Award: OCE-1559274

Tidal salt marsh ecosystems are common and act as an efficient processing system for river-borne and nearshore inventories of terrestrial particulate and dissolved chemicals. The process that we are investigating in these systems is very much like the sand filter you might have in your swimming pool or the filter that your municipality uses to filter particulates and dissolved chemicals out of river or lake water before turning it into drinking water. In those systems, a pump pushes water through sand particles and bacteria in the sand react with some of the chemicals in the water and the surface of the sand service as a trap for particulates. In this case the marsh sediments made up of sand, mud, plant roots and crab burrows operates as the filter system and the pump is the diurnal tides pushing water in and out of the marsh system. This process was investigated using a naturally occurring radionuclide that occurs on the sediment surfaces. The radionuclide is thorium 228 and when it decays, it forms a soluble daughter, radium 224. We can measure how fast the daughter is washed through the filter System as the difference between the inventory of the parent radionuclide and the daughter radium 224 that remains in the sediments. This can tell us how much water passes through this natural filter system. In our study, we found that a volume of water nearly equivalent to the entire annual river flow in SC was processed in our coastal marsh system. With this new approach, we can determine how effective this filter system in other regions, on a per area basis, to evaluate the value of salt march ecosystems as a water treatment processing plant for contaminants and nutrients in coastal and river waters. Last Modified: 02/24/2021 Submitted by: Timothy J Shaw