Georgi Zhelezov – GEOGRAPHIC ELEMENTS IN THE FIRST HISTORY OF BULGARIA BY PETER BOGDAN BAKSHEV – 1667

https://doi.org/10.35101/prg-2021.1.1

The presented research aims to present the fundamental work History ofB ulgaria by Petar Bogdan Bakshev (1667) in all its multifaceted character. Special emphasis is placed on the geographical elements in the work. The basic thesis’s in the book can observe in three general aspects – historical, geographical and development of national identity. The attempt to define the Bulgarian national space (land) with its natural characteristics and potential is important in the process of national self-determination and maturation.

Keywords: Peter Bogdan Bakshev, history, geography

Viacheslav Andreychouk, Petar Stefanov – SOME METHODOLOGICAL REMARKS CONCERNING OF KARST STUDIES FROM THE SYSTEM APPROACH PERSPECTIVE

https://doi.org/10.35101/prg-2021.1.2

A systemic approach in scientific research, including Earth and environmental sciences, has a fairly long history (over 50-70 years). It has demonstrated a high effectiveness in research, and its use is becoming more and more widespread. The article considers selected methodological issues that concern the systemic approach in the field of scientific knowledge about karst (karstology) and caves (speleology), such as: karst as a system-forming factor, holistic approaches in karst research, karst ecosystems and karst geosystem approaches, research methods of white box, grey box and black box testing. The authors suggest that the systemic approach is useful in karstology studies and should undoubtedly be used and developed.

Keywords: system approach, karst, ecosystem, geosystem

Plamena Raykova – SPACE-TEMPORAL DISTRIBUTION OF THE 2002 KRUMOVO EARTHQUAKE AFTERSHOCK SEQUENCE

https://doi.org/10.35101/prg-2021.1.3

The presence of seismic clusters has a significant impact on the study of the seismic regime in each area. In the present study the space-temporal distribution of the aftershock sequence observed after the earthquake on April 2002, with M_W4.6. in the village of Krumovo, city of Plovdiv, Maritsa seismogenic zone is analyzed. The spatial and temporal clustering of aftershocks is a dominant non-random element of the seismicity, so when the clusters are removed, the remaining activity can be modelled as a Poisson process. Space distribution of earthquakes described that the main shock and aftershock activity are clustering almost perpendicular to a defined structure. The properties of aftershock sequences allow time-dependent prediction of aftershock probabilities. On the assumption that aftershocks are distributed in time as a non-stationary Poisson process it use the maximum likelihood method for estimating the parameters (K, c and p) of the modified Omori formula. For testing the goodness of fit between the aftershock occurrence and different statistical models a transformation from the time scale t to a frequency-linearized time scale t is applied. The aftershock activity observed after the earthquake is studied for two different time intervals. There is a relatively good correlation between the theoretical and the observed distribution for both analyzed cases. Akaike’s information criteria is applied to compare models for the distribution of aftershock activity in time. The attenuation of aftershock activity is well described by the modified Omori formula and multipole activity with two secondary series was established. About 378 days after the main shock the cumulative number of aftershocks increases rapidly with t, showing a significant deviation from the prior trend. No large earthquake occurred in the region at that time. Therefore, this change in slope could be treated as a transition from aftershock activity to background seismicity.

Keywords: space-time distribution, aftershocks, Maritsa seismogenic zone

Velimira Stoyanova – HAZARD OF HEAVY METAL AND METALLOIDS ADMISSION OF SOIL BY FLOODING FROM DANUBE IN THE VIDINSKA LOWLAND

https://doi.org/10.35101/prg-2021.1.4

In this paper, we assess the hazard of heavy metal pollution of soil in the Vidinska Lowland (Bulgaria) in the case of inundation from the Danube. The assessment takes into account the following two parameters: degree of heavy metal pollution of river sediment (Ме) and topography (To). Each parameter is characterized by the following elements: weight (W), ranges, and ratings (R). Each parameter is evaluated by comparison with the others to determine its relative importance. The highest weight is given to the indicator ‘degree of heavy metal pollution of river sediment’ followed by the ‘topography’. Their weight coefficients are 2 and 1, respectively. The ranges of the parameters characterize the variety of environmental settings throughout the wetlands for the accumulation of heavy metals in the soils of the floodplain. Ratings (R) from 1 to 4 is assigned to each of the ranges of the individual variables. The MeTo index is calculated as the sum of the products of ratings (R) and weights (W) assigned to each of the parameters: MeTo=МеW*MeR+ToW*ToR. The minimum value of the MeTo index is 3 and the maximum is 12. The whole range is divided into six classes: 3 (negligible hazard), 4-5 (very low hazard), 6-7 (low hazard), 8-9 (moderate hazard), 10-11 (high hazard), and 12 (very high). Degree of heavy metal pollution of river sediment (Me). To elaborate on the raster file of the river sediment contamination, we used data on the concentration of As, Cu, Zn, Pb, Cr, and Ni in one representative sample of Danube overbank sediment deposited in the Vidinska Lowland. The index C_d is calculated to be 1.53 for the Danube overbank sediment in the lowland. This value falls in the range 1-3 of the index and is rated to 3. То delineate the limits of the lowland and the geomorphographic landforms, we extracted the slope, aspect, and hillshade from the DTM using the Spatial Analyst Tools – Surface in ArcGIS. The categories of the geomorphographic units are defined according to the classification of Mishev (1959) and Tcherkezova (2019). After classifying and analysing these indicators and comparing them with topographic maps, the following geomorphographic units are defined: low floodplain, high floodplain, and sandy ridges. The calculated values of the MeTo index for the Vidinska Lowland are within the range 3-6 and fall into two classes of a hazard: negligible hazard (26.51% of total area) and low hazard (73,49% of total area).

Keywords: geographic information systems (GIS), river sediment, low floodplain, high floodplain, sandy ridges

Dimitar Parlichev – THE CONCEPT OF “MORPHOSPHERE” – CLARIFICATIONS AND ADDITIONS

https://doi.org/10.35101/prg-2021.1.5

The morphosphere is the near-surface layer of the lithosphere on land, known in geology as the zone of hypergenesis. It is influenced by the the hydrosphere, atmosphere and biosphere through physical, chemical and biological processes, known under the general name of weathering of rocks, which are eroded washed away as solid runoff or solutions by the denudation processes (erosion, abrasion, deflation, etc.) to the oceanic depressions. There they form the so-called correlative deposits representing the oceanic type of morphosphere, which lies above the oceanic lithosphere and with it sinks into the subduction zones to form the future continental type of lithosphere. The morphosphere and morphospheric basins are the object and subject of the geomorphology.

Keywords: lithosphere, morphosphere, lithospheric plates, morphospheric basins

Nikolay Tsekov – SHRINKING OF POPULATION AND LABOR RESOURCES OF BULGARIAN REGIONS AT THE BEGINNING OF THE 21ST CENTURY

https://doi.org/10.35101/prg-2021.1.6

Depopulation and aging are the main factors that predetermine the changing demographic situation in Bulgaria over the past three decades. The aim of this study is to study the impact of the synergy of these negative processes on the socio-economic development of the country through changes in the age distribution of the entire population and the working age population for the country and municipalities. The object of the study are the relationships between the average annual rates of change in the population of Bulgarian municipalities and changes in their age structures. An analysis of the consequences of the demographic crisis on the spatial distribution of the population in three main age groups – people of working, overwork and under working age against the background of changes in the shares of people in young, middle and senior working age.

Keywords: demographic aging, depopulation, labor resources, demographic burden,
median age

Georgi Aleksiev – ACADEMICIAN TODOR NIKOLOV HAS LEFT US

https://doi.org/10.35101/prg-2021.1.7