Effect of paddy cultivation on the surface electrochemical properties of different‐sized particles of a Gleysol.

Background: Limited information is available on the changes in surface electrochemical properties of different‐sized particles of an Anthrosol, compared with the corresponding parental upland soil. Aims: Our overarching goal was to clarify the contribution of different‐sized particles to the soil surface charge. The specific objectives of this work were to examine the differences in the surface charge properties between the Anthrosol and its upland parental Gleysol and to reveal the properties of the different‐sized fractions separated from the Anthrosol, compared with those of the upland Gleysol. Materials and methods: The properties (e.g., negative surface charge, zeta potential, and particle sedimentation) of different‐sized fractions of nanoparticle (NP), coarse colloid, silt, and sand fractions separated from an upland Gleysol and its derived Anthrosol were compared. Results: NPs in both the Anthrosol and the Gleysol carried more negative charge than did the coarse colloids, with cation exchange capacities (CEC) being 186.5% and 58.8% greater, respectively. On the other hand, the presence of more positively charged Fe/Al (hydr)oxides compensated for the negative charge, resulted in a zeta potential of the NPs similar to that of the coarse colloids. More secondary minerals were observed in the coarse colloids of the Anthrosol than in the same fraction of the Gleysol, resulting in more negative charge on the surface of the Anthrosol coarse colloids. The coarse colloid fraction of the Anthrosol, therefore, had a greater CEC, despite representing a smaller mass fraction than in the Gleysol. Overall, the CEC of the Anthrosol was 21% lower than that of the parent Gleysol, which was consistent with the findings of the surface charge, using the cesium (Cs+)‐adsorption method. The sedimentation observations demonstrated that the suspension stability of the NPs was higher than that of the coarse colloids, and that they tended to disperse particularly under high pH conditions. Conclusions: Although the surface charge potential of the Anthrosol was lower than that of the upland Gleysol, the accumulation of organic matter and formation of secondary phyllosilicates resulted in maintenance of the nutrient‐ and pollutant‐binding capacity and agricultural productivity of the Anthrosol. [ABSTRACT FROM AUTHOR]