[Pollution Status and Pollution Behavior of Microplastic in Surface Water and Sediment of Urban Rivers].

Rivers have been a subject of great concern in recent years as they have been found to be the critical path for the transmission of microplastics from terrestrial land to the ocean. However, the pollution status of microplastics and their behavior in the surface waters and sediments of urban rivers located in different urban areas remain unclear. In this study, 16 samples of surface water and sediment from eight rivers in the central and suburban areas of Shanghai Megacity were obtained and analyzed. High-speed cameras and Fourier transform infrared spectrometers were used to identify the abundance, size, color, shape, type, and other characteristics of microplastics in these samples. The results showed that the average abundance of microplastics in the surface waters of urban rivers in Shanghai Megacity was (7.5±2.8) pieces·L-1, while the corresponding average abundance in the sediment reached (1575.5±758.4)pieces·kg-1 (wet weight). The abundance of microplastics was found to increase with the decreasing particle diameter. Among which, microplastics with a size of less than 500 µm, as well as the fibrous shape, transparent color, and Polyester composition, have always dominated in the urban rivers in Shanghai megacity. Comparably, microplastics in the sediments were more diverse in their morphology features and polymer compositions. Microplastic pollution in the urban rivers in Shanghai megacity was severe in comparison to that in other urban rivers worldwide. Among various urban rivers, the distribution of microplastics with different morphology features and polymer compositions is greatly influenced by a number of factors including the source (e.g., mainly laundry wastewater, personal care products, and refuse plastic waste), hydrodynamic conditions, and the physical and chemical properties of plastics. Furthermore, the pollution behavior (i.e., source, transmission, and fate) of microplastics occurring in urban rivers is discussed, and the potential impacts of various environmental factors are explained.

Spectroscopic investigations of the chiral interactions between lipase and the herbicide dichlorprop.

The enantioselective interaction between penicillium expansum alkaline lipase and chiral phenoxypropionic acid herbicide dichlorprop was studied by using UV differential spectrophotometry and fluorescence spectrophotometry in the presence of a pH 8, phosphate buffer solution. Chiral differences in the UV absorption and fluorescence spectra of lipase with dichlorprop were detected. (R)-Dichlorprop interacted the strongest with lipase as measured by both UV absorption and fluorescence spectrophotometry, followed by (Rac)-dichlorprop, while (S)-dichlorprop had the weakest interaction. The hydrophobic interaction seem to play the dominant role in the interactions and the (R)-enantiomer needed the minimum put of energy to drive the endothermic reaction, while the Rac-type and S-type compounds needed more for the reaction to take place. In the meantime, the catalytic hydrolysis of FDA with lipase show that (R)-DCPP could inhibit lipase the most strongly relatively at the same condition, perhaps because (R)-DCPP had a stronger combining effect and high enantiomeric selectivity on lipase than (Rac)-DCPP and (S)-DCPP.