Alexey Rusakov

Crystallization of calcium oxalate hydrates by interaction of calcite marble with fungus Aspergillus niger

Abstract The crystallization of calcium oxalates (weddellite and whewellite) by interaction of calcite marble with fungus Aspergillus niger, one of the most active stone destructors, was studied under in vitro conditions. The temporal development of acid production of fungus as well as the sequence of formation and morphogenesis of the growing oxalate hydrates crystals were investigated in detail. Furthermore, the relationships between morphology and growth conditions of crystals within the biofilms on the surface of carbonate rocks are discussed.

Refinement of the crystal structures of biomimetic weddellites produced by microscopic fungus Aspergillus niger

The single-crystal structures of four biomimetic weddellites CaC2O4 · (2 + x)H2O with different contents of zeolitic water (x = 0.10–0.24 formula units) produced by the microscopic fungus Aspergillus niger were refined from X-ray diffraction data (R = 0.029–0.038). The effect of zeolitic water content on the structural stability of weddellite was analyzed. The parameter a was shown to increase with increasing x due to the increase in the distance between water molecules along this direction. The water content and structural parameters of the synthesized weddellites are similar to those of weddellites from biofilms and kidney stones.

The Formation of Oxalate Patina on the Surface of Carbonate Rocks Under the Influence of Microorganisms

With the use of modern mineralogical and biological methods in natural and experimental conditions the research of mechanisms of oxalate patina formation on the carbonate rock surface has been carried out. On the result basis the role of microorganisms in metasomatic crystallization processes on marble and limestone surfaces was specified. The interdependence between biological and environmental factors of crystallization was found. It is shown that the phase composition of fungal crystallization products depends on the variable content of organic acids in fungal culture and the calcium carbonate is stimulating the oxalic acid excretion rate. It was shown that biogenic calcium oxalate crystallization starts from bi-pyramidal weddellite crystals, goes through crystal splitting and ends with the formation of dumb-bell shaped and later spherical whewellite and weddellite joints formation.The present results give a scientific basis for creating new methods of cultural heritage stone monument preservation with the use of modern biotechnologies.

Chronostratigraphy of the Cheremoshnik key section (Yaroslavl Volga region) based on new geochronological, palynological, and paleosol data

According to radiochemical and biostratigraphic studies of the buried peat layer in the Cheremoshnik key section on the East European plain, the first age dating of this peat was obtained and its assignment to the Mikulino interglacial was confirmed. The Th/U isotope age data obtained for the peat horizon allow us to state with confidence that it was formed during the MIS5e. It was found that a variety of signs, including the lithological characteristics of dated layers and climatic indexes, is evidence that the Cheremoshnik site and Borisoglebsk upland occurred in the periglacial zone during MIS3–MIS2.

Significance and Regulation of Acids Production by Rock-Inhabited Fungi

According to the results of screening acidification activity of 24 species of micromycetes in vitro, 18 of them produced organic acids in artificial medium. The fungi from genera Penicillium and strains of Aspergillus niger have the most active production of organic acids. The ratio of acids formed by fungi on a liquid glucose-containing medium changes during ontogenesis: gluconic acid and acids of the Krebs cycle dominated in a log phase of growth; oxalic acid accumulated in a stationary phase while concentrations of other organic acids reduced. Oxalic acid is the main acid produced by fungi in a culture and apparently in a natural habitat. Formation of gluconate improves the efficiency of other carbon substrates consumption by fungi. Citric, succinic, malic, and fumaric acids are produced only at higher concentrations of carbohydrate and high ratio of C/N. Production of oxalic acid by micromycetes increases on the media containing only nitrate nitrogen. Zn in concentration up to 2 mM induces secretion of oxalic acid on nitrate media. Copper has stimulation effect on oxalic acid production only in very low concentration (25 µM). Presence of Zn in culture leads to formation of oxalate Zn crystals on the surface of mycelium. On ammonium-containing culture Zn and Cu does not stimulate oxalic acid production, but induce significant morphological changes.

Chemodestructive fractionation of soil organic matter

The method of chemodestructive fractionation is suggested to assess the composition of soil organic matter. This method is based on determination of the resilience of soil organic matter components and/or different parts of organic compounds to the impact of oxidizing agents. For this purpose, a series of solutions with similar concentration of the oxidant (K2Cr2O7), but with linearly increasing oxidative capacity was prepared. Chemodestructive fractionation showed that the portion of easily oxidizable (labile) organic matter in humus horizons of different soil types depends on the conditions of soil formation. It was maximal in hydromorphic soils of the taiga zone and minimal in automorphic soils of the dry steppe zone. The portion of easily oxidizable organic matter in arable soils increased with an increase in the rate of organic fertilizers application. The long-lasting agricultural use of soils and burying of the humus horizons within the upper one-meter layer resulted in the decreasing content of easily oxidizable organic matter. It was found that the portion of easily oxidizable organic matter decreases by the mid-summer or fall in comparison with the spring or early summer period.

Buried Late Holocene Paleosols of the Nienshants Cultural-Historical Monument in St. Petersburg

Buried Late Holocene paleosols of the Nienshants historical monument at the junction of the Neva and Okhta rivers (St. Petersburg) have been studied. These soils developed from estuary deposits of the Littorina basin with abundant artifacts of the Neolithic and Early Iron ages (7–2 ka BP). The soil cover of the area consists of the mature dark-humus profile-gleyed soils on elevated elements of the mesotopography (3.0–3.5 a.s.l.) and dark-humus gley soils in the local depressions (2.0–2.6 m a.s.l.). The soils are characterized by the low to moderate content of humus of the fulvate-humate type. The beginning of humus formation in the dark-humus gley soil on the slope facing the Neva River is estimated at about 2600 yrs ago; for the darkhumus profile-gleyed soils of the studied paleocatena, at about 2000 and 1780 yrs ago; and for the darkhumus gley soil, at about 1440 years ago. Judging from the spore-pollen spectra, the development of these soils took place in the Subatlantic period under birch and pine-birch forests with the admixture of spruce and alder trees. The gleyed horizons of the buried soil at the depth of 1.6–1.2 m on the Neva-facing slope date back to the Late Subboreal period (2500–2600 yrs ago), when pine-birch-spruce forests were widespread in the area. The new data contribute to our knowledge of the environmental conditions during the Neolithic and Iron ages.

Crystallization conditions of biogenic calcium oxalates with different water content

Biogenic calcium oxalates are quite widespread in nature. Thus, weddellite, CaC2O4 · (2+x) H2O (x ≤ 0.5), occurs in peat and calcareous lake sediments, in biofilms on the surface of limestone, in plants. Whewellite, CaC2O4 · H2O, is often found in cracks and cavities in coalbed, sedimentary rocks containing organic substance (in bituminous shale, etc.) and in biological concretions. And both whewellite and weddellite are the main minerals of the human urinary system stones. The purpose of given work is to analyze the influence of crystallization conditions on the formation of different biogenic calcium oxalates: in renal stones and in biofilms on the surface of carbonate rocks, as well as to clarify the effect of additives on the weddellite formation with different amounts of zeolitic water. According to our collection (more than 1000 renal stones), 46% of samples contain weddellite, and 5% are monoweddellite. The results of thermodynamic calculations shows that whewellite is the stable phase of calcium oxalate under physiological conditions, despite the fact that the frequency of weddellite occurrence in calcium oxalate uroliths is very significant. In carrying out the biomimetic synthesis it was found that in human’s physiological liquid conditions (urine) simulating on the inorganic components only whewellite can be obtained. Joint crystallization of whewellite and weddellite occurs in the presence of organic substance (ovalbumin, gelatin, protein-containing media) or microorganisms (bacteria and viruses), as well as with the addition of magnesium ions and sodium to the solution. Metasomatic crystallization of calcium oxalate hydrates was investigated under the influence of Aspergillus niger strain, active producer of organic acids. The crystallization of calcium oxalate hydrates starts with formation of almost ideal dipyramidal and dipyramidalprismatic crystals of weddellite at pH values < 5. Morphology and size of the tetragonal weddellite crystals are closely related to the weddellite crystals observed in the oxalic patina on the surface of marble and limestone monuments in Tauric Chersonesos (Ukraine, Crimea). At lower pH values whewellite forms as well. It was found that weddellite crystals obtained in different conditions differs in values of a unit cell parameter as well as in ‘zeolitic’ water amount. Thus the values of a unit cell parameter for the weddellite crystals from renal stones range from 12.336 to 12.378 Å. The values of a unit cell parameter for the weddellite crystals obtained in the presence of bacteria and viruses range from 12.341 to 12.354 Å. Based on the a unit cell parameter, the range of ‘zeolitic’ water amount variations in the structures of weddellite crystals from biofilms (from 12.347 to 12.368 Ǻ) is substantially less than in the crystals synthesized under the action of microscopic fungi in vitro (от 12,329 до 12.368 Ǻ).The maximum value of x (0.37 a.p.f.u.) was determined for weddellite crystals from renal stones. According to the a unit cell parameter, the limiting value of x for the weddellite from biofilms formed on the surface of carbonate rocks are very close to this value.