title: Effects of an iron-silicon material, a synthetic zeolite and an alkaline clay on vegetable uptake of As and Cd from a polluted agricultural soil and proposed remediation mechanisms.
abstract: Economic and highly effective methods of in situ remediation of Cd and As polluted farmland in mining areas are urgently needed. Pot experiments with Brassica chinensis L. were carried out to determine the effects of three soil amendments [a novel iron-silicon material (ISM), a synthetic zeolite (SZ) and an alkaline clay (AC)] on vegetable uptake of As and Cd. SEM-EDS and XRD analyses were used to investigate the remediation mechanisms involved. Amendment with ISM significantly reduced the concentrations of As and Cd in edible parts of B. chinensis (by 84-94 % and 38-87 %, respectively), to levels that met food safety regulations and was much lower than those achieved by SZ and AC. ISM also significantly increased fresh biomass by 169-1412 % and 436-731 % in two consecutive growing seasons, while SZ and AC did not significantly affect vegetable growth. Correlation analysis suggested that it was the mitigating effects of ISM on soil acidity and on As and Cd toxicity, rather than nutrient amelioration, that contributed to the improvement in plant growth. SEM-EDS analysis showed that ISM contained far more Ca, Fe and Mn than did SZ or AC, and XRD analysis showed that in the ISM these elements were primarily in the form of silicates, oxides and phosphates that had high capacities for chemisorption of metal(loid)s. After incubation with solutions containing 800 mg L-1AsO42-or Cd2+, ISM bound distinctly higher levels of As (6.18 % in relative mass percent by EDS analysis) and Cd (7.21 % in relative mass percent by EDS analysis) compared to SZ and AC. XRD analysis also showed that ISM facilitated the precipitation of Cd2+as silicates, phosphates and hydroxides, and that arsenate combined with Fe, Al, Ca and Mg to form insoluble arsenate compounds. These precipitation mechanisms were much more active in ISM than in SZ or AC. Due to the greater pH elevation caused by the abundant calcium silicate, chemisorption and precipitation mechanisms in ISM treatments could be further enhanced. That heavy metal(loid)s fixation mechanisms of ISM ensure the remediation more irreversible and more resilient to environmental changes. With appropriate application rate and proper nutrients supplement, the readily available and economic ISM is a very promising amendment for safe crop production on multi-metal(loids) polluted soils.
authors.affiliation: School of Geography and Planning, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Aijun
authors.initials: A
authors.lastname: Yao
authors.affiliation: School of Geography and Planning, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Yani
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Geography and Planning, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Ling
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Yetao
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Division of Soil and Water Management, University of Leuven, 3001, Heverlee, Belgium.
authors.forename: Hao
authors.initials: H
authors.lastname: Qiu
authors.affiliation: Nanjing Institute of Environmental Science, Chinese National Ministry of Environmental Protection, 8 Jiangwangmiao Street, Nanjing, 210042, People's Republic of China.
authors.forename: Rongrong
authors.initials: R
authors.lastname: Ying
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China. eesqrl@mail.sysu.edu.cn.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China. eesqrl@mail.sysu.edu.cn.
authors.forename: Rongliang
authors.initials: R
authors.lastname: Qiu
mesh_terms: D000383:Agriculture; D000538:Aluminum Silicates; D001151:Arsenic / Q000032:analysis / Q000493:pharmacokinetics*; D018533:Biomass; D001937:Brassica / Q000187:drug effects / Q000378:metabolism*; D002104:Cadmium / Q000032:analysis / Q000493:pharmacokinetics*; D002681:China; D000077215:Clay; D052918:Environmental Restoration and Remediation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007501:Iron; D008906:Mining; D012825:Silicon; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000493:pharmacokinetics*; D014675:Vegetables / Q000378:metabolism*; D017641:Zeolites
chemical_list: D000538:Aluminum Silicates; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D017641:Zeolites; D007501:Iron; D001151:Arsenic; D000077215:Clay; D012825:Silicon
keywords: Alkaline clay; Amendment; Arsenic; Cadmium; Iron-silicon material; Mechanisms; Pollution; Remediation; Soil; Synthetic zeolite; Vegetable uptake