Nives Ogrinc

Fatty acid and stable carbon isotope characterization of Camelina sativa oil: implications for authentication.

The importance of authenticity characterization is an increasing and pressing requirement for all foods. Vegetable oil is one of the most studied foods because of its nutritional and medicinal properties in a correct diet. In this study, a total of 53 Camelina sativa samples, from all known growing areas, were chemically and isotopically characterized. The fatty acid content of camelina oil was determined by gas chromatography (GC), and the ratios of stable carbon isotopes ((13)C/(12)C) of individual fatty acids and seed/bulk oil were determined by gas chromatography-combustion-stable isotope ratio mass spectrometry (GC/C/IRMS) and elemental analysis-stable isotope ratio mass spectrometry (IRMS). A total of 17 different fatty acids were detected by GC, with omega3 R-linolenic acid (C(18:3n3)) being the most abundant (29.7-40.0 wt %). Oleic acid (C(18:1n9)), linoleic acid (C(18:2n6)) and eicosenoic acid (C(20:1n9)) all belong to the second group of major fatty acids. The stable carbon isotopic values (delta(13)C) fell into a range typical for C(3) plants. The use of delta(13)C(18:2n6) vs delta(13)C(18:3n3) correlation could show cases where impurity or adulteration is suspected, whereas principal component analysis clearly separates oil samples from different continents. Preliminary results on the camelina oil authentication procedure provide a basis for the investigation of geographical origin and the further distinction between camelina and camelina refined or other, less expensive oils.

Carbon and nitrogen natural stable isotopes in Slovene honey: adulteration and botanical and geographical aspects.

Isotope parameters (δ(13)C(honey), δ(13)C(protein), δ(15)N) were determined for 271 honey samples of 7 types (black locust, multifloral, lime, chestnut, forest, spruce, and fir honeys) from 4 natural geographical regions of Slovenia. Carbon and nitrogen stable isotope ratios were measured to elucidate the applicability of this method in the identification of the botanical and geographical origin of honey and in honey adulteration. Only 2.2% of the samples were adulterated according to the internal standard carbon isotope ratio analysis method. Botanical origin did not have any major influence on the honey isotope profiles; only black locust honey showed higher δ(13)C values. Some differences were seen across different production years, indicating that the influence of season should be further tested. Statistical and multivariate analyses demonstrated differences among honeys of various geographical origins. Those from the Alpine region had low δ(13)C (-26.0‰) and δ(15)N values (1.1‰); those from the Mediterranean region, high δ(13)C (-24.6‰) and medium δ(15)N values (2.2‰); those from the Pannonian region, medium δ(13)C (-25.6‰) and high δ(15)N value (3.0‰); and those from the Dinaric region, medium δ(13)C (-25.7‰) and low δ(15)N values (1.4‰).

A mass balance of carbon stable isotopes in an organic-rich methane-producing lacustrine sediment (Lake Bled, Slovenia)

Abstract The sources of dissolved inorganic carbon (DIC) were determined in subalpine lacustrine high-carbonate (>50%) sediments (Lake Bled, Slovenia) using a combination of chemical and carbon stable isotope analyses together with incubation experiments. The carbon dynamics in the sediment was simulated by a numerical model that accounts for all basic processes controlling the concentration and isotopic composition of DIC. The remineralized carbon (DIC plus CH4) has mean δ13C value of −28.4‰. The dominant carbon isotope effect expressed during early diagenesis of this organic matter is associated with methanogenesis. Methane produced at this site has a measured value of −69‰, while DIC is enriched in 13C (−12.6‰) because of the preferential synthesis of 12CH4. In sediment pore water, the isotopic composition of DIC reflects the combination from degradation of organic carbon using various electron acceptors and methanogenesis. It was found that the major contribution (38–78%) of DIC is derived from methanogenesis. The highest contribution of CaCO3 dissolution was observed in the spring (12%), characterized by lower bottom water temperatures and slower degradation of sedimentary organic matter.

Remediation of Mercury Polluted Sites Due to Mining Activities

During the 500 years of mercury mining in Idrija, large quantities of Hg were released into the environment. Due to chemical transformation (reduction, methylation, oxidation, demethylation) and the transport of mercury enriched particles into the river system and the Gulf of Trieste, the mercury problem is of local, regional, and global concern. The results of some studies indicate that Hg is actively accumulated in terrestrial and aquatic food webs, which leads to an increased exposure of inhabitants frequently consuming food, particularly, fish produced in a contaminated area. In order to understand the impact of mercury mining on the environment and human health, it is necessary to integrate the experience of various disciplines (e.g., chemists, biologists, geologists, hydrologists, epidemiologists, economists, etc.). Political support at the local and regional level in Slovenia and Italy is as well an ultimate requirement for the successful implementation of remediation, based on scientifically based criteria.

Decomposition of sedimentary organic matter and methane / formation in the recent sediment of Lake Bled Slovenia

Decomposition of sedimentary organic matter and methane formation in a eutrophic dimictic subalpine lake Lake Bled, . . NW Slovenia were investigated by measurement of in situ concentrations of dissolved inorganic carbon DIC in the pore water and its stable carbon isotopic composition, as well as by incubation experiments. The isotopic composition of carbon in the methane produced during incubation experiments was also studied. The ratio between methane produced by acetate fermentation and CO rH reduction was estimated from d 13 C-DIC vs. DIC concentration profiles in sediment pore water 22 w using a mathematical model developed by LaZerte LaZerte, 1981. The relationship between dissolved carbon dioxide and x its stable isotope ratio in aquatic sediments. Geochim. Cosmochim. Acta 45, 647-656 . It was found that in the spring acetate fermentation is dominant when about 65% of methane is produced by this reaction pathway, whereas in the autumn, over 90% of the methane results from CO reduction. d 13 C of methane released during a 6-week incubation experiment with 2

Mercury speciation driven by seasonal changes in a contaminated estuarine environment

In this study, seasonal changes of mercury (Hg) species in the highly variable estuary of Soča/Isonzo River (northern Adriatic Sea) were investigated. Samplings were performed on a seasonal basis (September 2009, May, August and October 2010) and Hg species (total Hg, methylmercury (MeHg), dissolved gaseous Hg (DGM)) in waters, sediments and pore waters were determined. In addition, a range of ancillary parameters were measured (salinity, nutrients, organic carbon (OC), nitrogen species). Hg values were interpreted using these parameters and hydrological conditions (river flow, wave height) around the time of sampling. There were no significant changes in Hg load from river to the gulf, compared to previous studies. The load was temporarily higher in May 2010 due to higher river flow. Wave height, through changing hydrostatic pressure, was most likely to cause resuspension of already deposited Hg from the bottom (August 2010). The estuary is a net source of DGM to the atmosphere as suggested by DGM profiles, with salinity, redox potential and organic matter as the most probable controls over its production. MeHg is produced in situ in sediment or in water column, rather than transported by river, as indicated by its correlation with OC of the marine origin. Calculated fluxes for THg and MeHg showed sediment as a source for both the water column. In pore waters, OC in part affects partitioning of both THg and MeHg; however other factors (e.g. sulphide and/or oxyhydroxides precipitation and dissolution) are also probably important.

Anoxic mineralization of biogenic debris in near-shore marine sediments (Gulf of Trieste, northern Adriatic).

Anoxic degradation of sedimentary biogenic debris using closed incubation experiments was studied at two sampling stations in the Gulf of Trieste (northern Adriatic). Production rates of dissolved inorganic carbon (DIC), NH4+, PO(4)3- and dissolved Si (dSi), and reduction rates of SO(4)2- were measured and anoxic mineralization rates were modeled using a first order G-model and multi-G approach. The depth profiles of these rates revealed an exponential decrease indicating that the largest fraction of mineralization of biogenic debris and SO(4)2- reduction occurs in the surficial sediment layer and on the sediment surface. Comparing the depth-integrated anoxic mineralization rates at both stations with benthic fluxes of DIC, NH4+, PO(4)3- and dSi measured at the in situ temperature in the dark, it appears that the DIC and PO(4)3- fluxes are higher because the mineralization mostly occurs at the sediment-water interface, and that besides SO(4)2- reduction, other electron acceptors are involved in the organic matter decomposition pathway in these surficial sediments. The NH4+ production was higher than the benthic fluxes because of NH4+ oxidation. The production of dSi was in good agreement with benthic fluxes implying that temperature is the main factor of dSi production and benthic fluxes in these sediments.

Oxic–anoxic transition of benthic fluxes from the coastal marine environment (Gulf of Trieste, northern Adriatic Sea)

The influence of O2 concentration on mineralisation processes was examined by sediment incubation experiments under controlled laboratory conditions over a sequence of oxic, anoxic and then reoxidising conditions. Sediments were studied from five locations representing marine, lagoonal and brackish environments in the Gulf of Trieste (northern Adriatic Sea). A complete depletion of dissolved O2 and nitrate were observed after ~6 –15 days in marine and lagoonal sediments, and after 5 days in brackish sediments. During the reoxygenation phase, nitrification occurred at some sites, as evidenced by increases in NO3– concentrations, but not at other sites, indicating an inhibited recovery response to intermittent oxic conditions. NH4+ and PO43– regeneration during mineralisation was much more extensive in sediments overlain by oxygen-depleted waters, driving additional eutrophication. During reoxygenation, an influx of phosphate was observed in all three sedimentary environments, removing soluble phosphorus through coagulation and finally precipitation. Two degraded organic matter (OM) types could be distinguished: OM degraded under oxic conditions in marine and brackish sediments v. OM rapidly degraded under anoxic conditions in lagoon sediments.

Mercury speciation in the Adriatic Sea

Mercury and its speciation were studied in surface and deep waters of the Adriatic Sea. Several mercury species (i.e. DGM – dissolved gaseous Hg, RHg – reactive Hg, THg – total Hg, MeHg – monomethyl Hg and DMeHg – dimethylmercury) together with other water parameters were measured in coastal and open sea deep water profiles. THg concentrations in the water column, as well as in sediments and pore waters, were the highest in the northern, most polluted part of the Adriatic Sea as the consequence of Hg mining in Idrija and the heavy industry of northern Italy. Certain profiles in the South Adriatic Pit exhibit an increase of DGM just over the bottom due to its diffusion from sediment as a consequence of microbial and/or tectonic activity. Furthermore, a Hg mass balance for the Adriatic Sea was calculated based on measurements and literature data.

Distribution of stable isotopes in surface water along the Danube River in Serbia

Stable hydrogen and oxygen isotopes were analysed in water samples from the River Danube and its tributaries during a longitudinal survey performed in August 2005 on Serbian territory. Danube river water data ranged from−80‰ to−66‰ for δ2H, and from−11.2‰ to−9.3‰ for δ18O with δ values increasing downstream. The isotopic signatures of the adjacent tributaries (the Tisza, the Sava and the Velika Morava) sampled at the locations close to their confluence with the Danube (Titel, Ostružnica and Ljubičevski most, respectively) just about the time of the campaign were enriched (−67‰ and−63‰ for δ2H, and−9.3‰ and−8.9‰ for δ18O) with respect to the Danube water because of their catchment effects. Hydrogen and oxygen stable isotope values were used in combination with measured physico-chemical and biological parameters to trace hydrological and transport processes in these river systems. The mixing relationships between the Danube main stream and its tributaries were estimated using the mass balance for isotopic composition and electrical conductivity as conservative parameters. Evidence of an incomplete mixing process at the Čenta location, 8 km below the confluence of the Tisza river, with its participation of 88% was shown by its oxygen-18 content. The correlations between river water isotope composition and physico-chemical and biological parameters are discussed. † Revised version of a paper presented at the 9th. Symposium of the European Society for Isotope Research (ESIR), 23 to 28 June 2007, Cluj-Napoca, Romania.