Pseudomorphs of barite and biogenic ZnS after phyto-crystals of calcium oxalate (whewellite) in the peat layer of a poor fen.

Beata Smieja-Król,Janusz Janeczek,Jerzy Wiedermann

doi:10.1007/s11356-014-2700-7

Abstract

Pseudomorphs of barite (BaSO4) and Cd-rich ZnS after whewellite (CaC2O4·H2O) occur within remnants of Scots pine bark tissues in the peat layer of a poor fen located near a zinc smelter in south Poland. A two-step formation of the pseudomorphs is postulated based on SEM observations: (1) complete dissolution of whewellite, possibly caused by oxalotrophic bacteria, and (2) subsequent bacterially induced precipitation of barite and spheroidal aggregates of ZnS together with galena (PbS) in voids left by the dissolved whewellite crystals. Local increase in pH due to microbial degradation of whewellite, elevated concentrations of Zn(II) and Ba(II) in pore water due to the decomposition of atmospheric particles of sphalerite and barite in the acidic (pH 3.5–3.8) environment, oxidation of S species during drying and rewetting of the peat layer, and subsequent partial reduction of sulfate anions by sulfur-reducing bacteria were all factors likely involved in the crystallization of ZnS and barite in the microenvironment of the post-whewellite voids.

Highlights

IntroductionThe interaction of disseminated metals with soil components is complex and includes sorption onto organic matter and mineral surfaces, incorporation in precipitates, release through desorption and dissolution of minerals or decomposition of organic matter, and interactions with plants and microbes (Li and Thornton 2001; Helal 2006; Gadd 2010; Violante et al 2010)
The contamination of soil and groundwater by potentially toxic metals (e.g., Pb, Cd, Zn, and Cu) is a serious problemResponsible editor: Stuart SimpsonB
The occurrence of barite (BaSO4) and unspecified polymorphs of ZnS and galena (PbS) within the space left after the dissolution of crystals of calcium oxalate monohydrate in a poor fen is documented

Summary

Introduction

The interaction of disseminated metals with soil components is complex and includes sorption onto organic matter and mineral surfaces, incorporation in precipitates, release through desorption and dissolution of minerals or decomposition of organic matter, and interactions with plants and microbes (Li and Thornton 2001; Helal 2006; Gadd 2010; Violante et al 2010). The occurrence of barite (BaSO4) and unspecified polymorphs of ZnS and galena (PbS) within the space left after the dissolution of crystals of calcium oxalate monohydrate (mineral whewellite, CaC2O4·H2O) in a poor fen is documented. Calcium oxalate is a common constituent in soil litter, formed in large quantities by plants and fungi (Arnott 1995; Horner and Wagner 1995; Hudgins et al 2003)

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Conclusion