BIOGEOCHEMICAL BEHAVIOUR OF TRACE METALS AND ORGANIC NUTRIENTS IN BELGIAN COASTAL AREAS

Scriptie/masterproef: Master's Thesis

Uittreksel

Anthropogenic activities such as metal industry, mining, burning of fossil fuel, have altered trace metal and organic nutrient distributions in various environment including aquatic ecosystems(Tchounwou, Yedjou, Patlolla, & Sutton, 2014). As trace metals can have adverse effects on individual organisms and communities, knowledge on biogeochemical behavior of trace metals is crucial for risk assessment and the protection of ecosystems. In this research, trace metals from coastal seawater samples were firstly separated into the dissolved and particulate phases by filtration using a 0.45 ┬Ám filter. Secondly, the filtered seawater samples were pre-concentrated by rmeasured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In comparison, trace metal concentrations were also directly analyzed by ICP-MS after ten times dilution. Thirdly, to measure the particulate metal fraction, Suspended Particulate Matter (SPM) was collected on the filters and were digested using acids in the lab and then trace metal concentrations were analyzed by ICP-MS. The Enrichment Factor (EF) was then calculated to indicate the SPM levels in the Belgian Coastal Zone (BCZ). Labile trace metal concentrations, which is a sub-fraction of the total dissolved phase and an indicator of element bioavailability, were quantitatively determined using a passive sampler which is an in situ technique called Diffusive Gradients in Thinfilms (DGT). The DGT technique is based on hydrogel layer properties to control the diffusive transport of labile trace metals from the bulk solution to a resin layer. 13C and 15N stable isotope signatures, Particulate Carbon (PC), and Particulate Nitrogen (PN) information are useful parameters to determine the origin of Particulate Organic Matter (POM) in the aquatic system. A large amount of organic matter can cause phytoplankton bloom by eutrophication in certain periods in seawater. In this study, a dual inlet Elemental Analyzer-Isotope Ratio Mass Spectroscopy (EA-IRMS) was used to detect the isotopic ratios of 13C/12C, 15N/14N, and C/N ratio was used to determine PC and PN. Human activities such as waste discharge is superimposed on natural processes and interfered estuaries, for example, the Scheldt estuary and the BCZ. The varying physical-chemical conditions in an estuary and coastal zone, make it an interesting area to study the relationships between environmental and bioaccumulated metal concentrations. The Scheldt estuary is located between Belgium and the Netherlands, and the middle part is close to the Antwerp harbor. A total of seven sampling sites in the Scheldt estuary were selected in this work: S01, S04, S07, S09, S12, S15, and S22. In BCZ, four sampling sites were also selected: HO-1, HO-2, HZ-1, and HZ-2, these sampling sites are close to Oostende harbor and Zeebrugge harbor. This study discusses the biogeochemical behavior of the dissolved and particulate trace metals, but also the labile trace metals of the Scheldt estuary and harbor zone of Belgium. Another major focus of this environmental analytical chemistry work is the isotopic determination of organic nutrients in the Belgian coastal area. Most labile trace metals show a stable trend and total dissolved trace metals show a diluted trend to the open sea in the Scheldt estuary. In the harbor areas, different trace metals show different distributions in the particulate and dissolved phase, and SPM concentrations in the harbor areas decreased from March 2018 to March 2019. POM shows its terrestrial origin and is mainly composed of fresh organic materials in March 2019.
Datum Prijssep 2018
TaalEnglish

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