Determination of the accumulation, spatial distribution and reduction of Cr in unsaturated Pseudochrobactrum saccharolyticum LY10 biofilms by X-ray fluorescence and absorption methods

A Cr(VI)-reducing bacteria (Pseudochrobactrum saccharolyticum LY10) was selected to simulate the biofilm grown in unsaturated habitats containing Cr(VI) and the X-ray fluorescence and absorption methods were used to characterize the temporal and spatial distributions of metal elements in the unsaturated biofilms in the present study. The results indicated that Cr and other elements (Fe, Mn, Ca, K, and Zn) were selectively accumulated in the unsaturated biofilms. Synchrotron radiation micro X-ray fluorescence microscopy (SR-μXRF) analysis revealed that Cr mainly existed in the 10-45 μm layer near the bottom biofilm-membrane interface after 24 h of Cr exposure. The analysis of Cr speciation by X-ray absorption near-edge structure (XANES) spectroscopy analysis further confirmed the bioreduction of Cr(VI) to Cr(III), and the precipitate formed in the biofilms after reduction were most similar to CrPO4. This systematic understanding of the accumulation, distribution and reduction process of Cr in the unsaturated biofilms will elaborate to enhance the bioremediation efficiencies for Cr pollution in soil and other environment.