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 precipitation, soil moisture, seismicity, relief, and lithological factor. The simulations for the current and future climate in the present study were performed for a reference period (1975–2004), which is representative of the current climate, and a second period, relating to the climate of the near future (2021–2050). The RCP8.5 scenario is used. The climate change model applied in the present study shows a slight decrease in the areas threatened by landslides. This is probably due to the reduced soil moisture parameters.
Toxic Hg species pose a global ecological threat due to the significant anthropogenic emissions of Hg to the atmosphere, particularly during coal combustion. An investigation about the content, association and modes of occurrence of Hg in diverse biomass ash (BA) varieties and its behaviour during biomass combustion was performed. These BAs belonging to woody, herbaceous, agricultural and aquatic biomass groups were examined with different chemical and mineralogical methods, as well as thermal and leaching procedures. The Hg contents in BAs are low and vary between 0.0032 and 0.0452 ppm (mean 0.0225 ppm). About 60–99% (mean 87%) and 63–100% (mean 91%) of Hg in biomass were volatilized at 500 °C and 700 °C, respectively, and only limited amounts of Hg were captured by BAs enriched mostly in salts such as carbonates, oxyhydroxides, phosphates, sulphates, and chlorides. The affinity of residual Hg in the BA system is towards relatively stable Fe-, P-, Ti- Al-, K-, and Si-bearing minerals (especially K aluminosilicates and Fe oxides), as well as less stable chlorides (particularly sylvite). The potential mode of Hg occurrence in BA is likely in the form of impurities in the above minerals. Alternative renewable fuels poor in Hg such as appropriate sustainable biomasses (0.001–0.043 ppm Hg) are suggested to partially or completely substitute the industrial coals enriched in Hg (0.14–0.57 ppm) and used in Bulgarian thermoelectric power plants and thus minimize the ecological problems related to this element.
In the Kraishte area, straddling the borders of Bulgaria, Serbia and North Macedonia, two major Alpine tectonic units are exposed – Vlasina-Morava and Struma. They exhibit quite differing geological evolution until the late Early Cretaceous compressional phase during which the Vlasina-Morava (Supragetic) was thrust onto the Struma (Getic) unit. The Vlasina-Morava Unit consists of Ediacaran-early Cambrian volcano-sedimentary sequence intruded by Cadomian age granites and covered by early Paleozoic marine sediments. The Struma Unit is built of tectonically imbricated Ediacaran–early Cambrian calc-alkaline magmatic rocks and ophiolites covered by Permian to Early Cretaceous sedimentary sequences. Part of the Ograzhden complex, consisting of high-grade ortho- and para-sequences of Ediacaran to Silurian age, is also considered as belonging to Struma autochthon. Post late Early Cretaceous orogenic extension was related to formation of low-angle normal faults associated with partial cooling and denudation in the area and volcanic-free sedimentation. The following Late Cretaceous to Paleogene compressional phase did not affect significantly the Kraishte area. Since the middle Eocene the area was affected by important crustal scale extension related to the formation of detachment faults and sedimentary basins characterised by continental to marine deposits and accompanied by magmatic activity. The following extensional phases, in the late Oligocene–earliest Miocene and middle Miocene–Quaternary time, were also related to faulting and formation of sets of sedimentary basins. These two phases were separated by a late early to middle Miocene strike-slip to transpressional phase characterised by formation of some minor thrust faults associated with major strike-slip fault zones.
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