The Colonization Process Of Microorganisms On The Surface Of Microplastics And Its Effect On The Adsorption/Desorption Behavior Of Pollutants

Microplastics are considered to be a new type of pollutant.Its particle size is less than 5 mm,which is the most detected type of plastic waste.In the environment,microplastics can enrich contaminants and bring them into the environment through migration,transport,and thus cause potentially toxic effects on organisms.Microplastics can be colonized by microorganisms capable of forming biofilms and enter the environment through wastewater treatment plants（WWTPs）,which can affect the bioaccessibility of contaminants in organisms.In this process,different types of plastics and different treatment groups can also cause differences in biofouling and even affect the behavior of contaminants in environmental desorption.In this thesis,we attempted to reveal the role of biofilms in the sorption behavior and bioaccessibility of microplastics associated with sulfamethazine（SMT）or Pb²⁺by culturing microplastics in the microcosms of aqueous and sedimentary environments to compare the differences in microbial communities on microplastics.Specific findings are as follows.（1）We firstly collected surface water and sediment samples to form a microecological culture environment,and the dynamic changes of microbial colonization on polypropylene（PP）microplastics under different treatments（original and aged）were investigated.After 60 days of incubation,the time-dependence of biofilm growth was observed by scanning electron microscopy（SEM）mapping.Fourier transform infrared spectroscopy（FTIR）was used to observe the generation of1044-1066 and 1651 cm-1 to new peaks（ring vibration of polysaccharides and carbonyl in peptide bonds）,and photoaging treatment led to reduced hydrophobicity and reduced the affinity of biofilm to microplastics.High-throughput sequencing analysis found that the microbial communities formed in microplastics were different from those in the surrounding environment.（2）We further elucidated the adsorption/desorption behavior of microplastics with antibiotics.Through adsorption equilibrium experiments,it was found that both biofilm formation and photoaging promote the adsorption of microplastics to SMT.In vitro experiments indicated that the critical effects were mainly related to the stronger interaction of gastrointestinal components（i.e.,pepsin,bovine serum albumin（BSA）,and（bile salts）Na T）with biofilm components（e.g.extracellular polymer substances）than with the pure surface of microplastics,which competed for binding sites in microplastics for SMT more significantly.At the same time,the accumulation of biofilm in aging microplastics is less,which reduces the enhancement effect of biofilm.（3）Finally,we investigated the differences in biofilms（biomass and microbial type）on different types of plastics PP and polystyrene（PS）and revealed the adsorption/desorption behavior of microplastics with heavy metal.When the desorption equilibrium was reached,the force between the original microplastics and heavy metals was lower than that between the microplastics formed by biofilm and heavy metals,thus inhibiting the desorption rate of heavy metals on the microplastics formed by biofilm.At the same time,the benzene ring structure of PS had a strong binding effect with heavy metals,which made the bioavailability of heavy metals on PP higher.In this paper,the desorption behavior of contaminated microplastics in organisms was investigated from in vitro experiments,which provides a valuable reference for a comprehensive evaluation of the potential toxicity of biofilm microplastics to organisms.This study is the first attempt to reveal the role of biofilms in the bioaccessibility of microplastics with associated antibiotics and heavy metals,and to provide insights into the combined risk of microplastics in the environment.Figure[26]Table[9]References[123]...