Dissolved organic carbon sorption dynamics in tidal marsh soils

Abstract

Coastal wetlands are significant sources of dissolved organic carbon (DOC) to adjacent waters and, consequently, exert a strong influence on the quantity and quality of DOC exported to the coastal oceans. Our understanding of the factors that control the exchange of DOC at the tidal marsh-estuarine interface, however, remains limited. We hypothesize that tidal marsh soils act as a regulator and that their physical characteristics, such as organic carbon content and mineral phase composition, are key controls on DOC exchange between soil surfaces and both surface and interstitial waters. To test this hypothesis, we generated traditional Langmuir sorption isotherms using anaerobic batch incubations of four tidal wetland soils, representing a range of soil organic carbon content (1.77% ± 0.12% to 36.2% ± 2.2%) and salinity regimes (freshwater to mixoeuhaline), across four salinity treatments. Results suggest that the maximum soil sorption capacity and DOC binding affinity increase and decrease with greater salinity, respectively, though the enhancement of maximum soil sorption capacity is somewhat mitigated in soils richer in poorly crystalline iron minerals. Initial natively sorbed organic carbon showed a significant positive correlation with soil specific surface area and K showed a moderate yet significant positive correlation with poorly crystalline iron mineral content. Taken together, these results point to a strong mineralogical control on tidal marsh sorption dynamics and a complex physicochemical response of those dynamics to salinity in tidal marsh soils.

Photochemical and Microbial Degradation of Chromophoric Dissolved Organic Matter Exported From Tidal Marshes

“…In the winter, Jug Bay had much lower CDOM absorption and fluorescence (expressed by a CDOM 300 and C1) compared to the other marshes. This is likely the result of the lack of emergent vegetation at Jug Bay during the winter and a smaller peat reserve and greater mineral content compared to the other marshes (Pinsonneault et al., 2020; Swarth et al., 2013). In addition, the observed high contributions of marine‐humic‐like and protein‐like CDOM fluorescence components at Jug Bay compared to the other marshes indicates a greater contribution of microbial CDOM and could be representative of the influence of wastewater treatment effluent at this site, given that the marine humic‐like component has been shown to be higher in sewage and wastewater (Guo et al., 2010).…”

Developing a Redox Network for Coastal Saltmarsh Systems in the PFLOTRAN Reaction Model

“…Measurements of porewater sulfate, hydrogen sulfide, methane, dissolved inorganic carbon (DIC), ammonium, pH, and salinity made seasonally at depths of 20, 40, and 80 cm in C3 wetlands were used for model calibration. GCReW soils are typically >80% organic content (Noyce & Megonigal, 2021) with sand, silt, and clay contents of 31.6 ± 9.8%, 60.4 ± 7.6%, and 8.1 ± 2.4% (Pinsonneault et al., 2020) Temperatures are typically between 0.3°C and 8.1°C (32.6°F–45.6°F) in the winter to 21.3°C–28.6°C (70.4°F–83.5°F) in the summer (National Weather Service, 2023). For more information on GCReW or to access available data, please refer to the Smithsonian Environmental Research Center's website: https://serc.si.edu/gcrew.…”

Effects of Added Humic Substances and Nutrients on Photochemical Degradation of Dissolved Organic Matter in a Mesocosm Amendment Experiment in the Gulf of Finland, Baltic Sea

“…Lauerwald et al (25) estimated that at least 25% of tDOM is removed before reaching the coast. The remaining tDOM fractions could be transformed in estuaries or coastal oceans (11,23,26,27), through biotic (28)(29)(30)(31)(32) and abiotic processes such as flocculation (33,34), sorption (35) and photodegradation (31,32,(36)(37)(38)(39)(40).…”