Spatiotemporal variations of redox conditions and microbial responses in a typical river bank filtration system with high Fe2+ and Mn2+ contents

• River bank filtration could be stabilized with 51%, 36%, and 21% decrease of Fe 2+ , Mn 2+ and NH 4 + , respectively, after 21 d of water extraction. • Detailed redox zonation mapping of geology, chemistry, microbiology is constructed. • The redox zones are divided by redox indices of DO, NO 3 − , Fe 2+ , Mn 2+ , and SO 4 2- . • Seasonality results in a 30% fluctuation of Fe 2+ and Mn 2+ contents in redox zones. • Fe 2+ and Mn 2+ contributed most to microbial variability with dominant bacteria of Pseudomonas, Flavobacterium, and Limnobacter. The redox conditions strongly affect redox kinetics, hydrochemical composition and microbial reactions under river bank filtration (RBF). For investigating the redox conditions, zonation factors, and microbial responses in a typical RBF with high Fe 2+ and Mn 2+ contents, three wells were established 20 m apart perpendicular to the south bank of the Songhua River with a constant flow rate of 400 m 3 /h. Redox zonation was identified from the redox sequences, redox products, reactions identified and seasonality. High-throughput sequencing, principal coordinates analysis, and redundancy analysis were used to identify the microbial responses to redox zonation. The results indicated that the RBF was stabilized after 21 d of water extraction with a 51%, 36% and 21% decrease of Fe 2+ , Mn 2+ and NH 4 + contents, respectively. Feature redox indices varied with strong regularity in the horizontal and vertical filtration directions, and the filtration area could be divided into O 2 /NO 3 − , Fe/Mn, and SO 4 2− reduction zones. Seasonality resulted in markedly fluctuation of Fe 2+ and Mn 2+ contents in groundwater. Pseudomonas, Flavobacterium , and Limnobacter were the dominant bacteria in the O 2 /NO 3 − , Fe/Mn, and SO 4 2− reduction zones, respectively. DO explained 21.1% of microbial variability in the fluctuation zone, while Mn 2+ and Fe 2+ explained 27.7%, and 26.2%, respectively, of microbial variability in the saturated zone.