Extensive production and evolution of free radicals during composting

The production of free radicals has been widely documented in natural systems, where they play an important role in most organic matter and contaminants transformation. Here, the production and evolution of free radicals were systematically investigated during composting. Results indicated that multiple reactive oxygen species and environmentally persistent free radicals (G-factor 2.003-2.004) were generated with dynamic changes during composting. The center dot OH yield fluctuated significantly with a maximum content of 365.7-1,262.3 mu mol/kg at the thermophilic phase of composting, which was closely correlated with the changes of Fe (II) (Pearson's r = 0.928-0.932) and the electron-donating capacity of humus (Pearson's r = 0.958-0.896) during composting. Further investigation suggested that microorganisms driven iron/humus redox conversion could contribute to the production and dynamic changes of free radical during composting. These findings highlight the abiotic processes involving free radicals, and provide a new perspective for humification and contaminants removal during composting.

Automated summary

This study systematically investigated the production and evolution of free radicals during composting, revealing a high content of hydroxyl radicals at the thermophilic phase, which was closely related to the changes in Fe(II) and humus. Microorganisms driven iron/humus redox conversion were found to contribute to the production and dynamic changes of free radicals during composting.