ANALYSIS AND PROGNOSIS OF THE AQUEOUS MIGRATION OF ARSENIC BASED ON COMPLEX STUDY OF OGOSTA RIVER VALLEY'S HYDROGEOLOGICAL ELEMENTS (AT SPECIFIC FLOODPLAIN SITE)

The presence of arsenic in the Ogosta River Valley's alluvial sediments is subject to historical contamination due to upstream located ore-factories, tailing ponds, and even industrial accidents from the past. In recent years, there have been several types of research focused on different aspects of the contaminated alluvial sediments in the floodplain of Ogosta River Valley, northwestern Bulgaria. The present study is based on a complex investigation of a particular floodplain site between Beli Mel village and Ogosta Dam site to get insights into the transport of arsenic in a soil-groundwater-river system. The performed investigations include local area analysis of geomorphologic conditions, Ogosta River fluctuations, and meteorological data. The specific site investigations performed in situ include geophysical VES prospecting; several trial pits with accompanied grain-size distribution analyses of the presented soils in the vadose zone of the study area. These investigations allowed specifying the parameters of the main hydrogeological elements. Based on the latter, two hydrogeological models are performed to clarify the movement of groundwater and the arsenic migration in the floodplain terrace.