Assessing the magnitude and impact of seawater/pore water exchange in salt marsh systems

Submarine groundwater discharge is a hydrological process that is important to study and understand as it impacts biogeochemical processes and hydrological cycles. Particularly in coastal salt marsh systems, it is an important process to analyze as these systems serve as crucial interfaces between terrestrial and marine waters and particulates. There is evidence that these systems, typically thought to have little exchange across the interface due to impermeable sediments, could actually allow for significant flow of water and particulates at shallow depths. In order to measure and quantify this flow, a method using 224Ra as a tracer has been tested. The extensive, gas-filled root system present in salt marshes could be a significant factor in an increased water/particulate circulation. This root system could also allow for oxygen gas exchange between roots and sediment and lead to rapid redox oscillations. Metal binding onto iron oxide nanoparticles under ambient conditions was studied using centrifuge filtration and ICP-MS (inductively coupled plasma mass spectrometry) to better understand the potential transport of redox reactive species.