Cable bacteria: Living electrical conduits for biogeochemical cycling and water environment restoration.

Since the discovery of multicellular cable bacteria in marine sediments in 2012, they have attracted widespread attention and interest due to their unprecedented ability to generate and transport electrical currents over centimeter-scale long-range distances. The cosmopolitan distribution of cable bacteria in both marine and freshwater systems, along with their substantial impact on local biogeochemistry, has uncovered their important role in element cycling and ecosystem functioning of aquatic environments. Considerable research efforts have been devoted to the potential utilization of cable bacteria for various water management purposes during the past few years. However, there lacks a critical summary on the advances and contributions of cable bacteria to biogeochemical cycles and water environment restoration. This review aims to provide an up-to-date and comprehensive overview of the current research on cable bacteria, with a particular view on their participation in aquatic biogeochemical cycles and promising applications in water environment restoration. It systematically analyzes (i) the global distribution of cable bacteria in aquatic ecosystems and the major environmental factors affecting their survival, diversity, and composition, (ii) the interactive associations between cable bacteria and other microorganisms as well as aquatic plants and infauna, (iii) the underlying role of cable bacteria in sedimentary biogeochemical cycling of essential elements including but not limited to sulfur, iron, phosphorus, and nitrogen, (iv) the practical explorations of cable bacteria for water pollution control, greenhouse gas emission reduction, aquatic ecological environment restoration, as well as possible combinations with other water remediation technologies. It is believed to give a step-by-step introduction to progress on cable bacteria, highlight key findings, opportunities and challenges of using cable bacteria for water environment restoration, and propose directions for further exploration.

Effects of risk exposure on emotional distress among Chinese adults during the COVID-19 pandemic: The moderating role of disruption of life and perceived controllability.

Background: COVID-19 affects not only the physical health of individuals but also their mental health and different types of risk exposures are believed to have different effects on individual emotional distress. Objective: This study explores the relationships between risk exposure, disruption of life, perceived controllability, and emotional distress among Chinese adults during the COVID-19 outbreak. Methods: This study is based on an online survey conducted during the COVID-19 pandemic, from 1 to 10 February 2020, with a total of 2,993 Chinese respondents recruited through convenience and snowball sampling. Multiple linear regression analysis were used to examine the relationships among risk exposure, disruption of life, perceived controllability, and emotional distress. Results: This study found that all types of risk exposures were significantly associated with emotional distress. Individuals with neighborhood infection, family member infection/close contact, and self-infection/close contact had higher levels of emotional distress (B = 0.551, 95% CI: -0.019, 1.121; B = 2.161, 95% CI: 1.067, 3.255; B = 3.240, 95% CI: 2.351, 4.129) than those without exposure. The highest levels of emotional distress occurred among individuals experiencing self-infection/close contact, while the lowest levels of emotional distress occurred among individuals experiencing neighborhood infection and the moderate levels of emotional distress occurred among individuals experiencing family member infection (Beta = 0.137; Beta = 0.073; Beta = 0.036). Notably, the disruption of life aggravated the effect of self-infection/close contact on emotional distress and family member infection/close contact on emotional distress (B = 0.217, 95% CI: 0.036, 0.398; B = 0.205, 95% CI: 0.017, 0.393). More importantly, perceived controllability lowered the strength of the association between self-infection/close contact and emotional distress, as well as family member infection/close contact and emotional distress (B = -0.180, 95% CI: -0.362, 0.002; B = -0.187, 95% CI: -0.404, 0.030). Conclusion: These findings shed light on mental health interventions for people exposed to or infected with COVID-19 near the beginning of the pandemic, particularly those who themselves had COVID or had family members with COVID-19 risk exposure, including being infected/having close contact with an infected person. We call for appropriate measures to screen out individuals or families whose lives were, or remain, more severely affected by COVID-19. We advocate providing individuals with material support and online mindfulness-based interventions to help them cope with the after-effects of COVID-19. It is also essential to enhance the public's perception of controllability with the help of online psychological intervention strategies, such as mindfulness-based stress reduction programs and mindfulness-oriented meditation training programs.

Water quality improvement and consequent N2O emission reduction in hypoxic freshwater utilizing green oxygen-carrying biochar.

Declines in dissolved oxygen (DO) levels in aquatic systems worldwide negatively influence biodiversity, nutrient biogeochemistry, drinking water quality, and greenhouse gas emission. As a response, oxygen-carrying dual-modified sediment-based biochar (O-DM-SBC) as a green and sustainable emerging material was utilized for simultaneous hypoxia restoration, water quality improvement, and greenhouse gas reduction. Column incubation experiments were carried out using the water and sediment samples from a tributary of the Yangtze River. The application of O-DM-SBC effectively increased the DO concentration from ~1.99 mg/L to ~6.44 mg/L and decreased the concentrations of TN and NH4+-N by 61.1 % and 78.3 %, respectively, during the 30-day incubation period. Moreover, the N2O emission was apparently inhibited by O-DM-SBC with a 50.2 % decrease in daily flux under the functional coupling of biochar (SBC) and oxygen nanobubbles (ONBs). Path analysis supported that the treatments (SBC, modification, and ONBs) had joint effects on N2O emission by changing the concentration and composition of dissolved inorganic nitrogen (e.g., NH4+-N, NO2--N and NO3--N). The nitrogen-transforming bacteria were found to be significantly promoted by O-DM-SBC at the end of the incubation, while the archaeal community seemed to be more active in the SBC groups without ONB, confirming their different mechanisms. The PICRUSt2 prediction results revealed that most nitrogen metabolism genes including nitrification (i.e., amoABC), denitrification (i.e., nirK and nosZ), and assimilatory nitrate reduction (i.e., nirB and gdhA) were largely enriched in O-DM-SBC, indicating the active nitrogen-cycling network was established, thus achieving simultaneous nitrogen pollution control and N2O emission reduction. Our findings not only confirm the beneficial effect of O-DM-SBC amendment on nitrogen pollution control and N2O emission mitigation in hypoxic freshwater, but also contribute to a more comprehensive understanding of the effect of oxygen-carrying biochar on nitrogen cycling microbial communities.

Continuous inactivation of human adenoviruses in water by a novel g-C3N4/WO3/biochar memory photocatalyst under light-dark cycles.

Viruses transmitted by water have raised considerable concerns for public health. A novel memory photocatalyst of g-C3N4/WO3/biochar was successfully developed for effective inactivation of human adenoviruses (HAdVs) in water, in which WO3 as an electron-storage reservoir and biochar as an electron shuttle is employed to synergistically improve photocatalytic activity of g-C3N4. The tertiary composite exhibited continuous photocatalytic performance for HAdVs inactivation without regrowth in water under light-dark cycles, i.e., ∼3.9-log inactivation under 6-h visible light irradiation and an additional ∼1.1-log inactivation under the following 6-h dark. The enhanced virucidal mechanism was attributed to the heterojunction formation and especially the electron-transfer pathway switching via biochar incorporation, contributing to electron transfer and storage in the light phase and then electron release in the dark phase, along with obviously increased generation of the virus-killing •OH radicals under light-dark cycles.

A novel TiO2-x/TiN@ACB composite for synchronous photocatalytic Cr(VI) reduction and water photothermal evaporation under visible/infrared light illumination.

Relatively large band-gap, fast charge carriers recombination, and mono-functionality of photocatalytic materials are still representing stumbling hurdles against their optimal usage for water cleaning. Herein, a novel black titanium oxide/plasmonic titanium nitride@activated coconut biochar (TiO2-x/TiN@ACB) composite was designed to have both photocatalytic and photothermal functions. Intermediate states of black TiO2-x, plasmonic effect of TiN, and high electrons (e-) capacity of biochar enhanced band-gap narrowing, light absorbance extension, and charge carriers separation respectively. Black TiO2-x and plasmonic TiN sensitization via visible/infrared (Vis/IR) portion of photonic spectrum in addition to the confirmed close contact of composite constituents explained the demonstrated major role of e- in photocatalytic mechanism through efficient excitation and facile transfer. Thanks to black photocatalytic semiconductor and carbonic materials for their ultimate photons harnessing and efficient photothermal conversion where the composite exhibited a remarkable photothermal water evaporation upon Vis/IR illumination as well. TiO2-x/TiN@ACB composite revealed 92.8 and 89.7% photocatalytic reduction of hexavalent chromium (Cr(VI)) and water evaporation efficiencies up to 92.9 and 51.1% upon IR and Vis light illumination respectively. This study proposes a new approach for efficient water cleaning by coupling of oxygen deficient and plasmonic semiconductors supported on naturally derived carbonic material as a broad spectrum harvester and bi-functional photocatalytic and photothermal material.

Promoted microbial denitrification and carbon dioxide fixation via photogenerated electrons stored in novel core/shell memory photocatalysts in darkness.

Excess nitrogen in water and greenhouse gases, especially atmospheric carbon dioxide (CO2) from the rapid development of modern society have become an acute threat to the environment. Herein, novel core/shell structured g-C3N4@WO3 memory photocatalyst was fabricated by coating g-C3N4 on the surface of WO3 nanoparticles and applied in the simultaneous coupling of memory photocatalysts and microbial communities (SCMPMC) for the synergistic removal of microbial nitrate and CO2 fixation in darkness. The results showed that ∼98.6% of nitrate was removed and ∼17.7% of CO2 was fixed in darkness by microorganisms in the presence of g-C3N4@WO3 memory photocatalyst within 48 h. Besides, the investigation of the mechanism evidenced that g-C3N4@WO3 memory photocatalyst can promote electron transfer in the SCMPMC system. Moreover, key enzyme activities (i.e., NAR, NIR, CAT, and ETSA) were accelerated, indicating that the activities of enzymes within microorganisms could be remarkably enhanced by the continuous release of stored electrons by the g-C3N4@WO3 memory photocatalyst in the dark. Furthermore, microbial community analysis revealed that the g-C3N4@WO3 memory photocatalyst increased the relative abundance of denitrifiers (i.e., Acidobacterota, Actinobacteria, Chloroflexi, and Proteobacteria) and CO2-assimilating microorganisms (i.e., Pseudomonas), in the treated communities compared with the original community in river sediment, demonstrating the positive effects of g-C3N4@WO3 memory photocatalyst on river sediment microbial communities. The results in this study could shed new light on the establishment of promising synergistic microbial nitrate removal and CO2 fixation methods and mechanisms in darkness.

Sustainable restoration of anoxic freshwater using environmentally-compatible oxygen-carrying biochar: Performance and mechanisms.

The long-term decline in dissolved oxygen (DO) levels in freshwater systems including rivers and lakes has become a worldwide concern, which can threaten biodiversity, nutrient biogeochemistry, water quality and ultimately human health. Herein, we report a sustainable restoration strategy for anoxic freshwater using local sediment-based biochar as novel oxygen nanobubble carriers. Column incubation experiments were conducted with water and sediment samples from an urban tributary of the Yangtze River. The oxygen-carrying sediment-based biochar (O-SBC) showed long-lasting re-oxygenation performance for anoxic river waters during 28-day period, in which DO was rapidly elevated from ∼0.14 to ∼7.87 mg/L and gradually maintained at ∼4.78 mg/L until the end. O-SBC with multiple functions switched the sediments from a source to a sink of nutrients, and its release of oxygen nanobubbles contributed further decrements of 66.3% NH4+-N and 142.9% PO43--P except for physical blocking and physicochemical adsorption. Notably, a comprehensive focus on restoration mechanism was explored in view of microbial community response. The re-oxygenation was followed by a ∼5.05% increase of bacterial diversity (Shannon index) in water, but a ∼2.40% decrease in sediments. A proliferation of some specific aerobic populations was observed, of which the nitrifying Nitrospira abundances were ∼10-fold higher in the water from O-SBC than the control. Additionally, functional genes involved in nitrous oxide reduction, polyphosphate synthesis/degradation, and thiosulfate oxidation were also enriched. Taken together, our findings can not only expand the promising candidates for oxygen nanobubble carriers based on sediment recycling, but also highlight the microbial molecular mechanisms for anoxic freshwater restoration based on nutrient cycle regulation.

A novel simultaneous coupling of memory photocatalysts and microbial communities for alternate removal of dimethyl phthalate and nitrate in water under light/dark cycles.

Efficient and sustainable removal of both organic and inorganic pollutants from contaminated water is an important but difficult task. Here, a novel chemical-biological coupling concept, namely simultaneous coupling of memory photocatalysts and microbial communities (SCMPMC), is proposed for the first time that alternates the removal of organic and inorganic pollutants under successive light/dark cycles. We established this novel coupling system with WO3/g-C3N4 memory photocatalysts and river sediment microbial communities, and applied it to alternately remove dimethyl phthalate (DMP) and nitrate under light/dark cycles. The performance of SCMPMC under the light/dark cycles (12/12 h) showed that ~84.90% of the DMP was removed mainly via robust photocatalytic oxidation during the light phase, and ~86.80% of the nitrate was removed via microbial reduction enhanced by photogenerated electrons stored in the WO3/g-C3N4 memory photocatalysts during the dark phase within one cycle. The microbial communities were positively affected by adding WO3/g-C3N4, as evidenced by increased enzyme activities, cellular antigen metabolism, and relative abundance of typical denitrifiers, including Proteobacteria and Bacteroidetes. These results will contribute to the development of promising decontamination methods and mechanisms to control water pollution driven by the natural day/night cycle.

Continuous photocatalysis via photo-charging and dark-discharging for sustainable environmental remediation: Performance, mechanism, and influencing factors.

Continuous photocatalysis via photo-charging and dark-discharging presents a paradigm shift in conventional photocatalysis with the requirement of continuous illumination to maintain the catalytic activity. This is expected to meet the ever-increasing demand for sustainable development of energy and environment driven by natural day-night cycles. Substantial advances in continuous photocatalysis for various environmental applications under light-dark cycles have been witnessed during the last decade. However, there lacks a systematic and critical review on basic but important information of continuous photocatalysis for environmental remediation, challenging robust scientific progress of this technology towards potential practical use. Here, the general description of continuous photocatalysis involving energy storage mechanisms (hole and electron storage) and characterizations (electron storage behaviors, release behaviors and storage capacity) has been first introduced. Importantly, the remediation performance and mechanism of continuous photocatalysis for environmental applications are qualitatively and quantitatively demonstrated, including chemical pollutant oxidation and reduction, microbial pathogen inactivation, and multifunctional treatment. In addition, key factors influencing its remediation performance are analyzed, for the first time, from both operational and environmental views. The ample opportunities in the field of continuous photocatalysis for sustainable environmental remediation are also pointed out, calling for more efforts to fill current knowledge gaps in the future.