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

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.