Intensified Disinfection Amid COVID-19 Pandemic Poses Potential Risks to Water Quality and Safety

Disinfectant-induced ammonia oxidation disruption in microbial N-cycling process in aquatic ecosystem after the COVID-19 outbreak

Anthropogenic activities significantly impact the elemental cycles in aquatic ecosystems, with the N-cycling playing a critical role in potential nutrient turnover and substance cycling. We hypothesized that measures to prevent COVID-19 transmission profoundly altered the nitrogen cycle in riverine ecosystems. To investigate this, we re-analyzed metagenomic data and identified 60 N-cycling genes and 21 host metagenomes from four urban reaches (one upstream city, Wuhan, and two downstream cities) along the Yangtze River. Our analyses revealed a marked decrease in the abundance of bacterial ammonia monooxygenase genes, as well as in the host, ammonia-oxidizing autotrophic Nitrosomonas, followed by a substantial recovery post-pandemic. We posited that discharge of sodium hypochlorite (NaOCl) disinfectant may be a primary factor in the reduction of N-cycling process. To test this hypothesis, we exposed pure cultures of Nitrosomonas europaea to NaOCl to explore the microbial stress response. Results indicated that NaOCl exposure rapidly compromised the cell structure and inhibited ammonia oxidation of N. europaea, likely due to oxidative stress damage and reduced expression of nitrogen metabolism-related ammonia monooxygenase. Using the functional tagging technique, we determined that NaOCl directly destroyed the ammonia monooxygenase protein and DNA structure. This study highlights the negative impacts of chlorine disinfectants on the function of aquatic ecosystems and elucidates potential mechanisms of action.

Insight into the surface discharge cold plasma efficient inactivation of Pseudomonas fluorescens in water based on exogenous reactive oxygen and nitrogen species: Synergistic mechanism and energy benefits

As well known, surface discharge cold plasma has efficient inactivation ability and a variety of RONS are main active particles for inactivation, but their synergistic mechanism is still not clear. Therefore, surface discharge cold plasma system was applied to treat Pseudomonas fluorescens to study bacterial inactivation mechanism and energy benefit. Results showed that energy efficiency was directly proportional to applied voltage and inversely proportional to initial concentration. Cold plasma treatment for 20 min was inactivated by approximately > 4-log10Pseudomonas fluorescens and application of •OH and 1O2 scavengers significantly improved survival rate. In addition, •OH and 1O2 destroyed cell membrane structure and membrane permeability, which promoted diffusion of RONS into cells and affecting energy metabolism and antioxidant capacity, leading to bacterial inactivation. Furthermore, accumulation of intracellular NO and ONOOH was related to infiltration of exogenous RNS, while accumulation of •OH, H2O2, 1O2, O2- was the result of joint action of endogenous and exogenous ROS. Transcriptome analysis revealed that different RONS of cold plasma were responsible for Pseudomonas fluorescens inactivation and related to activation of intracellular antioxidant defense system and regulation of genes expression related to amino acid metabolism and energy metabolism, which promoting cellular process, catalytic activity and other biochemical pathways.

Multiresidue determination and predicted risk assessment of emerging contaminants in sediments from Kongsfjorden, Svalbard

The present work provides the first data on the occurrence of different classes of pharmaceuticals and personal care products (PPCPs) in surface marine sediments from an Arctic fjord (Kongsfjorden, Svalbard Islands, Norway). The target compounds included: ciprofloxacin; enrofloxacin; amoxicillin; erythromycin; sulfamethoxazole; carbamazepine; diclofenac; ibuprofen; acetylsalicylic acid; paracetamol; caffeine; triclosan; N,N-diethyl-meta-toluamide; 17β-estradiol; 17α-ethinyl estradiol and estrone. Sampling was performed in the late summer, when high sedimentation rates occur, and over 5 years (2018-2022). Based on the environmental concentrations (MECs) found of emerging contaminants and the relative predicted no-effect concentrations (PNECs), an environmental risk assessment (ERA) for sediments was performed, including the estimation of the Risk Quotients (RQs) of selection and propagation of antimicrobial resistance (AMR) in this Arctic marine ecosystem. Sediments were extracted by Pressurized Liquid Extraction (PLE) and the extracts were purified by Solid Phase Extraction (SPE). Analytical determination was conducted with liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS). PPCPs were detected in the sediments along the fjord in all the years investigated, with overall concentrations similar in most cases to those reported in urbanized areas of the planet and ranging from a minimum of 6.85 ng/g for triclosan to a maximum of 684.5 ng/g for ciprofloxacin. This latter was the only antibiotic detected but was the most abundant compound (32 %) followed by antipyretics (16 %), hormones (14 %), anti-inflammatories (13 %), insect repellents (11 %), stimulants (9 %), and disinfectants (5 %). Highest concentrations of all PPCPs detected were found close to the Ny-Ålesund research village, where human activities and the lack of appropriate wastewater treatment technologies were recognized as primary causes of local contamination. Finally, due to the presence in the sediments of the PPCPs investigated, the ERA highlights a medium (0.1 < RQ < 1) to high risk (RQ > 1) for organisms living in this Arctic marine ecosystem, including high risk of the spread of AMR.

Effects of intensive chlorine disinfection on nitrogen and phosphorus removal in WWTPs

The increased use of disinfection since the pandemic has led to increased effective chlorine concentration in municipal wastewater. Whereas, the specific impacts of active chlorine on nitrogen and phosphorus removal, the mediating communities, and the related metabolic activities in wastewater treatment plants (WWTPs) lack systematic investigation. We systematically analyzed the influences of chlorine disinfection on nitrogen and phosphorus removal activities using activated sludge from five full-scale WWTPs. Results showed that at an active chlorine concentration of 1.0 mg/g-SS, the nitrogen and phosphorus removal systems were not significantly affected. Major effects were observed at 5.0 mg/g-SS, where the nitrogen and phosphorus removal efficiency decreased by 38.9 % and 44.1 %, respectively. At an active chlorine concentration of 10.0 mg/g-SS, the nitrification, denitrification, phosphorus release and uptake activities decreased by 15.1 %, 69.5-95.9 %, 49.6 % and 100 %, respectively. The proportion of dead cells increased by 6.1 folds. Reverse transcriptional quantitative polymerase chain reaction (RT-qPCR) analysis showed remarkable inhibitions on transcriptions of the nitrite oxidoreductase gene (nxrB), the nitrite reductase genes (nirS and nirK), and the nitrite reductase genes (narG). The nitrogen and phosphorus removal activities completely disappeared with an active chlorine concentration of 25.0 mg/g-SS. Results also showed distinct sensitivities of different functional bacteria in the activated sludge. Even different species within the same functional group differ in their susceptibility. This study provides a reference for the understanding of the threshold active chlorine concentration values which may potentially affect biological nitrogen and phosphorus removal in full-scale WWTPs, which are expected to be beneficial for decision-making in WWTPs to counteract the potential impacts of increased active chlorine concentrations in the influent wastewater.

Acute/chronic triclosan exposure induces downregulation of m6A-RNA methylation modification via mettl3 suppression and elicits developmental and immune toxicity to zebrafish

Triclosan (TCS), a prevalent contaminant in aquatic ecosystems, has been identified as a potential threat to both aquatic biota and human health. Despite its widespread presence, research into the immunotoxic effects of TCS on aquatic organisms is limited, and the underlying mechanisms driving these effects remain largely unexplored. Herein, we investigated the developmental and immune toxicities of environmentally relevant concentrations of TCS in zebrafish, characterized by morphological anomalies, histopathological impairments, and fluctuations in cytological differentiation and biomarkers following both acute (from 6 to 72/120 hpf) and chronic exposure periods (from 30 to 100 dpf). Specifically, acute exposure to TCS resulted in a significant increase in innate immune cells, contrasted by a marked decrease in T cells. Furthermore, we observed that TCS exposure elicited oxidative stress and a reduction in global m6A levels, alongside abnormal expressions within the m6A modification enzyme system in zebrafish larvae. Molecular docking studies suggested that mettl3 might be a target molecule for TCS interaction. Intriguingly, the knock-down of mettl3 mirrored the effects of TCS exposure, adversely impacting the growth and development of zebrafish, as well as the differentiation of innate immune cells. These results provide insights into the molecular basis of TCS-induced immunotoxicity through m6A-RNA epigenetic modification and aid in assessing its ecological risks, informing strategies for disease prevention linked to environmental contaminants.

Direct generation of DBPs from city dust during chlorine-based disinfection

Chlorine-based disinfectants, such as sodium hypochlorite, are extensively used in our daily lives. In particular, during the recent Covid-19 pandemic and post-pandemic period, excessive amounts of chlorine-based disinfectants were used both indoors and outdoors to interrupt virus transmission. However, the interaction between disinfectants and city dust during the disinfection process has not been sufficiently evaluated. In this study, we conducted a comprehensive investigation into the intrinsic characteristics (e.g. morphology, size, elemental composition, and organic content, etc.) of dust collected from various indoor and outdoor areas. The results showed that the organic carbon content of indoor dust reached 6.14 %, with a corresponding measured dissolved organic carbon value of 4.17 ± 0.23 mg/g (normalized to the dust weight). Concentrations of regulated DBPs, resulting from the interaction between dust and NaClO, ranged from 57.78 ± 2.72 to 102.80 ± 22.63 µg/g for THMs and from 119.18 ± 6.50 to 285.14 ± 36.95 µg/g for HAAs (normalized to the dust weight). More significantly, using non-target analysis through gas chromatography quadrupole time-of-flight mass spectrometry (GC-qTOF-MS), we identified a total of 68, 89, and 87 types of halogenated DBPs from three typical indoor and outdoor sites (R-QH, C-JS, and W-BR, respectively). These unknown DBPs included compounds with higher toxicity compared to regulated DBPs. These findings highlight that city dust is a significant source of DBP generation during chlorine-based disinfection, posing potential harm to both the ecological environment and human health.

Phytotoxicity of trihalomethanes and trichloroacetic acid on Vigna radiata and Allium cepa plant models

Disinfection by-products (DBPs) are a concern due to their presence in chlorinated wastewater, sewage treatment plant discharge, and surface water, and their potential for environmental toxicity. Despite some attention to their ecotoxicity, little is known about the phytotoxicity of DBPs. This study aimed to evaluate the individual and combined phytotoxicity of four trihalomethanes (THMs: trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) and their mixture (THM4)), and trichloroacetic acid (TCAA) using genotoxic and cytotoxic assays. The analysis included seed germination tests using Vigna radiata and root growth tests, mitosis studies, oxidative stress response, chromosomal aberrations (CA), and DNA laddering using Allium cepa. The results showed a progressive increase in root growth inhibition for both plant species as the concentration of DBPs increased. High concentrations of mixtures of four THMs resulted in significant (p < 0.05) antagonistic interactions. The effective concentration (EC50) value for V. radiata was 5655, 3145, 2690, 1465, 3570, and 725 mg/L for TCM, BDCM, DBCM, TBM, THM4, and TCAA, respectively. For A. cepa, the EC50 for the same contaminants was 700, 400, 350, 250, 450, and 105 mg/L, respectively. DBP cytotoxicity was observed through CAs, including C-metaphase, unseparated anaphase, lagging chromosome, sticky metaphase, and bridging. Mitotic depression (MD) increased with dose, reaching up to 54.4% for TCAA (50-500 mg/L). The electrophoresis assay showed DNA fragmentation and shearing, suggesting genotoxicity for some DBPs. The order of phytotoxicity for the tested DBPs was TCAA > TBM > DBCM > BDCM > THM4 > TCM. These findings underscore the need for further research on the phytotoxicity of DBPs, especially given their common use in agricultural practices such as irrigation and the use of sludge as manure.

Man-made reactive oxygen species as green disinfectants

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The occurrence, ecological risk, and control of disinfection by-products from intensified wastewater disinfection during the COVID-19 pandemic

Increased disinfection of wastewater to preserve its microbiological quality during the coronavirus infectious disease-2019 (COVID-19) pandemic have inevitably led to increased production of toxic disinfection by-products (DBPs). However, there is limited information on such DBPs (i.e., trihalomethanes, haloacetic acids, nitrosamines, and haloacetonitriles). This review focused on the upsurge of chlorine-based disinfectants (such as chlorine, chloramine and chlorine dioxide) in wastewater treatment plants (WWTPs) in the global response to COVID-19. The formation and distribution of DBPs in wastewater were then analyzed to understand the impacts of these large-scale usage of disinfectants in WWTPs. In addition, potential ecological risks associated with DBPs derived from wastewater disinfection and its receiving water bodies were summarized. Finally, various approaches for mitigating DBP levels in wastewater and suggestions for further research into the environmental risks of increased wastewater disinfection were provided. Overall, this study presented a comprehensive overview of the formation, distribution, potential ecological risks, and mitigating approaches of DBPs derived from wastewater disinfection that will facilitate appropriate wastewater disinfection techniques selection, potential ecological risk assessment, and removal approaches and regulations consideration.

Synergistic effects of sequential treatment using disinfectant and e-beam for inactivation of hepatitis a virus on fresh vegetables

Hepatitis A virus (HAV) has adversely affected public health worldwide, causing an economic burden on many countries. Fresh vegetables are reported as a source of HAV infections during production, harvesting, and distribution, which cause the emergence of foodborne illnesses. Therefore, in this study, the synergistic effects of chemical (sodium hypochlorite [NaOCl] and chlorine dioxide [ClO2]) and physical (electron-beam [e-beam] irradiation) sequential treatment for HAV inactivation on fresh vegetables were investigated, and the physicochemical quality changes of vegetables were evaluated after each treatment. On bell pepper and cucumber sequentially treated with NaOCl (50-500 ppm) and e-beam (1-5 kGy), the HAV titer was reduced by 0.19-4.69 and 0.28-4.78 log10 TCID50/mL, respectively. Sequential treatment with ClO2 (10-250 ppm) and e-beam (1-5 kGy) reduced the HAV titer on bell pepper and cucumber by 0.41-4.78 and 0.26-4.80 log10 TCID50/mL, respectively. The sequential treatments steadily decreased the HAV titers on each food by a significant difference (p < 0.05) compared to the controls. The treatment combinations of 500 ppm NaOCl and 3 kGy (e-beam) on bell pepper and 150 ppm NaOCl and 1 kGy (e-beam) on cucumber provided maximum synergistic effects. It was also found that sequential treatment with 50 ppm ClO2 and 5 kGy (e-beam) on bell pepper and 10 ppm ClO2 and 5 kGy (e-beam) on cucumber most efficiently inactivated HAV. Additionally, bell pepper and cucumber showed no significant quality changes (p < 0.05) after the treatment. Therefore, the sequential treatment with NaOCl or ClO2 and e-beam is expected to effectively control HAV on fresh vegetables without changing the food quality compared to either treatment alone.

Residual chlorine persistently changes antibiotic resistance gene composition and increases the risk of antibiotic resistance in sewer systems

During the COVID-19 pandemic, excessive amounts of disinfectants and their transformation products entered sewer systems worldwide, which was an extremely rare occurrence before. The stress of residual chlorine and disinfection by-products is not only likely to promote the spread of antibiotic resistance genes (ARGs), but also leads to the enrichment of chlorine-resistant bacteria that may also be resistant to antibiotics. Therefore, the potential impact of such discharge on ARG composition should be studied and the health risks should be assessed. Thus, this study combined high-throughput 16S rRNA gene amplicon sequencing and metagenomic analysis with long-term batch tests that involved two stages of stress and recovery to comprehensively evaluate the impact of residual chlorine on the microbial community and ARG compositions in sewer systems. The tests demonstrated that the disturbance of the microbial community structure by residual chlorine was reversible, but the change in ARG composition was persistent. This study found that vertical propagation and horizontal gene transfer jointly drove ARG composition succession in the biofilm, while the driving force was mainly horizontal gene transfer in the sediment. In this process, the biocide resistance gene (BRG) subtype chtR played an important role in promoting co-selection with ARGs through plasmids and integrative and conjugative elements. Moreover, it was further shown that the addition of sodium hypochlorite increased the risk of ARGs to human health, even after discontinuation of dosing, signifying that the impact was persistent. In general, this study strengthens the co-selection theory of ARGs and BRGs, and calls for improved disinfection strategies and more environmentally friendly disinfectants.

Effects of environmental disinfection on microbial population and resistance genes: A case study of the microecology within a panda enclosure

Widespread use of disinfectants raises concerns over their involvement in altering microbial communities and promoting antimicrobial resistance. This study explores the influence of disinfection protocols on microbial populations and resistance genes within an isolated enclosure environment and in the gut of giant pandas (GPs) held within. Samples of panda feces, air conditioning ducts, soil and bamboo were collected before and after disinfection. High-throughput sequencing characterized the microbial flora of GP gut and environmental microbes inside the artificial habitat. Microbial cultures showed that Escherichia coli (34.6%), Enterococcus (15.4%) and other pathogenic bacteria deposited in feces and the enclosure. Isolates exhibit a consistent resistance to disinfectant, with the greatest resistance shown to cyanuric acid, and the lowest to glutaraldehyde-dodecyl dimethyl ammonium bromide (GD-DDAB) and dodecyl dimethyl ammonium bromide (DDAB). The total number of the culturable bacteria in soil and bamboo were significantly diminished after disinfection but increased in the gut. After disinfection, the richness (Chao1 index) of environment samples increased significantly (P < 0.05), while the richness in gut decreased significantly (P < 0.05). Ten genera showed significant change in feces after disinfection. Metagenome sequencing showed that 126 types of virulence genes were present in feces before disinfection and 37 in soil. After disinfection, 110 virulence genes localized in feces and 53 in soil. Eleven virulence genes including ECP and T2SS increased in feces. A total of 182 antibiotic resistance genes (ARGs) subtypes, potentially conferring resistance to 20 classes of drugs, were detected in the soils and feces, with most belonging to efflux pump protein pathways. After disinfection, the number of resistance genes increased both in gut and soil, which suggests disinfection protocols increase the number of resistance pathways. Our study shows that the use of disinfectants helps to shape the microbial community of GPs and their habitat, and increases populations of resistant strain bacteria.

Inactivation of airborne pathogenic microorganisms by plasma-activated nebulized mist

The airborne microorganisms in the aerosols are one main transmission way of pathogenic microorganisms and therefore inactivation of microorganisms in aerosols could effectively prevent the transmission of pathogenic microorganisms to control epidemics. The mist nebulized by plasma-activated air could effectively inactivate bacteria and could be developed for the sterilization of microorganisms in aerosols. In this study, the plasma-activated nebulized mist (PANM) was applied for the inactivation of microorganisms in aerosols and efficiently inactivated the bacteria, yeast, and viruses in aerosols after 2-min treatment. The PANM treatment caused morphologic changes and damage to the bacteria cells in aerosols. The PANM could also inactivate the microorganisms attached to the surface of the treatment chamber and the bacteria attached to the skin of mice within 6-min treatment. The biosafety assays demonstrated that the PANM treatment exhibited no effects on the behavior, hematological and serum biochemical parameters of blood, and organs from the mice. This study would supply an efficient, broad-spectrum, and safe aerosol sterilization strategy based on plasma technology to prevent the transmission of airborne microorganisms.

Polyiodo Azole-Based Metal-Organic Framework Energetic Biocidal Material for Synergetic Sterilization Applications

Biological hazards caused by bacteria, viruses, and toxins have become a major survival and development issue facing the international community. However, the traditional method of disinfection and sterilization is helpless in dealing with viruses that spread quickly and are highly infectious. Metal-organic framework (MOF) biocidal materials hold promise as superior alternatives to traditional sterilization materials because of their stable framework structures and unique properties. Now, we demonstrate for the first time the synthesis of a MOF (TIBT-Cu) containing Cu metal centers and tetraiodo-4,4'-bi-1,2,4-triazole as the main ligand. This novel MOF biocidal material has good thermal stability (Td = 278 °C), excellent mechanical sensitivity, and a high bacteriostatic efficiency (>99.90%). Additionally, the particles produced by the combustion of TIBT-Cu are composed of active iodine substances and CuO particles, which can act synergistically against harmful microorganisms such as bacteria and viruses. This study provides a new perspective for the preparation of highly effective bactericidal materials.

Enhanced disinfection byproducts formation by fine iron particles intercepted in household point-of-use facilities

To cope with the demand for good-quality potable water, household point-of-use (POU) facilities such as polypropylene cotton filters (PCFs) are widely used. However, the behaviors of new and used PCFs under discoloration are unclear. In this study, we found that new PCF did not effectively intercept particles under discoloration within the initial 5 d of inflow. In addition, the particles, especially the fine ones, accumulated in the long-used PCF exacerbated the risks of disinfection byproducts (DBPs) and microbes. The concentrations of trihalomethanes (THMs) and haloacetonitriles (HANs) in the effluent run through the PCF all increased over time; interestingly, all sharply increased after 5 d in accordance with the decrease in effluent iron particles. During this stage, maximum increases rate of 117.89% in THMs and 75.12% in HANs were observed. For haloacetic acids (HAAs), it served as the dominant contaminants, with concentrations approximately 10-fold greater than those of THMs and HANs. The increase showed that used PCFs could exacerbate the risks in DBPs exposure. Adenosine triphosphate (ATP) also showed a similar trend, with a maximum increase from 0.0033 to 0.0055 nmol/mL. Thus, PCFs can act only as pretreatment units and should be replaced after yellow water events. This study offers important guidance for PCF usage in drinking water purification, especially under discoloration.

Assessment of heavy metals mobilization in road-deposited sediments induced by COVID-19 disinfection

Road-deposited sediments (RDS) on urban impervious surfaces are important carriers of heavy metals (HMs), and can contribute to urban runoff pollution. With the outbreak of COVID-19, chlorinated disinfectants (CDs) have been extensively sprayed on these surfaces. This practice may have a superposed or priming effect on HMs contaminants in RDS, yet this remains unknown. This study examined the effects of seven CDs concentration gradients (0, 250, 500, 1000, 2000, 5000, 60,000 mg/L) on the leaching and chemical forms of HMs (Cd, Cr, Ni, Pb, and Zn) in seven particle size fractions (<44, 44-63, 63-105, 105-149, 149-250, 250-450, 450-1000 μm). The results showed that CDs can promote the leaching of HMs in RDS, at the recommended CDs dose (2000 mg/L), except for Pb, the leaching amounts increased by 21.8%-237.2% compared with the untreated RDS. The alteration in the leaching were primarily attributed to the redistribution of chemical forms of HMs in RDS, specifically, the acid-extractable fractions percentage increased by 0.23%-24.39%, and the reducible fractions percentages decreased by 3.21%-38.35%. The lower oxidation-reduction potential (ORP) and alkalinity of CDs as strong oxidants were responsible for the redistribution of forms. The leaching and chemical forms of HMs vary among different particle sizes, but in any case, finer particle sizes (< 105 μm) still dominate their contribution. The current control measure of street sweeping is ineffective in removing these particles. These findings will facilitate the development of strategies for controlling urban diffuse pollution from RDS during the pandemic. Finally, this study suggests potential directions for future research.

Assessment of Residual Chlorine Interaction with Different Microelements in Stormwater Sediments

One consequence of intensive outdoor disinfection using chlorinated compounds is environmental pollution. It has been found that disinfectants are the most effective tool to avoid the spread of infections and viruses. Studies have shown that the use of chlorine-based disinfectants (sodium hypochlorite) leaves residual chlorine and other disinfection byproducts in the environment. They also have harmful effects on, inter alia, water quality, ecosystems, as well as exacerbating the corrosion of surfaces. To meet regulatory standards, monitoring of the presence of residual chlorine in the environment is vitally important. The aim of this study is to analyse the occurrence of residual chlorine in stormwater after outdoor disinfection using sodium hypochlorite and to investigate its interaction with different microelements as well their possible impacts. Stormwater samples collected at permanently disinfected locations were analysed via X-ray absorption spectroscopy. The concentrations of Cl and the following elements Na, Si, K, Ca, Cr, Fe, Ni, Cu, Zn were detected and their relationship with chlorine was determined using the Python programming language. The research presents Cl concentration values (%) that vary from 0.02 to 0.04. The results of the modelling revealed strong correlations between Cl and Fe (value 0.65) and Ca (value -0.61) and the occurrence of CaCl₂ and FeCl₃. The strong relationship between Cl and Fe explains the significant increase in surface corrosion after disinfection with chlorine-based substances.

Toxicity effects of disinfection byproduct chloroacetic acid to Microcystis aeruginosa: Cytotoxicity and mechanisms

Chlorine-based disinfectants are widely used for disinfection in wastewater treatment. The mechanism of the effects of chlorinated disinfection by-products on cyanobacteria was unclear. Herein, the physiological effects of chloroacetic acid (CAA) on Microcystis aeruginosa (M. aeruginosa), including acute toxicity, oxidative stress, apoptosis, production of microcystin-LR (MC-LR), and the microcystin transportation-related gene mcyH transcript abundance have been investigated. CAA exposure resulted in a significant change in the cell ultrastructure, including thylakoid damage, disappearance of nucleoid, production of gas vacuoles, increase in starch granule, accumulation of lipid droplets, and disruption of cytoplasm membranes. Meanwhile, the apoptosis rate of M. aeruginosa increased with CAA concentration. The production of MC-LR was affected by CAA, and the transcript abundance of mcyH decreased. Our results suggested that CAA poses acute toxicity to M. aeruginosa, and it could cause oxidative damage, stimulate MC-LR production, and damage cell ultrastructure. This study may provide information about the minimum concentration of CAA in the water environment, which is safe for aquatic organisms, especially during the global coronavirus disease 2019 pandemic period.

Degradation kinetics and formation of regulated and emerging disinfection by-products during chlorination of two expectorants ambroxol and bromhexine

Ambroxol hydrochloride (AMB) and bromhexine hydrochloride (BRO) are classic expectorants and bronchosecretolytic pharmaceuticals. In 2022, both AMB and BRO were recommended by medical emergency department of China to alleviate cough and expectoration for symptoms caused by COVID-19. The reaction characteristics and mechanism of AMB/BRO with chlorine disinfectant in the disinfection process were investigated in this study. The reaction of chlorine with AMB/BRO were well described by a second-order kinetics model, first-order in both AMB/BRO and chlorine. The second order rate reaction constant of AMB and BRO with chlorine at pH 7.0 were 1.15 × 10² M^-1s^-1 and 2.03 × 10² M^-1s^-1, respectively. During chlorination, a new class of aromatic nitrogenous disinfection by-products (DBPs) including 2-chloro-4, 6-dibromoaniline and 2, 4, 6-tribromoaniline were identified as the intermediate aromatic DBPs by gas chromatography-mass spectrometry. The effect of chlorine dosage, pH, and contact time on the formation of 2-chloro-4, 6-dibromoaniline and 2, 4, 6-tribromoaniline were evaluated. In addition, it was found that bromine in AMB/BRO were vital bromine source to greatly promote the formation of classic brominated DBPs, with the highest Br-THMs yields of 23.8% and 37.8%, respectively. This study inspired that bromine in brominated organic compounds may be an important bromine source of brominated DBPs.

Applications of vacancy defect engineering in persulfate activation: Performance and internal mechanism

The vacancy defects in heterogeneous catalysts have received extensive attention for persulfate (PS) activation. Vacancy defects can tune the electronic structure of metal oxides and generate unsaturated coordination sites. Meanwhile, the adsorption energy of reactants on catalyst surface is optimized. Thereby, the reaction energy barrier between catalysts and PS decreases, which could promote catalytic activation and accelerate pollutants degradation. Nowadays, oxygen vacancy (OV), nitrogen vacancy (NV), sulfur vacancy (SV), selenium vacancy (SeV) and titanium vacancy (TiV) have been widely studied with great potential for water remediation. So far, no review was reported regarding the vacancy activated persulfate systems. This paper summarized the types, preparation, mechanism and applications of vacancy in PS systems systematically. In addition, we put forward possible development of vacancy engineering in PS activation systems. It is expected that this review will contribute to the controllable synthesis and applications of vacancies in catalysts for PS activation and contaminants removal.

Degradation of natural organic matter and disinfection byproducts formation by solar photolysis of free available chlorine

Environment disinfection effectively curbs transmission of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). However, elevated concentration of free available chlorine (FAC) in disinfectants can be discharged into surface water, generating toxic disinfection byproducts (DBPs). The impact of solar photolysis of FAC on natural organic matter (NOM) to form DBPs has not been well studied. In this work, solar photolysis of FAC was found to result in higher formation of DBPs, DBPs formation potential (DBPsFP), total organic chlorine (TOCl) and lower specific ultraviolet absorbance at 254 nm (SUVA₂₅₄), compared to dark chlorination. In solar photolysis of FAC, formation of total DBPs was promoted by pH=8, but hindered by the addition of HCO₃^-, radical scavenger or deoxygenation, while addition of NO₃^-and NH₄⁺both enhanced the formation of nitrogenous DBPs. Differences in the formation of DBPs in solar photolysis of FAC under various conditions were influenced by reactive species. The formation of trichloromethane (TCM) and haloacetic acids (HAAs) in solar photolysis of FAC positively correlated with the steady-state concentrations of ClO^• and O₃. The steady-state concentrations of ^•NO and ^•NH₂ positively correlated with the formation of halonitromethanes (HNMs). HAAs and haloacetonitriles (HANs) mainly contributed to calculated cytotoxicity of DBPs. This study demonstrates that solar photolysis of FAC may significantly impact the formation of DBPs in surface water due to extensive use of disinfectants containing FAC during SARS-CoV-2 pandemic.

Effects of phosphate addition on the removal of disinfection by-product formation potentials by biological activated carbon filtration

In drinking water treatment plants (DWTPs), the widely used biological activated carbon filters (BACFs), as the last barrier before disinfection, can remove dissolved organic matter (DOM) known as precursors of disinfection by-products (DBPs). Whether phosphate addition can improve water purification and DBP control of BACFs is still controversial. This study investigated short-term and long-term effects of phosphate addition on controlling DBP formation potentials (FPs) by BACFs via column and batch experiments. The BAC columns presented good water purification performance: they removed around 50 % DOM, nearly all fulvic acid-likes and humic acid-likes as well as 5 %-70 % chlor(am)innated THM₄, HAA₉ and HAN₄ FPs (except chloraminated THM₄ FPs)， which was mainly contributed by aerobic bacteria not anoxic bacteria. Phosphate addition within 7-14 days further improved removals of DOM, aromatic organics, fluorescence fractions in DOM as well as HAA₉ and HAN₄ FPs (especially TCAA FP and TCAN FP) to different extent. However, this improvement did not last longer, and removals of DOM, aromatic organics, two fluorescence fractions (soluble microbial byproduct-likes and humic acid-likes) and DBP FPs decreased despite long-term phosphate addition. Oxic and anoxic batch experiments showed that the positive response of water purification to short-term phosphate addition was also mainly attributed to aerobic bacteria and not to anoxic bacteria. For example, the former decreased DOM and DBP FPs, while the latter increased protein- and tryptophan-like substances as well as chloraminated THM₄ FPs. Phosphate addition resulted in EPS increase in anoxic reactors and decrease in oxic reactors. These results indicated that a high dissolved oxygen in BACFs may be helpful for water purification and DBP control. Overall, short-term phosphate addition into phosphorus-limited water is beneficial for BACFs to control DBPs while long-term addition has no effect. Therefore, an intermittent phosphate addition into BACFs is suggested to control DBPs in DWTPs.

Triclosan and related compounds in the environment: Recent updates on sources, fates, distribution, analytical extraction, analysis, and removal techniques

Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.

Bacterial drug-resistance and viability phenotyping upon disinfectant exposure revealed by single-nucleotide resolved-allele specific isothermal RNA amplification

Disinfectant abuse poses a risk of bacterial evolution against stresses, especially during the coronavirus disease 2019 (COVID-19) pandemic. However, bacterial phenotypes, such as drug resistance and viability, are hard to access quickly. Here, we reported an allele specific isothermal RNA amplification (termed AlleRNA) assay, using an isothermal RNA amplification technique, i.e., nucleic acid sequence-based amplification (NASBA), integrated the amplification refractory mutation system (ARMS), involving the use of sequence-specific primers to allow the amplification of the targets with complete complementary sequences. AlleRNA assay enables rapid and simultaneous detection of the single nucleotide polymorphism (SNP) (a detection limit, a LOD of 0.5 % SNP) and the viability (a LOD of 80 CFU) of the quinolone resistant Salmonella enterica. With the use of AlleRNA assay, we found that the quinolone resistant S. enterica exhibited higher survival ability during exposure toquaternary ammonium salt, 75 % ethanol and peracetic acid, which might be attributed to the upregulation of stress response-associated genescompared with the susceptible counterparts. Additionally, the AlleRNA assay indicated the potential risk in a high-frequency occurrence of viable but nonculturable (VBNC) quinolone resistant S. enterica induced by disinfectants due to the depression of ATP biosynthesis. The excessive usage of disinfectants during the COVID-19 pandemic should be carefully evaluated due to the latent threat to ecological and human health.

An ESIPT-based ratiometric fluorescent probe for detecting H2O2 in water environment and biosystems

The outbreak of the COVID-19 has resulted in a great increase in the use of H₂O₂ disinfectant, which is listed as one of the commonly used disinfectants for COVID-19 by the U.S. Environmental Protection Agency. However, excessive use of H₂O₂ disinfectant can threaten human health and damage the water environment. Therefore, it's of great importance to detect H₂O₂ in aquatic environments and biological systems. Herein, we proposed a novel ESIPT ratio fluorescent probe (named probe 1) for detecting H₂O₂ in water environment and biosystems. Probe 1 emits blue fluorescence as the introduction of the phenylboronic acid disrupts the ESIPT process. After reacting with H₂O₂, the phenylboronic acid is oxidatively removed, and the ESIPT process is restored, which makes the fluorescence emission wavelength red-shifted. Probe 1 exhibited a short response time, high sensitivity, and a large Stokes shift to H₂O₂. Importantly, it has been successfully used to detect H₂O₂ not only in actual water samples, but also endogenous and exogenous H₂O₂ in living cells. The characteristics of probe 1 have a wide range of applications in environmental and biological systems.

Potential Disrupting Effects of Wastewater-Derived Disinfection Byproducts on Chinese Rare Minnow (Gobiocypris rarus) Transthyretin: An In Vitro and In Silico Study

The available information about whether wastewater-derived disinfection byproducts (DBPs) could elicit potential endocrine-related detrimental effects on aquatic organisms was scarce. Herein, the potential disrupting effects and underlying binding mechanism of 14 wastewater-derived aliphatic and aromatic DBPs and 12 other substances on Chinese rare minnow (Gobiocypris rarus) transthyretin (CrmTTR) were tested and revealed by in vitro and in silico methods. The amino acid sequences of CrmTTR were determined, and the recombinant CrmTTR with a molecular mass of 66.3 kDa was expressed and purified. In vitro assay results indicated that eight selected aromatic DBPs exhibited detectable CrmTTR disrupting ability. Meanwhile, six aliphatic DBPs were not CrmTTR binders. Molecular modeling results implied that hydrophobic hydrogen bonds and/or ionic pair interactions were non-negligible. Four binary classification models with high classification performance were constructed. A significant positive linear relationship was observed for the binding affinity data from CrmTTR and human TTR (n = 18, r = 0.922, p < 0.0001). However, the binding affinity for 13 out of 18 tested compounds with CrmTTR was higher than that with human TTR. All the results highlighted that some wastewater-derived DBPs may be potential disruptors on the aquatic organism endocrine system, and interspecies variation should not be neglected in future determination of the potential endocrine disrupting effects of wastewater-derived DBPs.

Airborne antibiotic resistome and human health risk in railway stations during COVID-19 pandemic

Antimicrobial resistance is recognized as one of the greatest public health concerns. It is becoming an increasingly threat during the COVID-19 pandemic due to increasing usage of antimicrobials, such as antibiotics and disinfectants, in healthcare facilities or public spaces. To explore the characteristics of airborne antibiotic resistome in public transport systems, we assessed distribution and health risks of airborne antibiotic resistome and microbiome in railway stations before and after the pandemic outbreak by culture-independent and culture-dependent metagenomic analysis. Results showed that the diversity of airborne antibiotic resistance genes (ARGs) decreased following the pandemic, while the relative abundance of core ARGs increased. A total of 159 horizontally acquired ARGs, predominantly confering resistance to macrolides and aminoglycosides, were identified in the airborne bacteria and dust samples. Meanwhile, the abundance of horizontally acquired ARGs hosted by pathogens increased during the pandemic. A bloom of clinically important antibiotic (tigecycline and meropenem) resistant bacteria was found following the pandemic outbreak. 251 high-quality metagenome-assembled genomes (MAGs) were recovered from 27 metagenomes, and 86 genera and 125 species were classified. Relative abundance of ARG-carrying MAGs, taxonomically assigned to genus of Bacillus, Pseudomonas, Acinetobacter, and Staphylococcus, was found increased during the pandemic. Bayesian source tracking estimated that human skin and anthropogenic activities were presumptive resistome sources for the public transit air. Moreover, risk assessment based on resistome and microbiome data revealed elevated airborne health risks during the pandemic.

Comprehensive insight into triclosan-from widespread occurrence to health outcomes

Humans are exposed to the variety of emerging environmental pollutant in everyday life. The special concern is paid to endocrine disrupting chemicals especially to triclosan which could interfere with normal hormonal functions. Triclosan could be found in numerous commercial products such as mouthwashes, toothpastes and disinfectants due to its antibacterial and antifungal effects. Considering the excessive use and disposal, wastewaters are recognized as the main source of triclosan in the aquatic environment. As a result of the incomplete removal, triclosan residues reach surface water and even groundwater. Triclosan has potential to accumulate in sediment and aquatic organisms. Therefore, the detectable concentrations of triclosan in various environmental and biological matrices emerged concerns about the potential toxicity. Triclosan impairs thyroid homeostasis and could be associated with neurodevelopment impairment, metabolic disorders, cardiotoxicity and the increased cancer risk. The growing resistance of the vast groups of bacteria, the evidenced toxicity on different aquatic organisms, its adverse health effects observed in vitro, in vivo as well as the available epidemiological studies suggest that further efforts to monitor triclosan toxicity at environmental levels are necessary. The safety precaution measures and full commitment to proper legislation in compliance with the environmental protection are needed in order to obtain triclosan good ecological status. This paper is an overview of the possible negative triclosan effects on human health. Sources of exposure to triclosan, methods and levels of detection in aquatic environment are also discussed.

Resolving the "health vs environment" dilemma with sustainable disinfection during the COVID-19 pandemic

The overuse of disinfection during the COVID-19 pandemic leads to an emerging "health versus environment" dilemma that humans have to face. Irresponsible and unnecessary disinfection should be avoided, while comprehensive evaluation of the health and environmental impacts of different disinfectants is urgently needed. From this discussion, we reach a tentative conclusion that hydrogen peroxide is a green disinfectant. Its on-demand production enables a circular economy model to solve the storage issues. Water, oxygen, and electrons are the only feedstock to generate H₂O₂. Upon completion of disinfection, H₂O₂ is rapidly converted back into water and oxygen. This model adopts several principles of green chemistry to ensure overall sustainability along the three stages of its whole life cycle, i.e., production, disinfection, and decomposition. Physical methods, particularly UV irradiation, also provide sustainable disinfection with minimal health and environmental impacts.

Assessment of residual chlorine in soil microbial community using metagenomics

Chlorine-containing disinfectants have been widely used around the world for the prevention and control of the COVID-19 pandemic. However, at present, little is known about the impact of residual chlorine on the soil micro-ecological environment. Herein, we treated an experimental soil-plant-microbiome microcosm system by continuous irrigation with a low concentration of chlorine-containing water, and then analyzed the influence on the soil microbial community using metagenomics. After 14-d continuous chlorine treatment, there were no significant lasting effect on soil microbial community diversity and composition either in the rhizosphere or in bulk soil. Although metabolic functions of the rhizosphere microbial community were affected slightly by continuous chlorine treatment, it recovered to the original status. The abundance of several resistance genes changed by 7 d and recovered by 14 d. According to our results, the chlorine residue resulting from daily disinfection may present a slight long-term effect on plant growth (shoot length and fresh weight) and soil micro-ecology. In general, our study assisted with environmental risk assessments relating to the application ofchlorine-containing disinfectants and minimization of risks to the environment during disease control, such as COVID-19.

Environmental impacts of the widespread use of chlorine-based disinfectants during the COVID-19 pandemic

Chlorinated disinfectants are widely used in hospitals, COVID-19 quarantine facilities, households, institutes, and public areas to combat the spread of the novel coronavirus as they are effective against viruses on various surfaces. Medical facilities have enhanced their routine disinfection of indoors, premises, and in-house sewage. Besides questioning the efficiency of these compounds in combating coronavirus, the impacts of these excessive disinfection efforts have not been discussed anywhere. The impacts of chlorine-based disinfectants on both environment and human health are reviewed in this paper. Chlorine in molecular and in compound forms is known to pose many health hazards. Hypochlorite addition to soil can increase chlorine/chloride concentration, which can be fatal to plant species if exposed. When chlorine compounds reach the sewer/drainage system and are exposed to aqueous media such as wastewater, many disinfection by-products (DBPs) can be formed depending on the concentrations of natural organic matter, inorganics, and anthropogenic pollutants present. Chlorination of hospital wastewater can also produce toxic drug-derived disinfection by-products. Many DBPs are carcinogenic to humans, and some of them are cytotoxic, genotoxic, and mutagenic. DBPs can be harmful to the flora and fauna of the receiving water body and may have adverse effects on microorganisms and plankton present in these ecosystems.

Treatment of hospital wastewater by electron beam technology: Removal of COD, pathogenic bacteria and viruses

The effective treatment of hospital sewage is crucial to human health and eco-environment, especially during the pandemic of COVID-19. In this study, a demonstration project of actual hospital sewage using electron beam technology was established as advanced treatment process during the outbreak of COVID-19 pandemic in Hubei, China in July 2020. The results indicated that electron beam radiation could effectively remove COD, pathogenic bacteria and viruses in hospital sewage. The continuous monitoring date showed that the effluent COD concentration after electron beam treatment was stably below 30 mg/L, and the concentration of fecal Escherichia coli was below 50 MPN/L, when the absorbed dose was 4 kGy. Electron beam radiation was also an effective method for inactivating viruses. Compared to the inactivation of fecal Escherichia coli, higher absorbed dose was required for the inactivation of virus. Absorbed dose had different effect on the removal of virus. When the absorbed dose ranged from 30 to 50 kGy, Hepatitis A virus (HAV) and Astrovirus (ASV) could be completely removed by electron beam treatment. For Rotavirus (RV) and Enterovirus (EV) virus, the removal efficiency firstly increased and then decreased. The maximum removal efficiency of RV and EV was 98.90% and 88.49%, respectively. For the Norovirus (NVLII) virus, the maximum removal efficiency was 81.58%. This study firstly reported the performance of electron beam in the removal of COD, fecal Escherichia coli and virus in the actual hospital sewage, which would provide useful information for the application of electron beam technology in the treatment of hospital sewage.

COVID-19 and organisational resilience in Brazil's water sector

The COVID-19 pandemic required a wide range of adaptations to the way that water sector operated globally. This paper looks into the impact of the COVID-19 pandemic on Brazilian water sector and evaluates the water sector's organisational resilience from the lens of water professionals. This study uses British Standard (BS 65000:2014)'s Resilience Maturity Scale method to evaluate organisational resilience in water sector under two defined scenarios of before and during the pandemic. For this purpose, the self-assessment framework developed by Southern Water in the United Kingdom (based on BS 65000:2014), comprising of the core resilience elements of Direction, Awareness, Alignment, Learning, Strengthening, and Assurance, are used for evaluations. A qualitative-quantitative surveying method is used for data collection. A total of 14 responses to the whole questionnaire were received from May 2021 to August 2021, each representing one water company in Brazil (four local companies and ten state-owned ones). The analyses identified COVID-19 as a threat multiplier particularly to already existing financial challenges due to the pre-existing threats in water sector. Bad debt and the COVID-19 emergency measures are recognised as the main challenges by 21 % and 14 % of the survey respondents. The state-owned and local companies scored an almost similar maturity level 3, 35 % and 34 % respectively, while the local companies scored much lower at maturity level 4 i.e., 26 % as opposed to 47 % in state-owned sector. This indicates that COVID-19 has a greater impact on local companies and the needs to increase preparedness. This study replicates an international experience to raise awareness on water sector's resiliency in Brazil and how it can be improved to withstand future external shocks. It sheds light on how and what existing challenges can be exacerbated facing a global shock and proposes opportunities for improvement of resilience maturity in water sector in Brazil.

Experimental Research on the Treatment of Stormwater Contaminated by Disinfectants Using Recycled Materials-Hemp Fiber and Ceramzite

Pollution caused by the use of disinfectants in public spaces is a relatively new form of environmental contamination. During the COVID-19 pandemic of 2020-2021, early research showed a sevenfold increase in the use of disinfectants to clean outdoor spaces and a corresponding increase in environmental pollution. Typically, after entering stormwater systems, disinfectants are carried to surface waters (e.g., rivers, seas and lakes) where they react with various elements to form harmful compounds. In the absence of data, it is not possible to determine accurate levels of pollution according to the latest scientific information. Our enquiry demonstrates that stormwater pollution indicators (pH, conductivity, turbidity and color intensity) change depending on the amounts of disinfectants present. Laboratory tests were conducted using hemp fiber and ceramzite, in which filtered stormwater samples contaminated with different amounts of disinfectants showed decreases in the amounts of active chlorine from 2.93 ppm to 1.0 ppm. Changes in pH levels, conductivity, turbidity and color intensity were monitored before and after filtration; pH indicators changed slightly (from 7.81 to 7.85), turbidity changes varied in the range of 0.070-0.145 NTU and the highest value of color intensity (1.932 AV) was obtained when 50 mL of disinfectant was added to the investigated sample water. This article presents the results of our research into the impact of disinfectants on stormwater. Further investigation is needed in order to determine the impacts of chemical substances on our water ecosystem.

A new-type HOCl-activatable fluorescent probe and its applications in water environment and biosystems

The outbreak and spread of Corona Virus Disease 2019 (COVID-19) has led to a significant increase in the consumption of sodium hypochlorite (NaOCl) disinfectants. NaOCl hydrolyzes to produce hypochlorous acid (HOCl) to kill viruses, which is a relatively efficient chlorine-based disinfectant commonly used in public disinfection. While people enjoy the convenience of NaOCl disinfection, excessive and indiscriminate use of it will affect the water environment and threaten human health. Importantly, HOCl is an indispensable reactive oxygen species (ROS) in human body. Whether its concentration is normal or not is closely related to human health. Excessive production of HOCl in the body contributes to some inflammatory diseases and even cancer. Also, we noticed that the concentration of ROS in cancer cells is about 10 times higher than that in normal cells. Herein, we developed a HOCl-activatable biotinylated dual-function fluorescent probe BTH. For this probe, we introduced biotin on the naphthalimide fluorophore, which increased the water solubility and enabled the probe to aggregate in cancer cells by targeting specific receptor overexpressed on the surface of cancer cell membrane. After reacting to HOCl, the p-aminophenylether moiety of this probe was oxidatively removed and the fluorescence of the probe was recovered. As expected, in the PBS solution with pH of 7.4, BTH could give full play to the performance of detecting HOCl, and it has made achievements in detecting the concentration of HOCl in actual water samples. Besides that, BTH had effectively distinguished between cancer cells and normal cells through a dual-function discrimination strategy, which used biotin to enrich the probe in cancer cells and reacted with overexpressed HOCl in cancer cells. Importantly, this dual-function discrimination strategy could obtain the precision detection of cancer cells, thereby offering assistance for improving the accuracy of early cancer diagnosis.

Making waves: Lessons learned from the COVID-19 anthropause in the Netherlands on urban aquatic ecosystem services provisioning and management

The anomalous past two years of the COVID-19 pandemic have been a test of human response to global crisis management as typical human activities were significantly altered. The COVID-instigated anthropause has illustrated the influence that humans and the biosphere have on each other, especially given the variety of national mobility interventions that have been implemented globally. These local COVID-19-era restrictions influenced human-ecosystem interactions through changes in accessibility of water systems and changes in ecosystem service demand. Four urban aquatic case studies in the Netherlands demonstrated shifts in human demand during the anthropause. For instance, reduced boat traffic in Amsterdam canals led to improved water clarity. In comparison, ongoing service exploitation from increased recreational fishing, use of bathing waters and national parks visitation are heightening concerns about potential ecosystem degradation. We distilled management lessons from both the case studies as well as from recent literature pertaining to ecological intactness and social relevance. Equally important to the lessons themselves, however, is the pace at which informed management practices are established after the pandemic ends, particularly as many communities currently recognize the importance of aquatic ecosystems and are amenable to their protection.

Smarter and Greener Cities After COVID-19: An Integrated Decision-Making Framework to Prioritize Investment Alternatives

Locking down cities to curb the transmission of coronavirus brought the global economy to a grinding halt. Cities are like engines of growth; when they stop, so does the growth. Therefore, it becomes paramount to build cities that continue to function and do not collapse amidst any crisis. Since economic recovery is underway, this paper examines priority areas for investment to expedite recovery and build back stronger cities. These areas are evaluated based on their contribution to revitalizing public health, economic, social, energy, and environmental sectors. For the analysis, analytical network process (ANP) and fuzzy-VIKOR are applied. ANP obtains the relative importance of sectors and their respective critical factors after solving a complex relationship among them. The economic sector has the highest weight of 25.8% among the five sectors, while job creation has the highest weight of 10.3% among the fifteen factors. Fuzzy-VIKOR is used to evaluate different areas and it is found that renewable energy has a greater contribution to the sustainable recovery of major sectors and the long-term aim of building inclusive green and resilient cities. These insights shall contribute to the conversations already ongoing among city governments, urban planners, civil society organizations, and city dwellers seeking practical solutions to unprecedented challenges posed by the pandemic.

Degradation of Triclosan in the Water Environment by Microorganisms: A Review

Triclosan (TCS), a kind of pharmaceuticals and personal care products (PPCPs), is widely used and has had a large production over years. It is an emerging pollutant in the water environment that has attracted global attention due to its toxic effects on organisms and aquatic ecosystems, and its concentrations in the water environment are expected to increase since the COVID-19 pandemic outbreak. Some researchers found that microbial degradation of TCS is an environmentally sustainable technique that results in the mineralization of large amounts of organic pollutants without toxic by-products. In this review, we focus on the fate of TCS in the water environment, the diversity of TCS-degrading microorganisms, biodegradation pathways and molecular mechanisms, in order to provide a reference for the efficient degradation of TCS and other PPCPs by microorganisms.

Light-Induced Anti-Bacterial Effect Against Staphylococcus aureus of Porphyrin Covalently Bonded to a Polyethylene Terephthalate Surface

Antimicrobial photodynamic inactivation represents a promising and potentially greener alternative to conventional antimicrobials, and a solution for multidrug-resistant strains. The current study reports the development and characterization of tetra-substituted diazirine porphyrin covalently bonded to polyethylene terephthalate (PET) and its use as an antimicrobial surface. The diazirine moiety on the porphyrin was activated using a temperature of 120 °C, which initiated a C-H insertion mechanism that irreversibly functionalized the PET surface. Activation of the surface with white LED light in phosphate-buffered saline (PBS) led to singlet oxygen generation, which was detected via the degradation of 9,10-anthracenediylbis(methylene)dimalonic acid (ADMA) over time. The bactericidal effect of the ¹O₂-producing surface against Staphylococcus aureus was determined qualitatively and quantitatively. The growth of the pathogen beneath porphyrin-functionalized PET coupons was reduced; moreover, the PET coupons resulted in a 1.76-log reduction in cell counts after exposure to white LED light for 6 h. This is a promising material and platform for the development of safer antimicrobial surfaces, with applications in healthcare, food packaging, marine surfaces, and other surfaces in the environment.

What is the relationship between land use and surface water quality? A review and prospects from remote sensing perspective

Good surface water quality is critical to human health and ecology. Land use determines the surface water heat and material balance, which cause climate change and affect water quality. There are many factors affecting water quality degradation, and the process of influence is complex. As rivers, lakes, and other water bodies are used as environmental receiving carriers, evaluating and quantifying how impacts occur between land use types and surface water quality is extremely important. Based on the summary of published studies, we can see that (1) land use for agricultural and construction has a negative impact on surface water quality, while woodland use has a certain degree of improvement on surface water quality; (2) statistical methods used in relevant research mainly include correlation analysis, regression analysis, redundancy analysis, etc. Different methods have their own advantages and limitations; (3) in recent years, remote sensing monitoring technology has developed rapidly, and has developed into an effective tool for comprehensive water quality assessment and management. However, the increase in spatial resolution of remote sensing data has been accompanied by a surge in data volume, which has caused difficulties in information interpretation and other aspects.

Indirect Impacts of COVID-19 on the Environment: A Global Review

Coronavirus (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus, which has plagued the Earth for the past two years and brought much controversy along with it. This report aims to analyze how the Covid-19 pandemic has had indirect effects on the environment. The onset of the pandemic has not only caused havoc disrupting routine average and businesses, but also claimed at least five million lives worldwide. This prompted the governments and the World Health Organization (WHO) to formulate measures to contain the transmission and the impact of the disease on the populations. Quarantine measures, movement restrictions, lockdowns and curfews, and travel bans are some of the most effective response methods that have helped the world contain the pandemic's spread. The adopted measures have had an indirect impact on the environment, opening the global community to numerous opportunities and threats. This report provides a critical analysis of how the Covid-19 pandemic has had indirect effects on the environment, examining how the response and containment measures have affected the environment. It focuses on air quality, water demand and quality, climate change, afforestation and deforestation, wildlife resurgence, littering, traffic congestion, noise reduction and changed human activities. It explores how the Covid-19 containment measures have had an environmental impact with a keen interest in the earlier areas.

Evaluation of N-acetylcysteine and glutathione as quenching agents for the analysis of halogenated disinfection by-products

Disinfection by-products (DBPs), formed from the reactions of disinfectants with natural organic matter and halides in drinking water, were considered to be cytotoxic and genotoxic, and might trigger various cancers. The relatively low concentration of DBPs in finished water (low µg/L or even ng/L levels) and the interference from water matrix inhibited in situ determination of DBPs. Moreover, the further formation and degradation of DBPs by disinfectants during the holding time (several hours to several days) from sample collection to analysis could adversely affect the determination of DBPs. To obtain accurate, precise and reliable data of DBP occurrence and formation, robust and reliable sample preservation is indispensable. However, the commonly used quenching agents (e.g., sodium sulfite, sodium thiosulfate, and ascorbic acid) for sample preservation can decompose reactive DBPs by reductive dehalogenation. This study evaluated the performance of N-acetylcysteine (NAC) and glutathione (GSH) as quenching agents for the analysis of halogenated DBPs by investigating the stoichiometry of the disinfectant-quenching agent reaction, the formation of DBPs during chlor(am)ination of NAC or GSH, and the effects of NAC or GSH on the stability of 18 individual DBPs and total organic halogen (TOX). Based on the results of this study, NAC and GSH were considered to be ideal quenching agents for the analysis of most DBPs and TOX, except halonitromethanes.

Degradation of 2,6-dichloro-1,4-benzoquinone by UV/H2O2/O3 treatment: Effectiveness, water matrix effects, and degradation mechanism

2,6-dichloro-1,4-benzoquinone (DCBQ), a typical representative of Halobenzoquinones, is an emerging aromatic disinfection by-product (DBP) with high toxicity and carcinogenicity, generated commonly through the chlorination in the drinking water disinfection process while there is still a lack of research on its removal. In this study, the effects of ultraviolet-based advanced oxidation processes (UV-AOPs) on the degradation of DCBQ were evaluated. The results showed that UV-AOPs are effective in degrading DCBQ. The removal of DCBQ by UV/H₂O₂/O₃ was more significant than by UV/H₂O₂ or UV/O_3, achieving a 96.7% removal rate at both the O₃ and H₂O₂ doses of 1 mg/L. The results also indicated the alkaline and weakly acidic environments could facilitate the degradation of DCBQ, inorganic anions could inhibit DCBQ degradation and the degree of inhibition increased as the matrix concentration increased. The degradation of DCBQ was inhibited more by the CO₃^2- than the other matrix components, such as Cl^- and NO₃^-. It was shown by the density functional theory simulations and the ultrahigh-performance liquid chromatography (UPLC) - Orbitrap mass spectra that the electrons in DCBQ are mainly on the chlorine atom connected to the carboatomic ring and that OH• can attack the chlorine atom to cause de-chlorination. The DCBQ degradation pathway may involve the oxidation of DCBQ to 3-hydroxy-2,6-DCBQ (HO-DCBQ) and 3,5-dichloro-1,2,4-pyrogallol, the further degradation of intermediate products by OH• to dechlorinated forms of HO-DCBQ and DCBQ.

Triclosan: A Small Molecule with Controversial Roles

Triclosan (TCS), a broad-spectrum antimicrobial agent, has been widely used in personal care products, medical products, plastic cutting boards, and food storage containers. Colgate Total^® toothpaste, containing 10 mM TCS, is effective in controlling biofilm formation and maintaining gingival health. Given its broad usage, TCS is present ubiquitously in the environment. Given its strong lipophilicity and accumulation ability in organisms, it is potentially harmful to biohealth. Several reports suggest the toxicity of this compound, which is inserted in the class of endocrine disrupting chemicals (EDCs). In September 2016, TCS was banned by the U.S. Food and Drug Administration (FDA) and the European Union in soap products. Despite these problems, its application in personal care products within certain limits is still allowed. Today, it is still unclear whether TCS is truly toxic to mammals and the adverse effects of continuous, long-term, and low concentration exposure remain unknown. Indeed, some recent reports suggest the use of TCS as a repositioned drug for cancer treatment and cutaneous leishmaniasis. In this scenario it is necessary to investigate the advantages and disadvantages of TCS, to understand whether its use is advisable or not. This review intends to highlight the pros and cons that are associated with the use of TCS in humans.

Human viruses lurking in the environment activated by excessive use of COVID-19 prevention supplies

Due to extensive COVID-19 prevention measures, millions of tons of chemicals penetrated into natural environment. Alterations of human viruses in the environment, the neglected perceiver of environmental fluctuations, remain obscure. To decipher the interaction between human viruses and COVID-19 related chemicals, environmental samples were collected on March 2020 from surroundings of designated hospitals and receivers of wastewater treatment plant effluent in Wuhan. The virus community and chemical concentration were respectively unveiled in virtue of virome and ultra-high-performance liquid chromatography-tandem mass spectrometry. The complex relationship between virus and chemical was ulteriorly elaborated by random forest model. As an indicator, environmental viruses were corroborated to sensitively reflect the ecological disturbance originated from pandemic prevention supplies. Chemicals especially trihalomethanes restrained the virus community diversity. Confronting this adverse scenario, Human gammaherpesvirus 4 and Orf virus with resistance to trihalomethanes flourished while replication potential of Macacine alphaherpesvirus 1 ascended under glucocorticoids stress. Consequently, human viruses lurking in the environment were actuated by COVID-19 prevention chemicals, which was a constant burden to public health in this ongoing pandemic. Besides, segments of SARS-CoV-2 RNA were detected near designated hospitals, suggesting environment as a missing link in the transmission route. This research innovatively underlined the human health risk of pandemic prevention supplies from the virus - environment interaction, appealing for monitoring of environmental viruses in long term.

A microfluidic system for viability determination of microalgae upon disinfectant treatment under continuous flow

The extensive use of quaternary ammonium compounds (QACs) has raised concerns regarding their environmental fate and potential risks to the ecosystem. As sensitive pollution indicators, green microalgae could readily monitor the aquatic toxicity of QACs as reflective of the changes in cell viability. Recent microfluidic-based systems have been designed for environmental biomonitoring and ecotoxicity studies while overall information of cell viability cannot be directly visualized under flowing conditions. In the present study, we developed a multifunctional microfluidic platform with the integration of analytical techniques including laser speckle contrast imaging and fluorescence spectroscopy for monitoring algal activity in response to QAC treatment. The biocidal efficiency of a representative QAC benzalkonium bromide (BAB) on a typical aquatic algae Chlorella vulgaris was determined by collecting the bio-speckles and chlorophyll autofluorescence in real-time, where dose-dependent and time-dependent decrease of algal growth was found with the increase of BAB concentration and interaction time. The integrated system was capable of rapid detection of the aquatic toxicity of QACs along with macroscopical visualization of algal activities under flowing conditions in time-course, which could be extended to future implementation for broad ecotoxicity analysis of versatile environmental samples.

Impacts of COVID-19 pandemic on the aquatic environment associated with disinfection byproducts and pharmaceuticals

In this study, concentrations of disinfection byproducts (DBPs) and COVID-19 related pharmaceuticals in wastewater effluents and surface water were measured two weeks, three months and eight months after the lockdown in Wuhan. Little temporal variation in DBP concentrations suggested intensified disinfection during the COVID-19 pandemic had limited impacts on the occurrence of DBPs in the aquatic environment. In contrast, the pandemic led to a significant increase in concentrations of lopinavir and ritonavir in wastewater effluents and surface water. The high detection frequency of these pharmaceuticals in surface water after the lockdown highlighted their mobility and persistence in the aquatic environment. The initial ecological risk assessment indicated moderate risks associated with these pharmaceuticals in surface water. As the global situation is still rapidly evolving with a continuous surge in the number of confirmed COVID-19 cases, our results suggest a pressing need for monitoring COVID-19 related pharmaceuticals as well as a systematic evaluation of their ecotoxicities in the aquatic environment.

Low-concentration of trichloromethane and dichloroacetonitrile promote the plasmid-mediated horizontal transfer of antibiotic resistance genes

Disinfection by-products (DBPs) are one of the unintended consequences of water disinfection that are commonly detected in various water environments. Although DBPs are known to induce antimicrobial resistance via stimulation of chromosomal mutations, it remains unclear whether low-concentration of DBPs could stimulate the conjugative transfer of antibiotic resistance genes (ARGs). The present study aimed to investigate the effect of two typical DBPs, namely trichloromethane (TCM) and dichloroacetonitrile (DCAN), on the conjugative transfer of RP4 plasmid in Escherichia coli genera. The results of the study demonstrated that exposure to low concentrations of TCM and DCAN significantly stimulated conjugative transfer of ARGs, wherein application of 25 μg/L of TCM and 10 μg/L of DCAN resulted in maximum fold change of ~5.5- and ~6.0-fold, respectively, at 16 h of exposure. Further, assessment of underlying mechanisms revealed the involvement of intracellular reactive oxygen species generation, SOS response, increase in cell membrane permeability, upregulation of expression of genes and proteins related to pilus generation, ATP synthesis, and RP4 gene expression. Our findings provided a better understanding of the hidden biological effects and the ecological risks of DBPs in the water environment, especially concerning their effect on the spread of antibiotic resistance.

Residual chlorine disrupts the microbial communities and spreads antibiotic resistance in freshwater

Chlorine disinfection is a key global public health strategy for the prevention and control of diseases, such as COVID-19. However, little is known about effects of low levels of residual chlorine on freshwater microbial communities and antibiotic resistomes. Here, we treated freshwater microcosms with continuous low concentrations of chlorine and quantified the effects on aquatic and zebrafish intestinal microbial communities and antibiotic resistomes, using shotgun metagenome and 16S rRNA gene sequencing. Although chlorine rapidly degraded, it altered the aquatic microbial community composition over time and disrupted interactions among microbes, leading to decreases in community complexity and stability. However, community diversity was unaffected. The majority of ecological functions, particularly metabolic capacities, recovered after treatment with chlorine for 14 d, due to microbial community redundancy. There were also increased levels of antibiotic-resistance gene dissemination by horizontal and vertical gene transfer under chlorine treatment. Although the zebrafish intestinal microbial community recovered from temporary dysbiosis, growth and behavior of zebrafish adults were negatively affected by chlorine. Overall, our findings demonstrate the negative effects of residual chlorine on freshwater ecosystems and highlight a possible long-term risk to public health.

Inhibition of nucleotide excision repair and damage response signaling by dibromoacetonitrile: A novel genotoxicity mechanism of a water disinfection byproduct

Dibromoacetonitrile (DBAN) is a carcinogenic disinfection byproduct (DBP) but how it precipitates cancer is unknown. Nucleotide excision repair (NER) is a versatile repair mechanism for removing bulky DNA lesions to maintain genome stability, and impairment of this process is associated with cancer development. In this study, we found that DBAN inhibited NER and investigated its mechanism with other DNA damage responses. Human keratinocytes HaCaT were treated with DBAN followed by ultraviolet (UV) as a model inducer of DNA damage, pyrimidine dimers, which require NER for the removal. DBAN pretreatment exacerbated UV-cytotoxicity, and inhibited the repair of pyrimidine dimers. DBAN treatment delayed the recruitment of NER proteins, transcription factor IIH (TFIIH) and xeroderma pigmentosum complementation group G (XPG), to DNA damaged sites, and subsequent gap filling process. Moreover, DBAN suppressed the UV-induced double strand breaks (DSBs) formation, as well as phosphorylated histone H2AX (γ-H2AX), a widely used DNA damage marker. Altogether, DBAN could negatively impact the NER process and phosphorylation pathway responding to DNA damage. This study was the first to identify the inhibition of NER and damage response signaling as a genotoxicity mechanism of a class of DBPs and it may serve as a foundation for DBP carcinogenesis.