Mesocosm experiment to determine the contribution of adsorption, biodegradation, hydrolysis and photodegradation in the attenuation of antibiotics at the water sediment interface

Exploring the role of carbon source types in trace-level sulfamethoxazole removal and greenhouse gas emissions in AnMBRs

The efficient removal of trace-level sulfamethoxazole (SMX) from wastewater remains a significant challenge. Different carbon sources can enrich distinct microbiomes, leading to variations in the functional capacity of the community. This makes it possible to select appropriate carbon sources that are conducive to enhancing SMX removal, thereby improving the overall SMX removal efficiency in WWTPs. In this study, acetate, citrate, and glucose were tested as carbon sources in anaerobic membrane bioreactors (AnMBRs) to investigate their effects on trace-level SMX removal. Glucose, as a carbon source, achieved the highest SMX removal efficiency, reduced the risk of resistance gene transmission, and maintained stable nutrient removal performance. The higher abundance of SMX-degrading bacteria and the higher content of extracellular polymeric substances in glucose-fed cultures are the reasons for the higher SMX removal rate. Additionally, GHG emissions, primarily methane, increase with the increase of SMX concentration within the range of 10-250 μg L-1. Methane production is predominantly driven by the acetate-to-methane pathway (M00357 KEGG). Higher SMX concentrations led to an increase in the abundance of SMX-resistant bacteria, causing a large amount of CH4 emissions. These findings provide valuable insights into optimizing carbon source selection and deepen our understanding of the relationship between trace-level SMX removal and GHG emissions in wastewater treatment processes.

Acclimation of sludge-derived biofilms for effective removal of emerging contaminants: Impacts of inoculum source and carbon supplementation

Contaminants of emerging concern (CECs) have gathered significant public attention due to their widespread occurrence, high persistence, and increasing exposure potential. In this study, we used polyethylene biocarriers for acclimating biofilms from singular or combined activated sludges collected from three wastewater treatment plants (R, P, and L) over 5 month-long cycles. The acclimated biofilms achieved an average removal rate at 0.333, 0.313, and 0.185 week-1 for N, N-diethyl-meta-toluamide (DEET), sulfamethoxazole (SMX), and carbamazepine (CBZ), respectively, when external carbon was supplemented, which were significantly higher (p < 0.05) than biofilms that did not receive external carbons. Metabolite screening revealed SMX transformation through ipso-hydroxylation and acetyl conjugation, while CBZ degradation could be initiated by epoxidation. Significant but slower degradation rates (0.024∼0.031 week-1) were observed for aminotriazole (AMT), lidocaine (LDC), and trimethoprim (TMP), whereas atrazine (ATZ) exhibited minimal removal, highlighting its high recalcitrance. Biofilms acclimated from individual R and P sludges, with external carbon supplementation, attained the greatest removal efficiencies for 7 CECs. Multivariate statistical correlations (p < 0.05) identified potential degraders, including Sphingomonas and Zoogolea for AMT, Labrys and Koazkia for CBZ, and Asprobacter, unclassified Cyclobacteriaceae (ELB16-189) and Bryobacteraceae (Fen-178) for LDC. Abundance distribution of potential degraders among biofilms revealed that Sludge R favored the enrichment of key degraders for AMT, CBZ and LDC, while Sludge P was more conducive to acclimating CBZ degraders. This study advances our understanding of strategies in biofilm acclimation to improve CEC removal and provides insights into degradation pathways and associated microbial communities for future research.

Antibiotic-induced multi-trophic effects and their cascades in a sub-tropical freshwater ecosystem

Antibiotics are commonly detected in aquatic ecosystems worldwide due to their extensive use and excretion by humans and animals, posing potential risks to the health of these ecosystems. This study aimed to assess the ecological effects of the antibiotic ciprofloxacin on both structural (microbes, phytoplankton, zooplankton, and macroinvertebrates) and functional endpoints of a sub-tropical freshwater ecosystem. Ciprofloxacin was applied at concentrations of 0, 0.5, 5, 50, and 500 µg/L for 21 consecutive days in outdoor mesocosms, followed by a five-week recovery period. Ciprofloxacin significantly affected the structure of microbial, phytoplankton, and zooplankton communities, with calculated NOECs of 5, 0.5, and 5 µg/L, respectively. Notably, the microbial community composition, particularly taxa within the phyla Cyanobacteria and Bacteroidetes, exhibited marked shifts. Among phytoplankton, the filamentous cyanobacterium Cylindrospermopsis sp. exhibited the largest negative response to ciprofloxacin, while Microcystis sp. displayed the largest increase in abundance. Ciprofloxacin exposure also indirectly led to significant increases in zooplankton populations belonging to Cladocera, Copepoda, and Rotifera. Significant effects of ciprofloxacin on physicochemical parameters related to carbon and nitrogen cycling were observed. Structural equation models revealed that ciprofloxacin induced both direct and indirect effects across multiple trophic levels through cascading effects, further impacting ecosystem-level endpoints. Overall, this study provides an understanding of the potential ecological risks posed by antibiotic pollution on freshwater ecosystems.

The treated wastewater enhances the biodegradation of sulfonamide antibiotics in biofilm-sediment downstream of the receiving river outlet

Although the treated wastewater meets the discharge standards, it can still become a potential transmitted stressor that affects aquatic organisms in receiving rivers. Biofilms and sediments as the main solid-phase substances in natural aquatic environments can biodegrade micropollutants. However, most of the current studies have selected a single solid-phase material, and there are relatively few studies that comprehensively consider the effect of treated wastewater on the dissipation of micropollutants in a composite biofilm-sediment system. Therefore, this study investigated the dissipation pathways of six sulfonamide antibiotics (SAs) in biofilm-sediment and the effect of treated wastewater on SAs dissipation. The results showed that biodegradation was the main pathway for SAs dissipation in biofilm-sediment. The input of treated wastewater increased the abundance of dominant degradation bacteria Burkholderiales and Pseudomonadale, thereby improving the biodegradation rate of SAs (approximately 1.5 times higher than upstream degradation rate). These genera could also be further integrated into downstream communities to continuously mediate the biodegradation of SAs. Through mass spectrometry and metagenomic sequencing analysis, it was found that the common degradation pathways of SAs in biofilm-sediment affected by treated wastewater are acetylation, formylation, hydroxylation, and bond cleavage. Acetyltransferase played an important role in the biodegradation of SAs. In addition, the enrichment of antibiotic resistant genes during biodegradation increased the risk of their spread in the aquatic environment. These findings provide new insights into the fate of antibiotics in aquatic environments and the impact of treated wastewater on downstream bacterial communities.

Pollution by antimicrobials and antibiotic resistance genes in East Africa: Occurrence, sources, and potential environmental implications

The escalating burden of antimicrobial pollution in East Africa poses severe threats to public health, environmental integrity, and economic stability. Environmental compartments such as soil and water serve as reservoirs for these pollutants such as antimicrobials and antibiotic resistance genes, creating selective pressure that accelerates the emergence of antimicrobial resistance (AMR). These dynamic fosters the proliferation of multidrug-resistant pathogens, or "superbugs," complicating infection management and amplifying health risks in a region already challenged by inadequate healthcare and sanitation infrastructure. Furthermore, pollution by antimicrobials and antibiotic resistance genes critically disrupts ecological processes, such as nutrient cycling and organic matter degradation, diminishing soil fertility, water quality, and agricultural productivity, thereby threatening food security and overall ecological health. Current surveillance efforts, including the Global Antimicrobial Resistance and Use Surveillance System (GLASS) and the East Africa Public Health Laboratory Networking Project (EAPHLNP), have made strides in tracking AMR trends and guiding policy decisions. However, these efforts remain insufficient to address the growing crisis. This study highlights the urgent need for integrated strategies, including stringent antibiotic usage regulations, advanced wastewater treatment technologies, and comprehensive environmental surveillance. Therefore, there is a need to address the intersections of health, agriculture, and environment, to mitigate AMR and its far-reaching consequences to ensure public health safety and sustainability.

Unveiling the characteristics of fluoroquinolones in China marginal seas: Spatiotemporal distribution, environmental fate, and mass inventory

Fluoroquinolones (FQs) are widely used antibiotics, frequently detected in marine environments with serious ecological risks. This study reviewed FQs usage in China, their spatiotemporal distribution in offshore waters, and their marine fates. FQs consumption initially declined but increased after 2013. Studies on antibiotics in China's offshore areas were concentrated in the Bohai Sea, particularly in Bohai Bay and Laizhou Bay, while fewer studies were conducted in the East and South China Seas. NOR, OFL, CIP, and ENR exhibited the highest detection frequencies and concentrations, with enoxacin (ENO) also commonly found in the South China Sea. The total concentration of FQs (∑FQs) in seawater ranged from 0.2 to 960 ng/L, following the order Bohai Sea > Yellow Sea ≈ East China Sea > South China Sea, with a decreasing trend in the Bohai and South China Seas since 2013. ∑FQs concentrations in sediments were lower, ranging from 0.02 to 170.18 ng/g, with no regional differences. Estimated ∑FQs mass inventories ranged from 7.42 to 671.13 tons in the Bohai Sea and from 7.90 to 478.23 tons in the Yellow Sea. Seawater exchange influenced FQs accumulation, with long-term discharge retention in the Bohai Sea and recent inputs in the Yellow Sea. A strong correlation was observed between FQs usage and their marine inventories, with NOR and CIP exhibiting higher environmental stability than OFL and ENR. This study provides important scientific evidence for a systematic understanding of the relationship between the use, occurrence, and environmental fate of FQs in China.

Remediation of sulfonamide antibiotic-containing wastewater by constructed wetlands: Importance and action mechanism of plants

Constructed wetlands (CWs) have been proved to be effective in treating sulfonamide antibiotics (SAs) wastewater. Nevertheless, as an essential element in CWs, the significance of plants, continues to be a topic of controversy. In this study, CWs with two different plant species were taken as the research object to investigate their treatment performance, in order to understand the impact of plants on the treatment of SAs wastewater in CWs and to discover the underlying action mechanisms. Experiment results showed that plants played an important role in the CWs, and significantly improved the efficiency of wastewater treatment, with average removal rates for conventional nutrients (COD, NH4+-N, NO3--N and TP) ranging from 73.69 % to 98.92 %, surpassing the non-plant control group (52.16 %-80.70 %). Similarly, for SAs, the removal efficiency in the plant-treated group was 74.15 %-83.67 %, higher than that in the non-plant control group (65.42 %-70.14 %). Although, as time passed, the efficacy of CWs had slightly decreased, but the rate of pollutant removal remained consistently over 60 %. Further analysis showed that plants promoted the removal of SAs through various mechanisms such as plant uptake, microbial degradation and substrate adsorption. Plants had the ability to absorb SAs from wastewater and eliminated them through metabolism or accumulation. Additionally, plants can improve soil enzyme activity to facilitate microbial degradation, indirectly promoting SAs removal. It's worth noting that most SAs can be degraded through plant metabolism after being absorbed by plants, while only a minority of SAs accumulated in plants in the form of parent compounds. Furthermore, the efficacy of CWs in treating wastewater differed between selected plant species. Specifically, Iris pseudacorus showed a higher purifing potential than Scirpus validus. These results revealed the effect of plants on the treatment of SAs wastewater in CWs, and provided a reference for the practical application of antibiotic wastewater removal by CWs.

Impact of riverbed renaturalization on the attenuation of antibiotics and antimicrobial resistance in wastewater effluent-dominated streams

Mediterranean streams contain substantial proportions of wastewater treatment plant effluent, occasionally constituting the entire water flow. Here, we analysed the seasonal occurrence of 23 antibiotics (AB) and antimicrobial resistance (AMR) by tracking 3 marker genes and bacterial community dynamics in two wastewater effluent-dominated streams. One stream was renaturalized with meanders and vegetation, while the other was linear and had a low vegetation density. The concentration of ABs in the effluents ranged from 33 to 1313 ng·L-1 during summer and 4 to 2337 ng·L-1 during winter. The attenuation of ABs 3.5 km downstream varied depending on the compound, ranging from 42 to 88%. The half-lives of ABs obtained for the streams were 0.2-4.1 h in summer and 0.6-12.6 h in winter. Most ABs had a half-life of <5 h, except sulfamethoxazole, acetyl-sulfamethoxazole, and trimethoprim. The vegetated stream exhibited a higher attenuation of ABs than the unaltered stream (88% vs. 67% on average), while also showing lower half-life values (on average 1.3 vs. 3.8 h). The bacterial community profiles in both streams were typical of effluents, with greater longitudinal dynamics in the vegetated stream during summer than in the other samplings. Similarly, AMR indicator genes decreased most in the vegetated stream during summer (0.8-1.1 log units). The ecotoxicological risk and the potential microbial risk selection values downstream at 3.5 km were reduced by > 45%. Overall, the results suggest that vegetation and meanders play an important role in the in-stream attenuation of ABs and AMRs.

Removal of Antibiotics in Breeding Wastewater Tailwater Using Microalgae-Based Process

Ciprofloxacin (CIP) and oxytetracycline (OTC) are commonly detected antibiotic species in breeding wastewater, and microalgae-based antibiotic treatment technology is an environmentally friendly and cost-effective method for its removal. This study evaluated the effects of CIP and OTC on Scenedesmus sp. in the breeding wastewater tailwater and the removal mechanisms of antibiotics. The results showed that Scenedesmus sp could increase antibiotic tolerance by enhancing antioxidant system activity. Compared to CIP, Scenedesmus sp showed better performance for OTC removal, the removal efficiencies were 100%, 96.87%, 95.75%, 90.18% and 83.91% at 0.1, 0.5, 1, 5, and 10 mg L- 1 OTC, respectively. The removal routes indicated that CIP was mainly removed by biodegradation (38.88%) and photolysis (14.30%) whereas OTC was mainly removed by hydrolysis (43.47%) and biodegradation (33.45%). Product toxicity predictions showed that most of the degradation products of CIP and OTC were less toxic than their parent compounds, confirming the feasibility of microalgae biotreatment for antibiotic removal.

Synthesis of TiO2-ZnO n-n Heterojunction with Excellent Visible Light-Driven Photodegradation of Tetracycline

Zinc oxide-based photocatalysts with non-toxicity and low cost are promising candidates for the degradation of tetracycline. Despite the great success achieved in constructing n-n-type ZnO-based heterojunctions for the degradation of tetracycline under full-spectrum conditions, it is still challenging to realize rapid and efficient degradation of tetracycline under visible light using n-n-type ZnO-based heterojunctions, as they are constrained by the quick recombination of electron-hole pairs in ZnO. Here, we report highly efficient and stable n-n-type ZnO-TiO2 heterojunctions under visible light conditions, with a degradation efficiency reaching 97% at 1 h under visible light, which is 1.2 times higher than that of pure zinc oxide, enabled by constructing an n-n-type heterojunction between ZnO and TiO2 to form a built-in electric field. The photocatalytic degradation mechanism of n-n TiO2-ZnO to tetracycline is also proposed in detail. The demonstration of efficient and stable heterojunction-type ZnO photocatalysts under visible light is an important step toward commercialization and opens up new opportunities beyond conventional ZnO technologies, such as composite ZnO catalysts.

Concentrations, probabilistic human and ecological risks assessment attribute to antibiotics residues in river water in China: Systematic review and meta-analysis

Antibiotics residues even low concentrations increases human health risk and ecological risk. The current study was conducted with the aims of meta-analysis concentrations of antibiotics in river water including amoxicillin (AMX), tetracyclines (TCN), sulfamethoxazole (SMX), ciprofloxacin (CIP), trimethoprim (TMP), azithromycin (AZM) and amoxicillin (AMX) and estimates human health and ecological risks. Search was performed in databases including Scopus, PubMed, Web of Science, Embase, Science direct, Cochrane, Science Direct, Google Scholar were used to retrieve scientific papers from January 1, 2004 to June 15, 2024. The concentration of antibiotics residues was meta-analyzed using random effects model in water river water based on type of antibiotics subgroups. Human health risk assessment from ingestion and dermal contact routs was estimated using target hazard quotient (THQ), total target hazard quotient (TTHQ), carcinogenic (CR) and ecological hazard quotient (EHQ) of antibiotics in river water was estimated using monte carlo simulations (MCS) model. Sixty-two papers on antibiotics in river water with 272 data-reports (n = 28,522) were included. The rank order of antibiotics residues in river water based on pooled concentration was SMX (66.086 ng/L) > CIP (26.005 ng/L) > TCN (17.888 ng/L) > TMP (6.591 ng/L) > AZM (2.077 ng/L) > AMX (0.029 ng/L). The overall pooled concentration of antibiotics residues in river water was 24.262 ng/L, 95 %CI (23.110-25.413 ng/L). TTHQ for adults and children due to antibiotics in water was 2.41E-3 and 2.36E-3, respectively. The sort of antibiotics based on their quota in TTHQ for adults and children was AMX > CIP > TMP > AZM > TCN > SMX. Total CR in adults and children was 2.41E-03 and 2.36E-03, respectively. The sort of antibiotics based on percentile 95 % EHQ was SMX (7.70E+03) > TCN (7.63E+01) > TMP (7.03E-03) > CIP (2.86E-03) > AMX (5.71E-04) and TEHQ values due to antibiotics in river water in China was equal to 7.78E+03. Current study suggests that conduct effective monitoring and water quality control plans to reduce concentration of antibiotics especially SMX, TCN, and CIP in river water of China.

Potential of nature-based solutions to reduce antibiotics, antimicrobial resistance, and pathogens in aquatic ecosystems. a critical review

This comprehensive scientific review evaluates the effectiveness of nature-based solutions (NBS) in reducing antibiotics (ABs), combating antimicrobial resistance (AMR), and controlling pathogens in various aquatic environments at different river catchment levels. It covers conventional and innovative treatment wetland configurations for wastewater treatment to reduce pollutant discharge into the aquatic ecosystems as well as exploring how river restoration and saltmarshes can enhance pollutant removal. Through the analysis of experimental studies and case examples, the review shows NBS's potential for providing sustainable and cost-effective solutions to improve the health of aquatic ecosystems. It also evaluates the use of diagnostic indicators to predict NBS effectiveness in removing specific pollutants such as ABs and AMR. The review concludes that NBS are feasible for addressing the new challenges stemming from human activities such as the presence of ABs, AMR and pathogens, contributing to a better understanding of NBS, highlighting success stories, addressing knowledge gaps, and providing recommendations for future research and implementation.

Classification, characteristics, harmless treatment and safety assessment of antibiotic pharmaceutical wastewater (APWW): A comprehensive review

The issues related to the spread of antibiotics and antibiotic resistance genes (ARGs) have garnered significant attention from researchers and governments. The production of antibiotics can lead to the emission of high-concentration pharmaceutical wastewater, which contains antibiotic residues and various other pollutants. This review compiles the classification and characteristics of antibiotic pharmaceutical wastewater (APWW), offers an overview of the development, advantages, and disadvantages of diverse harmless treatment processes, and presents a strategy for selecting appropriate treatment approaches. Biological treatment remains the predominant approach for treating APWW. In addition, several alternative methods can be employed to address the challenges associated with APWW treatment. On the other hand, the present safety assessment of the effluent resulting from APWW treatment is inadequate, necessitating more comprehensive research in this domain. It is recommended that researches in this area consider the issue of toxicity and antibiotic resistance as well. The PNECR model (similar to ecotoxicological PNECs but used to specifically refer to endpoints related to antimicrobial resistance) (Murray et al., 2024) is an emerging tool used for evaluating the antimicrobial resistance (AMR) issue. This model is, characterized by its simplicity and effectiveness, is a promising tool for assessing the safety of treated APWW.

Occurrence, Source Apportionment, and Risk Assessment of Antibiotics in Mangrove Sediments from the Lianzhou Bay, China

In recent years, the widespread application of antibiotics has raised global concerns, posing a severe threat to ecological health. In this study, the occurrence, source, and ecological risks of 39 antibiotics belonging to 5 classes in mangrove sediments from Lianzhou Bay, China, were assessed. The total concentrations of the antibiotics (∑39 antibiotics) ranged from 65.45 to 202.24 ng/g dry weight (dw), with an average of 142.73 ± 36.76 ng/g dw. The concentrations of these five classes of antibiotics were as follows: Sulfonamides (SAs) > Tetracyclines (TCs) > Fluoroquinolones (QUs) > Penicillin (PCs) > Macrolides (MLs). The spatial distribution of antibiotics varied as high tidal zone > middle tidal zone > low tidal zone. The total organic carbon (TOC), pH, nitrate (NO3--N), and nitrite (NO2--N) of the sediment significantly influenced the distribution of antibiotics (p < 0.05). A source analysis identified untreated sewage from aquaculture as the primary source of antibiotics in the local mangrove. A risk assessment revealed that ciprofloxacin, norfloxacin, ofloxacin of QUs, and tetracycline of TCs exhibited medium risks to algae in certain sampling sites, while other antibiotics exhibited low or no risks to all organisms. Nevertheless, the total risk of all the detected antibiotics to algae was medium in 95% of the sites. The overall ecological risk level of antibiotics in the middle tidal zone was slightly lower than in the high tidal zone and the lowest in the low tidal zone. In summary, the experimental results provided insights into the fate and transport behaviors of antibiotics in mangrove sediments from Lianzhou Bay.

Antibiotics in the rice-crayfish rotation pattern: Occurrence, prioritization, and resistance risk

Antibiotics are extensively utilized in aquaculture to mitigate diseases and augment the productivity of aquatic commodities. However, to date, there have been no reports on the presence and associated risks of antibiotics in the emergent rice-crayfish rotation (RCR) system. This study investigated the occurrence, temporal dynamics, prioritization, sources, and potential for resistance development of 15 antibiotics within the RCR ecosystem. The findings revealed that during the crayfish breeding and rice planting periods, florfenicol (FFC) predominated in the RCR's surface water, with peak and average concentrations of 1219.70 ng/L and 57.43 ng/L, and 1280.70 ng/L and 52.60 ng/L, respectively. Meanwhile, enrofloxacin (ENX) was the primary antibiotic detected in RCR soil and its maximum and average concentrations were 624.73 ng/L and 69.02 ng/L in the crayfish breeding period, and 871.27 ng/L and 45.89 ng/L in the rice planting period. Throughout the adjustment period, antibiotic concentrations remained relatively stable in both phases. Notably, antibiotic levels in surface water and soil escalated during the crayfish breeding period and subsided during the rice planting period, with these fluctuations predominantly influenced by FFC and ENX. Source analysis indicated that the antibiotics in RCR predominantly originated from aquaculture activities, supplemented by water exchange processes. Utilizing the entropy utility function and a resistance development model, FFC, clarithromycin (CLR), and roxithromycin (ROX) in surface water, along with ENX, CLR, and ROX in soil, were identified as priority antibiotics. FFC, ENX, and ROX exhibited a medium risk for resistance development. Consequently, this study underscores the necessity to intensify antibiotic usage control during the crayfish breeding period in the RCR system to mitigate environmental risks.

Migration and transformation behaviors of antibiotics in water-sediment system under simulated light and wind waves

Antibiotics can generally be detected in the water-sediment systems of lakes. However, research on the migration and transformation of antibiotics in water-sediment systems based on the influences of light and wind waves is minimal. To address this research gap, we investigated the specific impacts of light and wind waves on the migration and transformation of three antibiotics, norfloxacin (NOR), trimethoprim (TMP), and sulfamethoxazole (SMX), under simulated light and wind waves disturbance conditions in a water-sediment system from Taihu Lake, China. In the overlying water, NOR was removed the fastest, followed by TMP and SMX. Compared to the no wind waves groups, the disturbance of big wind waves reduced the proportion of antibiotics in the overlying water. The contributions of light and wind waves to TMP and SMX degradation were greater than those of microbial degradation. However, the non-biological and biological contributions of NOR to degradation were almost equal. Wind waves had a significant impact on the microbial community changes in the sediment, especially in Methylophylaceae. These results verified the influence of light and wind waves on the migration and transformation of antibiotics, and provide assistance for the risk of antibiotic occurrence in water and sediments.

Natural attenuation of sulfonamides and metabolites in contaminated groundwater - Review, advantages and challenges of current documentation techniques

Sulfonamides are applied worldwide as antibiotics. They are emerging contaminants of concern, as their presence in the environment may lead to the spread of antibiotic resistance genes. Sulfonamides are present in groundwater systems, which suggest their persistence under certain conditions, highlighting the importance of understanding natural attenuation processes in groundwater. Biodegradation is an essential process, as degradation of sulfonamides reduces the risk of antibiotic resistance spreading. In this review, natural attenuation, and in particular assessment of biodegradation, is evaluated for sulfonamides in groundwater systems. The current knowledge level on biodegradation is reviewed, and a scientific foundation is built based on sulfonamide degradation processes, pathways, metabolites and toxicity. An overview of bacterial species and related metabolites is provided. The main research effort has focused on aerobic conditions while investigations under anaerobic conditions are lacking. The level of implementation in research is laboratory scale; here we strived to bridge towards field application and assessment, by assessing approaches commonly used in monitored natural attenuation. Methods to document contaminant mass loss are assessed to be applicable for sulfonamides, while the approach is limited by a lack of reference standards for metabolites. Furthermore, additional information is required on relevant metabolites in order to improve risk assessments. Based on the current knowledge on biodegradation, it is suggested to use the presence of substituent-containing metabolites from breakage of the sulfonamide bridge as specific indicators of degradation. Microbial approaches are currently available for assessment of microbial community's capacities, however, more knowledge is required on indigenous bacteria capable of degrading sulfonamides and on the impact of environmental conditions on biodegradation. Compound specific stable isotope analysis shows great potential as an additional in situ method, but further developments are required to analyse for sulfonamides at environmentally relevant levels. Finally, in a monitored natural attenuation scheme it is assessed that approaches are available that can uncover some processes related to the fate of sulfonamides in groundwater systems. Nevertheless, there are still unknowns related to relevant bacteria and metabolites for risk assessment as well as the effect of environmental settings such as redox conditions. Alongside, uncovering the fate of sulfonamides in future research, the applicability of the natural attenuation documentation approaches will advance, and provide a step towards in situ remedial concepts for the frequently detected sulfonamides.

A review of the influence of environmental pollutants (microplastics, pesticides, antibiotics, air pollutants, viruses, bacteria) on animal viruses

Microorganisms, especially viruses, cause disease in both humans and animals. Environmental chemical pollutants including microplastics, pesticides, antibiotics sand air pollutants arisen from human activities affect both animal and human health. This review assesses the impact of chemical and biological contaminants (virus and bacteria) on viruses including its life cycle, survival, mutations, loads and titers, shedding, transmission, infection, re-assortment, interference, abundance, viral transfer between cells, and the susceptibility of the host to viruses. It summarizes the sources of environmental contaminants, interactions between contaminants and viruses, and methods used to mitigate such interactions. Overall, this review provides a perspective of environmentally co-occurring contaminants on animal viruses that would be useful for future research on virus-animal-human-ecosystem harmony studies to safeguard human and animal health.

Adsorption, natural attenuation, and microbial community response of ofloxacin and oxolinic acid in marine sediments

The pollution of quinolone antibiotics in the marine environment has attracted widespread attention, especially for ofloxacin (OFL) and oxolinic acid (OXO) due to their frequent detection. However, few studies have been conducted to assess the behaviors and microbial community response to these antibiotics in marine sediments, particularly for potential antibiotic-resistant bacteria. In this work, the adsorption characteristics, natural attenuation characteristics, and variation of microbial communities of OFL and OXO in marine sediments were investigated. The adsorption process of antibiotics in sediments occurred on the surface and internal pores of organic matter, where OFL was more likely to be transferred from seawater to sediment compared with OXO. Besides, the adsorption of two antibiotics on sediment surfaces was attributed to physisorption (pore filling, electrostatic interaction) and chemisorption (hydrogen bonding). The natural attenuation of OFL and OXO in marine sediment followed second-order reaction kinetics with half-lives of 6.02 and 26.71 days, respectively, wherein biodegradation contributed the most to attenuation, followed by photolysis. Microbial community structure in marine sediments exposure to antibiotics varied by reducing abundance and diversity of microbial communities, as a whole displaying as an increase in the relative abundance of Firmicutes whereas a decrease of Proteobacteria. In detail, Escherichia-Shigella sp., Blautia sp., Bifidobacterium sp., and Bacillus sp. were those antibiotic-resistant bacteria with potential ability to degrade OFL, while Bacillus sp. may be resistant to OXO. Furthermore, functional predictions indicated that the microbial communities in sediment may resist the stress caused by OFL and OXO through cyano-amino acid metabolism, and ascorbate and aldarate metabolism, respectively. The research is key to understanding fate and bacterial resistance of antibiotics in marine sediments.

Aqueous fate of furaltadone: Kinetics, high-resolution mass spectrometry - based elucidation and toxicity assessment of photoproducts

Furaltadone (FTD) is an antibiotic belonging to the nitrofurans group. It has been broadly used in livestock and aquaculture for therapeutic purposes, as well as for stimulating promotion. Although the European Union has imposed restrictions on the use of FTD since 1995 due to concerns regarding its toxicity, in many cases FTD has been excessively and/or illegally applied in productive animals in developing countries, because of its high efficacy and low-cost. Unlike other nitrofuran compounds, the hydrolytic and photolytic behavior of FTD in natural aquatic systems has not been thoroughly investigated. To this end, hydrolysis in different pH values and photolysis in aquatic environment, including lake, river and sea water have been both examined. Hydrolysis was found to have an insignificant impact on degradation of FTD in the aquatic environment relevant pH values, whereas indirect photolysis proved to be the main route of its elimination. The identification of tentative photoproducts (PPs) was performed using ultra high performance liquid chromatography coupled to hybrid LTQ/Orbitrap high resolution mass spectrometry. A possible pathway for photolytic transformation of FTD was proposed. Additionally, in silico simulations were used to evaluate the toxicity such as the mutagenicity of FTD and PPs. Complementary to the low-cost and time-limited simulations, an in vitro method (Vibrio Fischeri bioluminescence) was also used to assess ecotoxicity.

Microbial phylogenetic divergence between surface-water and sedimentary ecosystems drove the resistome profiles

Antibiotic pollution and the evolution of antibiotic resistance genes (ARGs) are increasingly viewed as major threats to both ecosystem security and human health, and have drawn attention. This study investigated the fate of antibiotics in aqueous and sedimentary substrates and the impact of ecosystem shifts between water and sedimentary phases on resistome profiles. The findings indicated notable variations in the concentration and distribution patterns of antibiotics across various environmental phases. Based on the partition coefficient (Kd), the total antibiotic concentration was significantly greater in the surface water (1405.45 ng/L; 49.5 %) compared to the suspended particulate matter (Kd = 0.64; 892.59 ng/g; 31.4 %) and sediment (Kd = 0.4; 542.64 ng/g; 19.1 %). However, the relative abundance of ARGs in surface water and sediment was disproportionate to the abundance of antibiotics concentration, and sediments were the predominant ARGs reservoirs. Phylogenetic divergence of the microbial communities between the surface water and the sedimentary ecosystems potentially played important roles in driving the ARGs profiles between the two distinctive ecosystems. ARGs of Clinical importance; including blaGES, MCR-7.1, ermB, tet(34), tet36, tetG-01, and sul2 were significantly increased in the surface water, while blaCTX-M-01, blaTEM, blaOXA10-01, blaVIM, tet(W/N/W), tetM02, and ermX were amplified in the sediments. cfxA was an endemic ARG in surface-water ecosystems while the endemic ARGs of the sedimentary ecosystems included aacC4, aadA9-02, blaCTX-M-04, blaIMP-01, blaIMP-02, bla-L1, penA, erm(36), ermC, ermT-01, msrA-01, pikR2, vgb-01, mexA, oprD, ttgB, and aac. These findings offer a valuable information for the identification of ARGs-specific high-risk reservoirs.

New insights into bioaugmented removal of sulfamethoxazole in sediment microcosms: degradation efficiency, ecological risk and microbial mechanisms

BACKGROUND

Bioaugmentation has the potential to enhance the ability of ecological technology to treat sulfonamide-containing wastewater, but the low viability of the exogenous degraders limits their practical application. Understanding the mechanism is important to enhance and optimize performance of the bioaugmentation, which requires a multifaceted analysis of the microbial communities. Here, DNA-stable isotope probing (DNA-SIP) and metagenomic analysis were conducted to decipher the bioaugmentation mechanisms in stabilization pond sediment microcosms inoculated with sulfamethoxazole (SMX)-degrading bacteria (Pseudomonas sp. M2 or Paenarthrobacter sp. R1).

RESULTS

The bioaugmentation with both strains M2 and R1, especially strain R1, significantly improved the biodegradation rate of SMX, and its biodegradation capacity was sustainable within a certain cycle (subjected to three repeated SMX additions). The removal strategy using exogenous degrading bacteria also significantly abated the accumulation and transmission risk of antibiotic resistance genes (ARGs). Strain M2 inoculation significantly lowered bacterial diversity and altered the sediment bacterial community, while strain R1 inoculation had a slight effect on the bacterial community and was closely associated with indigenous microorganisms. Paenarthrobacter was identified as the primary SMX-assimilating bacteria in both bioaugmentation systems based on DNA-SIP analysis. Combining genomic information with pure culture evidence, strain R1 enhanced SMX removal by directly participating in SMX degradation, while strain M2 did it by both participating in SMX degradation and stimulating SMX-degrading activity of indigenous microorganisms (Paenarthrobacter) in the community.

CONCLUSIONS

Our findings demonstrate that bioaugmentation using SMX-degrading bacteria was a feasible strategy for SMX clean-up in terms of the degradation efficiency of SMX, the risk of ARG transmission, as well as the impact on the bacterial community, and the advantage of bioaugmentation with Paenarthrobacter sp. R1 was also highlighted. Video Abstract.

Competitive adsorption and bioaccumulation of sulfamethoxazole and roxithromycin by sediment and zebrafish (Danio rerio) during individual and combined exposure in water

Antibiotics are extensively used for health protection and food production, causing antibiotic pollution in the aquatic environment. This study aims to determine the bioavailability and bioaccumulation of typical antibiotics sulfamethoxazole (SMX) and roxithromycin (RTM) in zebrafish under environmentally realistic conditions. Four different microcosms, i.e. water, water-sediment, water-zebrafish, and water-sediment-zebrafish were constructed, with three replicates in parallel. The concentrations of SMX and RTM in water, sediment and zebrafish were extracted and analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to assess their kinetic behavior and bioavailability. In the water-sediment system, the dissolved concentration of both SMX and RTM decreased with time following the first-order kinetic while their adsorption by sediment increased with time. In the water-zebrafish system, SMX and RTM bioaccumulation was increasing with time following the pseudo second-order kinetics. RTM bioaccumulation in zebrafish (up to 16.4 ng/g) was an order of magnitude higher than SMX (up to 5.2 ng/g), likely due to RTM being more hydrophobic than SMX. In addition, the bioaccumulation factor (BAF) value of SMX in zebrafish was greater than its sediment partition coefficient, while the opposite trend was observed for RTM, demonstrating the importance of antibiotics properties in affecting their bioavailability. Furthermore, increasing dissolved organic carbon concentration in water reduced SMX bioaccumulation, but increased RTM bioaccumulation at the same time. The findings are important in future studies of environmental fate and bioavailability of toxic chemicals with different pollution sources and physicochemical properties.

Transformation products of antibacterial drugs in environmental water: Identification approaches based on liquid chromatography-high resolution mass spectrometry

In recent years, the presence of antibiotics in the aquatic environment has caused increasing concern for the possible consequences on human health and ecosystems, including the development of antibiotic-resistant bacteria. However, once antibiotics enter the environment, mainly through hospital and municipal discharges and the effluents of wastewater treatment plants, they can be subject to transformation reactions, driven by both biotic (e.g. microorganism and mammalian metabolisms) and abiotic factors (e.g. oxidation, photodegradation, and hydrolysis). The resulting transformation products (TPs) can be less or more active than their parent compounds, therefore the inclusion of TPs in monitoring programs should be mandatory. However, only the reference standards of a few known TPs are available, whereas many other TPs are still unknown, due to the high diversity of possible transformation reactions in the environment. Modern high-resolution mass spectrometry (HRMS) instrumentation is now ready to tackle this problem through suspect and untargeted screening approaches. However, for handling the large amount of data typically encountered in the analysis of environmental samples, these approaches also require suitable processing workflows and accurate tandem mass spectra interpretation. The compilation of a suspect list containing the possible monoisotopic masses of TPs retrieved from the literature and/or from laboratory simulated degradation experiments showed unique advantages. However, the employment of in silico prediction tools could improve the identification reliability. In this review, the most recent strategies relying on liquid chromatography-HRMS for the analysis of environmental TPs of the main antibiotic classes were examined, whereas TPs formed during water treatments or disinfection were not included.