Seasonally inundated areas (SIA) within aquatic systems are characterized by elevated methylmercury (MeHg) production. Nevertheless, the response characteristics of dissolved organic matter (DOM) quality in SIA sediments, including its molecular compositions and structure, and their impacts on the MeHg production are not yet fully understood. This research gap has been addressed through field investigations and microcosm experiments conducted in a metal-polluted plateau wetland. The results revealed that DOM