Community Structure And Indicating Characteristics Of Benthic Microorganisms In The River Polluted By PFOA

Perfluorooctanoic acid (PFOA), as a new persistent organic pollutant, is one of the most representative Perfluoroalkyl substances (PFASs), which is widely used in industrial production and civilian areas. Now, PFOA has been widely detected in various environmental media. PFOA has unique physicochemical properties, such as environmental persistence and bioaccumulation. These properties cause scientists’ widespread concern and the increasing concern are mostly concentrated in toxic effects of PFOA towards model organisms, while the information on microorganisms is limited. The study will explore the impact of PFOA on bacterial community structure and mode species. Related results and conclusions are shown as follows:1. In order to reveal the relationship between PFASs contamination and the bacterial community composition, surface sediment samples were collected along the Xiaoqing River in Shandong Province in April and July 2014 (XQ1-XQ10), where many PFASs manufacturer were located in. PFASs were quantified by HPLC/MS-MS, related environmental factors affecting the microbial community structure were measured, and microbial community structure in surface sediments were measured by the second-generation sequencing technology Illumina Mi-Seq. The results not only revealed degree of PFASs pollution in the sediments of Xiaoqing River, but also illustrated the relationship between PFASs pollution and microbial community structure. Among the twelve kinds of PFASs detected in this study, PFOA was the predominant compound, and the highest PFOA concentrations were detected in the sample of XQ5 (April:456.2 ng·L-1; July:748.7 ng·L-1) located at the downstream of Xiaoqing River with many fluoropolymer producing facilities. Proteobacteria was the most abundant and largest phylum in each sample. The abundance of Thiobacillus increased with the increasing of the PFOA concentration in the sediment PFOA. This suggested that Thiobacillus was sensitive to PFOA pollution and might be the potential indicator to reveal the degree of PFOA pollution in sediment. PFOA contamination was the main factor affecting microbial community structure in April, accordingly community richness and evenness were significantly negative correlation with PFOA levels. No significant environmental factors on microbial community structure were observed in July, which needs to be further explored.2. Thiobacillus thioparus and Thiobacillus denitrificans were selected as model species to measure growth curve and pH under 10 different concentrations of PFOA. At the same time the residual amount of PFOA after growth cycles were also monitored. The results showed that an increasing concentrations of PFOA below 5000 ng·L-1 leaded to a obviously corresponding increase in growth rate of T. thioparus. PFOA promoted the growth of T. denitrificans in a small range of concentration, and the effect was not obvious. The addition of different PFOA concentrations had no effects on pH to both T. thioparus and T. denitrificans. In addition, PFOA in the liquid medium can reduce in the process of bacteria culturing. After their growth cycle, the removal rate of PFOA to T. thioparus was 21.1%-26.8%, and 13.5%-18.4% to T. denitrificans by HPLC-MS/MS method. The current findings indicated T. thioparus can not only as sensitive species response to PFOA but also effectively reduce PFOA content, which provided novel information for PFOA risk assessment and ecological restoration.