Andrius Garbaras

Stable isotopes measurements reveal dual carbon pools contributing to organic matter enrichment in marine aerosol

Stable carbon isotope ratios in marine aerosol collected over the Southern Indian Ocean revealed δ13C values ranging from −20.0‰ to −28.2‰. The isotope ratios exhibited a strong correlation with the fractional organic matter (OM) enrichment in sea spray aerosol. The base-level isotope ratio of −20.0‰ is characteristic of an aged Dissolved Organic Matter (DOM) pool contributing a relatively homogeneous background level of DOM to oceanic waters. The range of isotope ratios, extending down to −28.2‰, is characteristic of more variable, stronger, and fresher Particulate Organic Matter (POM) pool driven by trophic level interactions. We present a conceptual dual-pool POM-DOM model which comprises a ‘young’ and variable POM pool which dominates enrichment in sea-spray and an ‘aged’ but invariant DOM pool which is, ultimately, an aged end-product of processed ‘fresh’ POM. This model is harmonious with the preferential enrichment of fresh colloidal and nano-gel lipid-like particulate matter in sea spray particles and the observed depleted δ13C ratio resulting from isotope equilibrium fractionation coupled with enhanced plankton photosynthesis in cold water (−2 °C to +8 °C). These results re-assert the hypothesis that OM enrichment in sea-spray is directly linked to primary production and, consequently, can have implications for climate-aerosol-cloud feedback systems.

Aerosol source (biomass, traffic and coal emission) apportionment in Lithuania using stable carbon and radiocarbon analysis

ABSTRACT In the present study, a combination of the stable carbon isotope ratio (13C/12C) with radiocarbon data (14C) allowed us to perform the aerosol source apportionment. Filter samples of PM1 were collected during the warm and cold periods in rural and urban sites in Lithuania. The 14C/12C ratio of total carbon (TC) was measured using the single stage accelerator mass spectrometer quantifying of fossil and non-fossil derived aerosol emissions. The δ13C value was measured using an elemental analyser interfaced with an isotope ratio mass spectrometer. We have found that the highest fraction of contemporary carbon (fc = 0.82) was measured during a warm period in a rural location. A higher fraction of fossil fuel-derived carbon was observed for air masses transported from highly industrialized Western European regions during both seasons. Isotope mass balance calculations revealed that the traffic emissions composed 15 and 25 % in rural and urban sites, respectively, and did not change during either season. Input from coal-derived aerosol particles was estimated to be 15 % at an urban site during the cold period. The combination of the stable carbon isotope ratio with the radiocarbon data allowed us to distinguish coal, liquid fossil fuel combustion, and non-fossil derived aerosol particle emissions.

Dietary aspects of the West Lithuanian people during the Late Roman and Early Migration periods with reference to household and funerary pottery

Zusammenfassung Die vorliegende Studie präsentiert die Ergebnisse einer integrierten interdisziplinären Untersuchung von Rückständen verkohlten organischen Materials bzw. Lebensmittelkrusten, die auf der inneren Keramikoberfläche haften und eine wertvolle Informationsquelle für die menschliche Ernährung darstellen. FTIR und Isotopenverhältnis-Massenspektrometrie wurden verwendet, um Haushaltsgefäßen und Miniaturtöpfen zu analysieren, die in der Zeit zwischen dem 3. und der Mitte des 5. Jahrhunderts in Westlitauen mit Toten als Beigaben in Vestattungen gelangten. Die δ13C-Isotopenanalyse zeigt einen beträchtlichen Unterschied zwischen den Rückständen von Haushalts- und Grabkeramik. Die δ13C-Isotopenverhältnisse in den Proben von Miniaturpotentiometern variieren von −28,0 ‰ bis −28,8 ‰. Isotopenwerte in einem relativ engen Bereich weisen darauf hin, dass in den Töpfen vorhandenes organisches Material ähnlichen Ursprungs war. δ13C-Isotopenverhältniswerte lassen vermuten, dass niedergelgte Miniaturtöpfe mit Bier aus Gerste und/oder Hafer gefüllt waren. Der δ15N-Isotopenwert (δ15N = 8,0 ‰) und die Carboxyl-Gruppe der C-O-Gruppe sowie die Polysaccharide zeigen das Vorhandensein von Proteinen in einigen der Miniaturtöpfen an, so dass außerdem angenommen werden kann, dass diese mit fermentiertem Milchgetränk gefüllt waren. Die Miniaturtöpfe wurden in den Bestattungen platziert und mit einer symbolischen Menge Bier oder fermentierten Getränken auf Milchbasis gefüllt (40/50 bis 100 ml). Das Kohlenstoffisotopenverhältnis der Haushaltsgefäße variierte von −23,9 ‰ bis −27,9 ‰, was auf eine auf Getreide vom Typ C3 basierende Ernährung hindeutet. Die aus organischen Rückständen gewonnenen δ15N-Werte liegen zwischen 3,1 ‰ und 9,9 ‰, was als Hinweis zu verstehen ist, dass Bestandteil der menschlichen Ernähung auch Pflanzen- und Allesfresser waren. Zusammenfassend zeigt die Analyse, dass die konsumierte Nahrung terrestrischen Ursprungs ist und aus der Landwirtschaft und der Tierzucht stammt.

Rapid analysis method for the determination of 14C specific activity in irradiated graphite

14C is one of the limiting radionuclides used in the categorization of radioactive graphite waste; this categorization is crucial in selecting the appropriate graphite treatment/disposal method. We propose a rapid analysis method for 14C specific activity determination in small graphite samples in the 1–100 μg range. The method applies an oxidation procedure to the sample, which extracts 14C from the different carbonaceous matrices in a controlled manner. Because this method enables fast online measurement and 14C specific activity evaluation, it can be especially useful for characterizing 14C in irradiated graphite when dismantling graphite moderator and reflector parts, or when sorting radioactive graphite waste from decommissioned nuclear power plants. The proposed rapid method is based on graphite combustion and the subsequent measurement of both CO2 and 14C, using a commercial elemental analyser and the semiconductor detector, respectively. The method was verified using the liquid scintillation counting (LSC) technique. The uncertainty of this rapid method is within the acceptable range for radioactive waste characterization purposes. The 14C specific activity determination procedure proposed in this study takes approximately ten minutes, comparing favorably to the more complicated and time consuming LSC method. This method can be potentially used to radiologically characterize radioactive waste or used in biomedical applications when dealing with the specific activity determination of 14C in the sample.

Effect of the invasive New Zealand mud snail (Potamopyrgus antipodarum) on the littoral macroinvertebrate community in a temperate mesotrophic lake

The chief aim of the present study was to reveal changes in a littoral macroinvertebrate community induced by the invasion of the New Zealand mud snail (Potamopyrgus antipodarum). For that purpose, we compared relevant aspects of the lake littoral macroinvertebrate community in pre- and post-invasion periods and determined the trophic position of P. antipodarum in the lake food web by performing the stable isotope-ratio analysis. The analyses performed showed that P. antipodarum is a primary consumer that may utilise a wide range of primary food sources. Overall, our study showed the following effects of the P. antipodarum invasion on the macroinvertebrate community: a definite increase in the total macroinvertebrate biomass, a significant increase in the local macroinvertebrate family richness and diversity, a shift in the community composition from crustacean- to gastropod-dominated. However, P. antipodarum invasion was not found to affect the biomass of local macroinvertebrates, which remained unchanged.

Using Compound-Specific and Bulk Stable Isotope Analysis for Trophic Positioning of Bivalves in Contaminated Baltic Sea Sediments

Stable nitrogen isotopes (δ15N) are used as indicators of trophic position (TP) of consumers. Deriving TP from δ15N of individual amino acids (AAs) is becoming popular in ecological studies, because of lower uncertainty than TP based on bulk δ15N (TPbulk). This method would also facilitate biomagnification studies provided that isotope fractionation is unaffected by toxic exposure. We compared TPAA and TPbulk estimates for a sediment-dwelling bivalve from two coastal sites, a pristine and a contaminated. Chemical analysis of PCB levels in mussels, sediments, and pore water confirmed the expected difference between sites. Both methods, but in particular the TPAA underestimated the actual TP of bivalves. Using error propagation, the total uncertainty related to the analytical precision and assumptions in the TP calculations was found to be similar between the two methods. Interestingly, the significantly higher intercept for the regression between TPAA and TPbulk in the contaminated site compared to the pristine site indicates a higher deamination rate due to detoxification as a result of chronic exposure and a higher 15N fractionation. Hence, there is a need for controlled experiments on assumptions underlying amino acid-specific stable isotope methods in food web and bimagnification studies.

Yeast-assisted synthesis of polypyrrole: Quantification and influence on the mechanical properties of the cell wall

In this study, the metabolism of yeast cells (Saccharomyces cerevisiae) was utilized for the synthesis of the conducting polymer - polypyrrole (Ppy).Yeast cells were modified in situ by synthesized Ppy. The Ppy was formed in the cell wall by redox-cycling of [Fe(CN)6]3-/4-, performed by the yeast cells. Fluorescence microscopy, enzymatic digestions, atomic force microscopy and isotope ratio mass spectroscopy were applied to determine both the polymerization reaction itself and the polymer location in yeast cells. Ppy formation resulted in enhanced resistance to lytic enzymes, significant increase of elasticity and alteration of other mechanical cell wall properties evaluated by atomic force microscopy (AFM). The suggested method of polymer synthesis allows the introduction of polypyrrole structures within the cell wall, which is build up from polymers consisting of carbohydrates. This cell wall modification strategy could increase the usefulness of yeast as an alternative energy source in biofuel cells, and in cell based biosensors.

Stable isotope ratio method for the characterisation of the poultry house environment.

ABSTRACT Stable isotope analysis was applied to describe the poultry house environment. The poultry house indoor environment was selected for this study due to the relevant health problems in animals and their caretakers. Air quality parameters including temperature, relative humidity, airflow rate, NH3, CO2 and total suspended particles, as well as mean levels of total airborne bacteria and fungi count, were measured. Carbon isotope ratios (13C/12C) were obtained in size-segregated aerosol particles. The carbon (13C/12C) and nitrogen (15N/14N) isotope ratios were measured in feed, litter, scrapings from the ventilation system, feathers and eggs. Additionally, the distribution of δ13C and δ15N values in different tissues of the chicken was examined. The airborne bacteria and fungi extracted from the air filters collected from poultry farms were grown in the laboratory in media with known isotope values and measured for stable isotope ratios. Analysis of isotope fractionation between microorganisms and their media indicated the applicability of stable isotope analysis in bulk samples for the identification of source material. The analysed examples imply that stable isotope analysis can be used to examine the indoor environment along with its biology and ecology, and serve as an informative bioanalytical tool.