Influence of biofilms on the adsorption behavior of nine organic emerging contaminants on microplastics in field-laboratory exposure experiments.

Microplastics (MPs) are ubiquitous in aquatic environments, which are important carriers of emerging contaminants (ECs). Biofilms can be attached to the surface of MPs in a natural aquatic environment, which may influence chemical adsorption; however, knowledge of its impact is still limited. This study investigated the effect of biofilms on MPs on the adsorption of ECs through field-laboratory exposure experiments. Three types of MPs were naturally colonized with biofilms in lake. Then, biofilm-absent/biofilm-attached MPs were exposed to nine EC solutions at a concentration of 8 µg/L of each compound in laboratory. Most compounds exhibited 3.8 times lower concentrations on biofilm-attached MPs than on biofilm-absent MPs; only a few compounds showed enhanced adsorption. Pseudo-equilibrium was achieved within 72 h based on adsorption kinetics, implying fast adsorption of ECs on biofilm-attached MPs. The partition coefficients (Kd) for biofilm-attached MPs were 0.14 (diclofenac) to 535 (miconazole) L/kg and were positively correlated with octanol/water partition coefficients (Kow). This indicated that chemical properties (such as Kow) of the compounds determined their final adsorption amounts on MPs, although these were influenced by the presence of the biofilm. Hence, multiple influencing factors should be considered when evaluating the carrier potential of MPs for ECs in aquatic environments.

Profile and removal of bisphenol analogues in hospital wastewater, landfill leachate, and municipal wastewater in South China.

The presence of bisphenol analogues (BPs) in wastewater can have adverse effects to organisms in the environment. However, knowledge of the wastewater sources, such as hospitals and landfills, as well as the removal of BPs are still limited. Fifteen BPs were investigated in hospital, landfills, and municipal wastewater treatment plants (WWTPs) in South China. Eleven BPs were detected in various source wastewaters, and bisphenol A (BPA) is generally the dominant pollutant. In 4 hospitals, the total concentrations of BPs (∑BPs) in hospital wastewater and treated wastewater ranged from 122 to 1040 ng/L. In the landfill, ∑BPs in leachate and treated leachates were 32,130 and 145 ng/L, respectively. In 5 municipal WWTPs, ∑BPs was up to 17,200 ng/L in influents, 502 ng/L in effluents, and 291 ng/g in sludges. The modified A2/O process exhibited best removal profile for BPs, while the UNITANK process had no advantages. The annual mass load estimates of hospital treated wastewater, landfill treated leachate, and WWTP effluents in Guangdong Province, South China, were 630, 9.46, and 4697 kg/y, respectively. The risk quotient values in source effluents revealed low to medium estrogenic risks to receiving rivers. Control measures should be applied to further remove BPs not only from WWTP effluents but also from other sources.

One-step synthesis of water-dispersible silicon nanoparticles and their use in fluorescence lifetime imaging of living cells.

We report a novel method for synthesizing water-dispersible silicon nanoparticles (Si NPs) with a simple one-step procedure using mild reagents (3-aminopropyl) trimethoxysilane (APTES) and ascorbate sodium (AS). This is the first report of "green" synthesis of Si NPs on a large scale and at low cost. The method involves a quick reaction in a commonly used round bottom flask at room temperature and pressure without additional treatment and any special equipment. The as-prepared Si NPs have an average diameter of 2 nm and an emission band at 530 nm with a full width at half maximum height (FWHM) of 70 nm and a quantum yield (QY) of 0.21. Moreover, the fluorescence lifetime of these Si NPs is much longer than that of native fluorophores in living cells. Therefore, these Si NPs allow effective imaging of living cells with a fluorescence lifetime imaging microscope (FLIM). Using the time gating model in FLIM, an excellent image was obtained in which the auto-fluorescence interference of cellular fluorophores was suppressed demonstrating that the Si NPs are promising probes for cell imaging particularly using the FLIM technique.