Modeling sediment diagenesis processes on riverbed to better quantify aquatic carbon fluxes and stocks in a small watershed of the Mid-Atlantic region

Abstract

Background Despite the widely recognized importance of aquatic processes for bridging gaps in the global carbon cycle, there is still a lack of understanding of the role of riverbed processes for carbon flows and stocks in aquatic environments. Here, we added a sediment diagenesis and sediment carbon (C) resuspension module into the SWAT-C model and tested it for simulating both particulate organic C (POC) and dissolved organic C (DOC) fluxes using 4 years of monthly observations (2014–2017) in the Tuckahoe watershed (TW) in the U.S. Mid-Atlantic region. Results Sensitivity analyses show that parameters that regulate POC deposition in river networks are more sensitive than those that determine C resuspension from sediments. Further analyses indicate that allochthonous contributions to POC and DOC are about 36.6 and 46 kgC ha −1 year −1 , respectively, while autochthonous contributions are less than 0.72 kgC ha −1 year −1 for both POC and DOC (less than 2% of allochthonous sources). The net deposition of POC on the riverbed (i.e., 11.4 kgC ha −1 year −1 ) retained ca. 31% of terrestrial inputs of POC. In addition, average annual buried C was 0.34 kgC ha −1 year −1 , accounting for only 1% of terrestrial POC inputs or 3% of net POC deposition. The results indicate that about 79% of deposited organic C was converted to inorganic C (CH 4 and CO 2 ) in the sediment and eventually released into the overlying water column. Conclusion This study serves as an exploratory study on estimation of C fluxes from terrestrial to aquatic environments at the watershed scale. We demonstrated capabilities of the SWAT-C model to simulate C cycling from uplands to riverine ecosystems and estimated C sinks and sources in aquatic environments. Overall, the results highlight the importance of including carbon cycle dynamics within the riverbed in order to accurately estimate aquatic carbon fluxes and stocks. The new capabilities of SWAT-C are expected to serve as a useful tool to account for those processes in watershed C balance assessment.

A review of carbon monitoring in wet carbon systems using remote sensing

“…Watershed models that explicitly integrate terrestrial and aquatic carbon cycling processes are being developed to quantify the burial of particulate organic carbon (OC) in rivers. For example, Qi et al [476,477] incorporated OC deposition, resuspension, and diagenesis processes in the soil and water assessment tool and showed that a significant fraction of terrestrially originated POC is deposited on the bed of small streams and further decomposes into CO 2 and CH 4 . These results indicate that the inclusion of C burial in rivers and streams would improve the accounting of global C burial in inland waters.…”

Pronounced Increases in Future Soil Erosion and Sediment Deposition as Influenced by Freeze–Thaw Cycles in the Upper Mississippi River Basin

“…For example, the Soil and Water Assessment Tool (SWAT) is being used within the USDA Conservation Effects Assessment Project (CEAP) and EPA Hydrologic And Water Quality Modeling System (HAWQS) to support national scale conservation and water quality studies and policymaking. The SWAT model has been continuously modified to adapt to new socioeconomic and environmental conditions by adding improved physical/chemical functions and considering more diverse management practices. − Numerous examples of SWAT modifications and applications can be found at: . For example, the standard SWAT used a simple regression method to estimate soil temperature and FTCs as a function of air temperature, soil depth, and soil cover (both residue and snow), in which phase changes of soil water and snow insulation effects are not well addressed. ,, Such a simple FTC representation exhibited large biases in reproducing soil temperatures observed at sites of the U.S.…”

Utility of Remotely Sensed Evapotranspiration Products to Assess an Improved Model Structure

“…A hydrologic model coupled with a module that represents the fate and transport of carbon was found to effectively capture dissolved and particulate organic carbon loads [25]. A recent study further improved the carbon cycling within in-streams to better predict carbon fluxes [26]. A model coupled with a water temperature module showed improved predictions of water quality variables affected by water temperature [27].…”