Impact of Nanohydroxyapatite and Its Composites on Arsenic Accumulation in the Edible Biomass of Lettuce

ABSTRACT A thorough understanding of the role of nanohydroxyapatite (nHAP) and its composites in reducing arsenic (As) toxicity is important for ensuring food safety in As‐contaminated soils. Nanohydroxyapatite composites, namely, sheep wool hydrolysate modified nanohydroxyapatite‐(nWHAP), rice husk hydrolysate modified nanohydroxyapatite‐(nRHAP) and sheep wool and rice husk hydrolysate modified nanohydroxyapatite‐(nWRHAP) were utilised to lower As concentrations in lettuce grown under alkaline, acidic soil and hydroponic conditions. Functional and structural properties of these synthesised composite materials were characterised using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy before the experiments. The experimental treatments were as follows: control, As, As + triple superphosphate (TSP, 42% P 2 O 5 ), As + HAP, As + nWHAP, As + nRHAP and As + nWRHAP. Under alkaline conditions, the As concentration in lettuce plants decreased from 82.1 mg kg −1 to below 20 mg kg −1 with P sources. In acidic soil, while the As concentration in plants increased to 68.8 mg kg −1 with TSP application from an initial 23.7 mg kg −1 , it fell below 30 mg kg −1 with the application of nHAP and its composites. In hydroponic conditions, the As concentration in plants decreased from 22.8 mg kg −1 to below 10 mg kg −1 with nWHAP and nWRHAP. The potential of nHAP and its composite materials to lower As concentrations in edible plant parts offers a promising solution to the ongoing challenge of As contamination, contributing to safer food production and environmental sustainability. Testing these materials on other plants and for different heavy metals would be beneficial for food safety.