Biochar and hematite amendments suppress emission of CH4 and NO2 in constructed wetlands

Guosheng Zhang; Qingju Hao; Rongzhen Ma; Shixu Luo; Keqin Chen; Zhenghao Liang; Changsheng Jiang

doi:10.1016/j.scitotenv.2023.162451

Biochar and hematite amendments suppress emission of CH₄ and NO₂ in constructed wetlands

Sci Total Environ. 2023 May 20:874:162451. doi: 10.1016/j.scitotenv.2023.162451. Epub 2023 Feb 28.

Authors

Guosheng Zhang¹, Qingju Hao², Rongzhen Ma¹, Shixu Luo¹, Keqin Chen¹, Zhenghao Liang¹, Changsheng Jiang³

Affiliations

¹ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400715, China.
² Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Bio-resource for Bioenergy, College of Resources and Environment, Southwest University, Chongqing 400715, China.
³ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Bio-resource for Bioenergy, College of Resources and Environment, Southwest University, Chongqing 400715, China. Electronic address: jiangcs@126.com.

PMID: 36863587
DOI: 10.1016/j.scitotenv.2023.162451

Abstract

Constructed wetlands (CWs) are considered a widely used cost-effective technology for pollutant removal. However, greenhouse gas emissions are a non-negligible problem in CWs. In this study, four laboratory-scale CWs were established to evaluate the effects of gravel (CW_B), hematite (CW_Fe), biochar (CW_C), and hematite + biochar (CW_Fe-C) as substrates on pollutants removal, greenhouse gas emissions, and associated microbial characteristics. The results showed that the biochar-amended CWs (CW_C and CW_Fe-C) enhanced the removal efficiency of pollutants, with 92.53 % and 93.66 % of COD and 65.73 % and 64.41 % of TN removal, respectively. Both single and combined inputs of biochar and hematite significantly reduced CH₄ and N₂O fluxes, with the lowest average of CH₄ flux obtained in CW_C (5.99 ± 0.78 mg CH₄ m^-2 h^-1) and the least N₂O flux in CW_Fe-C (287.57 ± 44.84 μg N₂O m^-2 h^-1). The substantial reduction of global warming potentials (GWP) was obtained in the applications of CW_C (80.25 %) and CW_Fe-C (79.5 %) in biochar-amended CWs. The presence of biochar and hematite mitigated CH₄ and N₂O emissions by modifying microbial communities with higher ratios of pmoA/mcrA and nosZ genes abundances, as well as increasing the abundance of denitrifying bacteria (Dechloromona, Thauera and Azospira). This study demonstrated that biochar and the combined use of biochar and hematite could be the potential candidates as functional substrates for the efficient removal of pollutants and simultaneously reducing GWP emissions in the constructed wetlands.

Keywords: Biochar; Constructed wetlands; Functional genes; Global gas emission; Greenhouse gas emission; Hematite.

MeSH terms

Greenhouse Gases* / analysis
Methane / analysis
Nitrogen Dioxide
Nitrous Oxide / analysis
Wetlands*

Substances

biochar
Greenhouse Gases
ferric oxide
Nitrogen Dioxide
Nitrous Oxide
Methane