Simultaneous Emerging Contaminant Removal and H2O2 Generation Through Electron Transfer Carrier Effect of Bi─O─Ce Bond Bridge Without External Energy Consumption.

Conventional advanced oxidation processes (AOPs) require significant external energy consumption to eliminate emerging contaminants (ECs) with stable structures. Herein, a catalyst consisting of nanocube BiCeO particles (BCO-NCs) prepared by an impregnation-hydrothermal process is reported for the first time, which is used for removing ECs without light/electricity or any other external energy input in water and simultaneous in situ generation of H2O2. A series of characterizations and experiments reveal that dual reaction centers (DRC) which are similar to the valence band/conducting band structure are formed on the surface of BCO-NCs. Under natural conditions without any external energy consumption, the BCO-NCs self-purification system can remove more than 80% of ECs within 30 min, and complete removal of ECs within 30 min in the presence of abundant electron acceptors, the corresponding second-order kinetic constant is increased to 3.62 times. It is found that O2 can capture electrons from ECs through the Bi─O─Ce bond bridge during the reaction process, leading to the in situ production of H2O2. This work will be a key advance in reducing energy consumption for deep wastewater treatment and generating important chemical raw materials.

Enhanced purification of kitchen-oil wastewater driven synergistically by surface microelectric fields and microorganisms.

The stable structure and toxic effect of refractory organic pollutants in wastewater lead to the problem of high energy consumption in water treatment technology. Herein, we propose a synergistic purification of refractory wastewater driven by microorganisms and surface microelectric fields (SMEF) over a dual-reaction-center (DRC) catalyst HCLL-S8-M prepared by an in situ growth method of carbon nitride on the Cu-Al2O3 surface. Characterization techniques demonstrate the successful construction of SMEF with strong electrostatic force over HCLL-S8-M based on cation-π interactions between metal copper ions and carbon nitride rings. With the catalyst as the core filler, an innovative fixed bed bioreactor is constructed to purify the actual kitchen-oil wastewater. The removal efficiency of the wastewater even with a very low biodegradability (BOD5/COD = 0.33) can reach 60% after passing through this bioreactor. An innovative reaction mechanism is revealed for the first time that under the condition of a small amount of biodegradable organic matter, the SMEF induces the enrichment of electric active microorganisms (Desulfobulbus and Geobacter) in the wastewater, accelerates the interspecies electron transfer of intertrophic metabolism with the biodegradable bacteria through the extracellular electron transfer mechanism such as cytochrome C and self-secreted electron shuttle. The electrons of the refractory organic pollutants adsorbed on the surface of the catalyst are delocalized by the SMEF, which can be directly utilized by microorganisms through EPS conduction. The SMEF generated by electron polarization can maximize the utilization of pollutants and microorganisms in wastewater and further enhance degradation without adding any external energy, which is of great significance to the development of water self-purification technology.

Assessing the bioavailability of antibiotics in soil with the diffusive gradients in thin films (DGT).

The diffusive gradients in thin films (DGT) technique is an excellent method for investigating the dynamic processes of antibiotics in soils. However, whether it is applicable in antibiotic bioavailability assessment is yet to be disclosed. This study employed DGT to determine the antibiotic bioavailability in soil, and compared the results with plant uptake, soil solutions, and solvent extraction methods. DGT exhibited predictive capability for plant taking in antibiotics proved by the significant linear relationship between the DGT based concentration (CDGT) and antibiotic concentration in roots and shoots. Although the performance of soil solution was acceptable based on linear relationship analysis, its stability was weaker than DGT. The results based on plant uptake and DGT indicated the bioavailable antibiotic contents in different soils were inconsistent because of the distinct mobility and resupply of sulphonamides and trimethoprim in different soils, as represented by Kd and Rds, which were affected by soil properties. Plant species played an important role in antibiotic uptake and translocation. Antibiotic uptake by plants depends on antibiotic, plant and soil. These results confirmed the capability of DGT in determining antibiotic bioavailability for the first time. This work provided a simple and powerful tool for environmental risk evaluation of antibiotics in soils.

Identification and synergetic mechanism of TCE, H2 and O2 metabolic microorganisms in the joint H2/O2 system.

The sole H2 and O2 usually promote chlorinated hydrocarbons (CHCs) biotransformation by several mechanisms, including reductive dechlorination and aerobic oxidation. However, the mechanism of the CHCs transformation in joint H2 and O2 system (H2/O2 system) is still unclear. In this study, the degradation kinetics of trichloroethene (TCE) were investigated and DNA stable isotope probing (DNA-SIP) were used to explore the synergistic mechanism of functional microorganisms on TCE degradation under the condition of H2/O2 coexistence. In the H2/O2 microcosm, TCE was significantly removed by 13.00 µM within 40 days, much higher than N2, H2 and O2 microcosms, and 1,1-DCE was detected as an intermediate. DNA-SIP technology identified three anaerobic TCE metabolizers, five aerobic TCE metabolizers, nine hydrogen-oxidizing bacteria (HOB), some TCE metabolizers utilizing limited O2, and some anaerobic dechlorinating bacteria reductively using H2 to dechlorinate TCE. It is also confirmed for the first time that 3 OUTs belonging to Methyloversatilis and SH-PL14 can simultaneously utilize H2 and O2 as energy sources to grow and metabolize TCE or 1,1-DCE. HOB may provide carbon sources or electron acceptors or donors for TCE biotransformation. These findings confirm the coexistence of anaerobic and aerobic TCE metabolizers and degraders, which synergistically promoted the conversion of TCE in the joint H2/O2 system. Our results provide more information about the functional microbe resources and synergetic mechanisms for TCE degradation.

Water Self-Purification with Zero External Consumption by Livestock Manure Resource Utilization.

Improper disposal of waste biomass and an increasing number of emerging contaminants (ECs) in water environment are universal threats to the global environment. Here, we creatively propose a sustainable strategy for the direct resource transformation of livestock manure (LM) into an innovative catalyst (Fe-CCM) for water self-purification with zero external consumption. ECs can be rapidly degraded in this self-purification system at ambient temperature and atmospheric pressure, without any external oxidants or energy input, accompanied by H2O and dissolved oxygen (DO) activation. The performance of the self-purification system is not affected by various types of salinity in the wastewater, and the corresponding second-order kinetic constant is improved 7 times. The enhanced water self-purification mechanism reveales that intermolecular forces between anions and pollutants reinforce electron exchange between pollutants and metal sites on the catalyst, further inducing the utilization of the intrinsic energy of contaminants, H2O, and DO through the interfacial reaction. This work provides new insights into the rapid removal of ECs in complicated water systems with zero external consumption and is expected to advance the resource utilization of livestock waste.

[Changes of soil water budget in the area covered by biological soil crusts in Mu Us sandy land, China]. / æ¯›ä¹Œç´ æ²™åœ°ç”Ÿç‰©ç»“çš®è¦†ç›–åŒºåœŸå£¤æ°´åˆ†æ”¶æ”¯å˜åŒ–ç‰¹å¾.

Exploring and quantifying the impacts of biological soil crusts on soil hydrological processes and soil water budget in semi-arid ecosystems can provide a theoretical basis for vegetation restoration and reconstruction in deserts. Based on continuous observation of soil water content in different types of areas covered by biological soil crusts (e.g., algae, moss) and bare sand in the Mu Us sandy land during the growing season (May to October) from 2018 to 2020, we examined the effects of biological soil crusts on soil water budget at a depth of 0-40 cm. Results showed that algae and moss crusts significantly reduced soil water supplement below 40 cm by rainfall and increased soil water evaporation loss, compared with that under bare sand. In the relatively wet year (2018), the amount of soil water expenditure (seepage+evaporation) covered by bare sand and the various types of biological soil crusts was less than that of rainfall, resulting in net soil water income. In the relative dry years (2019 and 2020), the amount of soil water expenditure covered by dominant algae and moss crusts was higher than that of rainfall, causing net soil water deficit, but opposite for bare sand. Biological soil crusts led to the imbalance of soil water budget of 0-40 cm depth and even soil water deficit in relatively dry years, which may lead to the succession of plant communities to be dominated by shallow-rooted plants in this area.

Diversity and structure of phenanthrene degrading bacterial communities associated with fungal bioremediation in petroleum contaminated soil.

Fungal bioremediation is a promising technique for the cleanup of sites contaminated with polycyclic aromatic hydrocarbons (PAHs). However, due to limited understanding of the composition and dynamics of the native PAH-degrading microorganisms in contaminated sites, its application has been difficult. In the present study, DNA stable-isotope probing was performed to identify indigenous phenanthrene (PHE)-degrading bacteria and determine their diversity during the fungal bioremediation process. The results showed a total of 14 operational taxonomic units (OTUs) enriched in the heavy DNA fractions, which were related to seven genera (Sphingomonas, Sphingobacterium, Acidovorax, Massilia, Flavobacterium, Cupriavidus, Aeromicrobium, and unclassified Chitinophagaceae). Along with enhanced efficiency of PHE removal, the number and diversity of indigenous PHE-degrading bacteria in soil bioaugmented with fungi were significantly increased. Furthermore, based on the results of linear model analysis, we found that PHE degraders affiliated with the genus Sphingomonas were significantly enriched during fungal bioremediation. Moreover, fungal bioaugmentation promoted indigenous functional Proteobacteria involved in PAH degradation through co-metabolism, suggesting that PAH biodegradation was attributable to cooperative metabolism by fungi and indigenous bacteria. Our findings provide new insights into the diversity of PHE-degrading communities and support a more comprehensive view of the fungal bioremediation process.

Large-scale biogeographical patterns of antibiotic resistome in the forest soils across China.

Soil is a reservoir of environmental resistomes. Information about their distribution, profiles, and driving forces in undisturbed environments is essential for understanding and managing modern antibiotic resistance genes (ARGs) in human disturbed environments. However, knowledge about the resistomes in pristine soils is limited, particularly at national scale. Here, we conducted a national-scale investigation of soil resistomes in pristine forests across China. Although the antibiotics content was low and ranged from below limit of detection (LOD) to 0.290 µg/kg, numerous detected ARGs conferring resistance to major classes of modern antibiotics were identified and indicated forest soils as a potential source of resistance traits. ARGs ranged from 6.20 × 10-7 to 2.52 × 10-3 copies/16S-rRNA and were predominated by those resisting aminoglycoside and encoding deactivation mechanisms. Low abundance of mobile genetic elements (MGEs) and its scarcely positive connections with ARGs suggest the low potential of horizontal gene transfer. The geographic patterns of ARGs and ARG-hosts in pristine forest soils were mainly driven by soil physiochemical variables and followed a distance-decay relationship. This work focusing on pristine soils can provide valuably new information for our understanding of the ARGs in human disturbed environments.

Shifts in a Phenanthrene-Degrading Microbial Community are Driven by Carbohydrate Metabolism Selection in a Ryegrass Rhizosphere.

Plants usually promote pollutant bioremediation by several mechanisms including modifying the diversity of functional microbial species. However, conflicting results are reported that root exudates have no effects or negative effects on organic pollutant degradation. In this study, we investigated the roles of ryegrass in phenanthrene degradation in soils using DNA stable isotope probing (SIP) and metagenomics to reveal a potential explanation for conflicting results among phytoremediation studies. Phenanthrene biodegradation efficiency was improved by 8% after 14 days of cultivation. Twelve and ten operational taxonomic units (OTUs) were identified as active phenanthrene degraders in non-rhizosphere and rhizosphere soils, respectively. The active phenanthrene degraders exhibited higher average phylogenetic distances in rhizosphere soils (0.33) than non-rhizosphere soils (0.26). The Ka/Ks values (the ratio of nonsynonymous to synonymous substitutions) were about 10.37% higher in the rhizosphere treatment among >90% of all key carbohydrate metabolism-related genes, implying that ryegrass may be an important driver of microbial community variation in the rhizosphere by relieving the carbohydrate metabolism pressure and improving the survival ability of r-strategy microbes. Most Ka/Ks values of root-exudate-related metabolism genes exhibited little change, except for fumarate hydratase that increased 13-fold in the rhizosphere compared to that in the non-rhizosphere treatment. The Ka/Ks values of less than 50% phenanthrene-degradation-related genes were affected, 30% of which increased and 70% behaved oppositely. Genes with altered Ka/Ks values had a low percentage and followed an inconsistent changing tendency, indicating that phenanthrene and its metabolites are not major factors influencing the active degraders. These results suggested the importance of carbohydrate metabolism, especially fumaric acid, in rhizosphere community shift, and hinted at a new hypothesis that the rhizosphere effect on phenanthrene degradation efficiency depends on the existence of active degraders that have competitive advantages in carbohydrate and fumaric acid metabolism.

Land-use changes alter soil bacterial composition and diversity in tropical forest soil in China.

Tropical forests, under pressure from human activities, are important reservoirs of biodiversity and regulators of global biogeochemical cycles. Land-use and management are influential drivers of environmental change and ecosystem sustainability. However, only limited studies have analysed the impacts of planting age and vegetation type under land-use change on soil microbial community in tropical forests simultaneously. Here, we assessed soil bacterial community composition and diversity under different land-use in Hainan Province, China, using high-throughput sequencing combined with PICRUSt analysis. Land-use included natural forest, 5-year-old cropland, young (5-year-old) rubber tree plantation, and old (30-year-old) rubber tree plantation. Land-use changes altered the soil bacterial community composition but had a non-significant influence on alpha diversity (P > .05). We found that bacterial beta-diversity significantly decreased in young rubber tree plantation soils and cropland soils compared to natural forest as a control. In contrast, soil bacterial beta-diversity increased in old rubber tree plantation soils, indicating the effects of time since planting. There was no difference in microbial beta-diversity between soils from cropland and young rubber tree plantation. Soil bulk density and moisture, not pH, were the main environmental factors explaining the variability in microbial diversity. PICRUSt analysis of soil bacterial predicted gene abundances within metabolic pathways and indicated that land-use change altered soil functional traits, e.g., amino acid-related enzymes, ribosomes, DNA repair/recombination proteins and oxidative phosphorylation. Also, vegetation type, not planting age, had significant impacts on soil functional traits. Overall, planting age had the greatest influence on soil bacterial beta-diversity, while vegetation type was more crucial for soil functional traits (P < .05).

Biphenyl-Metabolizing Microbial Community and a Functional Operon Revealed in E-Waste-Contaminated Soil.

Primitive electronic waste (e-waste) recycling activities release massive amounts of persistent organic pollutants (POPs) and heavy metals into surrounding soils, posing a major threat to the ecosystem and human health. Microbes capable of metabolizing POPs play important roles in POPs remediation in soils, but their phylotypes and functions remain unclear. Polychlorinated biphenyls (PCBs), one of the main pollutants in e-waste contaminated soils, have drawn increasing attention due to their high persistence, toxicity, and bioaccumulation. In the present study, we employed the culture-independent method of DNA stable-isotope probing to identify active biphenyl and PCB degraders in e-waste-contaminated soil. A total of 19 rare operational taxonomic units and three dominant bacterial genera ( Ralstonia, Cupriavidus, and uncultured bacterium DA101) were enriched in the 13C heavy DNA fraction, confirming their functions in PCBs metabolism. Additionally, a 13.8 kb bph operon was amplified, containing a bphA gene labeled by 13C that was concentrated in the heavy DNA fraction. The tetranucleotide signature characteristics of the bph operon suggest that it originated from Ralstonia. The bph operon may be shared by horizontal gene transfer because it contains a transposon gene and is found in various bacterial species. This study gives us a deeper understanding of PCB-degrading mechanisms and provides a potential resource for the bioremediation of PCBs-contaminated soils.

Polychlorinated biphenyls and polybrominated diphenylethers in soils from planted forests and adjacent natural forests on a tropical island.

Transformation from natural forests to planted forests in tropical regions is an expanding global phenomenon causing major modifications of land cover and soil properties, e.g. soil organic carbon (SOC). This study investigated accumulations of POPs in soils under eucalyptus and rubber forests as compared with adjacent natural forests on Hainan Island, China. Results showed that due to the greater forest filter effect and the higher SOC, the natural forest have accumulated larger amounts of POPs in the top 20 cm soil. Based on correlation and air-soil equilibrium analysis, we highlighted the importance of SOC in the distribution of POPs. It is assumed that the elevated mobility of POPs in the planted forests was caused by greater loss of SOC and extensive leaching in the soil profile. This suggests that a better understanding of global POPs fate should take into consideration the role of planted forests.

Exploring the Influence of Environmental Factors on Bacterial Communities within the Rhizosphere of the Cu-tolerant plant, Elsholtzia splendens.

Bacterial communities of rhizospheric soils play an important role in the tolerance and uptake of metal-tolerant/hyperaccumulating plants to metals, e.g. the Cu-tolerant Elsholtzia splendens native to China. In this work, pyrosequencing of the bacterial 16S rRNA gene was firstly applied to investigate the rhizospheric bacterial community of E. splendens grown at Cu contaminated sites. The 47 phyla including 11 dominant phyla (>1%) in E. splendens rhizosphere were presented. The effects of Cu and other environmental factors (total organic carbon, total nitrogen and pH) on the rhizospheric bacterial community were studied comprehensively. The phyla abundances were affected by the environmental factors to different extent, and we found pH, instead of Cu concentration, influenced UniFrac distance significantly and was identified as the most important environmental factor affecting bacterial community. In addition, the influence of environmental factors on gene profiles was explored according to the predicted metagenomes obtained by PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states). Our study illustrates a view about Cu-tolerant E. splendens rhizospheric bacterial communities (composition, diversity and gene profiles) and their influencing factors, giving a hand for the understanding on bacterial community is formed and affected in rhizosphere.

Simultaneous enhanced removal of Cu, PCBs, and PBDEs by corn from e-waste-contaminated soil using the biodegradable chelant EDDS.

We evaluated the influence of the biodegradable chelant ethylenediamine disuccinic acid (EDDS) on plant uptake of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and Cu by corn from electronic waste (e-waste)-contaminated soil. The highest concentration and highest total uptake of Cu in corn were observed in the treatment with 5 mM EDDS, which resulted in a 4-fold increase of the Cu translocation factor (C(shoot)/C(root)) compared to the control. The concentrations of PCBs and PBDEs in shoots and roots increased with increasing application rates of EDDS, and 1.58- and 1.32-fold average increases in the concentrations of PCBs and PBDEs, respectively, were observed in shoots in the EDDS treatments. A significant positive correlation was observed between shoot Cu and shoot PCBs and PBDEs. We speculate that PCBs and PBDEs were activated by the EDDS-triggered dissolved organic carbon (DOC) and then indiscriminately taken up by roots and translocated to shoots following damage to the roots mainly by the increased extractable Cu resulting from the EDDS application.