Effects of biochar on the migration and transformation of metal species in a highly acid soil contaminated with multiple metals and leached with solutions of different pH

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Soil contamination by multiple metals poses environmental risks.
• Biochar is explored for metal immobilization, but its interaction with acid rain is less understood.
• Acid rain exacerbates metal mobility in soils.

Purpose of the Study:

• To investigate the impact of biochar on metal mobility (Cu, Pb, Zn, Cd) in acidic soil under simulated acid rain.
• To assess the effectiveness of maize straw-derived biochar in mitigating metal leaching.

Main Methods:

• Column leaching study using highly acidic soil.
• Application of biochar derived from maize straw pyrolyzed at 600°C.
• Leaching with simulated acid rain to evaluate metal mobility (Cu, Pb, Zn, Cd).

Main Results:

• All tested metals (Zn, Cd, Cu, Pb) were released during leaching, with Zn showing the highest mobility.
• High acidity in acid rain increased metal leaching, especially in later stages.
• Biochar amendment significantly reduced metal leaching, immobilizing >90% Cu, 26% Zn, and 72% Pb, but not Cd.
• Biochar effectively counteracted the metal-mobilizing effect of acid rain.

Conclusions:

• Biochar application is a viable strategy to reduce soil metal mobility, particularly in acid rain-affected areas.
• The efficacy of biochar varies among different metal species.
• Further research on metal speciation is crucial for optimizing biochar use in soil remediation and phytoremediation.