Biochar amendment combined with partial root-zone drying irrigation alleviates salinity stress and improves root morphology and water use efficiency in cotton plant

An adsorption experiment and a pot experiment were executed in order to explore the mechanisms by which biochar amendment in combination with reduced irrigation affects sodium and potassium uptake, root morphology, water use efficiency, and salinity tolerance of cotton plants. In the adsorption experiment, ten NaCl concentration gradients (0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 mM) were set for testing isotherm adsorption of Na+ by biochar. It was found that the isotherms of Na+ adsorption by wheat straw biochar (WSP) and softwood biochar (SWP) were in accordance with the Langmuir isotherm model, and the Na+ adsorption ability of WSP (55.20 mg g-1) was superior to that of SWP (47.38 mg g-1). The pot experiment consisted three factors, viz., three biochar amendments (no biochar, WSP, and SWP), three irrigation strategies (deficit irrigation, partial root-zone drying irrigation - PRD, full irrigation), and two NaCl concentrations gradients (0 mM and 200 mM). The findings indicated that salinity stress lowered K+ concentration, root length, root surface area, and root volume (RV), but increased Na+ concentration, root average diameter, and root tissue density. However, biochar amendment decreased Na+ concentration, increased K+ concentration, and improved root morphology. In particular, the combination of WSP and PRD increased K+/Na+ ratio, RV, root weight density, root surface area density, water use efficiency, and partial factor productivity under salt stress, which can be a promising strategy to cope with drought and salinity stress in cotton production.

Facile preparation of activated carbon supported nano zero-valent iron for Cd(Ⅱ) removal in aqueous environment

Activated carbon-supported nano-zero-valent iron (nZVI@AC) is considered to be one of the most promising materials for in-situ remediation of pollutants in aqueous environment, while liquid phase reduction (LPR) is one of the most commonly used preparation methods for nZVI@AC. However, the complex operation and the requirement of various agents limit the practical application of the traditional liquid-phase reduction (TLPR). In this study, an improved liquid phase reduction method (ILPR) was proposed, which was characterized by solid-state dosing of reducing agents. Compared with TLPR, ILPR simplified the preparation process, while there was no requirement of polyethylene glycol and ethanol. When the Cd(II) removal efficiency was used as the evaluation index, the preferred parameters of ILPR were as follows: AC/FeSO₄·7H₂O mass ratio was 15:1; NaBH₄ dosage was 8 g; ultrasonic time was 1 h; stirring time was 20 min. Moreover, the Cd(II) removal efficiency of nZVI@AC prepared by ILPR (nZVI@AC-I) was greater than 92.00%, which was superior to that of nZVI@AC prepared by TLPR (nZVI@AC-T). The characterization results showed that the pore parameters, surface functional groups and iron contents of nZVI@AC-I and nZVI@AC-T were basically the same. However, the distribution of iron-containing particles on the surface of nZVI@AC-I was more uniform. Furthermore, the Fe⁰ in nZVI@AC-I had a smaller particle size and a higher content. Overall, this study provided a promising approach for nZVI@AC preparation.