Metal dynamics in the sediments of the Krka River estuary

doctoral thesis

• Title (english): Dinamika metala u sedimentima estuarija rijeke Krke
• Author: Nuša Cukrov
• Mentor: Neven Cukrov (mentor)
• Committee member: Hana Fajković (predsjednik povjerenstva)
• Committee member: Kristina Pikelj (član povjerenstva)
• Committee member: Dario Omanović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geology); Zagreb
• Defense date and country: 2021-03-15, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geology; Geology and Paleontology
• Universal decimal classification (UDC): 55 - Geology. Meteorology. Hydrology

Abstract

In the estuaries, sediments may represent both a sink and a secondary source of metals, due to the various biological and physico-chemical processes which control the metal dynamics in the sediment and the overlying water column. To evaluate the sediment contamination by metals and to identify the main metal input pathways, surface sediments were sampled at 40 locations in the Krka River estuary, an environment so far regarded as relatively unpolluted. To study the dynamics of metal behaviour in the estuarine environment and to quantify metal exchanges at the sediment water interface, sediment cores were retrieved from 7 locations within the estuary. To achieve research objectives, a comprehensive approach was used, which included geochemical characterization of dissolved (pore water) and solid fraction of the sediment and the overlying water column, determination of mineralogical and granulometric composition of the sediment, measurement of physico-chemical parameters of the sediment and water column and dating of one sediment core. Two distinct areas were distinguished; the upper unpolluted estuary and the lower estuary where sediment profiles reflected the history of anthropogenic metal input associated with the city of Šibenik. Three main point sources of contamination were identified: the former Electrode and Ferroalloy Factory, the Port of Šibenik and nautical marina/repair shipyard. The mobility of metals in the sediment was mainly controlled by the degradation of organic matter, either through primary redox reactions in the sediment, such as reductive dissolution of Fe and Mn oxyhydroxides by which metals are released to the pore water, either through secondary reactions which may remove metals from the pore water through formation of the authigenic phase or increase metals solubility by forming metal-DOM, metal-(poly)sulphide or metal-sulphide-DOM complexes. According to calculated benthic diffusive fluxes, sediment in the Krka River estuary is dominantly acting as a source of metals.

Abstract (croatian)

U estuarijima, sedimenti mogu biti krajnje odredište metala, ali i njihov sekundarni izvor zbog djelovanja različitih bioloških i fizikalno-kemijskih procesa koji kontroliraju dinamiku metala u sedimentu i na granici faza sediment-vodeni stupac. Kako bi se procijenilo onečišćenje sedimenta metalima i odredili glavni izvori onečišćenja, površinski sediment je uzorkovan na 40 lokacija duž estuarija rijeke Krke koji je smatran relativno čistim okolišem. Kako bi se istražila dinamika metala u estuarijskom okolišu te kvantificirala izmjena metala na granici faza sediment-vodeni stupac, jezgre sedimenta su uzorkovane na 7 lokacija u estuariju. Za postizanje ciljeva istraživanja, primijenjen je sveobuhvatni pristup koji je uključivao geokemijsku karakterizaciju krute frakcije sedimenta i dijela frakcije koje je prešao u otopinu (porna voda) te vodenog stupca, određivanje mineraloškog i granulometrijskog sastava sedimenta, mjerenje fizikalno-kemijskih parametara u sedimentu i vodenom stupcu, te datiranje jedne sedimentne jezgre. Na temelju rezultata, estuarij se može podijeliti na dva područja; gornji, nezagađeni tok i donji tok, gdje udio metala u sedimentnim jezgrama odražava povijest antropogenog utjecaja grada Šibenika na okoliš. Tri su glavna izvora onečišćenja: bivša tvornica elektroda i ferolegura (TEF), Luka Šibenik i nautička marina/remontno brodogradilište. Mobilnost metala u sedimentu uglavnom je kontrolirana procesima razgradnje organske tvari, bilo primarnim redoks reakcijama u sedimentu, poput reduktivnog otapanja Fe i Mn oksihidroksida u suboksičnoj zoni sedimenta pri čemu se metali oslobađaju u pornu vodu, bilo kroz sekundarne reakcije koje mogu ukloniti metale iz porne vode stvaranjem autigenih minerala ili povećati topivost metala stvaranjem kompleksa metal-DOM, metal-(poli)sulfid ili metal-sulfid-DOM u anoksičnom sedimentu. Prema izračunatim difuznim tokovima, sedimenti u estuariju rijeke Krke većinom predstavljaju izvor metala za pridneni sloj vodenog stupca.

• Keywords: contamination assessment; early diagenesis; Krka River estuary; metals; pore water; sediment
• Keywords (croatian): procjena onečišćenja; rana dijageneza; estuarij rijeke Krke; metali; porna voda; sediment
• Language: english
• URN:NBN: urn:nbn:hr:217:696642
• Promotion: 2021
• Study programme: Title: Doctoral study of Geology; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje geologija (doktor/doktorica znanosti, područje prirodnih znanosti, polje geologija)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2022-03-15
• Created on: 2021-04-14 10:58:00