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

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.

Novel Applications for Oxalate-Phosphate-Amine Metal-Organic-Frameworks (OPA-MOFs): Can an Iron-Based OPA-MOF Be Used as Slow-Release Fertilizer?

“…Plants and other organisms actively release LMW-OAs into the rhizosphere to increase P-bioavailability [ 14 ]; and subject to soil type, oxalate has been found to be one of the more effective LMW-OAs [ 15 , 16 ]. Despite the quantities of oxalate produced by plants, few oxalate minerals persist in soils because of the bioprocessing, and they tend to build up in isolated niches [ 17 , 18 ].…”

The role of authigenic sulfides in immobilization of potentially toxic metals in the Bagno Bory wetland, southern Poland

“…Euhedral platy crystals of barite are common constituent of atmospheric dust in Upper Silesia due to the Ba-enriched coal burning (Jabłońska et al 2001 ). However, platy crystals of authigenic barite have been observed in another wetland in the outskirts of Upper Silesia (Smieja-Król et al 2014 ).…”

“…The precipitation of metal sulfides as a result of microbial sulfate reduction is one of the most important processes in aqueous metal reduction in constructed wetlands and other highly metal-contaminated organic-rich sediments (Johnson and Hallberg 2005 ; Batty et al 2006 ; Sheoran and Sheoran 2006 ; Faulwetter et al 2009 ; Lewis 2010 ; Yoon et al 2012 ; Smieja-Król et al 2014 ). Due to the low solubility of most sulfides, they provide a long-term sink for potentially toxic metals and keep the aqueous metal concentrations at environmentally permissible levels as long as the conditions remain anoxic (Kosolapov et al 2004 ).…”

“…Its nanocrystalline spheroidal aggregates, 1–5 μm in diameter, are composed of both ZnS polymorphs: sphalerite and wurtzite (Moreau et al 2004 ). Zinc sulfide microspherules are important in controlling Zn and Cd distribution in Zn-rich peatlands (Smieja-Król et al 2010 , 2014 ; Yoon et al 2012 ). Zinc sulfide microspherules were also confirmed to precipitate in a H 2 S-rich treatment wetland by Gammons and Frandsen ( 2001 ).…”