Roles of Chloride and Sulfate Ions in Controlling Cadmium Transport in a Soil-Rice System as Evidenced by the Cd Isotope Fingerprint

Abstract

Anions accompanying inorganic fertilizers, such as chloride and sulfate ions, potentially affect the solubility, uptake, and transport of Cd to rice grains. However, the role of anions in controlling Cd transport in the soil−soil solution−Fe plaque−rice plant continuum remains poorly understood. Cd isotope ratios were applied to Cd-contaminated soil pots, hydroponic rice, and adsorption experiments with or without KCl and K 2 SO 4 treatments to decipher transport processes in the complex soil−rice system. The chloride and sulfate ions increased the Cd concentrations in the soil solution, Fe plaque, and rice plants. Accordingly, the magnitude of positive fractionation from soil to the soil solution was less pronounced, but that between soil and Fe plaque or rice plant is barely varied. The similar isotope composition of Fe plaque and soil, and the similar fractionation magnitude between Fe plaque and the solution and between goethite and the solution, suggested that desorption-sorption between iron oxides and the solution could be important at the soil−soil solution−Fe plaque continuum. This study reveals the roles of chloride and sulfate ions: (i) induce the mobility of light Cd isotopes from soil to the soil solution, (ii) chloro-Cd and sulfato-Cd complexes contribute to Cd immobilization in the Fe plaque and uptake into roots, and (iii) facilitate second leaves/node II-to-grain Cd transport within shoots. These results provide insights into the anion-induced Cd isotope effect in the soil−rice system and the roles of anions in facilitating Cd migration and transformation.

Zinc isotope fractionation in soil-rice systems constrained by varying water regimes and Zn fertilizer application: implication for Zn biofortification

“…Strategies such as supplying Zn fertilizers and drainage regimes are generally adopted in practice; however, the molecular mechanisms underlying their uptake and transport have not been well elucidated owing to the complicated processes of Zn transport from soils to grains (Weiss et al, 2005;Jouvin et al, 2012;Tang et al, 2012). A combination of isotope and gene analyses may provide robust evidence for elucidating the underlying processes during uptake and transport (Zhong et al, 2021;2023). This study revealed that drainage regimes and Zn fertilizer could downregulate the ZIP family genes but upregulate OsHMA2 in roots and node I relative to ooding regimes.…”

“…The soil samples were extracted using 0.1 M CaCl 2 and 0.1 M HCl to attain exchangeable and acidic Zn in the soil (Arnold et al, 2015;Aucour et al, 2015). To extract the iron plaque on roots at the jointing stage, a mixture of 0.5 M HCl and 0.1 M HCl was added into a vial containing speci c root amounts, followed by ultrasonication with 15 min per treatment twice (Zhong et al, 2021;2023;2024). A proper amount of soil or rice tissue samples were added with a mixture of HNO 3 and HF and digested in a high-performance Milestone microwave digestion system (ETHOS UP, Italy) at 150 ℃ for 8 h, and then dried at 160 ℃ to remove the remaining uorine.…”

Cadmium Sorption on Alumina Nanoparticles and Mixtures of Alumina and Smectite: An Experimental and Modelling Study

“…In some cases, Cl − induces a higher Cd removal [20][21][22][23], while it seems to decrease Cd retention in other studies [24][25][26][27]. A recent publication states the importance of chloride and sulfate on the migration of Cd in soils and its subsequent uptake by plants [28].…”

Ferric Oxide Nanomaterials and Plant-Rhizobacteria Symbionts Cogenerate Iron Plaque for Removing Highly Chlorinated Contaminants in Dryland Soils

“…It not only acts as a barrier resistant to the upward transport of pollutants but also acts as a producer of interfacial reactive oxygen species (ROS) for pollutant degradation. For example, iron plaque on rice root surface prevented the migration of Cd and As, and ROS on the iron plaque surface were responsible for the degradation of propane and atrazine . However, iron plaque is known to exist only on the root surfaces of wetland plants such as Oryza sativa, Phragmites austra, Salix jiangsuensis, Spartina alterniflora, and Kandelia obovate due to the demanding submerged anaerobic conditions.…”