ContentsPetar Stefanov – INTEGRATED MONITORING OF THE SAEVA DUPKA CAVE SYSTEM (“SAEVA DUPKA” SPELEO-MIКS)Marian Varbanov, Atanas Kitev, Stefan Genchev, Kristina Gartsiyanova – ASSESSMENT OF OXYGEN BALANCE OF WATER IN THE TOPOLNITSA AND LUDA YANA RIVER BASINGeorgi Zhelezov – DYNAMIC OF WETLAND SYSTEMS IN ARCHARO-ORSOYSKA LOWLANDGeorgi Zhelezov, Aleksey Benderev, Sava Kolev, Kostadin Nikolov – RELATIONSHIP OF THE SPATIAL DISTRIBUTION OF HEAVY METALS IN THE SOIL WITH THE MORPHOLOGY OF CONTAMINATED RIVER FLOODPLAINS (TOPOMET)