Xiaohui Liu

Antibiotics in the aquatic environments: A review of lakes, China

The potential threat of antibiotics to the environment and human health has raised significant concerns in recent years. The consumption and production of antibiotics in China are the highest in the world due to its rapid economic development and huge population, possibly resulting in the high detection frequencies and concentrations of antibiotics in aquatic environments of China. As a water resource, lakes in China play an important role in sustainable economic and social development. Understanding the current state of antibiotics in lakes in China is important. Closed and semi-closed lakes provide an ideal medium for the accumulation of antibiotics and antibiotic resistance genes (ARGs). This review summarizes the current levels of antibiotic exposure in relevant environmental compartments in lakes. The ecological and health risks of antibiotics are also evaluated. This review concludes that 39 antibiotics have been detected in the aquatic environments of lakes in China. The levels of antibiotic contamination in lakes in China is relatively high on the global scale. Antibiotic contamination is higher in sediment than water and aquatic organisms. Quinolone antibiotics (QNs) pose the greatest risks. The contents of antibiotics in aquatic organisms are far lower than their maximum residual limits (MRLs), with the exception of the organisms in Honghu Lake. The lakes experience high levels of ARG contamination. A greater assessment of ARG presence and antibiotic exposure are urgent.

Residues and health risk assessment of typical antibiotics in aquatic products from the Dongting Lake, China—“Did you eat “Antibiotics” today?”

The contamination level of 12 antibiotics in 8 species of fish and shrimp from the Dongting Lake, China, was firstly studied. In total, the concentrations of antibiotics in fish and shrimp were lower, which were far lower than the maximum residue limits. The most abundant compound was enrofloxacin followed by sulfadiazine, sulfamethoxazole, sarafloxacin, and sulfadimidine with the highest content from 0.37 to 1.06xa0ngxa0g−1. The concentrations in Silurus asotus, Cyprinus carpio, and Palinuridae were higher. Concentrations in fish and shrimp from different water layers showed spatial difference, with the order of benthos and middle-lower species > middle-upper species. In addition, the antibiotic content could be affected by the diet, which showed the concentration level of antibiotics decreased in the order of carnivorous > omnivorous > phytophagous species. Human health risk assessment based on potential fish consumption indicates that main antibiotic risk factors were enrofloxacin and sarafloxacin, and main risk species were Silurus asotus and Palinuridae. The daily risk quotient of these antibiotics to rural residents was lower than townsmen. This study is the first report of antibiotic content in fish and shrimp from the Dongting Lake, which could enrich the research of emerging pollutants in aquatic products.

Occurrence, source, and ecological risk of antibiotics in Dongting Lake, China

AbstractThe pollution characteristics and ecological risk of 12 classified as sulfonamide, trimethoprim, quinolone, and tetracycline antibiotics in Dongting Lake, China, were studied. The total concentrations of the antibiotics ranged from 1.06 to 135.40xa0ngxa0L−1 for all sampling sites. The highest average concentration was observed for sulfadiazine, followed by sulfamethoxazole. The detection frequencies (over 60%) of sulfonamides were higher than those of other antibiotics. The direct discharge of the aquaculture, livestock, and poultry wastewater might be the main pollution sources of antibiotics in the Dongting Lake. The pollution levels of antibiotics decreased in the order of East Dongting Lake > South Dongting Lake > West Dongting Lake, which may be related to the distribution and the scale of the aquaculture, livestock, and poultry sources. The seasonal changes of antibiotic concentration were relatively diversified, with the dry season generally having higher concentrations than the wet season. The results of the ecological risk assessment indicated that sulfamethoxazole, ciprofloxacin, and sarafloxacin might pose a significant risk to the aquatic organisms in Dongting Lake, especially in Potou and Nandu. This study enriches the research of emerging pollutants in freshwater lake.n Graphical abstract

Adsorption of sulfamethoxazole (SMZ) and ciprofloxacin (CIP) by humic acid (HA): characteristics and mechanism

The adsorption behaviours and mechanisms of ciprofloxacin (CIP) and sulfamethoxazole (SMZ) as adsorptives on humic acid (HA) as adsorbents were studied. The adsorption isotherms of CIP and SMZ on HA fit the Freundlich equation better, and sorption equilibrium could be attained within 12 h. The maximum adsorption capacities of CIP and SMZ on HA were 13.64 mg g−1 and 7.54 mg g−1, both of which exhibited favourable adsorption. The kinetics results indicated that the adsorption of each antibiotic by HA followed pseudo-second-order kinetic models and that the adsorption process included the fast-adsorption stage first and the slow-adsorption stage thereafter. The adsorption efficiencies of HA to CIP were higher than those of SMZ. Compared to ionic strength, the effects of temperature and pH on adsorption were significant. The main adsorption mechanism of CIP and SMZ on HA could occur via hydrogen bonding. Competitive adsorption in coexistence systems of CIP and SMZ was observed on HA, and CIP was a stronger competitor to SMZ than SMZ was to CIP.

A review on removal of organophosphorus pesticides in constructed wetland: Performance, mechanism and influencing factors

The residues of organophosphorus pesticides (OPPs) have been widely detected in rivers, the gulf, and even groundwater and drinking water, which may pose a serious threat to aquatic ecosystems and human health. Compared to other treatments, constructed wetlands (CWs) have been demonstrated to be a cost-effective alternative risk mitigation strategy for non-point-source pesticide pollution. This review summarizes 32 studies related to the remediation of OPPs in 117 CWs during 2001-2017 worldwide. The performances, mechanisms and influencing factors in the studies are comprehensively and critically reviewed in this paper. Overall, the OPPs were efficiently removed with an efficiency up to 87.22u202f±u202f16.61%. The removal efficiency, differences and related reasons among different types of CWs in developed and developing countries and the different types of OPPs in CWs are well-evaluated in detail. In addition, the main processes for OPPs removal in CWs involve phytoremediation (plant uptake, phytoaccumulation, phytovolatilization and phytodegradation), substrate adsorption or sedimentation, and biodegradation. Based on the quantitative analysis by mass balance, for water-soluble pesticides, the dominant removal process was via microbiological degradation. This result was in contrast to findings obtained with hydrophobic OPPs, for which the dominant processes were biodegradation and sorption by substrate. Therefore, the behavior of microbial transformation prevails. Additionally, the presence of plants can facilitate the elimination of OPPs in CWs, promoting the process by an average percentage of approximately 6.19u202f±u202f9.46%. Statistical analysis shows that loading of inlet OPPs is the largest limiting factor and that the HRT and T are the most significant parameters that influence the efficiency of trapping OPPs in CWs. Simultaneously, we can also obtain suitable parameters for the design and operation of CWs. This review promotes further research on plant-microbe joint combined remediation and examines the different behaviors of water-soluble and hydrophobic OPPs in CWs.

Removal of nitrogen from low pollution water by long-term operation of an integrated vertical-flow constructed wetland: Performance and mechanism

The efficiency of nitrogen removal and its mechanism, aquatic organism distribution characteristics and regeneration capability of zeolite from an integrated vertical-flow constructed wetland (IVFCW) for low pollution water treatment were evaluated after steady and continuous operation for eight years. After running for eight years, better than average COD and NH4+-N removal were observed in the IVFCW. The NH4+-N removal rate in this system was controlled by ammoxidation and adsorption and ion exchange of zeolite. The low total nitrogen (TN) removal efficiency was due to NO3--N accumulation and zeolite desorption. In addition, this phenomenon indicated that because of poor organic carbon sources, nitrification was stronger than denitrification, consistent with the distribution of the functional genes for nitrification and denitrification. The biological activity in this system was abundant, especially that of spirogyra and navicula. The saturated adsorption capacity of zeolite was as high as 1.35u202fmgu202fg-1 with a desorption rate of <20%. There were no obvious differences among the effects of aeration, water cleaning, drained reoxygenation and steam stripping for zeolite regeneration (adsorption capacity of >50%). However, the drained reoxygenation performance of was better due to zero energy consumption and regeneration in situ.

A review on occurrence and risk of polycyclic aromatic hydrocarbons (PAHs) in lakes of China

Polycyclic aromatic hydrocarbons (PAHs) residues have attracted attention worldwide. This study summarizes the current levels of PAH exposure in the water environments of lakes. In addition, the risk levels from individual PAHs and ΣPAHs in the water environments of lakes in China were evaluated by incremental lifetime cancer risk (ILCR) assessment, the toxic equivalent concentration (TEQBaP), the risk quotient (RQ), the effects range-low (ERL) and the effects range-median (ERM). The results showed that the concentrations of ∑PAHs in water and sediment ranged from 4.0 to 12,970.8u202fngu202fL-1 and 6.52 to 7935.21u202fngu202fg-1, respectively, and the highest concentrations of individual PAHs were of naphthalene (Nap) (6525u202fngu202fL-1), followed by indeno(1,2,3‑cd)pyrene (IcdP) (3452.6u202fngu202fg-1). Concentrations in the Great Lakes region in China showed spatial difference, with the Qinghai-Tibet Plateau Lakes District and Mongolia-Xinjiang Lakes District being less polluted. However, the pollution level of PAHs in lakes is relatively high at the global scale. The ecological risk assessment found a moderate level of ∑PAHs in water, but benz(a)anthracene (BaA) and phenanthrene (Phe) had high RQ values, which might pose a significant risk to aquatic organisms in lakes. Although the contents of ∑PAHs in sediments are low, most individual PAHs pose potential risks, especially acenaphthene (Ace), fluorene (Flu) and dibenz(a,h)anthracene (DahA). This study revealed the pollution levels of PAHs across China and provided a scientific basis for PAH pollution control and environmental protection.

Equilibrium adsorption study of the adsorptive removal of Cd2+ and Cr6+ using activated carbon

The performance of activated carbon (AC) with respect to characterization, adsorption kinetics, thermodynamics, and isotherms was addressed in this study. The effects of initial concentration, pH, contact time, ion strength, and temperature on removal efficiency were also studied. The adsorption isotherms of Cd2+ and Cr6+ on activated carbon can fit the Langmuir model well, and correlation coefficients were above 0.99, all higher than the Freundlich and Temkin models. The maximum adsorption quantities of Cd2+ and Cr6+ were 19.380 and 19.305xa0mgxa0g−1 at 25xa0°C, respectively. The adsorption capacities of Cd2+ and Cr6+ are clearly pH dependent. The kinetics of the removal of Cd2+ and Cr6+ was in agreement with a pseudo-second-order model, and the adsorption efficiency of Cd2+ is higher than that of Cr6+. The thermodynamic results showed that increased temperature is favorable to adsorption. The speciation on activated carbon was mainly residual Cd2+ and Cr6+, and the potential ecological risk of Cd2+ is higher than that of Cr6+. The adsorptions of Cd2+ and Cr6+ on activated carbon were dominated by chelation and ion exchange, respectively.

Occurrence of typical antibiotics and source analysis based on PCA-MLR model in the East Dongting Lake, China

The antibiotics residues in freshwater lakes are being highlighted around the world because of high potential threat to environment and human health. Understanding the current state of antibiotics and potential sources in lakes are important. The potential sources of antibiotics (Sewage treatment plants (STPs)), livestock and poultry farms and fishponds in the East Dongting was studied. Compared with other surface water bodies, the concentration of antibiotic in the East Dongting Lake was at a moderate or low level. Ten of 12 antibiotics likely originated from veterinary applications in livestock and poultry farms, especially in swine farms, and concentrations at these sources (ND-1240.41u202fngu202fL-1) were 1-3 orders of magnitude higher than in the effluent of local sewage treatment plants and fishponds. Based on a principal component analysis with multiple linear regression (PCA-MLR) model, we estimated source contributions of 79.95% for livestock and poultry farms, 0.27% for STPs, and 19.79% for aquaculture source and livestock and poultry farms. Overall, the predominance of sulfonamides and livestock and poultry farms in the East Dongting Lake has been identified, which can provide important information for regulating their veterinary use and environmental management.

Response of ginger growth to a tetracycline-contaminated environment and residues of antibiotic and antibiotic resistance genes

The presence of antibiotic residues in vegetables has been highlighted as a risk to human health; antibiotics not only cause toxic effects to plants but can also induce antibiotic resistance gene (ARG) expression. Using a soil-free approach, this study aimed to explore the response of ginger growth to tetracycline (TC) pollution and to assess the levels of antibiotic residues in different plant organs and the presence of ARGs in the rhizome. Ginger growth in a highly TC-contaminated environment was remarkably inhibited. Photosynthetic parameters, fluorescence parameters, and some physiological indicators (oxidative substances, photosynthetic pigments, enzyme activity, etc.) were negatively influenced by TC contamination. Although the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity levels significantly increased, their effects appear to be limited. The accumulation of TC in the rhizome (28.1u202fmgu202fkg-1) was greater than that in the roots, stem, or leaves. All tested antibiotic resistance genes except for tetL were detectable in the rhizome, and their relative abundance was in the order integron1>tetGu202f>u202ftetAu202f>u202ftetCu202f>u202ftetBu202f>u202ftetM. The level of TC in ginger rhizomes was much higher than the maximum residue limits. The potential dose of TC acquired from the consumption of ginger grown in a highly TC-contaminated environment poses no obvious risk to adults but may be a threat to children.