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  • Interaction between Hg and macroaggregates in coastal waters (Gulf of Trieste, N. Adriatic)
    Koron, Neža ...
    Since rather great quantity of dissolved Hg in natural waters seems to be bonded onto colloidal organic matter (COM) it affects the Hg speciation, transport, biological availability and cycling. The ... interactions between Hg and COM are in great proportion dependent on the chemical composition and structure of COM. In addition to analytical difficulties, due to low concentrations of Hg and COM, the compositional and structural complexity of COM and their instability usually hinder their study. Macroaggregates (macrogels), produced episodically in the northern Adriatic bz agglomeration of dissolved organic macromolecules - mostly heteropolysaccharides, of prevalently phytoplankton (diatom) origin, offer a rare oportunity to study these problems. The chemical speciation of macroaggregate Hg in the Gulf of Trieste (northern Adriatic Sea) was studied using centrifugation discriminating between water insoluble (sediment) and water soluble (supernatant) fractions. Water soluble fraction was subsequently ultrafilteredthrough membranes with a nominal pore size of 30, 10 and 5 kDa cutoff in a cascade fashion, and fractions characterized bz carbohydrate, Corg. and Ntot. contents, FTIR and enyzmatic (Ž-amzlase, ß-glucosidase) cleavage. The results revealed that the highest carbohydrate content and the lower CžN ratio were associated with higher molecular weight (MW) fraction suggesting that glzcoproteins and aminopolysaccharides are important constituents of this fraction. FTIR showed the presence of organic nitriles inall fractions while the enyzmatic cleavage demonstrated the presence of ą- and ß-glzcosidic linkages in nearlz equimolar proportions. Analzses of MW of permeates, assayed by high-pressure size exclusion chromatographz (HPSEC), revealed that they are composed of macromolecules of rather narrow MW distribution and, moreover, because macromolecules exist in a variety of conformations they can pass through smaller cutoff membranes. Analyses of Hg concentrations, determined bz CV AFS, revealed low concentratios in all permeates suggesting the lack of binding sites. Higher Hg concentration observed in sediment, characterized bz relatively higher lipid content compared to polysaccharides, suggests the interaction between macrogel and HgS originating from Idrija (NW Slovenia) mining district. Comparatively higherparticulate Hg content in the area suggests the presence of efficient carriers, i.e. diatoms.
    Vir: ICMGP2009, 9th International Conference on Mercury as a Global Pollutant, June 7-12, 2009, Guiyang, China [Elektronski vir] (str. 20-05)
    Vrsta gradiva - prispevek na konferenci
    Leto - 2009
    Jezik - angleški
    COBISS.SI-ID - 2092623

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