For many years, the dispersal of modified clay (MC) has been used to control harmful algal blooms (HABs) in coastal waters of China. MC flocculation efficiency can be influenced by many factors in variable and complex natural environments, including high concentrations of dissolved organic matter (DOM) in the water to be treated. Since many HABs occur in nearshore waters where DOM concentrations are high, this is a significant problem that requires urgent attention. This study involved the use of humic acid as a representative form of DOM to study the influence of organic matter on the MC flocculation process. At high concentrations, humic acid was adsorbed onto MC particles, resulting in a decrease in surface potential and an increase in electrostatic repulsion between the clay particles; this decreased the MC settling rate and increased the water clarification time. Flocs were characterized by their relatively small particle size, high particle concentration, and low collision efficiency, which together resulted in slow clarification of the water after MC spraying. Based on the mechanism of the DOM-MC interaction and combined with the Derjaguin-Landau-Verwey-Overbeek theory and theoretical considerations of clay surface modification, the “ionic atmosphere compression” method was used to improve MC flocculation efficiency in high-organic water. This method increased the ionic strength of the clay stock solution by adding salt, thereby compressing the ionic atmosphere of MC particles and lowering the potential barrier, allowing the MC particles in the treated water to flocculate rapidly and form large flocs, followed by further floc growth and rapid settling via differential sedimentation. The settling rate of MCs improved by a factor of two and the removal efficiency of the HAB cells increased by 7–28%. This study provides important baseline information that will extend the application of MC to HAB control in water bodies with high organic loadings.

Microplastics are widespread in the aquatic environment and thus available for many organisms at different trophic levels. Many scientific papers focus their attention on the study of the effects of microplastics on different species at individual level. Here we performed a global scale meta-analysis focusing our work on the study of the effect of microplastics on the functional traits of aquatic benthic organisms. Overall, microplastics showed a moderate negative effect on the examined functional traits of benthic organisms. Our results show that some crucial functional traits, such as those linked to behaviour and feeding, appear to be unaffected by microplastics. In contrast, traits related to the capacity of organisms to assimilate energy are affected. Moreover, traits with possible effects at population level appear to be negatively affected by microplastics. We discuss how the direct impact of organismal performance may have indirect repercussions at higher levels in the ecological hierarchy and represent a risk for the stability and functioning of the ecosystem.

The presence of microplastics in the various food web raised concerns on human health, but little is known about the target cells and mechanism of toxicity of microplastics. In this study, we evaluated the toxicity of microplastics using relevant cell lines to the oral route of exposure. Approximately 100 μm-sized fragment-type polypropylene (PP) and polystyrene (PS) particles were prepared by sieving after pulverization and further applied the accelerated weathering using ultraviolet and heat. Thus, the panel of microplastics includes fresh PP (f-PP), fresh PS (f-PS), weathered PP (w-PP), and weathered PS (w-PS). The spherical PS with a similar size was used as a reference particle. Treatment of all types of PP and PS did not show any toxic effects to the Caco-2 cells and HepG2 cells. However, the treatment of microplastics to THP-1 macrophages showed significant toxicity in the order of f-PS > f-PP > w-PS > w-PP. The weathering process significantly reduced the reactive oxygen species (ROS) generation potential of both microplastics because the weathered microplastics have an increased affinity to bind serum protein which acts as a ROS scavenger. The intrinsic ROS generation potential of microplastics showed a good correlation with the toxicity endpoints including cytotoxicity and pro-inflammatory cytokines in THP-1 macrophages. In conclusion, the results of this study suggest that the target cell type of microplastics via oral administration can be macrophages and the pathogenic factor to THP-1 macrophages is the intrinsic ROS generation potential of microplastics. Nevertheless, the toxic effect of microplastics tested in this study was much less than that of nano-sized particles.

Anthelmintics, drugs against parasitic worms, are frequently used in livestock and might act as danger environmental microcontaminants. The present study was designed to monitor the possible circulation of common anthelmintic drug albendazole (ABZ) and its metabolites in the real agriculture conditions. The sheep were treated with the recommended dose of ABZ. Collected faeces were used for the fertilization of a field with fodder plants (alfalfa and clover) which served as feed for sheep from a different farm. The selective ultrasensitive mass spectrometry revealed surprisingly high concentrations of active ABZ metabolite (ABZ-sulphoxide) in all samples (dung, plants, ovine plasma, rumen content and faeces). Our results prove for the first time an undesirable permeation of ABZ metabolites from sheep excrement into plants (used as fodder) and subsequently to other sheep in real agricultural conditions. This circulation causes the permanent exposition of the ecosystems and food-chain to the drug and can promote the development of drug resistance in helminths.

Oral bioaccessibility (BAc) is a surrogate for the bioavailability (BAv) of a broad range of substances, reflecting the value that the approach offers for assessing oral exposure and risk. BAc is generally considered to have been validated as a proxy for oral BAv for the important soil contaminants Pb, Cd, and As. Here, using literature data for Ni BAc and BAv, we confirmed that Ni BAc (gastric only, with HCl mimicking stomach conditions) is a conservative measure of BAv for the oral exposure pathway. Measured oral BAv of Ni in soil was shown to be 50–100 times less than the simplest oral BAc estimates (%BAv = 0.012(%BAc) - 0.023 (r = 0.701, 95%CI [0.456, 0.847], n = 30)) in rats, demonstrating a significant conservatism for exposure assessment. The relationship between the oral BAv and BAc of nickel sulfate hexahydrate (NSHH) was comparable to that of soil, with measured oral BAv of NSHH (1.94%) being a small fraction of NSHH gastric BAc (91.1%). BAc and BAv reflect the underlying Ni speciation of the sample, with the bioaccessible leaching limits being represented by the highly soluble Ni salts and the poorly soluble Ni monoxide, and the environmental (e.g. soil properties) or gastric (e.g. food present) conditions. BAc has potential utility for chemical classification purposes because pure Ni substances can be grouped by %BAc values(using standardized methodologies for the relevant exposure routes), these groupings reflecting the underlying chemistry and speciation of the samples of substances tested here, with 0.008% %BAc for alloys (SS304, SS316, Inconel, Monel), <1% in green NiO and Ni metal massives, 0.9–23.6% for Ni powders, 9.8–22.7% for Ni sulfides, 26.3–29.6% for black oxidic Ni, and 82–91% for the soluble Ni salts. Oral BAc provides realistic yet conservative estimates of BAv for the hazard classification and risk assessment of Ni substances.

Urban street canyons formed by high-rise buildings restrict the dispersion of vehicle emissions, which pose severe health risks to the public by aggravating roadside air quality. However, this issue is often overlooked in city planning. This paper reviews the mechanisms controlling vehicle emission dispersion in urban street canyons and the strategies for managing roadside air pollution. Studies have shown that air pollution hotspots are not all attributed to heavy traffic and proper urban design can mitigate air pollution. The key factors include traffic conditions, canyon geometry, weather conditions and chemical reactions. Two categories of mitigation strategies are identified, namely traffic interventions and city planning. Popular traffic interventions for street canyons include low emission zones and congestion charges which can moderately improve roadside air quality. In comparison, city planning in terms of building geometry can significantly promote pollutant dispersion in street canyons. General design guidelines, such as lower canyon aspect ratio, alignment between streets and prevailing winds, non-uniform building heights and ground-level building porosity, may be encompassed in new development. Concurrently, in-street barriers are widely applicable to rectify the poor roadside air quality in existing street canyons. They are broadly classified into porous (e.g. trees and hedges) and solid (e.g. kerbside parked cars, noise fences and viaducts) barriers that utilize their aerodynamic advantages to ease roadside air pollution. Post-evaluations are needed to review these strategies by real-world field experiments and more detailed modelling in the practical perspective.

Heavy metal risks to human health in farmland of wastewater-irrigated areas have long been recognized. It remains to be shown whether farmland heavy metals from wastewater irrigation can migrate to deeper soil at a regional scale. In this study, nine soil cores deep to 30 m from three transects (A, B and C) of a linear wastewater reservoir and the adjacent farmland topsoils and wheat grains were sampled. Heavy metals including As, Cd, Cr, Cu, Pb and Zn in the soils and wheat grains were determined, and the grains’ health risks were assessed using the Target Hazard Quotient (THQ). Considerably high contents of heavy metals in both total and soluble forms were detected in deep soils, especially for the transect B where total As of 73.0 mg kg⁻¹ at 29 m, Cd of 3.80 mg kg⁻¹ at 13 m and Pb of 214 mg kg⁻¹ at 30 m were detected. The silty clayey and silty layers of the transect B had higher contents of As, Cr, Cu, Pb and Zn compared with the sandy layers. Across the studied area, 19.5%–34.1% of the topsoil samples were contaminated by As, Cd, Cu, Pb and Zn, and 34.1% and 19.5% of the wheat grains were contaminated by Cd and Pb, respectively. Wheat grains from all the sampling sites had a combined target hazard quotient (TTHQ) value of >1, with As and Cd being the most important contributors. Our study revealed a wider and deeper risk of typical heavy metals originated from long-term wastewater irrigation in the sampling area, which may pose substantial health risks to the local residents via wheat grains and groundwater.

Antibiotic resistance is exacerbated by the exchange of antibiotic resistance genes (ARGs) between microbes from diverse habitats. Plasmids are important ARGs mobile elements and are spread by horizontal gene transfer (HGT). In this study, we demonstrated the presence of multi-resistant plasmids from inhalable particulate matter (PM) and its effect on gene horizontal transfer. Three transferable multi-resistant plasmids were identified from PM in a hospital, using conjugative mating assays and nanopore sequencing. pTAir-3 contained 26 horizontal transfer elements and 10 ARGs. Importantly pTAir-5 harbored carbapenem resistance gene (blaOXA) which shows homology to plasmids from human and pig commensal bacteria, thus indicating that PM is a media for antibiotic resistant plasmid spread. In addition, 125 μg/mL PM₂.₅ and PM₁₀ significantly increased the conjugative transfer rate by 110% and 30%, respectively, and augmented reactive oxygen species (ROS) levels. Underlying mechanisms were revealed by identifying the upregulated expressional levels of genes related to ROS, SOS, cell membranes, pilus generation, and transposition via genome-wide RNA sequencing. The study highlights the airborne spread of multi-resistant plasmids and the impact of inhalable PM on the horizontal transfer of antibiotic resistance.

Perfluorobutanesulfonate (PFBS) is an emerging pollutant in aquatic environments and potently disrupts the early developmental trajectory of teleosts. Considering the persistent and toxic nature of PFBS, it is necessary to develop in situ protective measures to ameliorate the toxic damage of PFBS. Probiotic supplements are able to mitigate the growth retardation defects of PFBS. However, the interactive mechanisms remain elusive. To this end, this study acutely exposed zebrafish larvae to a concentration gradient of PFBS (0, 1, 3.3 and 10 mg/L) for 4 days, during which probiotic bacteria Lactobacillus rhamnosus were added in the rearing water. After exposure, alterations in gene transcriptions and key hormones along the hypothalamus–pituitary–interrenal (HPI), growth hormone/insulin–like growth factor (GH/IGF) and hypothalamus–pituitary–thyroid (HPT) axes were examined. The results showed that PFBS single exposure significantly increased the cortisol concentrations, suggesting the induction of stress response, while probiotic supplementation effectively decreased the cortisol levels in coexposed larvae in an attempt to relieve the stress of PFBS toxicant. It was unexpected that probiotic additive significantly decreased the larval GH concentrations independent of PFBS, thereby eliminating the contribution of GH/IGF axis to the growth improvement of probiotics. In contrast, probiotic bacteria remarkably increased the concentration of thyroid hormones, particularly the thyroxine (T4), in zebrafish larvae. The pronounced down-regulation of uridinediphosphate glucoronosyltransferases (UDPGT) gene pointed to the blocked elimination process of T4 by probiotics. Furthermore, proteomic fingerprinting found that probiotics were potent to shape the protein expression pattern in PFBS-exposed zebrafish larvae and modulated multiple biological processes that are essential for the growth. In summary, the present findings suggest that HPI and HPT axes may cooperate to enhance the growth of fish larvae under PFBS and probiotic coexposures.

The present study aimed to show that nickel and fluoride exhibited synchronized co-inhibited uptake in the aromatic rice cultivar, Gobindobhog, since bioaccumulation of the two elements was lower than that during individual stress, so that overall growth under combined stress was similar to control seedlings. On the contrary, lead and fluoride stimulated their co-uptake which triggered oxidative damages, NADPH oxidase activity, methylglyoxal accumulation, photosynthetic inhibition, membrane-protein damages, necrosis and genomic template degradation. Accumulation of proline, anthocyanins, non-protein thiols and phytochelatins was stimulated for systemic protection against reactive oxygen species (ROS) and xenobiotic-mediated injuries during lead-fluoride toxicity. ROS accumulation during nickel-fluoride stress was insignificant due to which enhanced accumulation of most antioxidants was not required. Glutathione depletion during combined lead-fluoride toxicity was due to its utilization in the glyoxalase cycle and also inhibition of glutathione reductase. However, the nickel-fluoride-treated sets maintained glutathione reserves and glyoxalase activity similar to those in control. Presence of fluoride ‘safeguarded’ the glutathione-utilizing enzymes like glutathione reductase, glutathione peroxidase and glutathione-S-transferase during dual lead-fluoride stress. This was because these enzymes showed higher activity compared to that under lead toxicity alone. Enzymatic antioxidants like superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase were activated during lead-fluoride toxicity due to altered iron and copper homeostasis. Catalase activity was strongly inhibited, resulting in the inability to scavenge H₂O₂ and suppression of the fluoride-adaptable phenotype. However, none of the enzymatic antioxidants were inhibited during nickel-fluoride stress, which cumulatively allowed the seedlings to maintain normal physiology. Overall our findings holistically reveal the physiological plasticity of Gobindobhog in response to two different heavy metals under the influence of fluoride.