摘要 In order to investigate the degradation process of commercial polylactic acid (PLA) plastics in freshwater sediments, a laboratory sediment system was established and the alternation in surface property, the attached biofilm and the microorganism communities on biodegradable plastic bag (PLAB), plastic straw (PLAS) and plastic cup (PLAC), with PLA as the main component, were identified. The results showed that the surface of plastics became rougher after 180days incubation in sediment, and PLAB with numerous protrusions, cracks and holes on the surface exhibited a mass loss (7.30%), showing the highest degree of degradation. Meanwhile, the infrared spectrum of PLAB changed significantly, with increased peak intensities of characteristic peaks such as C=O and C-O as well as a 13.65% increase in carbonyl index. The XPS spectra indicated that the O/C value of PLAB and PLAS were increased by 13.89% and 5.17%, respectively. The relative content of RO-C=O in the three plastics were reduced, indicating that all the studied plastics underwent degradation. At the end of the experiment, the surface of plastics was colonized by PLA degrading bacteria (Pseudomonas) and Desulfobacterota which may drive the degradation of PLA. PLAB had the strongest fluorescence intensity of mature biofilm, and its biofilm biomass in surface sediment was significantly higher than that of control (P<0.05). PLAB favored the formation of biofilm and the growth of the surrounding microbes, which may be attributed from its roughest surface. In addition, as components of PLAB, poly (butyleneadipate-co-terephthalate) (PBAT) displayed higher hydrolysis rate, which may be responsible for its most obvious degradation among the three plastics. Moreover, PLA plastics increased the microbial diversity in surface sediment and changed the relative abundance of dominant phyla, and may affect element cycles.
Abstract：In order to investigate the degradation process of commercial polylactic acid (PLA) plastics in freshwater sediments, a laboratory sediment system was established and the alternation in surface property, the attached biofilm and the microorganism communities on biodegradable plastic bag (PLAB), plastic straw (PLAS) and plastic cup (PLAC), with PLA as the main component, were identified. The results showed that the surface of plastics became rougher after 180days incubation in sediment, and PLAB with numerous protrusions, cracks and holes on the surface exhibited a mass loss (7.30%), showing the highest degree of degradation. Meanwhile, the infrared spectrum of PLAB changed significantly, with increased peak intensities of characteristic peaks such as C=O and C-O as well as a 13.65% increase in carbonyl index. The XPS spectra indicated that the O/C value of PLAB and PLAS were increased by 13.89% and 5.17%, respectively. The relative content of RO-C=O in the three plastics were reduced, indicating that all the studied plastics underwent degradation. At the end of the experiment, the surface of plastics was colonized by PLA degrading bacteria (Pseudomonas) and Desulfobacterota which may drive the degradation of PLA. PLAB had the strongest fluorescence intensity of mature biofilm, and its biofilm biomass in surface sediment was significantly higher than that of control (P<0.05). PLAB favored the formation of biofilm and the growth of the surrounding microbes, which may be attributed from its roughest surface. In addition, as components of PLAB, poly (butyleneadipate-co-terephthalate) (PBAT) displayed higher hydrolysis rate, which may be responsible for its most obvious degradation among the three plastics. Moreover, PLA plastics increased the microbial diversity in surface sediment and changed the relative abundance of dominant phyla, and may affect element cycles.
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