Transient electromagnetic pulse (TEMP) modified biochar mitigate greenhouse gas emissions from a subtropical...

Enhancing biochar's surface properties through physical modification offers a promising avenue for optimizing its carbon sequestration potential. Therefore, it is essential to clarify the effects of modified biochar on soil carbon dioxide (CO₂), as well as methane (CH₄) and nitrous oxide (N₂O) emissions. Transient electromagnetic pulse (TEMP) modification, as a physical modification approach, circumvents the secondary pollution risks associated with traditional chemical modification and holds potential as an innovative strategy for soil carbon sequestration. However, the impact of TEMP-modified biochar on CO₂, CH₄, and N₂O emissions remains unclear. This study investigated the effects of TEMP-modified biochar, characterized by different particle sizes, on CO₂, CH₄, and N₂O emissions in subtropical grassland soils. Results demonstrated that TEMP modification increased biochar's specific surface area and enhanced its pore structure, while decreasing the proportion of C-O-C functional groups in biochar. Notably, TEMP-modified biochar with a particle size of 0.5-1 mm exhibited the strongest inhibitory effect, reducing CO₂, CH₄, and N₂O emissions by 7.47 %, 83.44 %, and 25.27 %, respectively, compared to unmodified biochar. By contrast, TEMP-modified biochar with particle sizes of <0.154 mm and 1-2 mm did not significantly affect these emissions. Multiple regression and structural equation modeling were employed to quantify the pathways through which modified biochar influences CO₂, CH₄, and N₂O emissions. We found that the physical protection effect of TEMP-modified biochar suppresses CO₂ emissions. The enhanced porosity of modified biochar promotes its adsorption capacity for CH₄ and N₂O. Additionally, TEMP-modified biochar increased the content of dissolved organic carbon and available phosphorus, which, in turn, inhibit denitrifying microbes, thereby reducing N₂O emissions. These findings suggest that TEMP technology enhances carbon sequestration in grassland soils by stabilizing biochar and reducing CO₂, CH₄, and N₂O emissions.