Smaller sizes of polyethylene terephthalate microplastics mainly stimulate heterotrophic N2O production in aerobic granular sludge systems
Yingrui Liu, Yingrui Liu, Yanying He, Qian Lu, Tingting Zhu, Yufen Wang, Yindong Tong, Yingxin Zhao, Bing‐Jie Ni, Yiwen Liu, Yiwen Liu
Abstract
• Effects of PET MPs with different particle sizes on N 2 O turnovers are firstly uncovered. • PET MPs (especially 0.1 mm) stimulate total N 2 O production by denitrification in the AGS system. • 0.1 mm PET MPs induce N 2 O accumulation by decreasing electron transport during denitification. • 0.1 mm PET MPs further restrain N 2 O-sink capability by reducing key genes related to N 2 O reduction. Widespread polyethylene terephthalate microplastics (PET MPs) have played unintended role in nitrous oxide (N 2 O) turnovers (i.e., production and consumption) at wastewater treatment plants (WWTPs). Mainstream aerobic granular sludge (AGS) systems possess potentially strong N 2 O-sink capability, which may be reduced by PET MPs stress through altering N 2 O-contributing pathways, electron transfer, and microbial community structures. In this study, the effects of PET MPs with two common particle sizes of effluent from WWTPs (0.1 and 0.5 mm) on N 2 O turnovers, production pathways and N 2 O-sink capability were systematically disclosed in AGS systems by a series of biochemical tests and molecular biological means to achieve the goal of carbon neutrality. The results indicated that 0.1 mm PET MPs could more significantly stimulate N 2 O production in AGS systems by inhibiting denitrifying metabolism, compared with control and 0.5 mm PET MPs systems. Specifically, 0.1 mm PET MPs slightly increased the relative abundance of Nitrosomonas , reducing N 2 O yields via promoting the hydroxylamine (NH 2 OH) oxidation pathway during nitrification. Also, 0.1 mm PET MPs inhibited the electron transport system activities and the relative abundance of N 2 O reductase, hindering N 2 O reduction during denitrification. Most importantly, 0.1 mm PET MPs more apparently reduced the N 2 O-sink capability based on the ratio of N 2 O reductase gene and nitrite reductase gene.