Elucidating the Effects of Biochar on Eco-Toxicity of Lead and Microplastic in a Soil-Plant System

Abstract

Microplastics are a growing concern in both aquatic and terrestrial environments, with multiple sources contributing to contamination of soils. These sources include primary microplastics, such as synthetic materials, and the breakdown of larger plastic particles into secondary microplastics. Microplastics can have both positive and negative impacts on soil properties. They can act as vectors for contaminant transfer in terrestrial environments, interacting with various contaminants including pesticides, heavy metals, and antibiotics. This contamination can result in potential health risks for humans and other organisms, as microplastics and their associated chemicals can accumulate across multiple trophic levels. Although several studies have examined microplastic contamination in marine environment, their transport, sources, fate, however, their effects in terrestrial environments remain largely unexplored. Addressing these issues in contaminated agricultural soil through effective remediation technologies is essential for ensuring sustainable crop production and food security. Biochar, a carbonaceous soil amendment, holds great promise in improving crop growth by modifying soil conditions due to its unique physicochemical properties. Biochar has a high cation exchange capacity and rich pore structure with abundant oxygen-containing functional groups and has a large surface area. Therefore, this study investigates the impact of biochar on wheat (botanical name) growth and physiology in a heavy metal and microplastic (MP) contaminated agricultural soil. An experiment on plant growth was carried out in a controlled glasshouse environment, introducing biochar at a concentration of (0, 0.5% (w/w)) into agricultural soil contaminated with Lead (Pb) (200 ppm, 300 ppm) and Polyvinylchloride (PVC-MP, 0, 0.25%, and 0.5% (w/w)). The presence of pollutants (Pb and PVC-MP) does not only reduce wheat crop growth but also overall dry matter yield. Although shoot length was increased compared to roots, but the overall plant dry weight was decreased. Biochar amendment improved the photosynthetic and antioxidant activity of wheat plants exposed to lead and PVC-MP stress. Biochar with PVC-MP reduced the uptake of heavy metals in plants. The findings of this study provide valuable insights into the potential of biochar as a soil remediation strategy for mitigating the adverse effects of heavy metals and microplastics.