Distribuição de manganês, ferro, matéria orgânica e fosfato nos sedimentos do manguezal do Rio Piranji, Ceará

Abstract

The determination of background values of the concentration and distribution of iron, phosphate, organic matter (MO) and manganese are of fundamental importance for the understanding and management of any region’s environment. The mangrove forests in Ceará State, Brazil have been studied to a small extent, thus the purpose of this work is to determine the content and vertical distribution of Fe, Mn, PO4 3- and organic matter in the sediments of the Piranji River’s mangrove forest, as well any relation with sediment granulometry, based on five cores surveys which resulted in 74 samples. The samples were digested using HF+ HCl+HNO3 (6:3:1) under pressure, at 150º C, and organic matter was analyzed for it humid via. The concentration ranged varied as follows: OM (ND – 4.65%); Fe (0.37 - 5.03%); PO4 3- (13.0 - 478 µg.g1 ) and Mn (14.8 - 480 µg.g-1). A strong association was found to exist between the analyzed elements and fine-grain sediments (silt and clay). Further, their import into the mangrove forest by means of the tidal movement was highlighted by the high concentrations of those elements in the sampled areas where the flooding frequency is higher.