Natural attenuation mechanism of hexavalent chromium in a wetland: Zoning characteristics of abiotic and biotic effects

Kaidi Jiang; Jia Zhang; Zhihui Deng; Samuel Barnie; Jingjie Chang; Yawen Zou; Xiangyu Guan; Fei Liu; Honghan Chen

doi:10.1016/j.envpol.2021.117639

Natural attenuation mechanism of hexavalent chromium in a wetland: Zoning characteristics of abiotic and biotic effects

Environ Pollut. 2021 Oct 15:287:117639. doi: 10.1016/j.envpol.2021.117639. Epub 2021 Jun 21.

Authors

Kaidi Jiang¹, Jia Zhang², Zhihui Deng¹, Samuel Barnie³, Jingjie Chang¹, Yawen Zou¹, Xiangyu Guan⁴, Fei Liu¹, Honghan Chen¹

Affiliations

¹ Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, China.
² Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, China. Electronic address: zjia@cugb.edu.cn.
³ Department of Water and Sanitation, University of Cape Coast, Cape Coast, Ghana.
⁴ Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences, Beijing, 100083, China; School of Ocean Sciences, China University of Geosciences, Beijing, 100083, China.

PMID: 34171730
DOI: 10.1016/j.envpol.2021.117639

Abstract

Natural wetland has great retention effect on Cr(VI) migration due to its abiotic and biotic reduction abilities, however, the zoning characteristics of dominating reduction mechanism along Cr(VI) pollution plume in wetland is still unclear. In this study, a Cr(VI) contaminated natural wetland was explored to investigate the distributions of Cr and Fe in groundwater and sediment, and their relationship with microorganisms according to metagenomics, aiming to reveal the natural attenuation mechanism of Cr(VI) from the perspective of zoning characteristics of abiotic and biotic effects. The wetland was divided into contaminated zone, transition zone and uncontaminated zone according to the contamination states of groundwater and sediment. At the upstream of contaminated zone, Cr(VI) concentration in groundwater was as high as 26.7 mg L^-1, which has significant inhibition effect on microbial growth, and thus chemical reduction of Cr(VI) by natural organic matters (NOMs) dominated in this area, leading to the increasing of H/C and O/C ratios of NOMs because of the oxidation of aromatic moieties. At the downstream of contaminated zone, Cr(VI) concentration in groundwater decreased to less than 4.46 mg L^-1 resulting from dilution and attenuation, but the microbial community was altered substantially, chromate resistant bacteria with ChrA, ChrR, NemA and AzoR genes were enriched, such as Sphingomonas, Mesorhizobium and Comamonadaceae, and thus the direct microbial reduction of Cr(VI) dominated in this area. While at the transition zone, which is located at the front edge of the pollution plume, Cr(VI) could only reached in this area intermittently, and the microbial community remained similar to that of the uncontaminated zone, dominated by Chloroflexi and Acidobateria phylum with dissimilatory ferric iron reduction capacity, and thus Cr(VI) was indirectly reduced by Fe²⁺ intermediately in this area.

Keywords: Groundwater; Hexavalent chromium; Iron reduction; Microbial reduction; Wetland.

MeSH terms

Chromium / analysis
Groundwater*
Water Pollutants, Chemical* / analysis
Wetlands

Substances

Water Pollutants, Chemical
Chromium
chromium hexavalent ion