The Influence of Root Exudate Flavonoids on Sulfur Species Distribution in Mangrove Sediments Polluted with Cadmium

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WETLANDS RESTORATION

The Influence of Root Exudate Flavonoids on Sulfur Species Distribution in Mangrove Sediments Polluted with Cadmium Zhang Youli 1,2 & Li Jian 3,4 & Leng Zhanrui 3 & Du Daolin 3 Received: 10 August 2019 / Accepted: 31 March 2020 # Society of Wetland Scientists 2020

Abstract To evaluate the influence of flavonoids on the biogeochemistry of sulfur in mangrove sediments polluted with Cd, Avicennia marina individuals were cultivated in rhizoboxes under different concentrations of Cd and flavonoid. The reduced inorganic sulfur concentrations in the rhizosphere and non-rhizosphere sediments were examined. According to the results, acid-volatile sulfide concentrations in non-rhizosphere sediments were from 12.77 ± 1.01 to 19.21 ± 0.05 umol/g (DW) and significantly higher than those in rhizosphere, and flavonoids increased acid-volatile sulfide concentrations under Cd stress. High Eh (from 103.00 ± 3.21 to 197.33 ± 14.74 mV) and Cd stress in the rhizosphere led to more elemental sulfur formation, and flavonoid applications significantly increased elemental sulfur in both rhizosphere and non-rhizosphere sediments. Chromium-reducible sulfur from the non-rhizosphere was the source of the Chromium-reducible sulfur in the rhizosphere sediments, in addition to acid-volatile sulfide and elemental sulfur in both rhizosphere and non-rhizosphere sediments. In the rhizosphere with high Eh microenvironments, acid-volatile sulfide could be converted into Chromium-reducible sulfur effectively, while its conversion efficiency was significantly lower in non-rhizosphere. In addition, flavonoid applications reduced acid-volatile sulfide to Chromium-reducible sulfur conversion efficiency. In conclusion, flavonoid treatments in mangrove rhizosphere sediments polluted with Cd increased reduced inorganic sulfur concentrations and influenced sulfur biogeochemistry significantly. Keywords Sulfur biogeochemistry . Reduced inorganic sulfur . Heavy metal . Avicennia marina . Rhizosphere

Introduction As isolated and entire ecosystems, Coastal wetlands maintain energy flow and material circulation. Their anaerobic reduction of sulfate (SO42−) accounts for 50% of all organic

* Li Jian [email protected] 1

Agronomy College, Heilongjiang Bayi Agricultural University, Daqing 163319, Heilongjiang, China

2

National Coarse Cereals Engineering Research Center, Heilongjiang Bayi Agricultural University, Daqing 163319, Heilongjiang, China

3

Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China

4

Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/ Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environment Protection Institution, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China

mineralization in coastal and continental shelf ecosystems and consume more than half the organic matter in sediments and aquatic environments (Rickards et al. 2017). The