The distribution of soil particle sizes is closely related to soil health condition. In this study, grasslands under different grazing intensities and different cultivation ages grasslands were selected to evaluate the dynamics of soil particle size redistribution in different soil layers. When the grazing intensity increased, the percentage of 2000~150-μm soil particles in the 0–10-cm soil layer decreased; 150~53-μm soil particles remained relatively stable among the grazing intensities—approximately 28.52%~35.39%. However, the percentage of less than 53-μm soil particles increased. In cultivated grasslands, the larger sizes (>53 μm) of soil particles increased and the smaller sizes (<53 μm) decreased significantly (p < 0.05) in the 0–10 cm-soil layer with increasing cultivation ages. The increase in small soil particles (<53 μm) in topsoil associated with grazing intensity increased the potential risk of further degradation by wind erosion. The increase in big soil particles (>53 μm) in topsoil associated with cultivation ages decreased the soil capacity of holding water and nutrient. Therefore, to maintain the sustainability of grassland uses, grazing grasslands need to avoid heavy grazing, and cultivated grasslands need to change current cultivation practices.

A series of the magnetic CuFe2O4-loaded corncob biochar (CuFe2O4@CCBC) materials was obtained by combining the two-step impregnation of the corncob biochar with the pyrolysis of oxalate. CuFe2O4@CCBC and the pristine corncob biochar (CCBC) were characterized using XRD, SEM, VSM, BET, as well as pHZPC measurements. The results revealed that CuFe2O4 had a face-centered cubic crystalline phase and was homogeneously coated on the surface of CCBC. The as-prepared CuFe2O4@CCBC(5%) demonstrated a specific surface area of 74.98 m2·g−1, saturation magnetization of 5.75 emu·g−1 and pHZPC of 7.0. The adsorption dynamics and thermodynamic behavior of Pb(II) on CuFe2O4@CCBC and CCBC were investigated. The findings indicated that the pseudo-second kinetic and Langmuir equations suitably fitted the Pb(II) adsorption by CuFe2O4@CCBC or CCBC. At 30 °C and pH = 5.0, CuFe2O4@CCBC(5%) displayed an excellent performance in terms of the process rate and adsorption capacity towards Pb(II), for which the theoretical rate constant (k2) and maximum adsorption capacity (qm) were 7.68 × 10−3 g·mg−1··min−1 and 132.10 mg·g−1 separately, which were obviously higher than those of CCBC (4.38 × 10−3 g·mg−1·min−1 and 15.66 mg·g−1). The thermodynamic analyses exhibited that the adsorption reaction of the materials was endothermic and entropy-driven. The XPS and FTIR results revealed that the removal mechanism could be mainly attributed to the replacement of Pb2+ for H+ in Fe/Cu–OH and –COOH to form the inner surface complexes. Overall, the magnetic CuFe2O4-loaded biochar presents a high potential for use as an eco-friendly adsorbent to eliminate the heavy metals from the wastewater streams.

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