Regulatory mechanism of microplastics on arsenic bioavailability in a subtropical estuary, China

The increasingly prominent microplastics (MPs) pollution may affect the dynamics of arsenic (As) in estuarine sediments, but the effect of MPs on the bioavailable arsenic (bio-As) and its regulatory mechanism are still unclear. In this study Min River estuary, a typical subtropical estuary, was selected, and DGT technology was used to explore the pattern of change, composition characteristics and regulatory mechanism of bio-As in sediment under the influence of MPs (type: polylactic acid (PLA) and polyethylene terephthalate (PET); dose: 1 % and 5 %) through incubation experiments. The results showed that (1) the low-dose PET significantly increased the concentration of bio-As, (2) during the incubation experiment, the effect of MPs on the composition of the bio-As was phased. In general, PLA and 5 % PET inhibited the oxidation of As(III), respectively, while 1 % PET did the opposite, (3) the low-dose PET significantly increased the diversity of microbial community, (4) Bacteroidetes, Firmicutes, Proteobacteria, Desulfobacterota, and Chloroflexi were the most dominant microbial groups. (5) PET decreased the abundances of Bacteroides, Desulphurobacteria and Chlorocurvula, but increased the abundances of Proteobacteria. PLA decreased the abundance of Firmicutes and Chlorocurvula, and increased the abundance of desulphurobacteria and Proteobacteria, and (6) Marinobacter and Pseudomonas would directly promote the redox reaction of As. The bacteria Bacillus, Alkaliphilus, Haloplasma, Caminicella, Clostridiisalibacter, Desulfopila, and Desulfuromonas were able to influence the change of As by changing environmental factors.