Biochar blended humate and vermicompost enhanced immobilization of heavy metals, improved wheat productivity, and minimized human health risks in different contaminated environments

Abstract

Application of biochar blended humate (BBH) might be considered as a promising material for potential toxic elements (PTEs) immobilization and improvement in crop yield but has not yet been studied. For this purpose, different soil amendments such as vermicompost (VC), biochar (BI), BBH and zeolite (Z) were applied to different soil types in various depositional environments include lacustrine (LA), fluvial (FL), and marine (M). The aim was to explore the potential impact of such amendments on the immobilization of Cd, Ni and Pb, metal transfer, and the consequent risk to human health, as well as improve wheat growth, yield and quality in different contaminated environments. Application of amendments, particularly BBH and VC significantly decreased the mobile fraction of tested heavy metals in all depositional environments. Consequently, application of BBH decreased the content of tested metals in wheat grains by 36.2%, 26.6% and 16.7% respectively compared to control averaged over three soil types. The highest reduction in human health risk index (HRI) was achieved when soil treated with VC followed by BBH compared to other amendments. The HRI decreased by 23.2%, 22.2%, and 25.7% in fluvial, lacustrine, and marine respectively in response to application of VC compared to untreated soil. Furthermore, application of VC and BBH improved wheat growth, yield and quality in the studied soils. Despite its complexity in production, the use of a synthesized Z in heavy metal immobilization is not recommended. In conclusion, the novel material (BBH) showed a significant immobilization of tested PTEs, and VC achieved higher yields of wheat and lower HRI, confirming the importance of both materials as promising low-cost and environmentally friendly amendments for PTEs immobilization, producing higher yields of good quality and decreasing human health risks.