Simultaneous Dissemination of Nanoplastics and Antibiotic Resistance by Nematode Couriers.

Nanoplastics (NPs) are increasingly recognized as a newly emerging pollutant in the environment. NPs can enable the colonization of microbial pathogens on their surfaces and adsorb toxic pollutants, such as heavy metals and residual antibiotics. Although the dissemination of plastic particles in water bodies and the atmosphere is widely studied, the dissemination of NPs and adsorbed pollutants on land, via biological means, is poorly understood. Since soil animals, such as the bacterivorous nematode Caenorhabditis elegans (C. elegans), are highly mobile, this raises the possibility that they play an active role in disseminating NPs and adsorbed pollutants. Here, we established that antibiotic-resistant bacteria could aggregate with antibiotic-adsorbed NPs to form antibiotic-adsorbed NP-antibiotic resistant bacteria (ANP-ARB) aggregates, using polymyxins (colistin) as a proof-of-concept. Colistin-resistant mcr-1 bearing Escherichia coli from a mixed population of resistant and sensitive bacteria selectively aggregate with colistin-ANPs. In the soil microcosm, C. elegans fed on ANP-ARB clusters, resulting in the rapid spread of ANP-ARB by the nematodes across the soil at a rate of 40-60 cm per day. Our work revealed insights into how NPs could still disseminate across the soil faster than previously thought by "hitching a ride" in soil animals and acting as agents of antibiotic-resistant pathogens and antibiotic contaminants. This poses direct risks to ecology, agricultural sustainability, and human health.

Source Apportionment, Hydrodynamic Influence, and Environmental Stress of Pharmaceuticals in a Microtidal Estuary with Multiple Outlets in South China.

Pharmaceutical residues in the environment are of great concern as ubiquitous emerging contaminants. This study investigated the presence of 40 pharmaceuticals in water and sediment of the Pearl River Estuary (PRE) in the wet season of 2020. Among psychiatric drugs, only diazepam was found in water samples while six of them were detected in the sediment. The Σantibiotics levels ranged from 6.18 to 35.9 ng/L and 2.63 to 140 ng/g dry weight in water and sediment samples, respectively. Fluoroquinolones and tetracyclines were found well settling in the outlet sediment, while sulfonamides could be released from disturbed sediment under stronger tidal wash-out conditions. After entering the marine waters, pharmaceuticals tended to deposit at the PRE mouth by the influence of the plume bulge and onshore invasion of deep shelf waters. Low ecological risks to the aquatic organisms and of causing antimicrobial resistance were identified. Likewise, hydrological modeling results revealed insignificant risks: erythromycin-H2O and sulfamethoxazole discharged through the outlets constituted 30.8% and 6.74% of their environmental capacity, respectively. Source apportionment revealed that pharmaceutical discharges through the Humen and Yamen outlets were predominantly of animal origin. Overall, our findings provide strategic insights on environmental regulations to further minimize the environmental stress of pharmaceuticals in the PRE.

Polyelectrolyte Microcapsules Dispersed in Silicone Rubber for in Vivo Sampling in Fish Brains.

Direct detection of fluoxetine and its metabolite norfluoxetine in living fish brains was realized for the first time by using a novel solid-phase microextraction fiber, which was prepared by mixing the polyelectrolyte in the oligomer of silicone rubber and followed by in-mold heat-curing. The polyelectrolyte was finally encased in microcapsules dispersed in the cured silicone rubber. The fiber exhibited excellent interfiber reproducibility (5.4-7.1%, n = 6), intrafiber reproducibility (3.7-4.6%, n = 6), and matrix effect-resistant capacity. Due to the capacity of simultaneously extracting the neutral and the protonated species of the analytes at physiological pH, the fiber exhibited high extraction efficiencies to fluoxetine and norfluoxetine. Besides, the effect of the salinity on the extraction performance and the competitive sorption between the analytes were also evaluated. Based on the small-sized custom-made fiber, the concentrations of fluoxetine and norfluoxetine in the brains of living fish, which were exposed to waterborne fluoxetine at an environmentally relevant concentration, were determined and found 4.4 to 9.2 and 5.0 to 9.2 times those in the dorsal-epaxial muscle. The fiber can be used to detect various protonated bioactive compounds in living animal tissues.

Bioinspired polydopamine sheathed nanofibers for high-efficient in vivo solid-phase microextraction of pharmaceuticals in fish muscle.

In this study, electrospun nanofibers were used as solid-phase microextraction (SPME) fiber coatings after substituting the water-soluble sheath of the emulsion electrospun polystyrene (PS)@Plurinic F-127 core-sheath nanofibers with biocompatible and water-stable polydopamine (PDA) and subsequently being appropriately cross-linked with glutaraldehyde (GA) to enhance the strength of the electrospun architecture. The novel custom-made PS@PDA-GA coating was wettable in aqueous solutions and thus exhibited much higher extraction efficiency than the nonsheathed PS nanofiber coating and the thicker polydimethylsiloxane (PDMS) coating. The novel coating also possessed excellent stability (relative standard deviations (RSDs) less than 7.3% for six sampling-desorption cycles), interfiber reproducibility (RSDs less than 14.3%), and antibiofouling ability, which were beneficial for in vivo sampling. The PS@PDA-GA fiber was used to monitor pharmaceuticals in dorsal-epaxial muscle of living fish, and satisfactory sensitivities with the limits of detection in the range of 1.1 (mefenamic acid) to 8.9 (fluoxetine) ng·g(-1) and comparable accuracies to liquid extraction were achieved. In general, this study explored a convenient and effective method to sheath nanofibers for high-efficient in vivo SPME of analytes of interest in semisolid tissues.

Occurrence, spatial distribution, and partitioning behavior of marine lipophilic phycotoxins in the Pearl River Estuary, South China.

The occurrence, spatial distribution, and partitioning behavior of 17 marine lipophilic phycotoxins (MLPs) in surface and bottom seawater, particulate organic matter (POM), and surface sediment from the Pearl River Estuary (PRE) were investigated to understand current contamination and the potential risks to marine ecosystems in this region. Nine MLPs were detected, including azaspiracid1-3, gymnodimine, okadaic acid, dinophysistoxin 1-2, pectenotoxin2 (PTX2), and homoyessotoxin, with Σ17MLP concentrations ranging 545-12,600 pg L-1 and 619-8,800 pg L-1 in surface and bottom seawater, respectively; 0-294 ng g-1 and 0.307-300 ng g-1 dry weight (dw) in surface and bottom POM, respectively; and 3.90-982 pg g-1 dw in surface sediment. Lower Σ17MLP levels in the seawater were found at the mouth of the PRE, and gradually increased with increasing distance offshore. According to the calculated partition coefficient, the affinity of MLPs for the aquatic environment components was as follows (from highest to lowest): POM > seawater > sediment. Overall, the distribution and migration of MLPs in the PRE may depend on partition coefficients, the organic carbon fraction, and environmental factors.

A systematic study of microplastic occurrence in urban water networks of a metropolis.

The release of microplastics from sewage treatment works (STWs) into the oceans around coastal cities is well documented. However, there are fewer studies on the microplastic abundance in stormwater drains and their emissions into the coastal marine environment via sewage and stormwater drainage networks. Here, we comprehensively investigated microplastic abundance in 66 sewage and 18 sludge samples collected from different process stages at three typical STWs and 36 water samples taken from six major stormwater drains during the dry and wet seasons in Hong Kong, which is a metropolitan city in south China. The results showed that microplastics were detected in all the sewage and stormwater samples, with the abundance ranging from 0.07 to 91.9 and from 0.4 to 36.48 particles/L, respectively, and in all the sludge samples with the abundance ranging from 167 to 936 particles/g (d. w.). There were no significant seasonal variations in the microplastic abundance across all samples of sewage, sludge, and stormwater. For both waterborne sample types, a smaller size (0.02-0.3 mm) and fiber shape were the dominant characteristics of the microplastics. Polyethylene terephthalate (PET) and polypropylene (PP) were the most abundant polymer types in the sewage samples, while polyethylene (PE), PET, PP, and PE-PP copolymer were the most abundant polymer types in the stormwater samples. The estimated range of total daily microplastic loads in the effluent from STWs in Hong Kong is estimated to be 4.48 × 109 - 2.68 × 1010 particles/day, demonstrating that STWs are major pathways of microplastics in coastal environments despite the high removal percentage of microplastics in sewage treatment processes examined. This is the first comprehensive study on microplastics in the urban waters of a coastal metropolis. However, further studies on other coastal cities will enable an accurate estimation of the microplastic contribution of stormwater drains to the world's oceans.

Intra-day microplastic variations in wastewater: A case study of a sewage treatment plant in Hong Kong.

Wastewater treatment plants (WWTPs) in coastal region play a primary role in transferring microplastics into the marine environment. Wastewater is closely related to anthropogenic activities, thus the intra-day variation of abundance of microplastics in the influent should be large and could have significant impact on their estimation of the daily mass load. In this study, a 2-hour interval sampling campaign was conducted at a secondary WWTP in Hong Kong to investigate the intra-day variations and daily loads of microplastics in influent. Results show that the average microplastic abundances increased from 7.1 ± 6.0 to 12.8 ± 5.8 particles/L over time, with predominant particle sizes ranging 1-5 mm. Approximately 80% of the microplastics in samples collected from 9:30-15:00 were polyethylene and polyester, while most samples collected at 17:00 were polypropylene and polyurethane. Microplastic loads exhibited large intra-day variations ranging 6.60 × 108-1.16 × 109 particles/day, indicating that calculated daily microplastic loads based on a specific sampling period may inaccurately estimate the actual daily load.