Gypsic soils in the Brazilian Semiarid

Abstract

Globally, soils with gypsic horizons cover approximately 1 million km², predominantly in arid climates. The formation of pedogenic gypsum in soils has been a topic of discussion in pedological studies for some time, with gypsification representing the process responsible for secondary gypsum accumulation. Even though international classification systems acknowledge the existence of gypsic horizons, there is a paucity of documented evidence concerning their occurrence in Brazilian soils. This study aimed to identify and describe a soil with secondary gypsum accumulation in the Brazilian semiarid region, employing the established criteria for in situ identification and classification. The study was conducted on a soil profile in the semiarid region of Pernambuco State, Brazil, that is undergoing salinization. Morphological descriptions of gypsum precipitates and chemical and mineralogical analysis were evaluated for their suitability for characterizing the material. Turbidimetric methods are more suitable for gypsum determination in hypersaline soils, while thermogravimetric analysis is the most accurate method for its mineralogical identification. This study establishes the first national record of gypsification in Brazilian soils and underscores the necessity of incorporating gypsum presence criteria into the Brazilian Soil Classification System (SiBCS) for effective soil management and environmental conservation.