The relationship between geochemical parameters and the communities of arsenite-oxidizing bacteria in Rayong groundwater basin

Abstract

As is one of toxic metalloid commonly found on the earth's surface. In groundwater, arsenite (As3+) and arsenate (As5+) are most predominant As species. Arsenite is more toxic than arsenate. As removal through bioremediation technique can be applied as an alternative method. This study aimed to investigate the community of arsenite-oxidizing bacteria in As-contaminated groundwater and to correlated them to the geochemical parameters. Nineteen groundwater samples were collected from Ban-khai and Muang districts, Rayong province, Thailand. The communities of arsenite-oxidizing bacteria were detected by using PCR-cloning-sequencing techniques, targeting aioA gene. The results showed that the detected arsenite-oxidizing bacteria were associated with α-, β-, and γ-Protebacteria. The γ-Protebacterial cluster was detected in groundwater with low to moderate As concentrations, while it was undetected in groundwater with high As concentration. PHREEQC geochemical model was used to identify the major As species in all groundwater samples. The predominant As species in most groundwater samples is arsenite (As3+) which presented in the form of H3AsO3. In addition, the statistical analysis demonstrated that the geochemical parameters affecting the distribution of arsenite-oxidizing bacteria in this study were Fe, Mn, As3+ and As5+. Fe, Mn, and As3+ showed the positive relationship to the β-Proteobacterial cluster, whereas As5+ positively correlated with α-Proteobacterial cluster. The knowledge gain from this study will help better understand the distribution of arsenite-oxidizing bacteria found in groundwater with a broad range of As concentrations.