Research highlights — 2019 – Earth Science Institute SAS

Sulfur-bearing methane inclusions with up to 74 wt. % H₂S in Proterozoic quartzite from Bastar Craton (India) exhibit common n₁ vibration modes of H₂S and CH₄ at 2609 cm^-1 and 2919 cm^-1, respectively, associated with unknown Raman bands at 2488-2574 cm^-1. Quantum chemistry modeling based on the density functional theory confirmed that the unknown vibrations correspond to polysulphane-sulphur complexes. The H₂S-CH₄ gas phase was transformed into H₂-CH₄ mixture with negligible H₂S concentration after short irradiation of the associated sulphur with 532 nm photons emitted by a 25mW Nd-YAG laser. However, no H₂S splitting occurred in the inclusions devoid of sulphur. We infer that photolytic breakdown of the sulphur-bound polysulphanes provided accelerated H^· radicals capable of breaking the strong S-H bond in the molecular H₂S at room temperature. The polysulphane-supported photolysis combines benefits of toxic H₂S deactivation with hydrogen recovery, and as such it could be utilized for the environment-friendly processing and hydrogen recovery from super-soar natural gas.

The recent unique finding of amber in the Central Carpathian Paleogene sediments near the Slovak-Polish border represented an ideal opportunity to obtain valuable information about the origin and fate of this fossilized more than 20 million years old resin, as well as the nature of the environment, from which the amber came. Our research suggests that amber is a fossilized resin that had originally been exuded from a conifer tree of the Araucariaceae family. At present, this plant species is no longer naturally present in the Northern Hemisphere. Resin-producing forests grew in the humid subtropical zone on the coast of the Paleogene Sea, and extensive peatlands spread out around the mouth of the river. Forest and peatlands were affected from time to time by wildfires and floods. Peats and surface vegetation fires could reach temperatures between 370-750 °C. Even the amber itself was briefly exposed to a fire-temperature of about 250 °C. Analysis of char particles indicated recurring high-severity wildfires that could reach temperatures well above 980 °C. Such high temperatures are typical of intense forest fires that spread in the treetops. During the flood, the altered amber was flushed into the river and transported along with the sediments to the deep-sea environment. As a result of the rapid burial under that sediments, amber remained relatively well preserved to the present day.

The accuracy and efficiency of numerical simulations of seismic wave propagation and earthquake ground motion in realistic models strongly depend on discrete grid representation of the material heterogeneity and attenuation. We have developed a new orthorhombic representation of a heterogeneous viscoelastic medium with interfaces. Heterogeneity of the medium in a finite-difference cell is represented by an averaged medium with an orthorhombic anisotropy. Effective material grid parameters are evaluated numerically as volume orthorhombic averages in the grid cells centred at the grid positions of the corresponding stress components. The representation is applicable to the velocity–stress, displacement–stress and displacement FD schemes on staggered, partly staggered, Lebedev and collocated grids. We also found an optimal procedure for a joint determination of the anelastic coefficients and relaxation frequencies for an arbitrary Q(ω) law.

The substorm electrojet, which along with the auroral oval appeared over the territory of Central Europe on 17.11.1848. Auroras were observed even in northern Italy that day. The electrojet caused an extremely rapid short-term change in the geomagnetic field, which was recorded by the Prague Observatory Clementinum. The positions of the upward and downward field aligned currents are plotted. These currents connected the electrojet with the region in the centre of the magnetospheric tail and caused variations in magnetic declination.

We analyzed two extremely intensive magnetic storms. The event of 17.11.1848, which has been unknown to the scientific community, was observed in Prague by means of Gauss's type bifilar magnetometer. The storm of 4.2.1872, however, is known to be the most intense storm in the modern history, as regards the extent of accompanying auroras. Both events were characterized by swift depression of the horizontal intensity (>400 nT and >500 nT) and the auroral oval appeared at low latitudes. We interpreted the storm of 1848 to be due to the substorm electrojet and attributed the unusual course of the 1872 event to a combination of a ring-current storm with the eastward electrojet. Contrary to the theory accepted so far, the studied events demonstrate that the violent events which are well known in high magnetic latitudes, may appear at lower latitudes too and present dangerous phenomena for the environment there.

Montane forests in the High Tatra Mountains are exposed to high ambient ozone (O₃) concentrations that may adversely affect the physiological processes and health of plants. The harmful influence of ozone on forest trees can be indicated by the model-based value of the phytotoxic ozone dose (POD). In this work, we analyzed the effect of environmental factors (fENVI) on the POD obtained by the deposition model DO₃SE for dwarf mountain pine (Pinus mugo Turra). We determined a moderate limitation of O₃ uptake due to environmental factors (fENVI) such as air temperature and´humidity, solar radiation, and soil water availability in the temperate mountain forest. In addition, maximal stomatal conductance (Gmax) derived from gasometric field measurement in local conditions was included in the model. It appears that Gmax is more relevant for annual POD than fENVI. We developed a site-specific stomata response function for dwarf mountain pine using the symbolic regression approach that confirmed the robust performance of the DO₃SE model for stomatal conductance (Gsto).

Natural and induced earthquakes are nucleated in areas where shear stress is close to fault strength. In many situations, these asperities are very elongated; for example, in the case of a fault intersecting a reservoir subject to fluid-injection, or the stress concentration along the bottom of a seismogenic zone induced by deep fault creep. Theoretical estimates of the minimum asperity size leading to runaway rupture and of the final size of self-arrested ruptures are only available for 2D problems and for 3D problems with an asperity aspect ratio close to 1. We studied how the nucleation of ruptures on elongated asperities, and their ensuing arrest, depends on the size and aspect ratio of the asperity and on the background stress. We found that if the shortest asperity side is smaller than the 2D critical length, the problem reduces to a 2D problem, in which the shortest length of the asperity controls rupture evolution. Otherwise, rupture is controlled by the asperity area, as in a 3D problem. In the context of induced seismicity, our model provides insights into the conditions leading favourable or challenging conditions for traffic light systems.

Seasonal hypoxic conditions leading to mass mortalities and the collapse of shallow-water seagrass communities characterized the history of marine communities in the northern Adriatic Sea in the late 20th century. These changes can be detected and quantified in stratigraphic sections visible in sediment cores. We quantified paleoecological trends in the composition and diversity of molluscan communities in two sediment cores collected in the southern Gulf of Trieste at locations with very slow sedimentation rates. Time averaging of 5-10 cm-thick core increments attains 1,000-2,000 years and stratigraphic decline in diversity and in population density of molluscs that occurred over the past 200 years are obscured by bioturbation. However, with stratigraphic unmixing based on radiometric dating, we were able to show that a strong decline in abundance of species associated with seagrasses occurred at the 19th-20th century transition.

International consortium guided by P. Vršanský contributed to knowledge on evolutionary dynamics of aquatic insects. Comparative material was calibrated at 300, 270, 220, 151, 127, 115 and 98 Ma. For study of living equivalents, two expedition to primeval rainforests were conducted (UNESCO BR SUMACO, Equador). Discovery resulted in global analysis of all aquatic animals. 6 000 records of evolution of aquatic insects from the Mississippian to the present reveal that insect are incapable of returning to land once adapted to aquatic lifestyle. Originally, the partition of aquatic groups was small, and this ratio stabilized during the Triassic and is for nearly 250 million years constant. Majority aquatic lineages still survive, which is contrary to terrestrial lineages. In insect history 236 invasions to water occurred, but reversal is absent at all (0). This contrast with vertebrates, which frequently return to land. Thus it is doubtful that the first insect was aquatic. Living aquatic cockroaches in Ecuador swim extremely rapidly (1 ms-1) and though they are without a single macroscopic adaptation, adaptations are disclosed in nanosurfaces. They belong to the most progressive lineages.

Research highlights — 2019

Basic research

Applied research

Research related to international collaboration