Arsenic migration and transformation, greenhouse gas dynamics, and their coupled relationships in paddy fields

Paddy fields are a critical nexus where arsenic (As) contamination and greenhouse gas (GHG) emissions pose dual environmental threats. While traditionally studied separately, these processes are biogeochemically interdependent through shared microbial communities, competing electron acceptors, and overlapping responses to agronomic practices. This review provides an integrated synthesis of As and GHG dynamics in rice paddies using a progressive three-tiered framework: from independent mechanisms, to systematic coupling, to integrated management. We first summarize the microbial drivers of As migration and transformation, along with their functional genes and key environmental regulators. We then review the microbial pathways of CO₂, CH₄, and N₂O production and consumption. Centrally, we critically synthesize the coupled interactions between As behaviors and each GHG, identify shared environmental drivers, and evaluate existing co-mitigation strategies and their trade-offs. We conclude by identifying persistent knowledge gaps-particularly the lack of mechanistic clarity on electron partitioning between As(V) reduction and methanogenesis, and the scarcity of simultaneous in-field measurements of As and GHG fluxes-and outline priority research directions for region-specific, co-beneficial management.