Hypocreales and Mortierellales and the possible bacteria genus Rubritalea and strengthen the relationships between these primary fungi. Two metabolites metolachlor oxanilic (MOXA) and moetolachlor ethanesulfonic acid (MESA) are detected in soil and earthworms in the high concentration treatments. Earthworms stimulate the formation of MOXA and yet inhibit the formation of MESA in soil. Another metabolite metolachlor-2-hydroxy (M2H) is also detected in earthworms, which is reported firstly. The study provides an important information for the remediation of metolachlor-polluted soil.

The effect of chlorination degree and substitution pattern on the interactions of polychlorinated biphenyls with model bacterial membranes

Polychlorinated biphenyls (PCB) are persistent organic pollutants that due to their chemical resistivity and inflammability found multiple applications. In spite of the global ban for PCB production, due to their long half-lives periods, PCB accumulate in the soils, so effective bioremediation of the polluted lands is of crucial importance. Some of the 209 PCB congeners exhibit increased toxicity to soil bacteria and their presence impoverish the soil decomposer community and slows down the degradation of environmental pollutants in the soils. The exact mechanism of PCB antimicrobial activity is unknown, but it is strictly related with the membrane activity of PCB. Therefore, to shed light on these interactions we applied Langmuir monolayers formed by selected phospholipids as model bacterial membranes. In our studies we tested 5 PCB congeners differing in the degree of chlorination and the distribution of the chlorine substituents around the biphenyl frame. Special attention was paid to tetra-substituted PCB because of their increased presence in the environment and disubstituted PCB being their degradation products. To characterize the model membranes as Langmuir monolayers, we used surface pressure measurements, Brewster angle microscopy and Grazing Incidence X-ray Diffraction. It turned out that among the tetra-substituted PCB the ortho-substituted non-dioxin like compound was much more membrane destructive than the flat dioxin-like congener. On the contrary, among the di-substituted PCB the flat para-substituted 2,2'-dichlorobiphenyl turned out to exhibit high membrane activity.

Microbial diversity assessment of polychlorinated biphenyl-contaminated soils and the biostimulation and bioaugmentation processes

The aim of this study was to know the biodiversity of total microorganisms contained in two polychlorinated biphenyl-contaminated aged soils and evaluate the strategies of bioaugmentation and biostimulation to biodegrade the biphenyls. Besides, the aerobic cultivable microorganisms were isolated and their capacity to biodegrade a commercial mixture of six congeners of biphenyls was evaluated. Biodiversity of contaminated soils was dominated by Actinobacteria (42.79%) and Firmicutes (42.32%) phyla, and others in smaller proportions such as Proteobacteria, Gemmatimonadetes, Chloroflexi, and Bacteroidetes. At the genus level, the majority of the population did not exceed 7% of relative abundance, including Bacillus, Achromobacter, Clostridium, and Pontibacter. Furthermore, four autochthonous bacterial cultures were possible isolates from the soils, which were identified by partial sequencing of the 16S rRNA gene, as Bacillus sp., Achromobacter sp., Pseudomonas stutzeri, and Bacillus subtilis, which were used for the bioaugmentation process. The bioaugmentation and biostimulation strategies achieved a biodegradation of about 60% of both soils after 8 weeks of the process; also, the four isolates were used as mixed culture to biodegrade a commercial mix of six polychlorinated biphenyl congeners; after 4 weeks of incubation, the concentration decreased from 0.5 mg/L to 0.23 mg/L.

Enhancement effect of earthworm (Eisenia fetida) on acetochlor biodegradation in soil and possible mechanisms

Acetochlor is a widely used chloroacetanilide herbicide and has posed environmental risks in soil and water due to its toxicity and high leaching capacity. Earthworm represents the dominant invertebrate in soil and can promote the decomposition of organic pollutants. The effect of earthworm on acetochlor degradation in soil was studied by soil column experiment with or without acetochlor and earthworm in sterile and natural soils. The degradation capacities of drilosphere components to acetochlor were investigated by microcosm experiments. Bacterial and fungal acetochlor degraders stimulated by earthworm were identified by high-throughput sequencing. The degradation kinetics of acetochlor suggested that both indigenous microorganisms and earthworm played important roles in acetochlor degradation. Acetochlor degradation was quicker in soil with earthworms than without earthworms, with the degradation rates increased by 62.3 ± 15.2% and 9.7 ± 1.7% in sterile and natural treatments respectively. The result was related to the neutralized pH, higher enzyme activities and enhanced soil microbial community diversity and richness in the presence of earthworms. Earthworm cast was the degradation hotpot in drilosphere and exhibited better anaerobic degradation capacity in microcosm experiments. The acetochlor degradation rate of cast in anaerobic environment was 12.0 ± 0.1% quicker than that in aerobic environment. Residual acetochlor in soil conferred a long-term impairment on fungal community, and this inhibition could be repaired by earthworm. Earthworm stimulated indigenous degraders like Sphingomonas and Microascales and carried suspected intestinal degraders like Mortierella and Escherichia_coli to degradation process. Cometabolism between nutrition cycle species and degraders in casts also contributed to its faster degradation rates. The study also presented some possible anaerobic degradation species like Rhodococcus, Pseudomonas_fulva and Methylobacillus.

Biotransformation of Sulfluramid (N-ethyl perfluorooctane sulfonamide) and dynamics of associated rhizospheric microbial community in microcosms of wetland plants

Although the use of Sulfluramid (N-ethyl perfluorooctane sulfonamide (N-EtFOSA)) has been restricted by the Stockholm Convention, it is still frequently detected in the environmental matrices and in use in some countries. Employing constructed wetlands as treatment systems requires understanding of the biodegradation process in the rhizosphere and the effect of contaminants on the microbes of wetlands. This study aimed to investigate the interactions between the microbial community and N-EtFOSA under aerobic and anaerobic conditions. Aerobic biotransformation of N-EtFOSA occurred with a half-life of 0.51 day and yielded 85.1 mol% PFOS of after 91 days. Kinetic modelling revealed that cleavage of the SN was the rate-limiting degradation step. Biotransformation was not observed under anaerobic and anoxic conditions, suggesting that N-EtFOSA is recalcitrant to biodegradation without dissolved oxygen. Under aerobic condition, the presence of N-EtFOSA and its biotransformation products decreased the microbial richness and diversity and exerted selective pressure on the microbial community. Enrichment of Methylocaldum was significant (49%) in the presence of N-EtFOSA compared to unexposed conditions (11%), suggesting that Methylocaldum is relatively tolerant to N-EtFOSA and potentially degrading N-EtFOSA. Under anaerobic conditions, the microbial richness and diversity were not significantly altered by the presence of N-EtFOSA. Only Methanomethylovorans increased significantly in the spiked microcosm (30% vs. 20%). These findings provide knowledge for comprehending the contribution of N-EtFOSA to other PFASs in various environmental conditions, information about microbial community changes in response to PFASs and robust microbial species which can degrade N-EtFOSA in the environment.

Intracellular toxicity exerted by PCBs and role of VBNC bacterial strains in biodegradation

Polychlorinated biphenyls (PCBs) are xenobiotic compounds that persists in the environment for long-term, though its productivity is banned. Abatement of the pollutants have become laborious due to it's recalcitrant nature in the environment leading to toxic effects in humans and other living beings. Biphenyl degrading bacteria co-metabolically degrade low chlorinated PCBs using the active metabolic pathway. bph operon possess different genetic arrangements in gram positive and gram negative bacteria. The binding ability of the genes and the active sites were determined by PCB docking studies. The active site of bphA gene with conserved amino acid residues determines the substrate specificity and biodegradability. Accumulation of toxic intermediates alters cellular behaviour, biomass production and downturn the metabolic activity. Several bacteria in the environment attain unculturable state which is viable and metabolically active but not cultivable (VBNC). Resuscitation-promoting factor (Rpf) and Rpf homologous protein retrieve the culturability of the so far uncultured bacteria. Recovery of this adaptive mechanism against various physical and chemical stressors make a headway in understanding the functionality of both environmental and medically important unculturable bacteria. Thus, this paper review about the general aspects of PCBs, cellular toxicity exerted by PCBs, role of unculturable bacterial strains in biodegradation, genes involved and degradation pathways. It is suggested to extrapolate the research findings on extracellular organic matters produced in culture supernatant of VBNC thus transforming VBNC to culturable state.

Assessment of biodegradation potential at a site contaminated by a mixture of BTEX, chlorinated pollutants and pharmaceuticals using passive sampling methods - Case study

The present study describes a pilot remediation test of a co-mingled plume containing BTEX, chlorinated pollutants and pharmaceuticals. Remediation was attempted using a combination of various approaches, including a pump and treat system applying an advanced oxidation process and targeted direct push injections of calcium peroxide. The remediation process was monitored intensively and extensively throughout the pilot test using various conventional and passive sampling methods, including next-generation amplicon sequencing. The results showed that the injection of oxygen-saturated treated water with residual hydrogen peroxide and elevated temperature enhanced the in situ removal of monoaromatics and chlorinated pollutants. In particular, in combination with the injection of calcium peroxide, the conditions facilitated the in situ bacterial biodegradation of the pollutants. The mean groundwater concentration of benzene decreased from 1349μg·L^-1 prior to the test to 3μg·L^-1 within 3months after the calcium peroxide injections; additionally, monochlorobenzene decreased from 1545μg·L^-1 to 36μg·L^-1, and toluene decreased from 143μg·L^-1 to 2μg·L^-1. Furthermore, significant degradation of the contaminants bound to the soil matrix in less permeable zones was observed. Based on a developed 3D model, 90% of toluene and 88% of chlorobenzene bound to the soil were removed during the pilot test, and benzene was removed almost completely. On the other hand, the psychopharmaceuticals were effectively removed by the employed advanced oxidation process only from the treated water, and their concentration in groundwater remained stagnant due to inflow from the surroundings and their absence of in situ degradation. The employment of passive sampling techniques, including passive diffusion bags (PDB) for volatile organic pollutants and their respective transformation products, polar organic compound integrative samplers (POCIS) for the pharmaceuticals and in situ soil microcosms for microbial community analysis, was proven to be suitable for monitoring remediation in saturated zones.

Pharmaceuticals, benzene, toluene and chlorobenzene removal from contaminated groundwater by combined UV/H2O2 photo-oxidation and aeration

This study was performed to test the feasibility of several decontamination methods for remediating heavily contaminated groundwater in a real contaminated locality in the Czech Republic, where a pharmaceuticals plant has been in operation for more than 80 years. The site is polluted mainly by recalcitrant psychopharmaceuticals and monoaromatic hydrocarbons, such as benzene, toluene and chlorobenzene. For this purpose, an advanced oxidation technique employing UV radiation with hydrogen peroxide dosing was employed, in combination with simple aeration pretreatment. The results showed that UV/H₂O₂ was an efficient and necessary step for degradation of the pharmaceuticals; however, the monoaromatics were already removed during the aeration step. Characterization of the removal mechanisms participating in the aeration revealed that volatilization, co-precipitation and biodegradation contributed to the process. These findings were supported by bacterial metabolite analyses, phospholipid fatty acid analysis, qPCR of representatives of the degradative genes and detailed characterization of the formed precipitate using Mössbauer spectroscopy and scanning electron microscopy. Further tests were carried out in a continuous arrangement directly connected to the wells already present in the locality. The results documented the feasibility of combination of the photo-reactor employing UV/H₂O₂ together with aeration pretreatment for 4 months, where the overall decontamination efficiency ranged from 72% to 99% of the pharmaceuticals. We recorded even better results for the monoaromatics decontamination except for one month, when we encountered some technical problems with the aeration pump. This demonstrated the necessity of using the aeration step.

Microbiology Meets Archaeology: Soil Microbial Communities Reveal Different Human Activities at Archaic Monte Iato (Sixth Century BC)

Microbial ecology has been recognized as useful in archaeological studies. At Archaic Monte Iato in Western Sicily, a native (indigenous) building was discovered. The objective of this study was the first examination of soil microbial communities related to this building. Soil samples were collected from archaeological layers at a ritual deposit (food waste disposal) in the main room and above the fireplace in the annex. Microbial soil characterization included abundance (cellular phospholipid fatty acids (PLFA), viable bacterial counts), activity (physiological profiles, enzyme activities of viable bacteria), diversity, and community structure (bacterial and fungal Illumina amplicon sequencing, identification of viable bacteria). PLFA-derived microbial abundance was lower in soils from the fireplace than in soils from the deposit; the opposite was observed with culturable bacteria. Microbial communities in soils from the fireplace had a higher ability to metabolize carboxylic and acetic acids, while those in soils from the deposit metabolized preferentially carbohydrates. The lower deposit layer was characterized by higher total microbial and bacterial abundance and bacterial richness and by a different carbohydrate metabolization profile compared to the upper deposit layer. Microbial community structures in the fireplace were similar and could be distinguished from those in the two deposit layers, which had different microbial communities. Our data confirmed our hypothesis that human consumption habits left traces on microbiota in the archaeological evidence; therefore, microbiological residues as part of the so-called ecofacts are, like artifacts, key indicators of consumer behavior in the past.

Bioremediation of long-term PCB-contaminated soil by white-rot fungi

The objective of this work was to test the PCB-degrading abilities of two white-rot fungi, namely Pleurotus ostreatus and Irpex lacteus, in real contaminated soils with different chemical properties and autochthonous microflora. In addition to the efficiency in PCB removal, attention was given to other important parameters, such as changes in the toxicity and formation of PCB transformation products. Moreover, structural shifts and dynamics of both bacterial and fungal communities were monitored using next-generation sequencing and phospholipid fatty acid analysis. The best results were obtained with P. ostreatus, which resulted in PCB removals of 18.5, 41.3 and 50.5% from the bulk, top (surface) and rhizosphere, respectively, of dumpsite soils after 12 weeks of treatment. Numerous transformation products were detected (hydoxylated and methoxylated PCBs, chlorobenzoates and chlorobenzyl alcohols), which indicates that both fungi were able to oxidize and decompose the aromatic moiety of PCBs in the soils. Microbial community analysis revealed that P. ostreatus efficiently colonized the soil samples and suppressed other fungal genera. However, the same fungus substantially stimulated bacterial taxa that encompass putative PCB degraders. The results of this study finally demonstrated the feasibility of using this fungus for possible scaled-up bioremediation applications.

Removal of polychlorinated biphenyl congeners in mixture Delor 103 from wastewater by ozonation vs/and biological method

Polychlorinated biphenyls (PCBs) produced in Slovakia as a commercial mixture Delor 103 cause the main contamination of sediment, water and fish in the eastern part of Slovakia. Delor 103 is a mixture of 40% PCB congeners, nine of them: PCB 8 (2,4'-dichlorobiphenyl), PCB 28 (2,4,4'-trichlorobiphenyl), PCB 52 (2,2',5,5'-tetrachlorobiphenyl), PCB 101 (2,2',4,5,5'-pentachlorobiphenyl), PCB 118 (2,3',4,4',5-pentachlorobiphenyl), PCB 138 (2,2',3,4,4',5'-hexachlorobiphenyl), PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl), PCB 180 (2,2',3,4,4',5,5'-heptachlorobiphenyl), and PCB 203 (2,2',3,4,4',5,5',6-octachlorobiphenyl), were monitored for their removal by ozonation and biodegradation using Achromobacter xylosoxidans. Ozonation improved the removal of PCB 52, 118, 153, 138, 180, and 203 using biological method with A. xylosoxidans. Degradation of 55% of the total amount of nine selected PCB congeners was achieved by the biological method with A. xylosoxidans, while 86% of the total amount of the nine selected PCB congeners were removed by the ozonation method; using a combination of biological and chemical methods, ozonation and A. xylosoxidans, showed a 94% removal efficiency of the selected PCB congeners present in mixture Delor 103.

Effect of Medicago sativa L. and compost on organic and inorganic pollutant removal from a mixed contaminated soil and risk assessment using ecotoxicological tests

Several Gentle Remediation Options (GRO), e.g., plant-based options (phytoremediation), singly and combined with soil amendments, can be simultaneously efficient for degrading organic pollutants and either stabilizing or extracting trace elements (TEs). Here, a 5-month greenhouse trial was performed to test the efficiency of Medicago sativa L., singly and combined with a compost addition (30% w/w), to treat soils contaminated by petroleum hydrocarbons (PHC), Co and Pb collected at an auto scrap yard. After 5 months, total soil Pb significantly decreased in the compost-amended soil planted with M. sativa, but not total soil Co. Compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and shoot Pb concentrations [3.8 mg kg(-1) dry weight (DW)]. Residual risk assessment after the phytoremediation trial showed a positive effect of compost amendment on plant growth and earthworm development. The O2 uptake by soil microorganisms was lower in the compost-amended soil, suggesting a decrease in microbial activity. This study underlined the benefits of the phytoremediation option based on M. sativa cultivation and compost amendment for remediating PHC- and Pb-contaminated soils.

Aerobic Degradation of Sulfadiazine by Arthrobacter spp.: Kinetics, Pathways, and Genomic Characterization

Two aerobic sulfadiazine (SDZ) degrading bacterial strains, D2 and D4, affiliated with the genus Arthrobacter, were isolated from SDZ-enriched activated sludge. The degradation of SDZ by the two isolates followed first-order decay kinetics. The half-life time of complete SDZ degradation was 11.3 h for strain D2 and 46.4 h for strain D4. Degradation kinetic changed from nongrowth to growth-linked when glucose was introduced as the cosubstrate, and accelerated biodegradation rate was observed after the adaption period. Both isolates could degrade SDZ into 12 biodegradation products via 3 parallel pathways, of which 2-amino-4-hydroxypyrimidine was detected as the principal intermediate product toward the pyrimidine ring cleavage. Compared with five Arthrobacter strains reported previously, D2 and D4 were the only Arthrobacter strains which could degrade SDZ as the sole carbon source. The draft genomes of D2 and D4, with the same completeness of 99.7%, were compared to other genomes of related species. Overall, these two isolates shared high genomic similarities with the s-triazine-degrading Arthrobacter sp. AK-YN10 and the sulfonamide-degrading bacteria Microbacterium sp. C448. In addition, the two genomes contained a few significant regions of difference which may carry the functional genes involved in sulfonamide degradation.

Plants Rather than Mineral Fertilization Shape Microbial Community Structure and Functional Potential in Legacy Contaminated Soil

Plant-microbe interactions are of particular importance in polluted soils. This study sought to determine how selected plants (horseradish, black nightshade and tobacco) and NPK mineral fertilization shape the structure of soil microbial communities in legacy contaminated soil and the resultant impact of treatment on the soil microbial community functional potential. To explore these objectives, we combined shotgun metagenomics and 16S rRNA gene amplicon high throughput sequencing with data analysis approaches developed for RNA-seq. We observed that the presence of any of the selected plants rather than fertilization shaped the microbial community structure, and the microbial populations of the root zone of each plant significantly differed from one another and/or from the bulk soil, whereas the effect of the fertilizer proved to be insignificant. When we compared microbial diversity in root zones versus bulk soil, we observed an increase in the relative abundance of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria or Bacteroidetes, taxa which are commonly considered copiotrophic. Our results thus align with the theory that fast-growing, copiotrophic, microorganisms which are adapted to ephemeral carbon inputs are enriched in the vegetated soil. Microbial functional potential indicated that some genetic determinants associated with signal transduction mechanisms, defense mechanisms or amino acid transport and metabolism differed significantly among treatments. Genetic determinants of these categories tend to be overrepresented in copiotrophic organisms. The results of our study further elucidate plant-microbe relationships in a contaminated environment with possible implications for the phyto/rhizoremediation of contaminated areas.

Effect of altitude and season on microbial activity, abundance and community structure in Alpine forest soils

In the current context of climate change, the study of microbial communities along altitudinal gradients is especially useful. Only few studies considered altitude and season at the same time. We characterized four forest sites located in the Italian Alps, along an altitude gradient (545-2000 m a.s.l.), to evaluate the effect of altitude in spring and autumn on soil microbial properties. Each site in each season was characterized with regard to soil temperature, physicochemical properties, microbial activities (respiration, enzymes), community level physiological profiles (CLPP), microbial abundance and community structure (PLFA). Increased levels of soil organic matter (SOM) and nutrients were found at higher altitudes and in autumn, resulting in a significant increase of (soil dry-mass related) microbial activities and abundance at higher altitudes. Significant site- and season-specific effects were found for enzyme production. The significant interaction of the factors site and incubation temperature for soil microbial activities indicated differences in microbial communities and their responses to temperature among sites. CLPP revealed site-specific effects. Microbial community structure was influenced by altitudinal, seasonal and/or site-specific effects. Correlations demonstrated that altitude, and not season, was the main factor determining the changes in abiotic and biotic characteristics at the sites investigated.

Polycyclic aromatic hydrocarbons degradation and microbial community shifts during co-composting of creosote-treated wood

The feasibility of decontaminating creosote-treated wood (CTW) by co-composting with agricultural wastes was investigated using two bulking agents, grass cuttings (GC) and broiler litter (BL), each employed at a 1:1 ratio with the matrix. The initial concentration of total polycyclic aromatic hydrocarbons (PAHs) in CTW (26,500 mg kg(-1)) was reduced to 3 and 19% after 240 d in GC and BL compost, respectively. PAH degradation exceeded the predicted bioaccesible threshold, estimated through sequential supercritical CO2 extraction, together with significant detoxification, assessed by contact tests using Vibrio fisheri and Hordeum vulgare. GC composting was characterized by high microbial biomass growth in the early phases, as suggested by phospholipid fatty acid analyses. Based on the 454-pyrosequencing results, fungi (mostly Saccharomycetales) constituted an important portion of the microbial community, and bacteria were characterized by rapid shifts (from Firmicutes (Bacilli) and Actinobacteria to Proteobacteria). However, during BL composting, larger amounts of prokaryotic and eukaryotic PLFA markers were observed during the cooling and maturation phases, which were dominated by Proteobacteria and fungi belonging to the Ascomycota and those putatively related to the Glomeromycota. This work reports the first in-depth analysis of the chemical and microbiological processes that occur during the co-composting of a PAH-contaminated matrix.

Draft Genome Sequence of Arthrobacter sp. Strain SPG23, a Hydrocarbon-Degrading and Plant Growth-Promoting Soil Bacterium

We report here the 4.7-Mb draft genome of Arthrobacter sp. SPG23, a hydrocarbonoclastic Gram-positive bacterium belonging to the Actinobacteria, isolated from diesel-contaminated soil at the Ford Motor Company site in Genk, Belgium. Strain SPG23 is a potent plant growth promoter useful for diesel fuel remediation applications based on plant-bacterium associations.