Key process for reducing grains arsenic by applying sulfate varies with irrigation mode: Dual effects of microbe-mediated arsenic transformation and iron plaque

Quan Zhang; Tianchi Ma; Haifei Chen; Lei He; Qiren Wen; Qihong Zhu; Daoyou Huang; Chao Xu; Hanhua Zhu

doi:10.1016/j.envpol.2023.122569

Key process for reducing grains arsenic by applying sulfate varies with irrigation mode: Dual effects of microbe-mediated arsenic transformation and iron plaque

Environ Pollut. 2023 Nov 15:337:122569. doi: 10.1016/j.envpol.2023.122569. Epub 2023 Sep 16.

Authors

Quan Zhang¹, Tianchi Ma¹, Haifei Chen², Lei He¹, Qiren Wen³, Qihong Zhu¹, Daoyou Huang¹, Chao Xu¹, Hanhua Zhu⁴

Affiliations

¹ Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China.
² College of Resources and Environment, Hunan Agricultural University, Changsha, China.
³ Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China; College of Resources and Environment, Hunan Agricultural University, Changsha, China.
⁴ Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China. Electronic address: hhzhu@isa.ac.cn.

PMID: 37722477
DOI: 10.1016/j.envpol.2023.122569

Abstract

Sulfate affects the transformation of arsenic (As) in soil and its absorption by plant roots. However, the influence of sulfate and irrigation interactions on the mobility of As in the soil-rice system remains poorly understood. To address this gap, we conducted a pot experiment with varying sulfate levels and irrigation modes to examine their effects on rice As translocation, soil As forms, iron plaque formation, and microorganisms involved in As transformation. The addition of exogenous sulfate significantly reduced grain As levels by a maximum of 60.1%, 46.7%, and 70.5% under flooding (F), flooding-moist alternate (FM), moist (M) conditions, respectively. However, the changes in soil available As did not fully correspond to grains As content. Soil available As was only reduced by sulfate under the FM treatment, which limited grains As accumulation under this condition. The reduction in grains As content under F and M conditions was mainly attributed to sulfate-induced increases in soil pH, which in turn inhibited As translocation and promoted iron plaque formation. Additionally, both irrigation mode and sulfate fertilization independently or interactively influenced the abundance of Sulfuritalea, Koribacter, Geobacter, and Sulfuriferula, thereby affecting the As forms in soil through the Fe/S redox process. Specifically, under F and FM conditions, SO₄^2--S inhibited Geobacter but stimulated Fe-oxidizing bacteria, possibly resulting in increased As bound to Fe/Mn oxides (As-F3). Under M condition, SO₄^2--S levels regulated As adsorption and release through the participation of Fe/S cycle bacteria, specifically influencing the adsorbed As fraction (As-F2). Therefore, the addition of SO₄^2--S hindered As translocation to grains by promoting As sequestration in the iron plaque and facilitating microbe-mediated As immobilization through the Fe/S cycle, which was dependent on soil moisture. These results can be used as a guide for sulfur fertilizer application under different soil moisture with the goal of minimizing rice grain As.

Keywords: Arsenic; Fe/S bacteria; Immobilization; Iron plaque; Sulfate.

MeSH terms

Arsenic* / analysis
Iron / chemistry
Oryza* / metabolism
Plant Roots / metabolism
Soil / chemistry
Soil Pollutants* / analysis
Sulfates / metabolism
Sulfur Oxides

Substances

Iron
Arsenic
Sulfates
Sulfur Oxides
Soil
Soil Pollutants