The origin of gley colors in hydromorphic vertisols: the study case of the coastal plain of the Río de la Plata estuary

COMERIO, MARCOS; LOFFLER, JULIA; MONTES, LUCIANA; MERCADER, ROBETO; GÓMEZ SAMUS, MAURO; BOFF, LAURA; BIDEGAIN, JUAN CARLOS

Environmental Earth Sciences

Springer Science and Business Media Deutschland GmbH

Año: 2021 vol. 80 p. 1 - 15

1866-6280

This work aims to contribute to the interpretation of soil colors, mainly to identify the pigments thatgenerate the greenish colors bound to the hydromorphic conditions (gley colors) in vertisols of the coastalplain of the Río de la Plata Estuary. These colors are of cold hues, generally greenish (olive-gray), andoccur in poorly drained soils with prolonged water accumulation. For this purpose, samples of Bssghorizons of hydromorphic vertisols from the coastal plain of the Río de la Plata estuary were analyzedusing routine and chemical analyses, Mössbauer spectroscopy, determination of magnetic parameters, Xraydiffraction, thermogravimetric and differential thermal analysis and petrographic-electronicmicroscopy. The pigments associated with the gley colors of these soils are dominated by ferric iron,forming minerals such as ferric iron-rich smectites (nontronite/Fe-rich beidellite) whose colors rangefrom green to yellow and very fine yellow goethite. These minerals, combined with gray or blackcomponents (e.g., manganese compounds and/or organic matter), contribute to the generation of the usualgley colors in the analyzed soils of the Pampean plain. These results allow to reanalyze some assumptionsabout the pigments associated to olive colors in hydromorphic soils that traditionally were assigned toferrous iron compounds.