Aglaida Toteva

• PhD Professor (Assistant) at Bulgarian Academy of Sciences Geological Institute

The present study examines the change in landslide susceptibility under climate change conditions. The Landslide Susceptibility Index for the territory of Bulgaria was determined using the Mora and Vahrson method, based on the weighted assessment of various adverse conditions and destabilizing factors on slope stability. The input data include prec...

Radon as a daughter product from the radioactive uranium family, is present in all rocks and soils in the geosphere. Its half-life (3.82 d) allows the element to migrate from the terrestrial environment to the surface. This migration can be intensified through preferential degassing pathways, such as faults or fracture systems Geogenic radon potent...

Indoor radon exposure is recognized as a significant cause of lung cancer, as shown by various epidemiological studies. One possible pathway for radon transport is through faults, where radon can escape into fractures and open spaces in rocks. Numerous studies link fault systems to elevated radon levels at the surface or within buildings. In Bulgar...

Water balance calculation is an important stage of the groundwater research. Surface runoff in open karst conditions is usually absent, and the outflow of karst system occurs through springs. The aim of the study is to analyze the water regime and balance of two karst springs near the town of Kyustendil in West Bulgaria. WaterbalANce software is us...

Mercury and its compounds are listed as hazardous substances and prohibited by Bulgarian regulations for discharge in groundwater. Regional studies on the natural distribution of mercury in groundwater are scarce but in recent decades a significant amount of data has been accumulated in the National Environmental Monitoring System. We analysed grou...

Radon (222Rn) is a radioactive gas formed as a result of the radioactive decay of radium (226Ra). Radon is identified as one of the dominant sources of population exposure that could lead to lung cancer, accounting for between 3% and 14% of all lung cancers. Rocks in the Earth’s crust are a primary source of radon in the atmosphere. In this context...

Groundwater is an important component of river runoff, the quantification of which provides valuable information for water management. This study aims to evaluate the spatial and temporal variations in the contribution of groundwater to the river flow in the Mesta River Basin. Two tasks were performed with corresponding research methods and study p...

Urbanisation poses significant challenges to a water resource management, especially in areas where water demand is increasing. This study focuses on the impact of the urban environment on surface and groundwater recharge in Sofia, Bulgaria, using a geographic information system (GIS) approach. The study integrates geospatial data and land use anal...

The northern part of the Municipality of Brezovo falls within the range of a fractured massif, which predetermines the presence of springs with a limited flow rate, insufficient for water supply for the villages there, which necessitates the localization of suitable locations for boreholes drilling. After a complex assessment of the geological-hydr...

Groundwater in the Botеvgrad Kettle (West Bulgaria) is important for the local population. Despite the information available for this area, the catchment area of this kettle is poorly studied from a hydrogeological perspective. Therefore, the objective of this current study is to assess the hydrogeological conditions based on existing information f...

Groundwater vulnerability to contaminant infiltration from the surface, and to state deterioration, is related to the spatial distribution of rocks with diverse porosities, flow characteristics and unsaturated zone thickness. For the present regional assessment of groundwater vulnerability, it is considered most appropriate to adopt a method based...

Spatial and seasonal changes in the chemical composition of groundwater in the upper Pontian aquifer have been monitored. The results of the monitoring and the changes of the chemical parameters over time were evaluated based on GIS and statistical processing of the data.

Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the content of radium (226Ra), part of the 238U family, in the lithosphere. One of the indicators for evaluating the impact of radon on a certain area/terrain, including on the biota, is the so-called geogenic radon potential. Different types of rocks and soil...

The Upper Pontian aquifer occupies the central part of the Lom Depression. The geological position determines its gradual dipping from the periphery to the central parts. It is one of the most water-abundant aquifers in Northwestern Bulgaria and is associated with the sands of the Archar Formation. The chemical composition of the waters is of inter...

Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the content of radium (226Ra), part of the 238U family, in the lithosphere. Different types of rocks and soils possess different 226Ra content and different permeability. Radon has high mobility and is driven by diffusion and convection with the soil gas throu...

Study region: Lom depression, Bulgaria. Study focus: A multi-tracer investigation was applied to identify the recharge conditions and isotope hydrological character of four aquifers in the Lom depression (Northwest Bulgaria) using environmental isotopes (δ18O, δ2H, δ13C, 3H, 14C) and noble gases. The radiocarbon age model of Ingerson and Pearson w...

“Shipkovo” thermal water field is one of the few in the country formed in karstified carbonate rocks. Initially, there was a natural spring with elevated temperature, located at the boundary of Triassic karstified limestones and dolomites and Lower Cretaceous terrigenous rocks, sinking in depth to the east. Later, drilling operations were carried o...

Groundwater is a valuable natural resource and an important source of drinking and domestic water supply. There are two types of groundwater in the Mesta River Basin: HCO3- > Ca2++Mg2+ (1st type waters) and HCO3- < Ca2++Mg2+ < HCO3-+SO42- (2nd type waters). The waters of the first type formed in the silicate rocks, are widespread in the high mounta...

The ground surface relief, geological settings, river network and hydrogeological conditions along the Bulgarian-Greek border are analysed. As a result three transboundary aquifers are identified: the alluvial aquifer in Maritsa River valley and the Neogene porous aquifer Svilengrad-Orestiada in the eastern part of the border, and the karst aquifer...

A major issue in groundwater and surface water management and monitoring is transboundary groundwater flow between neighbouring countries. The subject of our study is the assessment of the groundwater flow across the state border between Bulgaria and Greece, which is characterized by complex natural features. We present a study on the factors that...

The Arda River is the main river course in the mountain range Rhodopes located in Southern Bulgaria. Its river basin is characterized by highly variable relief and diversified geological and hydrogeological conditions. The groundwater is recharged mostly from precipitation and forms baseflow of the Arda River and its tributaries. The aim of the stu...

This work is an environmental isotope investigation of groundwater samples from a multi-layered aquifer system in the Lom depression of Danubian Plain in Bulgaria. Our previous studies in the Carpathian-Pannonian Region had been convinced through groundwater researches using noble gas temperatures that the recharge temperature difference between th...

In the recent years there has been a steady increase in the concentrations of arsenic in the Kobilyak karst spring. After a complex research, the Ogosta River was found to be the source of pollution, and the reason is the accelerated lateral and bottom erosion of the river, which relieves the infiltration of river waters into the karst limestones a...