Environmental Protection and Disaster Risks

The operational Bulgarian Chemical Weather Forecast System (BgCWFS) was modified and applied for assimilation of satellite retrieved atmospheric chemistry parameters—Aerosol Optical Depth (AOD) and columnar values of NO₂ and SO₂. The work outlines the methodology based on calculation of correction factors between model estimated and assimilated satellite derived parameters. Simulations by two versions of the system were performed for two months (August 2017 and February 2019) for all 5 domains of BgCWFS. The first version, mod-run, is without satellite data assimilation, the second one, sat-run assimilates satellite data. The effects of the assimilation is demonstrated for different pollutants analysing the difference between the results of the two versions on particular days in different model domains and as domain mean values for the Balkan Peninsula and for Bulgaria. The domain mean monthly particulate matter concentrations increase by more than 100% in summer and by about 50% in winter. The increase in the domain mean monthly SO₂ concentrations is about 110% in summer and 130% in winter.

The present paper is continuation of our recent study and analyzes the potential changes of residential heating and cooling degree-days as well as three stakeholder-relevant indices of agro-meteorological change (growing season length, sum of the active and sum of the effective temperatures) for Central and Southeast Europe over near past (1975–2004), near (2021–2050) and far (2070–2099) future periods. All indicators were calculated from the output data of our simulations with the regional climate model RegCM driven by the ERA-Interim reanalysis for the near past and by the global circulation model HadGEM2-ES under RCP8.5 CMIP5 radiative forcing scenario for the future periods. The validation of the model-based indices against their counterparts, computed from the observational dataset E-OBS, shows that the model reproduces their spatial variability and magnitude generally well. A linear bias correction of the considered indices is also demonstrated. Consistent with the general trend of the mean and extreme temperatures over the region, the study reveals a decrease of the heating degree days and considerable increase of the cooling degree days and the agro-meteorological indices practically over the whole domain in the future. The detected changes are fairly not symmetrical - the relative increase of the cooling degree days is significantly bigger than the decrease of the heating degree-days.

The present study assesses the changes in the exceedances of the joint extremes of temperature and precipitation quantiles as well as the trend magnitude and statistical significance of these changes. Following the Beniston’s idea, the combination of cool/dry, cool/wet, warm/dry and warm/wet modes in projected future climate over Europe up to the end of the twenty first century is investigated in consistent manner. These modes are defined as excedances of fixed quantile thresholds, the lower and the upper quartile respectively. The use of joint quantiles allows an exploration of climate statistics that in many instances would be overlooked by simply analyzing single thresholds of temperature or precipitation. The used for the computation of the quantiles data for the mean 10-day temperature and 10-day precipitation sum are obtained as ensemble multi-model median from the bias-corrected output of 5 CMIP5 global models, forced with all 4 RCP emission scenarios. The model output is accessed from the section of the Inter Sectoral Impact Model Intercomparison Project in the Copernicus Data Store. Generally, the obtained results are coherent with the consolidated outcomes of the most recent studies, considering the projected future changes of the mean temperature and the precipitation across Europe. Key finding is, however, the revealed steady and statistically significant increase of the number of the extreme warm and dry events over the whole Mediterranean basin. The consequences of such tendency could be manifold, including several adverse effects on the ecosystems as well as on managed systems (e.g., agriculture and water supply sector).

The study of the Planetary Boundary Layer vertical structure in coastal areas is of particular importance due to the fact that a large number of urban areas and their industrial activities are located on the shores of the seas, oceans or large lakes. Based on long-term (August 2008–October 2016) sodar measurements at a Bulgarian Black Sea coastal site, the mean characteristics of the two main types of nocturnal air flows (marine and land air masses) are obtained. Typical parameters for the investigated region, such as the heights of the marine, the internal and planetary boundary layers, as well as wind and turbulence vertical structure details are revealed exploring this high spatial (10 m) and temporal (10 min) resolution data. The observation site is near the town of Ahtopol in Southeast Bulgaria. The analyses are based on averaging of the measured profiles of 12 output sodar parameters and calculated Buoyancy Production mean profiles. The seasonal variability of all characteristics is explored. The nocturnal land air masses are found to be with neutral and slightly stable stratification, Planetary Boundary-Layer height of 410–430 m and corresponding Surface-Layer height of 50–80 m. The nocturnal marine air masses are found to be with neutral and slightly unstable stratification, Internal Boundary-Layer height of about 40–50 m and a nocturnal marine Planetary Boundary-Layer height of about 300 m. The study contributes to disclosure and understanding the coastal nocturnal wind and turbulence regime in a region with modest observation networks. The obtained results can be also used for evaluation of the various theoretical, mesoscale and air quality models performance.

Long-term sodar measurements (Aug 2008–Oct 2016) of wind and turbulence profiles with high spatial (10 m) and temporal (10 min) resolution were performed at the southern Bulgarian Black Sea coast. This data has provided an opportunity to define “rare” values of meteorological parameters within their statistical distributions and to identify them as extreme events according to the Intergovernmental Panel on Climate Change. The statistical analysis of wind speed profiles has been performed for the eight-year period using the two parameter Weibull distribution. The determination of the ninety-percentile of this statistical distribution (at every sodar measurement level from 30 up to 600 m) has given values (“rare” events) that have defined the theoretical extreme wind speed profile (reference profile). On this basis, the extreme profiles during the reviewed period have been determined. Analysis of the distribution of the situations with extreme weather events by months and hours for the entire period has been performed. The multiple time series with the registered extreme profiles have been used to derive averaged parameters defining the vertical structure of the coastal boundary layer during extreme events. The thermodynamic state of the coastal boundary layer according to the Pasquill-Gifford classification has been revealed.

The Sun is the main source of energy for all Earth’s geosystems, including climate, weather, mean sea level, winds, precipitation, and etc., mainly through Total Solar Irradiance (TSI), whose variations during solar activity cause various changes on the Earth surface. Climate processes, interactions between atmosphere-and ocean system, various local, regional and global hydrological cycles are the main mediator between solar activity and a number of geophysical processes on the Earth surface. The temperature at the Earth surface is widely used climate index, whose variations consist of significant seasonal oscillations, trend and long-term cycles. The global warming due to greenhouse gases grout produces significant temperature rise in the last decades, while the solar activity cycles drive periodic oscillations of the temperature. The variations of temperature over Bulgaria, due to anthropogenic and solar influences, is investigated by means of several long time series of meteorological observations. The changes of seasonal components of temperature and long-term oscillations are analyzed in narrow frequency bands by means of the Partial Fourier Approximation (PFA). These temperature variations are compared with the corresponding cycles of solar activity. The determined linear trends of temperature rise in the last decades are associated with the anthropogenic factors of the global warming.

The aim of this work is to present and discuss newly obtained data for the chemical composition of precipitation (RW) and cloud water (CW) at a high-elevation site in Bulgaria. Sampling of RW and CW was organized in 2017 and 2018 during field experiments at Cherni Vrah, the highest peak in Vitosha Mountain. Passive collectors designed and constructed at NIMN were used. All collected samples (118) were analyzed for acidity (pH), conductivity (EC), main anions—SO₄²⁻, NO₃⁻, Cl⁻, ammonium ions (NH₄⁺), macro and micro elements (Na, K, Mg, Ca, Fe, Si, Zn, Cu). The average pH values for both types of samples were in the acidity range (<5.0). The values of EC varied from 5 to 89.2 µS cm⁻¹ for RW and from 0.7 to 202 µS cm⁻¹ for CW. The ion composition was dominated by nssSO₄²⁻, NO₃⁻, Ca and NH₄⁺ which made up more than 63% of the total ionic content for RW and 75% for CW. The relative contribution of the major compounds to the CW and RW composition is presented and discussed. The volume weighted mean (VWM), fractional acidity and neutralization factor are also calculated. The effect of long-range transport processes is studied for some selected periods of 2018 using HYSPLIT air mass backward trajectory analysis.

The main objective of this study is to evaluate the performance of some well-known and widely used operational air quality modelling systems (EMEP-MSC-W, and the models at the Copernicus Atmosphere Monitoring Service (CAMS)) for simulations of ground-level particulate matter in Bulgaria. The analysis is focused on two months—a summer one (August 2017) and a winter one (February 2019). The comparison of models to observations from regular air quality background stations is based on statistical indicators and various plots (box plots, kernel density estimations, and scatter plots). The EMEP and CAMS regional models underestimate the observed concentrations, on average by about 50% for PM₁₀ and by about 22% for PM_2.5. These models perform better at a rural remote (mountain) site than at urban background stations indicating that the outputs of the models could be used for indicative values of PM background concentrations. The model inter-comparison consists of an analysis of the spatial distribution of monthly mean concentrations and values for domain averaged model concentrations. The CAMS global model simulates in summer different spatial distribution due to the assimilation of satellite data providing information for dust storms and wildfires.

The environmental thermal comfort is one of the issues not only these days, but also in the future, concerning the results from the climate projections. The objective of this paper is to study the human discomfort in winter and summer in Sofia and its surroundings. Weather Research and Forecasting (WRF) model numerical simulations were used to calculate two characteristics called indexes, of the thermal environmental properties from the human point of view. They estimate the deviation of the environmental conditions from the human thermal comfort. The first one—Wind Chill index describes the thermal discomfort in low temperatures (winter), depending on air temperature and wind speed. The second one—Heat Index describes the deviation from the summer thermal comfort in high air temperatures (summer), depending on the air temperature and relative humidity. Numerical experiments with combination of different parameterization schemes for atmospheric boundary layer and microphysical processes were carried out. Model performance for the temperature, wind speed and relative humidity were used for estimation of the best model options for calculation of the Wind Chill and Heat Index in the corresponding conditions when they are applicable.

The air quality of the city of Sofia is a result of a complex interplay between anthropogenic and natural factors. In the present paper the aerosol pollution of Sofia is investigated through case studies during different seasons of 2019—two days in spring, four in summer and four in winter. Experimental measuring campaigns for particle concentrations add more extensive knowledge on the distribution and levels of the main problematic pollutants, such as particulate matter (PM). Laser particle counter measurements near an intensive traffic boulevard are presented and discussed. The daily variation with high temporal resolution (10–15 min) of aerosol particle concentrations (number and mass) in channels 0–2.5 µm and 2.5–10 µm are analyzed together with meteorological conditions and results from WRF-GDAS, HYSPLIT and BSC dust models. The influence of long-range transport of dust on the aerosol concentrations is assessed.

The impact of Air Quality (AQ) on human health and quality of life is an issue of great social significance. Evaluating this impact will provide a scientifically robust basis for elaborating efficient short term measures and long term strategies for mitigation of the harmful effects of air pollution on human health and quality of life. The AQ impact on human health and quality of life is evaluated in the terms of Air Quality Indices (AQI), which give an integrated assessment of the impact of pollutants and directly measuring the effects of AQ on human health. The objectives of the present work are evaluations in different years and for the different seasons in selected years, based on extensive computer simulations of the AQ for Sofia city carried out with good resolution using up-to-date modelling tools and detailed and reliable input data. Some extensive numerical simulations of the atmospheric composition fields have been performed recently. The US EPA Model-3 system was used as modelling tool. A fairly extensive data base was developed from simulations which were used for studies of the atmospheric composition and including the AQ climate. The simulations are for 12 years from 2008 to 2019 and calculated on five domains: Europe, Balkan Peninsula, Bulgaria, Sofia Municipality and Sofia City with increasing space resolution to 1 km for the territory of Sofia City.

The air quality US EPA models-3 system consisting of SMOKE—emission model and pre-processor, MM5—meteorological driver, and CMAQ—chemical-transport model, is used in many studies of the air quality in the Balkan Peninsula, and in particular Bulgaria. It runs in different model resolutions, depending on the domain, from European to city scale. The EMEP-MSC-W model is another chemical transport model, widely used in air quality modelling. Two of the processes involved in the concentration change of some pollutant are the dry and wet depositions. The air quality modelling capability depends on many factors, for example, meteorology and emissions. We study the differences in the simulation of the wet and dry depositions for Nitrogen and Sulphur compounds, between the CMAQ and the EMEP-MSC-W model for a period of 8 years.

Most of CFD urban models are based on the so called RANS approach (Reynolds averaged Navier Stokes equations). Recently, the advance of computer capabilities has pushed the inclusion of Large Eddy Simulation technique (LES) which has a different approach by using a spatial filter resolving the large eddies in the atmosphere and modelling the small eddies. One of the recent open models with LESS approach is the PALM4U model developed by the Leibnitz Hannover University in Germany. We have used an area in the downtown of Madrid city to set up the PALM4U model with 2 m spatial resolution. The vertical extent of the model is set up on 300 m with the same equally spaced resolution. The system receives the boundary and initial conditions from the WRF/Chem mesoscale air quality model developed by NOAA/ESRL/GSD (US) team. WRF/Chem is a well know state-of-the-art meteorological and chemical models for mesoscale applications. Results of the simulations show a high sensitivity to the changes in type of trees in urban parks with strong impacts (hot spots) in several areas located several hundreds of meters away of the part. The system composed by both models is a reliable tool to be use for studying the impact of natural based solutions (NBS) in urban environments and for other pollution applications with very high spatial resolution. Hot spots, energy efficiency and health impact assessments at urban level are also areas where this complex tool can be applied.

Future climate simulations have been produced for three 5-year periods until the end of twenty-first century using the WRF-ARW numerical weather prediction model for the greater area of Thessaloniki in the framework of the forecasting System for urban heaT Island effect (LIFE-ASTI) programme. In the present study, we analyse the characteristics of heat wave days in present and future at a central urban region of Thessaloniki and a rural region around the city in order to investigate the urban heat island effect under extreme heat. The number of heat wave days until 2100 is expected to increase by >12 times more than in the present. It is notable that more than 60% of the heat wave days within the urban area will be characterized by minimum temperatures ≥30 °C, while this percentage will be ~12% for the rural area. Finally, while in the present the urban heat island intensity during heat wave days presents mostly values 1–3 °C, in the future the intensity will be larger, in a few cases exceeding even 6 °C.

The present work aims at characterizing particulate matter (PM) of different size, emitted during biomass gasification in a drop tube furnace (DTF) at 1000 °C. The elemental composition was determined using X-ray fluorescence (XRF) and Electron Paramagnetic Resonance (EPR) analyses. Overall 19 elements were determined and the relative mass concentration of their oxides was identified as macro- (above 3%) and micro-concentration (below 3%). The elements Fe, Mn and S were found in each type of particulates, regardless of the used biomass and gasifying agent. The dominant macro component of char (cyclone particles >10 µm) was Ca (50.56–100% of the total CaO), followed by K, Fe, S, Mn and Cr. Only colza char contained significant portion of P and much lower Fe. The primary macro constituents of PM_10–2.5 were Fe, Mn and S. The volatile ash compounds K and Cl are typical constituents of the submicron sized ultrafine particles (UFP), when biomass from agricultural residue was gasified. This confirms the hypothesis that elements, having low boiling point significantly influence UFP formation through the nucleation. Two EPR spectra were obtained for the char samples: a broad signal with g ≈ 2.1–2.6, and a narrow sharp signal with g ≈ 2.002–2.003. The broad EPR signal was attributed to the paramagnetic metal ions Fe³⁺ and Mn²⁺, which was in agreement with the XRF analysis. The narrow signal was attributed to the appearance of soot particles.

Statistical analysis was performed, which reveals statistical parameters of the seismic setting before the earthquake in the region of Crete (01.04.2011 with coordinates 26.56^o E, 35.64^o N; M_l = 6.2, h = 63 km and T₀ = 13: 29: 10.5). For this purpose, the spatial and temporal changes in the b-value and the value of the Z-seismic lull were estimated. The temporary change in the b-value shows that the average value of b decreased from 1.75 ± 0.02 between 1985 and 2002 to 1.4 ± 0.02 between 2003 and 2011. A significant decrease in the b-value and clear anomalies of calm in the Z-value in early 2011 were also observed in several neighbouring areas. The epicenter of the earthquake falls in an area with a relatively low value of the a-parameter estimated for the entire previous period. In the study area, the abnormal decreasing trend of the b-value may be an indicator of increased stress, and the increasing trend of the Z-value may indicate areas of calm before the studied earthquake.

Global seismic risk and vulnerability to earthquakes are increasing steadily as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. In the present study both deterministic and probabilistic earthquake scenarios for the city of Ruse are generated. The study is guided by the perception that usable and realistic, based on both local seismic history and tectonic conditions, ground motion maps have to be produced for urban areas. The consideration of the earthquake scenarios into the policies for seismic risk reduction will allow focusing on the prevention of earthquake effects rather than on the activities following the disasters.

The objective of this work is to investigate the influence of Saharan dust events on the chemical composition of rain samples collected at three sites in Bulgaria during 2017–2018. Saharan dust intrusions were identified through a combination of satellite retrieved aerosol data and results from dust forecasting models and from backward trajectory model. The chemical composition of the samples (acidity pH, conductivity EC, main ions and elements) is analysed in view of the direction of the approaching air masses—“direct” influence (south-west), and “indirect” influence from other directions and regions, already impacted by Saharan dust. The samples were characterised by pH from 4.1 to 7.4, elevated values for EC (max 202 µS cm⁻¹) and for Si, Ca, Fe, Mg concentrations. For cases with direct influence Si and Ca values were up to 1.5 and 25 mg l⁻¹. In most of the indirect cases increased concentrations of sulphate, nitrate and ammonium were observed (up to 39.5, 23.1 and 8.3 mg l⁻¹).

Karpathos is one of the biggest Greek islands, located between Crete and Rhodes in Aegean Sea. As the most of the islands in the area Karpathos is prone to earthquakes and tsunamis. The event of 9 February 1948 (M 7.1) near the eastern coast of the island caused local tsunami with damages in the area of Pigadia bay, nevertheless tsunamis also from regional sources are expected. The tsunami hazard for the Karpathos Island, focusing on the city of Karpathos and the Airport area, is modelled merging the data from simulation of tsunamis generated by three seismic sources: Eastern Hellenic Arc (EHA referring the 1303 A.D. event, Mw = 8.0); near Rhodes (hypothetical scenario earthquake, Mw = 7.3); and near the coast of Karpathos, based on the 1948, Mw = 7.3 earthquake. Numerical calculations are made using the code UBO-TSUFD on a set of nested grids. Tsunami observables, such as maximal water column height, maximum velocity flux, inundation, are computed for each individual scenario and merged to individuate the areas most exposed to tsunami. The seismic source EHA dominates in the tsunami hazard maps: moreover, the impact over the southern part of Karpathos has biggest risk since the airport and the main city of the island are located in this part.

Present research analyses the human exposure at one of the most dangerous earthquake zones in Bulgaria-Blagoevgrad region and propose a detailed seismic scenario for the main city. Seismic hazard is modelled using GIS and overlaid with one square kilometer grid of population distribution in order to determine the population exposure in the region. We define a parameter called “population exposure index” (PEI) which has five classes: Minor, Low, Moderate, High and Major. As was expected, the seismic hazard levels of Blagoevgrad region are in the upper part of the classification scale. The total population in the Blagoevgrad region (NUTS II) is around 323,000 people. Results show that more than 130,000 people are exposed to the highest level of seismic hazard. City of Blagoevgrad gathers nearly 22% of the population in the region. A specially developed seismic scenario for the city accounting the soil conditions as well is used for detailed assessment of the people exposed to seismic hazard. The obtained values of Peak Ground Acceleration (PGA) varying between 0.29 and 0.45 g are crossed with the population living in each building to determine the levels of population exposure. Our results show that people living in 398 buildings are majorly exposed to the seismic hazard in Blagoevgrad city. Another 1465 buildings are determined as highly exposed to this threat. Delineation of these buildings might be very important for the regional authority and focusing on the prevention of possible earthquake effects.

A new methodology for forecasting the propagation of HF radio waves by reflection from the ionosphere over Bulgaria in the absence of ionosonde data is presented. The proposed methodology contains three main parts. Based on the long-term ionosonde data an empirical model of the critical E region frequency (foE) has been built; the latter depends on the season, local time and the level of solar activity described by the solar radio flux at 10.7 cm wavelength (F10.7). The critical frequency of the F2-layer (foF2) and the maximum usable frequency at a propagation of 3000 km (MUF3000) are obtained by means of the proposed empirical relationships between these two critical frequencies and the Total Electron Content (TEC). Based on these three ionospheric characteristics a modeled electron density profile is compiled by using the method of Di Giovani-Radicella (Giovanni and Radicella in Adv Space Res 10:27–30, 1990 [1]). The constructed in this way electron density profile allows calculating the lowest and maximum usable frequency at a given distance up to 500 km according to the theory of radio wave propagation in the ionospheric plasma, namely the equivalence theorem and the secant law, as well as the law of reduction of the group velocity of propagation depending on the ionosphere electron density.

Wildfires occur traditionally in the southern situated countries of Europe. However, in the last few years northern states are experiencing wildland fires (vegetation fires) which sustain their propagation for more than few hours. Reasons for this new situation have been discussed during the CMINE Wildfire Task Group meetings (DRIVER+ project with a mandate of one year—2019). In our paper we will summarize our main findings, which refer to two basic topics—landscape management and climate change. There are more and more parcels of land which have become abandoned because of numerous reasons, but the outcome is the same. The absent people are not cutting the trees, and the people do not bring their cattle or sheep to graze the grass and shrubs. This vegetation grows every spring and lies down on the ground every autumn as potential fire propagation fuel waiting for an ignition. Climate change is another global issue which is creating dangerous weather conditions with extreme high temperatures during the summer season plus mild winters, which is leading to wildfire occurrence in some parts of Europe year round. In our paper we will describe two case studies from Portugal and South Wales, having the same conclusions—no land management strategy and extreme weather are the best conditions for life threatening wildfires.

The weather forecast of good quality is essential for the humans living and operating in the Bulgarian Antarctic base (BAB), located on the Livingston Island coast at 62.64\(^\circ \) S and 60.36\(^\circ \) W. The numerical weather prediction models in southern high latitude regions still need improvement as the user community is limited, little test cases are documented and validation data are scarce. In this study, we suggest several ways to improve the local weather forecast model skill by modifications of the land cover and ocean temperature. We tested the sensitivity of the numerical weather prediction modelling system based on the Weather Research and Forecasting (WRF) model, configured for the BAB area, to the Sea surface temperature (SST) of the ocean around the island. The model configuration is described and details on the model performance are given. Several experiments with SST coming from different sources are performed, as well as experiments where the SST is scaled linearly. The conducted sensitivity experiments show that all of the considered meteorological variables are affected by the sea surface temperature, the most prominent differences being observed in the 2 m temperature field. With a uniform rise in SST, the corresponding tendencies are: an increase of the 2 m temperature, a decrease of the sea level pressure and an increase of the average wind speed. For the BAB region, the best results with unmodified SST data are obtained when using SST from the Copernicus Marine Service ocean model.

In this paper we propose a model for implementation of value eco-innovations of clean production through ecodesign in the SMEs of the food industry in Bulgaria. The clean production is a preventative approach to managing environmental aspects. The paper presents the essence of clean production through ecodesign, the methods for its achievement and outlining the possible options and barriers for SMEs from the food industry in Bulgaria to implement the relevant value eco-innovations. The ecological footprint of the food industry makes the need for an integrated implementation of clean production practices from raw material extraction to packaging and waste disposal of final consumer.

Coastal benthic sediments play an important role in regulating water column nutrient concentrations and primary production via nutrient regeneration and exchanges at the sediment-water interface. This study aimed to characterize the porewater concentrations and diffusive benthic fluxes of NH₄⁺, NO₃⁻, PO ₄ ⁻³ , and O₂ in some of the most common shallow sedimentary habitats (fine and coarse sands, seagrass beds, and unvegetated patches within the seagrass beds) along the Bulgarian coast, and their changes under organic loading, through a laboratory experiment. Ammonium was the dominant form of nitrogen in porewaters, and its concentration generally increased under organic loading in most sediment types. Nitrate concentrations were high in the overlying water, and decreased with depth within the sediments, becoming depleted at ~3 cm with the development of anoxic conditions. Phosphate concentrations were low, and tended to increase with depth by the end of the experiment in most sediment types and especially under organic loading. Nutrient fluxes were dominated by a release of NH₄⁺ to the water column in all sediment types, and a parallel uptake of NO₃⁻ by the sediments; both fluxes increased under organic loading, possibly indicating stimulation of nitrate reduction within the sediments. The PO ₄ ⁻³ fluxes were smaller, and the sediments mostly acted as a source for phosphorus under organic loading. O₂ was taken up from the overlying water in all treatments and sediment types, and this flux increased under organic loading, probably in relation to the decomposition of the organic matter and spontaneous chemical oxidation of sulphide ions, released during sulphate reduction within the sediments. The study contributes towards the understanding of nutrient cycling and the role of the benthic compartment in Black Sea coastal soft-bottom habitats.

This work investigates the extend of oil pollution released by the sunken cargo ship Mopang, located in the Bourgas bay on the Western Black Sea shelf. We have analysed the available Synthetic Aperture Radar (SAR) data from the Sentinel-1 mission for the years 2017 and 2018 and identified the surface features which could be referred to oil pollution, originating from Mopang for the given timeframe. To detect the oil leaks an adaptive threshold algorithm is used and the detections are visualized cumulatively in order to estimate the continuity and intensity of the leak throughout the period. The radar acquisitions from both the ascending and descending pass of the Sentinel-1A and B satellites with oil detections visible for three dates are plotted together with the surface currents in attempt to study the evolution of the leak and its dependence on the marine conditions. The possibility to simulate the dispersion of oil pollution on the surface with a Lagrangian particle model is tested for one of the dates. Three seeding scenarios are run: (1) release from a shape, such as the one of the morning detection; (2) release from a point source; and (3) continuous release from a point source for the entire simulation period. The numerical simulations are performed with the OpenDrift trajectory model and the results after 12-h run are validated against the satellite images.