부산대학교 도서관

Redox processes, aqueous and solid‐phase chemistry, and pH dynamics are key drivers of subsurface biogeochemical cycling and methanogenesis in terrestrial and wetland ecosystems but are typically not included in terrestrial carbon cycle models. These omissions may introduce errors when simulating systems where redox interactions and pH fluctuations are important, such as wetlands where saturation of soils can produce anoxic conditions and coastal systems where sulfate inputs from seawater can influence biogeochemistry. Integrating cycling of redox‐sensitive elements could therefore allow models to better represent key elements of carbon cycling and greenhouse gas production. We describe a model framework that couples the Energy Exascale Earth System Model (E3SM) Land Model (ELM) with PFLOTRAN biogeochemistry, allowing geochemical processes and redox interactions to be integrated with land surface model simulations. We implemented a reaction network including aerobic decomposition, fermentation, sulfate reduction, sulfide oxidation, methanogenesis, and methanotrophy as well as pH dynamics along with iron oxide and iron sulfide mineral precipitation and dissolution. We simulated biogeochemical cycling in tidal wetlands subject to either saltwater or freshwater inputs driven by tidal hydrological dynamics. In simulations with saltwater tidal inputs, sulfate reduction led to accumulation of sulfide, higher dissolved inorganic carbon concentrations, lower dissolved organic carbon concentrations, and lower methane emissions than simulations with freshwater tidal inputs. Model simulations compared well with measured porewater concentrations and surface gas emissions from coastal wetlands in the Northeastern United States. These results demonstrate how simulating geochemical reaction networks can improve land surface model simulations of subsurface biogeochemistry and carbon cycling. Plain Language Summary: Coastal wetlands can store carbon rapidly but are difficult to represent in current models for accurate accounting of how much carbon can be trapped. This difficulty is due to the complex interactions between tides, chemical reactions, and water salinity, which strongly affect the decay of organic matter and the production of greenhouse gases. We enhanced an existing model by linking it to a powerful chemical reaction simulator such that organic matter decomposition was tightly connected to chemical reactions involving key components such as sulfur, iron, oxygen, and methane. We used this model to compute the effect of salinity on organic matter decomposition and greenhouse gas production in saline and freshwater wetlands. The model predicted much lower methane emissions from saltwater‐affected wetlands, which compared well to field measurements from coastal wetland sites in Massachusetts, USA. This model improves the accounting of carbon in wetland ecosystems and opens a broad range of possibilities for representing complex chemistry in land models. Key Points: Coastal wetlands store large amounts of carbon and are sensitive to chemical interactions driven by salinity and tidal fluctuationsWe coupled a land surface model to a reactive transport model to simulate biogeochemical cycling in saline and fresh tidal wetlandsSulfate availability in saline wetlands lowered simulated methane emissions, which compared well with site measurements [ABSTRACT FROM AUTHOR]