Whether hurricane Katrina impacted trace metal and dioxin depositional histories in marshes of St. Louis Bay, Mississippi.

Salt marsh sediments generally undergo steady accumulation over time and thus are widely used to reconstruct the depositional histories of various anthropogenic contaminants derived from atmospheric and fluvial sources. Major hurricanes can significantly affect coastal landscapes by eroding and re-distributing sediment. Thus, each major hurricane can leave distinct signals in coastal wetland sediments. On the other hand, early-diagenetic remobilization of Fe and Mn in organic rich marsh sediment is a common phenomenon. However, remobilization of Fe and Mn across the redox boundary can induce remobilization of other trace elements and thus can disturb their depositional histories. Four short (~1m) sediment cores were collected from the fringing marshes of St. Louis Bay, Mississippi (located ~30km east of Hurricane Katrina's track) during 2010-2011 to investigate possible impacts of Hurricane Katrina (2005), and early-diagenetic remobilization of Fe and Mn, on trace metal and dioxin depositional histories in these sediments. Results from Pb, Cs, stable Cs, particulate organic carbon (POC), sediment bulk density and grain size indicate significant impact of hurricane event layers on anthropogenic stable Cs, while deposition profiles of V, Ni and Cr are impacted by Fe and Mn remobilization to a limited extent.