Mitigation effects of solar-driven metalloporphyrins on CO2 and N2O emissions from an agricultural soil.

Developing green technologies to mitigate soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions is critical for sustainable agriculture. Here, we investigated the effects of two water-soluble metalloporphyrins (FeTPPS and MnTPPS), with and without glucose addition, on CO2 and N2O emissions and the associated mechanisms in an agricultural soil under natural solar irradiation. Metalloporphyrin effects depended on metal identity and labile carbon (C) availability. FeTPPS alone significantly reduced cumulative CO2 emissions by 9.9%, and FeTPPS with glucose reduced emissions by 7.2% relative to the glucose treatment. These effects were accompanied by redistribution of organic C into < 250 μm aggregates, suppressed cellulase activity, and decreased humic-like DOM components, suggesting altered organic C accessibility and aggregate-associated C distribution. However, FeTPPS did not significantly alter cumulative N2O emissions. MnTPPS exhibited a biphasic effect on CO2 flux, but still significantly reduced cumulative CO2 emissions by 13.3%, consistent with increased abundances of cbbL/cbbM. MnTPPS also significantly reduced cumulative N2O emissions by 63.3%, despite increased urease activity and abundances of nitrification-related genes, and this reduction coincided with increased nosZII abundance. However, glucose addition eliminated the suppressive effects of MnTPPS on CO2 and N2O emissions, recovered cellulase activity, and did not alter cbbL/cbbM abundances, indicating that labile C can override MnTPPS-induced changes in CO2 and N2O emissions. Overall, these results demonstrate that solar-driven metalloporphyrin catalysis can regulate soil CO2 and N2O emissions, and its effectiveness depends on labile C availability. These findings provide useful information for developing innovative strategies to mitigate soil CO2 and N2O emissions.