Bioavailability and geochemical characteristics of recent marine sediment of Makirina bay (Northern Dalmatia, Republic of Croatia)

Osnovni cilj doktorske disertacije je podati oceno onesnaženosti zaliva Makirina v Severni Dalmaciji. Analizirali smo recentni morski sediment (peloid), morsko vodo in bioto (floro in favno) zaliva Makirina. Določena je bila zrnavost, mineralna, elementna in mikrobiološka sestava peloida, vsebnost organske snovi in mobilnost PTE (potencialno toksičnih elementov) ter REE (elementov redkih zemelj) v peloidu. Poleg tega je bila podrobneje opredeljena tudi vsebnost PTE in REE v morski vodi ter bioti zaliva Makirina. Koncentracije večine PTE v peloidu ne presegajo stopnje PEL (Probable Effect Level) in dovoljenih mejnih vrednosti snovi v tleh v Republiki Sloveniji (UL RS, št. 68/96) ter na Hrvaškem (NN RH, št. 39/13), prav tako so njihove vsebnosti primerljive s koncentracijami v peloidih, ki so že v uporabi v različnih velnes centrih po svetu. Metoda zaporednega izluževanja je pokazala, da so PTE v peloidu vezani na različne frakcije. Največji delež večine obravnavanih PTE je vezan v preostanku, kar pomeni, da za bioto ne predstavljajo potencialne nevarnosti, saj so vezani v kristalni strukturi mineralov (alumosilikatov) in se pod pogoji, ki so običajno prisotni v naravi, ne morejo izlužiti. Med nerezidualnimi frakcijami je najpomembnejša oksidativna frakcija, v kateri so PTE povezani z organsko snovjo in/ali sulfidi. Glede na izračunan kriterij RAC (Risk Assessment Code), PTE (z izjemo Cd in Mo) v peloidu predstavljajo nizko do srednjo nevarnost za vodno okolje. Rezultati metode zaporednega izluževanja delno sovpadajo z ugotovitvami, ki smo jih pridobili z izračunom BSAF (biota-sediment akumulacijski faktor). Porazdelitev PTE v morski vodi iz zaliva Makirina je podobna porazdelitvi PTE v peloidu. Izjema so koncentracije Cr, ki so v peloidu med najvišjimi, medtem ko so v morski vodi pod mejo detekcije. Ker pri koncentracijah nekaterih PTE v peloidu in morski vodi ne moremo popolnoma izključiti vpliva antropogenih dejavnosti, v okolici zaliva Makirina predlagamo vzpostavitev okoljevarstvene politike, ki bi omejevala uporabo gnojil in škropiv na bližnjih kmetijskih površinah.The primary purpose of the dissertation is to estimate the pollution status of Makirina Bay, situated in Northern Dalmatia. Within the research framework, a detailed analysis of recent marine sediments (peloid), seawater and marine biota (flora and fauna) of Makirina Bay has been carried out. Grain size distribution, mineral, elemental and microbiological composition of peloid have been determined, as well as its organic carbon content, PTE (Potentially Toxic Elements) and REE (Rare Earth Elements) mobility. PTE and REE concentrations were also identified in seawater and biota of Makirina Bay. The concentrations of most PTE in the peloid do not exceed the PEL (Probable Effect Level) value and permissible levels for soils in Slovenia and Croatia. Moreover, the contents are comparable to their respective concentrations in peloids already used in various wellness centers around the world. The results of the sequential extraction method showed that PTE in recent marine sediment are bound to different factions. The major proportion of most PTE is bound to the residual. The PTE in residual are retained within the crystal lattices of minerals, and thus the PTE bound to this component are regarded as stable and are not susceptible to remobilization in normal environmental conditions. Among non-residual fractions, the oxidative fraction is the most important, wherein the PTE are associated with organic matter and/or sulfides. The calculated RAC (Risk Assessment Code) value indicated that the PTE (except Cd and Mo) pose a low to medium risk to the aquatic environment. The sequential extraction method results coincide partly with the findings gained with the BSAF (Biota-Sediment Accumulation Factor) calculation. Distribution of the PTE in seawater is similar to the PTE distribution in recent marine sediment. According to the comparison, only the Cr concentrations stand out. The concentrations of Cr are among the highest in recent marine sediment, while in seawater below detection limit. For some PTE concentrations in recent marine sediments and seawater the impact of anthropogenic activity cannot be completely excluded. Therefore, an environmental policy is advisable for the Makirina Bay and its surroundings