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Contamination of water and soil with toxic metals is a serious environmental issue. To study the Pb, Cu, Cd, and Zn sorption behavior by diatomite, batch experiments were carried out with increasing levels of initial concentration (0–200 mg/L) under different contact times (0–360 min) and temperatures (283, 293, 303, and 313 K). The effects of concentration (0–200 mg/L), pH (3–6), and ionic strength (0.01–0.06 mol/L) on the sorption were modeled using response surface methodology (RSM). Results showed that adsorption data were well‐fitted by the Langmuir equation. The sorption of metals intensified by increasing initial concentration and pH but ionic strength had inverse effect. High value for R2 (0.99) and adjusted R2 (0.99) showed that the removal of ions can be described by response surface method. One‐way ANOVA showed (p‐value < 0.0001) that quadratic model is the best model for determining the interaction of variables. The values of the sorption energy parameter from Dubinin–Radushkevich model (E < 8 kJ K−1 mol−1) and negative values of ∆G showed that the sorption of the metals was physical and spontaneous. The positive values of enthalpy (ΔH) indicated that the sorption reaction of metals was endothermic at 283–313 K. Practitioner points Applications of diatomite increased the sorption of Pb, Cd, Zn, and Cu from aqueous solutions. Diatomite, as low‐cost adsorbent, had significant potential to sorption of ions. The sorption of heavy metals by adsorbent intensified by increasing initial concentration and pH but ionic strength had inverse effect. High value for R2 (0.99) and adj‐R2 (0.99) showed that removal of metals can be described by response surface method (RSM) and the initial concentration of metal was the most significant factor.

High concentration of labile metals in soil directly affects soil quality, water health and human safety. Decreasing mobility of metals, especially in contaminated soils, by cost-effective amendments may alleviate environmental problems. Natural diatomite was investigated to immobilize toxic elements of zinc, lead, copper and cadmium in a contaminated calcareous soil. The diatomite was characterized using X-ray fluorescence spectrometry and scanning electron microscopy. Contaminated soil was incubated with 0, 2 and 5 weight-% of diatomite at 25 °C for 8 weeks. Tessier sequential extraction method was also used as a suitable method for identification of chemical forms of heavy metals; metal stability index and mobility factor were calculated. Results showed that application of diatomite in soil significantly decreased the metals in the exchangeable fraction and increased them in the residual fraction. The exchangeable metal fractions decreased by 66-88%, and residual fractions increased by 18-94% in the 5 weight-% of diatomite treatment after 8-week incubation. With an increase in the amount of diatomite applied and the incubation time, metal mobility factor values significantly decreased and soil pH values increased. Application of diatomite caused the heavy metals redistribution toward more stable forms and leads to an increase in stability index values. In conclusion, in situ immobilization of heavy metals by application of diatomite, as a low-cost amendment, had a significant potential to stabilize metals in the contaminated calcareous soil.

Post-harvest senescence is one of the crucial challenges limiting the commercialization of cut flowers. Long vase life is the most important factor determining the economic value of cut flowers. Major factors limiting the vase life of lisianthus cut flower included sensitivity to ethylene, inability to absorb water resulting in bending and suppression of bud opening and coloring, which must be considered at the post-harvest stage. Therefore, the present study was carried out to investigate three types of growth regulators, salicylic acid (SA), sodium nitroprusside (SNP) and spermidine (Sp), each with four concentrations and in four replicates, on the vase life and quality of Lisianthus cut flowers in post-harvest stage. The three regulators have a positive effect on the longevity of Lisianthus cut flowers and reduce ion leakage, malondialdehyde and hydrogen peroxide and increase the activity of the antioxidant enzymes, ascorbate peroxidase and guaiacol peroxidase, and preserving the degradation of lipid membrane and cell stability. The most appropriate concentrations in this study included 1- and 2-mM salicylic acid and/or spermidine as well as sodium nitroprusside concentrations of 40 and 60 µM.

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