Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures.

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

Multienzyme Biocatalytic Cascade Systems in Porous Organic Frameworks for Biosensing.

Multienzyme biocatalytic cascade systems (MBCS) have attracted widespread research in the field of biosensing due to selective substrate transformations and signal amplification function. However, the poor stability of enzymes significantly restricts their effectiveness in practical applications. The spatial organization of MBCS within porous organic frameworks (POFs), such as metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks, is regarded as a promising strategy to overcome these challenges. This advanced biotechnology sets up a POFs microenvironment for enzymes immobilization, and thus make it possible to shield the enzyme from the external stimulus by POFs-guided structural confinement. Simultaneously, the tailorable porous structure of POFs shell allows for the selective transport of substrates into interior enzymes, thereby accelerating the sensing process. Herein, we present the concept of this POFs-confined MBCS, wherein enzymes were completely encapsulated into, rather than adsorption onto, the POFs. We highlight the new strategies for MBCS spatial organization through rational POFs support, and describe how this new bio-nanosystem that integrates framework and enzymes functions can be designed as a versatile biosensing platform. In addition, the challenges and outlooks are also discussed.

Geographical origin traceability and identification of refined sugar using UPLC-QTof-MS analysis.

Authentication of geographical origin is essential to the food safety of refined sugar. This study aimed to determine the geographical origin traceability and authenticity of refined sugar in China. Ultra performance liquid chromatography-quadrupole time-of-flight Mass Spectrometry (UPLC-QTof-MS), instead of conventional stable isotope ratio mass spectrometer (IRMS), was used to detect the mass fragment ratios (Rδ-sucrose and Rδ-glucose) of refined sugar. These ratios could reflect the cultivation practice and environmental conditions. A total of 108 batches of samples were collected from six regions in China, and additional 72 samples were verified with support vector machines (SVM) model, in order to evaluate the accuracy of origin identification and composition prediction. Our results showed that 83.3% of the refined sugar was correctly classified based on the geographical region of origin under different environmental conditions. These findings indicate that the specified mass fragment ratio may be a promising approach for assessing the traceability and authenticity of refined sugar.

Adsorption of dissolved organic matter (DOM) on polystyrene microplastics in aquatic environments: Kinetic, isotherm and site energy distribution analysis.

Microplastics and dissolved organic matter (DOM) are ubiquitous in aquatic environments. The adsorption behavior of DOM on microplastics in aquatic environments is a prominent concern. In this study, the adsorption of two types of DOM, Suwannee River Humic Acid (HA) and Suwannee River Fulvic Acid (FA), on polystyrene microplastics (PSMPs, 10 µm) in aquatic environments was investigated. The adsorption of both HA and FA on PSMPs could be well described by using pseudo second-order and Freundlich models. The adsorption of HA and FA on PSMPs was low pH-dependent, particularly for FA adsorption. However, the elevated ionic strength slightly increased the adsorption of HA and FA on PSMPs. Based on Freundlich model, the site energy distribution of HA and FA adsorption on PSMPs under the experimental conditions were estimated. HA and FA first occupied the high-energy adsorption sites and then diffused to the low-energy adsorption sites on PSMPs. With higher site energies, HA demonstrated a much stronger adsorption affinity to PSMPs than FA. The adsorption site heterogeneity (σe*) on PSMPs under the experimental conditions were close. Hydrophobic interaction and π-π electron donor acceptor interaction acted simultaneously in the HA and FA adsorption on PSMPs. The results of this study suggested that the environmental behaviors of microplastics would be influenced by the amount and the type of DOM as well as solution chemistry.

Aggregation kinetics of microplastics in aquatic environment: Complex roles of electrolytes, pH, and natural organic matter.

Microplastics are an emerging contaminants of concern in aquatic environments. The aggregation behaviors of microplastics governing their fate and ecological risks in aquatic environments is in need of evaluation. In this study, the aggregation behavior of polystyrene microspheres (micro-PS) in aquatic environments was systematically investigated over a range of monovalent and divalent electrolytes with and without natural organic matter (i.e., Suwannee River humic acid (HA)), at pH 6.0, respectively. The zeta potentials and hydrodynamic diameters of micro-PS were measured and the subsequent aggregation kinetics and attachment efficiencies (α) were calculated. The aggregation kinetics of micro-PS exhibited reaction- and diffusion-limited regimes in the presence of monovalent or divalent electrolytes with distinct critical coagulation concentration (CCC) values, followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The CCC values of micro-PS were14.9, 13.7, 14.8, 2.95 and 3.20 mM for NaCl, NaNO3, KNO3, CaCl2 and BaCl2, respectively. As expected, divalent electrolytes (i.e., CaCl2 and BaCl2) had stronger influence on the aggregation behaviors of micro-PS as compared to monovalent electrolytes (i.e., NaCl, NaNO3 and KNO3). HA enhanced micro-PS stability and shifted the CCC values to higher electrolyte concentrations for all types of electrolytes. The CCC values of micro-PS were lower than reported carbonaceous nanoparticles CCC values. The CCC[Ca2+]/CCC [Na+] ratios in the absence and presence of HA at pH 6.0 were proportional to Z-2.34 and Z-2.30, respectively. These ratios were in accordance with the theoretical Schulze-Hardy rule, which considers that the CCC is proportional to z-6-z-2. These results indicate that the stability of micro-PS in the natural aquatic environment and the possibility of significant aqueous transport of micro-PS.

Occurrence and distribution of organophosphate esters in urban soils of the subtropical city, Guangzhou, China.

67 soil samples from the road greenbelts, the paddy/vegetable fields, the parks, the commercial and residential areas in the subtropical city, Guangzhou, China, were collected and analyzed for 11 organophosphate esters (OPEs) and triphenylphosphine oxide (TPPO). OPEs were detected in all soil samples analyzed, which indicate that OPEs are ubiquitous environmental contaminants. The ∑11OPEs concentrations ranged from 0.041 mg kg-1-dry weight (dw) to 1.37 mg kg-1-dw, with the mean and median concentrations of 0.25 mg kg-1-dw and 0.24 mg kg-1-dw, respectively. High concentrations of OPEs were observed in the roadside soils collected from the commercial areas with heavy traffic and extensive anthropogenic activities. Of 11 OPEs, tris(2-butoxyethyl) phosphate (TBOEP), tri-cresyl-phosphate (TMPP), tributyl phosphate (TNBP) and tris(2-chloroethyl) phosphate (TCEP) were the most abundant OPEs, contributing 42.8 ± 15.4%, 17.2 ± 11.9%, 10.9 ± 6.85% and 9.70 ± 9.56% of ∑11OPEs, respectively. Principal component analysis (PCA) suggested that OPEs accumulation in the urban soils derived from different sources. As compared to the results for other studies, the urban soils of Guangzhou were moderately polluted by OPEs.

Occurrence and distribution of phthalate esters in riverine sediments from the Pearl River Delta region, South China.

Sixty-eight sediment samples collected from Dongjiang River, Xijiang River, Beijiang River and Zhujiang River in the Pearl River Delta (PRD) region, Southern China, were analyzed for 16 phthalate esters (PAEs). PAEs were detected in all riverine sediments analyzed, which indicate that PAEs are ubiquitous environmental contaminants. The Σ16PAEs concentrations in riverine sediments in the PRD region ranged from 0.567 to 47.3 µg g(-1) dry weight (dw), with the mean and median concentrations of 5.34 µg g(-1) dw and 2.15 µg g(-1) dw, respectively. Elevated PAEs concentrations in riverine sediments in the PRD region were found in the highly urbanized and industrialized areas. Of the 16 PAEs, diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs, with the mean and median concentrations of 1.12 µg g(-1)dw, 0.420 µg g(-1) dw and 3.72 µg g(-1) dw, and 0.429 µg g(-1) dw, 0.152 µg g(-1) dw and 1.55 µg g(-1) dw, respectively, and accounted for 94.2-99.7% of the Σ16PAEs concentrations. Influenced by local sources and the properties of PAEs, a gradient trend of concentrations and a fractionation of composition from more to less industrialized and urbanized areas were discovered. As compared to the results from other studies, the riverine sediments in the PRD region were severely contaminated with PAEs. Information about PAEs contamination status and its effect on the aquatic organisms in the PRD region may deserve further attention.