Effects of Exogenous Phosphorus on Cadmium Bioavailability and Greenhouse Gas Emissions in Mangrove Sediments

Mangrove ecosystems,critical intertidal zones between terrestrial and marine environments,are increasingly affected by pollutants (e.g.,cadmium,Cd) and nutrient inputs (e.g.,phosphorus,P) from industrialization and human activities.This study investigated the effects of exogenous phosphorus on cadmium bioavailability,organic carbon pools,and greenhouse gas emissions in Cd-contaminated mangrove sediments through controlled incubation experiments with varying P concentrations (0mg/L,5mg/L,10mg/L).Results demonstrated that phosphorus input significantly reduced Cd bioavailability in sediments.At 10mg/L P input,exchangeable Cd concentration decreased by 25.85%,attributed to Cd adsorption and precipitation induced by phosphorus.Concurrently,CO₂ emissions increased by 32.98% and 57.22%,while N₂O fluxes increased by 47.42% and 25.68% under 5mg/L and 10mg/L P treatments,respectively,though CH₄ emissions remained unaffected.The underlying mechanism involves phosphorus stimulation of microbial activity,which enhances respiratory processes and nitrification-denitrification,thereby elevating greenhouse gas emissions.Additionally,phosphorus inputs increased microbial biomass carbon and dissolved organic carbon concentrations,indicating activation of organic carbon pools.This study provides scientific insights for balancing pollution remediation and greenhouse gas mitigation in mangrove wetland management,emphasizing the necessity of regulating both heavy metal contamination and phosphorus levels to sustain ecosystem functions.