Cd and Zn Concentrations in Soil and Silage Maize following the Addition of P Fertilizer

et al. 2023

IJERPH

To understand contamination characteristics and identify sources of heavy metals in soil affected by complex mine activities, a detailed survey of soil heavy metals from different land cover types was investigated around the Xikuangshan (XKS) antimony mine in south-central China. Soil samples had average concentrations of Sb, As, Cd, Cr, Hg, Pb, Cu, Zn and Ni exceeding their background level in the Hunan province. Sb, As and Cd were the main pollutants. A total of 86.8% of samples were severely polluted, characterized by the Nemerow’s comprehensive index, and 68.4% of samples were of very high potential ecological risk, primarily contributed by Sb, Cd and Hg. Among different land cover patterns, Hg, Pb and Cd concentrations showed a statistically significant difference. The application of Pearson correlation, principal component analysis (PCA) and hierarchical cluster analysis (HCA) combined with spatial interpolation GIS mapping revealed that Ni, Cr and Cu were mainly from natural parent materials, whereas other heavy metals were related to anthropogenic sources. Pb, As and Hg were mainly derived from smelting processes of sulfide minerals in the XKS area. The agricultural practice is the main factor for the accumulation of Cd and Zn, and sphalerite smelting also contributed to high Zn concentrations. Particularly, spatial variation of soil Sb concentrations was affected by multiple factors of complex antimony mine activities related to mining, beneficiation and smelting in the XKS area. These results are useful for the prevention and reduction of heavy metal contamination in soils by various effective measures in typical regions affected by antimony mine activities.

Section: Spatial Distribution Of Heavy Metal Concentrationsmentioning

confidence: 98%

Heavy Metals in Soil around a Typical Antimony Mine Area of China: Pollution Characteristics, Land Cover Influence and Source Identification

Tang

et al. 2023

IJERPH

Effect of Thermal Activation Temperature of Nanoscale Phosphate and Silicate on the Morphological Transformation Characteristics of Cd in Heavy Metal Contaminated Soils

Zou

2023

Agronomy

Purpose. The problem of heavy metal Cd pollution in the soil is still very serious. The widely used treatment measure is in situ passivation chemical remediation technology. Some studies have shown that the single application of phosphate or silicate can control soil cadmium pollution, but few studies have been conducted on the effect of the thermal activation temperature of nano phosphate and silicate-combined application on the transformation of Cd form in the soil. Materials and methods. Cadmium-contaminated soil was indoor-simulated, after which the 2.0% soil-weight dose of potassium dihydrogen phosphate was mixed with thermal activation nano serpentine or nano zeolite (potassium dihydrogen phosphate: thermal activation nano serpentine or nano zeolite = 1:2) at different temperatures (0, 350, 550, 700, 850 °C) and compared with the simulated cadmium-contaminated soil without adding a mixture of phosphate and silicate; cadmium content in soil was determined by Tessier five-step continuous extraction method after incubating for 0, 7, 14, 28, and 56 d in jars in the constant-temperature box. Results and discussion. Thermal activation temperature of nano phosphate and silicate could reduce the amount of exchangeable Cd content in the soil to a different degree; the content of Cd in carbonate-bound form, Fe–Mn–oxide-bound form, organically-bound form, and residual form increased. The order of effect of nanoscale potassium dihydrogen phosphate and serpentine or zeolite thermal activation temperature on remediation of Cd contaminated soil is nPS700-2.0 > nPS550-2.0 > nPS850-2.0 > nPS350-2.0 > nPS0-2.0, nPF700-2.0 > nPF550-2.0 > nPF850-2.0 > nPF350-2.0 > nPF0-2.0 (n, P, S, and F represent nanometer, KH2PO4, serpentine, and zeolite, respectively; 0, 350, 550, 700, and 850 represent different activation temperatures T); 700 °C treatments performed better than other thermal activation temperature treatments, and nPS700-2.0 was better than nPF700-2.0. Conclusion. Thermal activation temperature of nano phosphate and silicate-combined application can stabilize heavy metal Cd to some extent and promote the transition of Cd from a bioavailable state to a biounavailable state. The results showed that the combined application of thermal activation temperature of nano phosphate and silicate has a certain potential to control soil cadmium pollution.

Effects of Phosphate and Silicate Combined Application on Cadmium Form Changes in Heavy Metal Contaminated Soil

Zou

Liu³

2023

Sustainability

Pollution by heavy metal cadmium (Cd) in soil is still serious and control measures are constantly updated. In this paper, one indoor culture method was applied to investigate the effect of phosphate and thermo-activated nano silicate combined application on soil cadmium (Cd) speciation transformation. A total of 7 treatments were designed, which were: simulated cadmium-contaminated soil without phosphate and silicate recorded as the reference (CK) treatment; mixtures of 0.5%, 1.0%, and 2.0% soil heavy dose of potassium dihydrogen phosphate and 700 °C thermo-activated nano serpentine (potassium dihydrogen phosphate: thermo-activated nano serpentine ratio = 1:2) added to simulated cadmium-contaminated soil, denoted as nPS700-0.5, nPS700-1.0, and nPS700-2.0, respectively; and 0.5%, 1.0%, and 2.0% soil heavy dose of potassium dihydrogen phosphate and 700 °C thermo-activated nano zeolite mixture (potassium dihydrogen phosphate: thermo-activated nano zeolite ratio = 1:2) added to simulated cadmium-contaminated soil, denoted as nPF700-0.5, nPF700-1.0, and nPF700-2.0, respectively. The results showed that the combined application of potassium dihydrogen phosphate with thermo-activated nano serpentine or potassium dihydrogen phosphate with thermo-activated nano zeolite reduced the soil exchangeable Cd content to varying degrees and increased levels of carbonate-bound, Fe-Mn oxide-bound, organic-bound, and residual Cd forms to different degrees. In combined application of phosphate and thermo-activated nano silicate, the higher the dosage level, the greater the reduction of exchangeable Cd content and the better the effect on Cd-contaminated soil remediation: nPS700-2.0 > nPS700-1.0 > nPS700-0.5, nPF700-2.0 > nPF700-1.0 > nPF700-0.5 (N, P, S, and F represent nano, KH2PO4, serpentine, and zeolite, respectively, and 700 represents the activation temperature). At the same dosage level, the combined application of potassium dihydrogen phosphate and thermo-activated nano serpentine was more effective than that of potassium dihydrogen phosphate and thermo-activated nano zeolite in repairing Cd-contaminated soil (nPS700-2.0 > nPF700-2.0, nPS700-1.0 > nPF700-1.0, nPS700-0.5 > nPF700-0.5), which indicated that the combination of phosphate and thermo-activated nano silicate can passivate heavy metal cadmium (Cd) to a certain extent and promote the transformation of bioavailable Cd into an unusable state. The reason why potassium dihydrogen phosphate, zeolite, and serpentine can absorb heavy metal cadmium after entering the soil is because the silicate mineral itself can directly absorb cadmium. Second, after nano treatment and thermal activation, the specific surface areas and pores of the minerals increase, which enhances the adsorption performance. Third, because the pH value of the mineral itself is high, the pH value of the soil environment will rise, thereby transforming H2PO4− into PO43−, which is conducive to the adsorption of Cd2+.