Unveiling the Role of Dissolved Organic Matter on the Hg Phytoavailability in Biochar-Amended Soils

Wenhao Chen, Zhigang Yu, Xu Yang, Tantan Wang, Zihao Li, Xin Wen, Yubo He and Chang Zhang ()
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Wenhao Chen: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Zhigang Yu: Australian Centre for Water and Environmental Biotechnology (Formerly AWMC), The University of Queensland, Brisbane, QLD 4072, Australia
Xu Yang: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Tantan Wang: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Zihao Li: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Xin Wen: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Yubo He: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
Chang Zhang: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China

IJERPH, 2023, vol. 20, issue 4, 1-17

Abstract: Biochar can effectively reduce the phytoavailability of mercury (Hg) in soil, but the mechanisms are not fully understood. In this study, the dynamic changes in Hg content adsorbed by the biochar (BC-Hg), Hg phytoavailability in the soil (P-Hg), and soil dissolved organic matter (DOM) characteristics were determined over a 60-day treatment period. Biochar obtained at 300 °C, 500 °C and 700 °C reduced the P-Hg concentration assessed by MgCl 2 extraction by 9.4%, 23.5% and 32.7%, respectively. However, biochar showed a very limited adsorption on Hg, with the maximum BC-Hg content only accounting for 1.1% of the total amount. High-resolution scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) results showed that the proportion of Hg atoms in biochar after 60 d was barely detectable. Biochar treatment can shift soil DOM toward higher aromatic content and molecular weight. Additionally, the addition of high-temperature biochar increased more humus-like components, but low-temperature biochar increased more protein-like components. Correlation analysis and partial least squares path modeling (PLS-PM) showed that biochar promoted humus-like fractions formation to reduce the Hg phytoavailability. This research has deepened the understanding of the mechanisms by which biochar stabilizes Hg in agricultural soils.

Keywords: biochar; mercury; pyrolysis temperature; dissolved organic matter; soil remediation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2023
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