Effects of Soil Amendments on Heavy Metal Immobilization and Accumulation by Maize Grown in a Multiple-Metal-Contaminated Soil and Their Potential for Safe Crop Production

Abstract

Soil amendments have been proposed for immobilizing metallic contaminants, thus reducing their uptake by plants. For the safe production of crops in contaminated soil, there is a need to select suitable amendments that can mitigate heavy metal uptake and enhance crop yield. The present experiment compared the effects of three amendments, hydroxyapatite (HAP), organic manure (OM), and biochar (BC), on plant growth and heavy metal accumulation by maize in an acidic soil contaminated with Cd, Pb, and Zn, and their potential for safe crop production. Toxicity characteristic leaching procedure (TCLP) tests, energy dispersive X-ray spectroscopy (EDS) analysis, and X-ray diffraction (XRD) analysis were used to evaluate the effectiveness and mechanisms of heavy metal immobilization by the amendments. The results showed that shoot and root biomass was significantly increased by HAP and 1% OM, with an order of 1% HAP > 0.1% HAP > 1% OM, but not changed by 0.1% OM and BC (0.1% and 1%). HAP significantly decreased Cd, Pb, and Zn concentrations in both shoots and roots, and the effects were more pronounced at the higher doses. OM decreased the shoot Cd and Pb concentrations and root Zn concentrations, but only 1% OM decreased the shoot Zn and root Pb concentrations. BC decreased the shoot Cd and Pb concentrations, but decreased the shoot Zn and root Pb concentrations only at 1%. HAP decreased the translocation factors (TFs) of Cd, Pb, and Zn (except at the 0.1% dose). OM and BC decreased the TFs of Cd and Zn, respectively, at the 1% dose but showed no significant effects in other cases. Overall, plant P, K, Fe, and Cu nutrition was improved by HAP and 1% OM, but not by 0.1 OM and BC. Soil pH was significantly increased by HAP, 1% OM, and 1% BC, following an order of 1% HAP > 1% OM > 0.1% HAP > 1% BC. The TCLP levels for Cd, Pb, and Zn were significantly reduced by HAP, which can be partly attributed to its liming effects and the formation of sparingly soluble Cd-, Pb-, and Zn-P-containing minerals in the HAP-amended soils. To some extent, all the amendments positively influenced plant and soil traits, but HAP was the optimal one for stabilizing heavy metals, reducing heavy metal uptake, and promoting plant growth in the contaminated soil, suggesting its potential for safe crop production.

Assessment of Heavy Metal Accumulation in Soil and Garlic Influenced by Waste-Derived Organic Amendments

“…Results obtained regarding decreased heavy metal concentration due to organic fertilizers application are also in accordance with [ 4 ]. Our results are also corroborated by an earlier study [ 32 ] that reported immobilization of heavy metals with the application of organic manure. The permissible maximum limits reported by [ 24 ] of the trace metals is Cd 3, Co 65, Cr 100, Cu 50, Pb 300, Fe 21000, Mn 2000, and Zn 200 mg kg −1 deposited in soil.…”

Una alta diversidad de hongos micorrízicos arbusculares influye en la absorción de cadmio y crecimiento vegetal del cacao

“…La influencia de los HMA en la absorción de metales de las plantas varía según las concentraciones de éstos (Zhang et al, 2015). Se pudo comprobar que los hongos micorrízicos redujeron la acumulación de Cd en los tallos de plantas de cacao, presumiblemente mediante el aumento de la retención del metal dentro de las raíces (Wang et al, 2020). Figura 6.…”

Contribution of Nano-Zero-Valent Iron and Arbuscular Mycorrhizal Fungi to Phytoremediation of Heavy Metal-Contaminated Soil

“…The soil was sampled from the surface layer (0–20 cm) of an abandoned paddy field contaminated with Cd, Pb and Zn, which was described in our recent study [ 21 ]. The soil was passed through a 2 mm sieve and sterilized at 121 °C for 2 h and then air-dried for plant culture.…”