Salt marsh sediment and metal fluxes in response to rainfall
2012
Chen, Si | Torres, Raymond | Bizimis, Michael | Wirth, Edward F.
Lay AbstractWe hypothesize that rainfall during low tide is an important process that affects the cycling of materials (nutrients and metals) in estuaries. We simulated a 45-min rainfall event in a salt marsh to examine the effects of a low-tide summer storm on the sediment surface. Surface runoff (sediment concentration (SC), discharge, and rainfall rate) at the downslope end of a 1- 2-m plot was collected and analyzed chemically in the laboratory. SC peaked at 6100 mg L–1 after 3 min and remained elevated for 15 min before declining. The metal content of the sediments varied considerably with time but was consistently higher than the average background content by a factor of 4–4000. Based on these experimental results, we estimated that 4.8–8.4 tonnes of sediment per square kilometer per minute can be entrained by rainfall during low tide, or up to 96–168 tonnes per year. We also estimated the annual loading of heavy metals that occurs in larger subtidal channels fed by intertidal creeks draining the salt marsh in response to rainfall. Our results demonstrate that rainfall-entrained sediment during low tides is an important process affecting the cycling of materials in estuarine ecosystems.
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