Chemical Speciation and Dissolved Iron in the Pore Water of Patos Lagoon Sediments - Brazil

Sediments can sink or deliver elements to water column. Iron is considered an essentialelement for the development of cyanobacteria and a limitant to phytoplankton growth.Studies on the chemical speciation of iron in seawater have been conducted, but there isno information about its chemical speciation in pore water, as reported here. This paperpresents a voltammetric method to analyze dissolved iron and its chemical speciation insediment pore water, using adsorptive cathodic stripping voltammetry (AdCSV) and thetechnique of competitive ligand exchange (CLE-AdCSV), respectively. The limit ofdetection (LOD = 0.30 10−6 mol L−1), the quantification (LOQ = 0.90×10−6 mol L−1),precision (RSD = 4.9%) and accuracy (98%), were calculated from experiments usingcertified reference material SLRS-4 (National Research Council Canada). The chemicalspeciation of pore water from sediment samples collected during April 2009, in thePatos Lagoon Estuary (RS, Brazil), was analyzed for the first time, revealing that theratio (labile iron to dissolved iron) is significantly lower in pore water extracted fromsediments of the upper layer (0 to −5 cm), than from the overlaying water or of the porewater extracted from sediments of the lower layer (−15 to −20 cm)