Caracterização de gleissolos com e sem tiomorfismo da região litorânea do estado de Pernambuco

Abstract

The floodplain soils of Pernambuco state - Brazil have been widely used to agriculture and their improperly management has promoted, in those with sulphidric materials, the sulfurization process, generating acidity in the soil, and release of heavy metals such iron. The aim of this study was to characterize Gleysol in areas of coastal wetlands along the shoreline of Pernambuco state cultivated with sugar cane, trying to understand genesis and occurrence of acid sulphate soils. Thus, we studied three floodplain soils along the shoreline of Pernambuco: floodplain soil in Goiana river (profile 1), floodplain soils in Sirinhaém river (profiles 2, 3 and 4) and floodplain soils in Ipojuca river (profiles 5, 6 and 7). Were realized a morphological characterization of soils, chemical analyzes for the purpose of soil classification, sequential extraction and total content of iron, and mineralogical analysis using XRD. Was observed predominance of the clay fraction in all profiles, which is consistent with the depositional environment in waters with low kinetic energy. The profiles 2, 3 and 4 showed extremely acidic reaction, with pH values below 2.5, indicating the presence of sulfuric horizon. The presence of sulphidric materials in the profiles 2, 3 and 4, confirmed the presence of sulfuric horizon. The sulfuric horizons in the profiles 2, 3 and 4 had high EC values between 9 and 21 dS m-1, being consistent with the high concentrations of sulphate generated by sulfurization process. The higher levels of iron were found associated with forms of poorly crystalline oxyhydroxides, values between 0.03 and 1.56 mmol kg-1. The assembly mineralogical soil had become very influenced by the geology of the basin of the rivers that bathe the floodplains. In the clay fraction were identified illite, kaolinite, goethite and smectite (beidellite/montmorillonite and nontronite), the silt fraction were: Illite, kaolinite, quartz and feldspar, in the sand fraction were: quartz, feldspar, mica and kaolinite. The floodplain soils showed morphological, physical, chemical and mineralogical related to the origin of the sediments and their position in the landscape. The occurrence of acid sulphate soils was detected only in the floodplain of Sirinhaem river.