Geophysics Field Camp “Sozopol 2019” UNIVERSITY OF MINING AND GEOLOGY “ST. IVAN RILSKI” The Vromos bay – contamination mapping and monitioring GEOPHYSICS FIELD CAMP “SOZOPOL 2019” After a subsequent processing of these block-models with the Zond-IP program, multiple SUPPORTED BY SEG FOUNDATION AND TGS iterative procedures were performed and the resistivity distribution in the subsurface The Vromos beach is located in Vromos bay, 22 km south of Burgas and 16 km north of Sozopol, just west space along the studied lines is determined. For this purpose, a compound analysis is of town of Chernomorets. It occupies an area of 203 944 sq.m. THE CURRENT PROJECT IS A TRADITIONAL CONTINUATION OF THE MAIN IDEA AND THE ACTIVITIES SET OUT IN FIELD CAMPS ORGANIZED THE LAST FOUR YEARS, NAMELY GEOPHYSICS FIELD CAMP “SOZOPOL 2015” PROJECT, GEOPHYSICS FIELD CAMP performed, taking into consideration the available information about the lithological From 1954 to 1977 the beach is contaminated by copper ore flotation tailings of increased Uranium “SOZOPOL 2016”, GEOPHYSICS FIELD CAMP “SOZOPOL 2017” AND GEOPHYSICS FIELD CAMP “SOZOPOL 2018” PROJECTS. types, the grain-size characteristics, the water levels and the groundwater chemical content. In this period approximately 8 000 000 t waste from the Burgas copper mines was dumped in composition in the studied part of the subsurface area down to a depth of about 20-25 m. the sea. Part of the waste formed a costal layer 1300 m long, 120 m wide and 2–3 m thick. The sand mass THE FIELD CAMP PROJECT STARTED ON 7/8/2019 AND HAD 12 FIELDWORK DAYS BETWEEN 8TH AND 19TH JULY. (black sand) was dominated by magnetite and contained up to 60 wt.% Fe2O3+FeO. The increased specific activity of radionuclides was associated with increased contents of 238U and 226Ra due to the presence of U-minerals in the ore. Numerous research projects in the period from 1979 to 1993 followed Investigations for seawater intrusion in the area of Alepu lagoon by contaminated sands removal from 1991 to 1998 resulted in decrease of total activity (238U, 226Ra, 232Th, 40K) from 74–10 175 Bq/kg in 1979 to 83–400 Bq/kg in 1998. Seawater intrusion into coastal aquifers is causing a progressive salinization of the associated freshwater basins and prevents the sustainable development of historically established ecosystems. These processes are also characteristic for the aquifer horizons developed in the lagoons and the estuaries along the Bulgarian Black Sea coast. A typical example of this is the Alepu protected area, part of the Ropotamo complex, declared a wetland of international importance under the Ramsar Convention and Natura 2000 Protected Area BG0001001. The name Alepu comes from Greek (αλεπού) and literally means fox, therefore the landmark is also known as the Swamp of Foxes. Alepu swamp is located about 7 kilometers south of Sozopol, near the old road to Primorsko, immediately after Dyuni Holiday Village, opposite the bay enclosed by St. Agalina cape to the north and Humata cape to the south. HISTOGRAMS OF THE DISTRIBUTION OF THE MEASURED PHYSICAL VALUES ALONG THE COASTLINE OF VROMOS BAY: BACKGROUND RADIATION (LEFT) AND MAGNETIC SUSCEPTIBILITY (RIGHT) RESISTIVITY MODELS According to the preliminary results of the radiometry and the magnetometry there are no indications for dangerous gamma radiation in the beach area. The values of the ionizing radiation dose do not The electrical resistivity sections along all studied lines are transformed into exceeds the norm and varies between 0.13 and 0.31 µSv/h. The highest values are concentrated in the hydrogeological models of saline water intrusion through key criteria, which determine western part of the beach. That matches the spreading of the highest values measured in the magnetic field and the magnetic susceptibility data values. the degree of salinity of groundwater as a function of the determined resistivity distribution. Data on the specific hydrogeological conditions in the studied area are used, as well as some classification schemes quoted in publications related to the studied problem. GROUND MAGNETIC AND GRAVITY RESULTS FROM A PROFILE LINE ALONG THE SHORE OF THE WESTERN HALF OF THE VROMOS BAY) With purpose of preliminary assessment of the spatial boundaries and salinity level of the coastal aquifer complex, limited geophysical studies were carried out in the area - vertical electrical sounding (VES). Using the results from the initial processing of field measurements in 97 points and applying the Zond-IP computer program, resistivity block- models are developed along the four studied lines. GROUND MAGNETIC AND GRAVITY RESULTS FROM A PROFILE LINE ALONG THE SHORE OF THE WESTERN HALF OF THE VROMOS BAY In order to demonstrate the main techniques behind conducting seismic measurements and processing the seismic data, as well as to show how to work with the used equipment, two seismic profile lines were projected and measured along an old road behind the trees following the southern part of the Vromos Bay shore . HYDROGEOLOGICAL MODELS Acknowledgments We are very grateful to the SEG Foundation and TGS for the financial support of the Geophysics Field Camp “Sozopol 2019”. Once again, this support gave us the priceless opportunity to organize and fulfill geophysical practice in real environment and helped to support students in gaining in professional experience. In addition, the Geophysics Field Camp "Sozopol 2019" team would like to thank the University of Mining and Geology “St. Ivan Rislki”, the Department of Applied Geophysics, the Center for Underwater Archaeology – Sozopol and the Institute of Oceanology at the Bulgarian Academy of Science for the support and for providing the Field Camp with the necessary geophysical equipment. We’d like to thank to the Geomagnetic Observatory Panagyurishte - PAG, the Department of Meteorology and Geophysics, the Institute of Oceanology, the RESULTS FROM SEISMIC REFRACTION SURVEYS NEAR VROMOS BAY SITE, INCL. HODOGRPAHS, VELOCITY MODELS AND INVERSION RESISTIVITY BLOCK-MODEL DEVELOPED ACCORDING TO DATA FORM VES FIELD MEASUREMENTS Center for Underwater Archaeology – Sozopol and Villa “South” personnel for their participation, cooperation and hospitality..