Iron and manganese transformation in Louisiana salt and brackish marsh sediment

The kinetics of the release of dissolved iron [Fe(II)], manganese [Mn(II)], and phosphate in salt and brackish marsh sediment and the exchange with th e overlying water column were investigated. Sediment was incubated in labor atory microcosms and in sediment water columns in studying these exchanges. The rate constants of the dissolved Fe(II), Mn(II), and phosphate release in sediment suspensions were 2.02-2.28, 0.08-0.117, and 4.18-5.38 mu mol g( -1) dry sediment d(-1), respectively. In sediment-water column studies, the rate constants (K) of dissolved Fe(II), Mn(II), and phosphate removal from the overlying water into the sediment were 0.755-0.989, 0.0695-0.0949, and 0.315-0.448, day(-1), respectively. The flux of dissolved Fe(II), Mn(II), and phosphates fi om the salt and brackish marsh sediment to the overlying water in the column studies were 2.56-4.93, 1.05-1.689, and 208.6-428.9 mg m(-2) d(-1), respectively. The fluxes from salt marsh were slightly greater than those measured in brackish marsh, although these differences were not statistically significant.