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Mineralogical and geochemical studies of secondary mineral assemblages related to deterioration of building materials

Marszałek Mariola, Dudek Krzysztof, Gaweł Adam, Czerny Jerzy

Geological Quarterly

2019

Vol. 63, No. 4

683--698

The study was aimed at mineralogical and geochemical characteristics of secondary phases related to deterioration of historic building materials. The investigations, carried out in the Holy Trinity Basilica in Kraków, Poland, focused on the southern facade of the 17th-century Myszkowskis Chapel, built of the Miocene Pińczów limestone. Lower part of the facade is covered with a cement render, and the exposed foundations are made of Jurassic limestone and Cretaceous sandstone, both of local origin from the Kraków region and neighbouring Carpathians, in the form of irregular blocks bound with a cement mortar. The wall surface exhibits clear signs of damage; from dark grey soiling and scaling to efflorescences. Sampled materials, deteriorated, altered crusts and efflorescences were analysed with optical and scanning electron microscopy, X-ray diffraction, and Raman microspectroscopy methods. The secondary minerals distinguished include abundant gypsum CaSO42H2O, less common thenardite Na2SO4 (and/or mirabilite Na2SO410H2O), aphthitalite (K, Na)3Na(SO4)2, darapskite Na3(SO4)(NO3)H2O, ettringite Ca6Al2(SO4)3(OH)12 26H2O, monosulphite Ca4Al2O6SO311H2O, as well as scarce nitre KNO3, nitratine NaNO3 and halite NaCl. Gypsum usually forms surface crusts and fills the pores inside some materials. The efflorescences, sampled from the exposed foundations, consisted of thenardite and/or mirabilite, aphthitalite and darapskite, whereas ettringite and monosulphite were connected with cement renders. Traces of nitre, nitratine and halite were detected at various elements of the chapel facade and foundations. The origin of the salts is related to composition and physicochemical properties of the building materials, as well as to anthropogenic factors.

Weathering in a regolith on the Werenskioldbreen Glacier forefield (SW Spitsbergen). 2. Speciation of Fe, Mn, Pb, Cu and Zn in the chronosequence

Rzepa Grzegorz, Manecki Maciej, Jakubski Grzegorz, Kwaśniak-Kominek Monika, Czerny Jerzy, Górniak Dorota

Annales Societatis Geologorum Poloniae

2019

Vol. 89, No. 3

317--341

The evolution of chemical speciation of Fe, Mn, Pb, Cu, and Zn was investigated in the chronosequence of young sediments, exposed by a currently retreating Arctic glacier on Spitsbergen. Werenskioldbreen is a 27 km2 subpolar, land-terminated, polythermal glacier in recession, located near the SW coast of West Spitsbergen. Three samples of structureless till were collected at locations exposed for 5, 45 and 70 years. Four grain-size fractions were separated: > 63, 20–63, 2–20, and < 2 µm. Speciation of Fe, Mn, Pb, Cu, and Zn was determined using a 6-step sequential chemical extraction method: 1) 1 M sodium acetate, 2) 1 M hydroxylamine hydrochloride in acetic acid, 3) sodium dithionite in buffer, 4) acid ammonium oxalate, 5) boiling HCl, 6) residuum. The weathering in the proglacial area of the retreating glacier is very fast. The geochemical fates of the metals in question correlate with each other, reflecting a) the geochemical similarities between them, b) the similarities of their primary mineral sources, c) the significant role of incongruent dissolution. The weathering processes dominating the system are redox reactions and incongruent dissolution, followed by precipitation of secondary phases and partial sorption of aqueous species. As a result, the elements released from weathering minerals are only partially transported away from the system. The remaining part transforms by weathering from the coarse-grained fraction (dominated by fragments of primary minerals) into the fine-grained fraction (in the form of secondary, authigenic minerals or as species sorbed onto a mineral skeleton). This is very strongly pronounced within the chronosequence: the content of each of the metals studied correlates identically with the grain size, despite the differences in their chemical character and affinities. The microscope study presented herein indicates that the role of incongruent dissolution previously was underestimated. Also, the formation of coatings of secondary phases on primary mineral surfaces was observed. All these rapid weathering processes affect the mineral speciation of initial soils as well as the composition of mineral suspensions transported away by rivers to the nearby ocean.