EFFECTS OF AEROBIC/ANAEROBIC ENVIRONMENTS ON MICROBIAL DEGRADATION EFFICIENCY OF TYPICAL MICROPLASTICS
This study evaluated the degradation efficiency of three typical microplastics(PHA(polyhydroxyalkanoate),PLA(polylactic acid),and PVC(polyvinyl chloride))under different aerobic and anaerobic environments in ambient temperatures.The experimental results of scanning electron microscope(SEM),differential scanning calorimetry(DSC),Fourier transform infrared spectroscopy(FTIR),average mass,and microbial activity ratio analysis showed that PHA exhibited similar degradation rates in both aerobic and anaerobic environments,approximately 25.72 mg C/d.The surface of PHA microplastic exhibited prominent grooves and cracks,along with decreased ester group abundance,crystallinity,and average mass.On the other hand,PLA and PVC practically did not degrade due to their intrinsic structural stability and great crystallinity.Calculations of the carbon balance when PHA was degraded showed that the carbon was predominantly broken down into CH3COOH,CH4,and carbon in biomass.The proportions of these three products in aerobic and anaerobic environments differed significantly,namely 5.23％vs.0.27％,4.28％vs.12.24％,and 87.05％vs.82.50％,respectively.This may be due to different microbial numbers and critical enzyme activity involved in PHA breakdown between the aerobic and anaerobic environments.This study investigated the effects of aerobic and anaerobic settings on degradation rates and product variations of microplastics in detail,which may help formulate important theoretical guidelines for determining the environmental risk of microplastics.
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