● Small molecular chains formed on photo-aged polylactic acid microplastics (MPs).● Oxygen-containing functional groups generated on photo-aged polyamide MPs.● Photo-aging has the opposite influence on the imidacloprid adsorption on two MPs.● Electrostatic interactions and hydrogen bonds were the main mechanisms.● High pH value and low ionic strength increase the adsorption capacity. The photo-aging behavior of microplastics (MPs) in natural environment has become a global concern. The ultraviolet radiation has enough energy to change the polymer structure and physical-chemical properties of MPs. Less attention has focused on the interactions of the photo-aged polar and biodegradable MPs with organic pollutants. This work investigated the structural properties of aged polar polyamide (PA) MPs and biodegradable polylactic acid (PLA) MPs exposed to ultraviolet irradiation and their adsorption behavior and mechanism for neonicotinoid insecticide imidacloprid (IMI). The results showed that the MPs had extensive changes in surface morphology and chemical properties after photo-aging. The C–N bond of PA MPs was disrupted to form more carbonyl groups. The oxygen-containing functional groups on the surface of aged PLA MPs were broken and generated relatively smaller molecules. The adsorption capacity of IMI on PA MPs decreased by 19.2 %, while the adsorption capacity of IMI on PLA MPs increased by 41.2 % after photo-aging. This depended on the natural structure of the MPs and their ability to absorb ultraviolet light. The electrostatic interactions, hydrogen bonds, van der Waals interactions, and polar-polar interactions were the main adsorption mechanisms of IMI on MPs. High initial solution pH and low ionic strength favored the adsorption of IMI by altering charge distribution on the MPs surface. The formation of the humic acid-IMI complexes decreased the concentration of IMI in the water phase and further decreased the adsorption on MPs. These results are enlightening for a scientific comprehension of the environmental behavior of the polar MPs. 相似文献
● EE2 photodegradation behavior in the presence of four WWTPs’ DOM was explored. ● The 3DOM* played a major role in the EE2 photodegradation mediated by WWTPs’ DOM. ● The A2/O process DOM contained more aromatic and oxygen-containing substances. ● Possible photosensitivity sources of DOM in the A2/O process were proposed. Dissolved organic matter (DOM) from each treatment process of wastewater treatment plants (WWTPs) contains abundant photosensitive substances, which could significantly affect the photodegradation of 17α-ethinylestradiol (EE2). Nevertheless, information about EE2 photodegradation behavior mediated by DOM from diverse WWTPs and the photosensitivity sources of such DOM are inadequate. This study explored the photodegradation behavior of EE2 mediated by four typical WWTPs’ DOM solutions and investigated the photosensitivity sources of DOM in the anaerobic-anoxic-oxic (A2/O) process. The parallel factor analysis identified three varying fluorescing components of these DOM, tryptophan-like substances or protein-like substances, microbial humus-like substances, and humic-like components. The photodegradation rate constants of EE2 were positively associated with the humification degree of DOM (P < 0.05). The triplet state substances were responsible for the degradation of EE2. DOM extracted from the A2/O process, especially in the secondary treatment process had the fastest EE2 photodegradation rate compared to that of the other three processes. Four types of components (water-soluble organic matter (WSOM), extracellular polymeric substance, humic acid, and fulvic acid) were separated from the A2/O process DOM. WSOM had the highest promotion effect on EE2 photodegradation. Fulvic acid-like components and humic acid-like organic compounds in WSOM were speculated to be important photosensitivity substances that can generate triplet state substances. This research explored the physicochemical properties and photosensitive sources of DOM in WWTPs, and explained the fate of estrogens photodegradation in natural waters. 相似文献
We measured the concentrations of Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg, and the stable isotope ratios( δ13C and δ15N) in 87 fish samples within 12 economic fish species collected from the Dongting Lake, the second largest freshwater lake in China. With few exceptions in concentration of Cr, most of fish species showed lower concentrations of the 8 metals than legislation thresholds. Piscivorous fishes had significantly higher values of δ15N(possessing higher trophic... 相似文献