Use of hydroxyapatite to reduce Cd pollution in agriculture soils for Chenopodium quinoa cultivation

Cadmium is a metal distributed in low concentrations in the environment without biological function, but it can be toxic at high concentration for plants, animals, and/or humans. This element is one of the major soil pollutant, with high mobility and availability under the conditions of many agricultural soils. The use of nanoremediation techniques can be an effective solution for the in situ recovery of contaminated soils with Cd, although the existing information about the consequences of using nanoparticles in soils is still very scarce. In this context. Hydroxyapatite nanoparticles can be an effective amendment for remediation of soils. Quinoa (Chenopodium quinoa Will) is a seed-producing crop that has been cultivated in the Andes for several thousand years but with a good adaptation to different climatic conditions. Currently, quinoa is an emerging multipurpose crop in other parts of the world, due to its high nutritional potential for both human food and animal feedstock and a good alternative to cereals, leading to significant demand and, consequently, cultivation. In this study, we investigated the capacity of hydroxyapatite nanoparticles for recovering artificially contaminated soils with Cd where grown quinoa. For this, seeds of C. quinoa were sown in two different soil (Arenosol and Anthrosol) artificially contaminated with Cd²⁺ (0; 5, 25 and 50 mg kg^-1) and amended or not with 1% (w/w) of hydroxyapatite nanoparticles. The pot assay was carried out under controlled conditions and in a greenhouse for three months. Initial soils were characterized physicochemically and at the end of the assay multielemental concentrations were determined in soil (total and available fraction and plants (shoots). Germination rate, shoot height and dry biomass were measured, as well as pigments, glutathione, ascorbate and H₂O₂ contents were analysed in plant shoots in order to evaluate plant development and their physiological status. In parallel, a sequential chemical extraction was carried out to determine the Cd distribution in the different geochemical soil phases. Preliminary results indicated that hydroxyapatite nanoparticles have a high capacity to retain Cd. These nanoparticles seem to favour C. quinoa growth even with the highest concentration of Cd added. Therefore, this study will serve as a basis for further scientific research on the potential use of hydroxyapatite in agriculture soils with different characteristics and Cd problems for secure C. quinoa cultivation.

Acknowledgements

This research and postdoc contract from Arenas-Lago D. was supported by the project ED481D 2019/007 (Xunta de Galicia), and Portuguese funds through Fundação para a Ciência e Tecnologia within the scope of the project UID/AGR/04129/2020 (LEAF).