| Abstrakt: |
The effect of microplastics on the environment is currently one of the hotspots in environmental research. Biodegradable plastics will inevitably replace most of the traditional plastics. However, there are few reports on the effect of their natural degradation process on freshwater sediment. This study constructed a water column reactor indoors to simulate the environment of shallow freshwater lake, and investigated the effects of two commonly used biodegradable plastics, PLA and PBAT, on sediment at different time periods (90 and 365 days). The analysis of physicochemical parameters showed that the two degradable plastics significantly increased the total organic carbon (TOC) and total nitrogen (TN) concentrations of interstitial water in the short term (90 days) (P<0.05). PLA and PBAT significantly promoted the α diversity of bacterial communities over a long period of time (365 days) and increased the relative abundance of Proteobacteria. The number of denitrifying nirS genes in PLA and PBAT during the 90-day period was (2.33±0.33)x108 copies/g sediment and (2.16±0.09)x108 copies/g sediment respectively and the number of denitrifying nirK gene was (1.24±0.18)x107 copies/g sediment and (1.37±0.23)x107 copies/g sediment respectively, both of them were significantly higher than the control group (P<0.05). However, within 365 days, the number of nirS and nirK genes and anammox bacteria in degradable plastic groups were all significantly lower than the control group (P<0.05). Besides, the number these two kinds of bacteria in PBAT group was significantly lower than those of PLA group. Redundancy analysis revealed that the number of nirS and nirK genes was positively correlated with NH4+-N, TN, and TOC, and negatively correlated with total phosphorus. The correlation between anammox bacteria and environmental factors was completely opposite to that of denitrifying genes. This study preliminarily investigates the effects of different biodegradable plastics on sediment at different time periods, which may play an important role in further understanding the environmental effects and effect mechanisms of biodegradable plastics. [ABSTRACT FROM AUTHOR] |
