The effects of remediation under different substrate conditions and environmental behavior of heavy metals

This study analyzed changes in physicochemical properties of the soil under various substrate conditions, as well as the interactions between ryegrass and heavy metals. Results indicated that biochar significantly improved soil physicochemical properties, such as an increase in electrical conductivity by 34.8%, enhancement of pH from 7.13 to 7.32, and augmentation in organic matter by 152%. Moreover, readily available phosphorus and alkali-hydrolyzable nitrogen increased by 237% and 122% respectively, while soil cation exchange capacity rose by 135%. This contributes to plant growth and the maintenance of soil fertility. The biochar addition also led to a decrease in the proportion of fine soil particles by 20%, significantly enhancing structure and stability of soil aggregates and promoting the formation of larger aggregates, crucial for improving soil aeration, water retention, and root permeability. The addition of biochar notably altered the chemical forms of heavy metals in soil, promoting their transformation from bioavailable forms to more stable and less toxic forms, effectively reducing the bioavailability and mobility of heavy metals, and decreasing their environmental toxicity. The addition of biochar, by changing the chemical forms of heavy metals, not only enhanced germination rate of ryegrass seeds but also improved the overall growth state of ryegrass.