Acid sulfate soils from Antarctica: genesis and properties along a climatic gradient.

Rafael G Siqueira,Fábio S De Oliveira,Elpídio Inácio Fernandes Filho,Davi V Lopes,Caroline D Souza,Carlos Ernesto G.R Schaefer,José João L.L De Souza

doi:10.1590/0001-3765202120210625

Abstract

Sulfurization is a pedogenic process that involves pyrite oxidation and strong soil acidification, accounting for the formation of acid sulfate soils. In Antarctica, acid sulfate soils are related to specific parent materials, such as sulfide-bearing andesites in Maritime Antarctica and pyritized sedimentary rocks in James Ross Archipelago. The hypothesis is that the acid sulfate soils of these regions vary according with a climate gradient. The reviewing of current data showed that the acid sulfate soils of warmer and wetter Maritime Antarctica have a greater weathering degree, higher acidity, leaching, phosphorus adsorption capacity, structural development, and well-crystallized iron oxides and kaolinite formation. On the other hand, the sulfurization at the drier region of James Ross Archipelago is counterbalanced by the semiaridity, resulting in lower acidity and higher base contents combined with little morphological and mineralogical evolution besides presence of weatherable minerals in the clay fraction. The sulfurization process interplays with other pedogenic processes, such as the phosphatization in Maritime Antarctica and salinization in James Ross Archipelago. Higher temperatures and soil moisture enhance the pedogenesis, showing that even the Antarctic sulfate soils, which originated from specific parent materials, have their development and characteristics controlled by a clear climatic gradient.

Highlights

Sulfurization is a microbiologically mediated process that involves the oxidation of sulfide minerals, such as pyrite, accumulation of sulfoxyanions, and precipitation of hydroxysulfates, such as jarosite and schwertmannite, with occasional Feoxyhydroxides (Bigham & Nordstrom 2000)
The present study aims to evaluate the characteristics and variability of acid sulfate soils in a well-defined climatic gradient across the Maritime Antarctica and James Ross Archipelago to understand the interplay between the sulfurization and the Antarctic Peninsula climate diversity
The acid sulfate soils from Maritime Antarctica showed higher weathering degree and pedogenic development than the acid sulfate soils from James Ross Archipelago (Weddell Sea), pyrite oxidation is the origin of both groups of soils

Summary

Introduction

Sulfurization is a microbiologically mediated process that involves the oxidation of sulfide minerals, such as pyrite, accumulation of sulfoxyanions, and precipitation of hydroxysulfates, such as jarosite and schwertmannite, with occasional Feoxyhydroxides (Bigham & Nordstrom 2000). The process generates extreme acidification due to sulfuric acid production, enhancing the chemical weathering of the affected soils and substrates (Dent 1986, Tatur et al 1993). The sulfurization products are known as acid sulfate soils, characterized by pH value of. 3.5 or less (Soil Survey Staff 2014), besides acid drainage formation and yellowish colors due to the jarosite (Dent & Pons 1995). The acid sulfate soils present morphological, chemical, and mineralogical changes in relation to their parent material (Tatur et al 1993). These soils occur worldwide where sulfidic materials are exposed to O2-rich conditions through drainage driven by sea- or base-level change, or human

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