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824 Ergebnisse:

Combined cluster and discriminant analysis: An efficient chemometric approach in diesel fuel characterization
Forensic Science International (2017)
Márton Novák, Dóra Palya, Zsolt Bodai, Zoltán Nyiri, Norbert Magyar, József Kovács, Zsuzsanna Eke

Combined cluster and discriminant analysis (CCDA) as a chemometric tool in compound specific isotope analysis of diesel fuels was studied. The stable carbon isotope ratios (δ13C) of n-alkanes in diesel fuel can be used to characterize or differentiate diesels originating from different sources. We investigated 25 diesel fuel samples representing 20 different brands. The samples were collected from 25 different service stations in 11 European countries over a 2 year period. The n-alkane fraction of diesel fuels was separated using solid-state urea clathrate formation combined with silica gel fractionation. The stable carbon isotope ratios of C10–C24 n-alkanes were measured with gas chromatography–isotope ratio mass spectrometry (GC–IRMS) using perdeuterated n-alkanes as internal standards. Beside the 25 samples one additional diesel fuel was prepared and measured three times to get totally homogenous samples in order to test the performance of our analytical and statistical routine. Stable isotope ratio data were evaluated with hierarchical cluster analysis (HCA), principal component analysis (PCA) and CCDA. CCDA combines two multivariate data analysis methods hierarchical cluster analysis with linear discriminant analysis (LDA). The main idea behind CCDA is to compare the goodness of preconceived (based on the sample origins) and random groupings. In CCDA all the samples were compared pairwise. The results for the parallel sample preparations showed that the analytical procedure does not have any significant effect on the δ13C values of n-alkanes. The three parallels proved to be totally homogenous with CCDA. HCA and PCA can be useful tools when the examining of the relationship among several samples is in question. However, these two techniques cannot be always decisive on the origin of similar samples. The initial hypothesis that all diesel fuel samples are considered chemically unique was verified by CCDA. The main advantage of CCDA is that it gives an objective index number about the level of similarity among the investigated samples. Thus the application of CCDA supplemented by the traditionally used multivariate methods greatly improves the efficiency of statistical analysis in the CSIA of diesel fuel samples.
Schlagworte: carbon , oilg , poll , gaschrom

Resource partitioning in gurnard species using trophic analyses: The importance of temporal resolution
Fisheries Research (2017)
Joo Myun Park, Troy F. Gaston, Jane E. Williamson

Dietary habits and intra- and inter-specific trophic ecology of co-occurring Lepidotrigla mulhalli and L. vanessa from south-eastern Australia were analysed using stomach content and stable isotope ratios (δ13C and δ15N). Both species are bottom-feeding carnivores that consumed mainly benthic crustaceans, but teleosts were also abundant in the diet of larger L. vanessa. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) of dietary data revealed significant inter-specific dietary differences; i.e. food resource partitioning. Carbon (δ13C) and nitrogen (δ15N) stable isotope values were similar between L. mulhalli and L. vanessa, however, suggesting similar trophic positioning. Ontogenetic changes in diet composition and stable isotope values were evident. As L. vanessa grew, they preyed upon larger individuals, such as teleosts and caridean shrmips, but no such trend was observed in the diets of L. mulhalli. Adults of both species were significantly enriched in 15N relative to juvenile conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e. stomach content and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring L. mulhalli and L. vanessa off Tasmanian waters.
Schlagworte: carbon , nitrogen , ecol , elem

Nitrification inhibitors mitigate N2O emissions more effectively under straw-induced conditions favoring denitrification
Soil Biology and Biochemistry (2017)
Di Wu, Mehmet Senbayram, Reinhard Well, Nicolas Brüggemann, Birgit Pfeiffer, Nadine Loick, Barbara Stempfhuber, Klaus Dittert, Roland Bol

The application of reactive nitrogen (N) in the form of synthetic/organic fertilizers plays a central role in supporting a larger human population, but also contributes to global warming through the emission of nitrous oxide (N2O). The use of nitrification inhibitors (NIs) has repeatedly been shown to minimize N2O emissions; however, their effectiveness in reducing N2O emissions varies greatly under different environmental conditions. A better understanding of how and to what extent NIs can mitigate fertilizer-related soil-borne N2O emissions under a range of different conditions is required. In the present study, we carried out a soil incubation experiment in a fully automated continuous-flow incubation system under conditions favoring either nitrification- or denitrification-derived N2O emissions. Additionally, the abundance of AOB amoA, and AOA amoA genes was quantified and N2O isotopic signatures were analyzed. We mixed a common NI (PIADIN®) with mineral fertilizer (ammonium sulfate) and examined the N2O mitigation potential of the NI in a fertilized sandy soil (low denitrification potential) and a sandy soil mixed with wheat straw (high denitrification potential) at 70% water holding capacity (WHC). In non-NI treatments, the addition of straw led to a drastic increase of CO2 and N2O emissions compared to the non-straw-amended soils, suggesting stimulated microbial activity and higher denitrification rate. The NI reduced N2O emissions in the straw-amended treatment by 41%, whereas in the treatment without straw this was only 17%. With the combination of N2O isotopic signatures and functional gene abundances, fungal denitrification was considered to be the major process contributing to the higher N2O fluxes specifically in straw-amended soils. Overall, our study indicated that NI can be used as an effective method for mitigating N2O emissions in cropland specifically when the denitrification potential is high, e.g. in moist N-fertilized and straw-amended soils.
Schlagworte: nitrogen , oxygen , soil , gashead

Isotope constraints on seasonal dynamics of dissolved and particulate N in the Pearl River Estuary, South China
Journal of Geophysical Research: Oceans (1970)
Feng Ye, Guodong Jia, Luhua Xie, Gangjian Wei, Jie Xu

Isotope measurements were performed on dissolved NO3−, NH4+ and suspended particulate total N along a salinity gradient in the Pearl River Estuary (PRE) to investigate seasonal changes in main N sources and its biogeochemical processing under the influence of monsoon climate. Our data revealed that municipal sewage and re-mineralized soil organic N were the major sources of DIN (NO3− and/or NH4+) in freshwater during winter and summer, respectively, whereas phytoplankton biomass was a major component of PN in both seasons. In low salinity waters (<2–3), nitrification was proved to be a significant NO3− source via NH4+ consumption, with N isotope effects of −15.3‰ in summer and −23.7‰ in winter for NH4+ oxidation. The contribution of nitrification to the total NO3− pool was smaller in summer than in winter, most likely due to freshwater dilution. At mid-salinities (3–20), δ15N values of PN were similar to those of NO3− and NH4+ in summer, reflecting a strong coupling between assimilation and remineralization. In winter, however, higher δ15NNH4 but lower δ15NNO3 than δ15NPN were observed, even though δ15NPN was similar between summer and winter. Intense sediment-water interaction and resuspension of sediments during winter appeared largely responsible for the decoupling. At high salinities, the greater enrichment in δ18ONO3 than in δ15NNO3 (up to 15.6‰) in winter suggests that atmospheric deposition may contribute to NO3− delivery during the dry season. Overall, these results show the importance of seasonal variability in physical forcing on biological N sources and its turnover processes in the highly dynamic river-dominated estuary
Schlagworte: nitrogen , oxygen , geol , gashead

Eating in prosperity: First stable isotope evidence of diet from Palatial Knossos
Journal of Archaeological Science: Reports (2016)
Argyro Nafplioti

This paper discusses the first stable isotope evidence of diet from Protopalatial to Neopalatial Knossos on Crete to reconstruct individual long-term dietary records for people from the site, spanning the period circa 1900 to 1600BC. The aim is to shed light onto the lifeways and social organization of the respective communities, and to investigate people's everyday life for evidence of the site's politico-economic supremacy in the Neopalatial period. Eighty-one human and 12 animal individuals from two Palatial cemeteries at Knossos were sampled for cortical bone and the extracted collagen was analyzed for stable carbon and nitrogen isotope ratios to trace relative proportions of (broad categories of) foodstuffs that they consumed on a day-to-day basis. The human collagen stable isotope signatures follow a broad distribution that reflects a range of diets, where animal protein, including marine in addition to terrestrial, was consumed at different levels. Faunal isotope values from the site are consistent with a terrestrial C3 trophic context with apparently no C4 protein input. The observed dietary variation in the human stable isotope ratios shows no clear sex-, tomb-, or cemetery-pattern; it rather follows a temporal trend that is in tune with contemporary socio-economic and political developments and the increasing prosperity of Knossos in the period investigated. Moreover, the study yielded the first positive human palaeodietary evidence for marine food consumption in Prehistoric Crete.

Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a
Nature Geoscience (2016)
B. D. A. Naafs, J. M. Castro, G. A. De Gea, M. L. Quijano, D. N. Schmidt, R. D. Pancost

During the Aptian Oceanic Anoxic Event 1a, about 120 million years ago, black shales were deposited in all the main ocean basins1. The event was also associated with elevated sea surface temperatures2, 3 and a calcification crisis in calcareous nannoplankton4. These environmental changes have been attributed to variations in atmospheric CO2 concentrations2, 3, 5, 6, but the evolution of the carbon cycle during this event is poorly constrained. Here we present records of atmospheric CO2 concentrations across Oceanic Anoxic Event 1a derived from bulk and compound-specific δ13C from marine rock outcrops in southern Spain and Tunisia. We find that CO2 concentrations doubled in two steps during the oceanic anoxic event and remained above background values for approximately 1.5–2 million years before declining. The rise of CO2 concentrations occurred over several tens to hundreds of thousand years, and thus was unlikely to have resulted in any prolonged surface ocean acidification, suggesting that CO2 emissions were not the primary cause of the nannoplankton calcification crisis. We find that the period of elevated CO2 concentrations coincides with a shift in the oceanic osmium-isotope inventory7 associated with emplacement of the Ontong Java Plateau flood basalts, and conclude that sustained volcanic outgassing was the primary source of carbon dioxide during Oceanic Anoxic Event 1a.
Schlagworte: carbon , geol , clim , elem , gaschrom

Historic commodity of sulfur prevailed during the early to middle 19th century in Japan: A stable isotopic analysis for tracing the provenance
Journal of Archaeological Science: Reports (2016)
Chitoshi Mizota, Toshiro Yamanaka, Ryoko Furukawa, Yuki Furukawa

Demands for native volcanic sulfur as one of the ingredients of gunpowder reached a maximum during the early to middle 19th century, when abrupt changes in the political regime occurred in Japan. The historic commodity of sulfur prevailing during this time was analyzed for stable isotopic ratios (expressed as δ34S) to examine the provenance. The sampled sulfur involves the Siebold collection (acquisition by P. F. von Siebold in Nagasaki, northern Kyushu and kept in Naturalis, Leiden, The Netherlands) and Egawa library (Nirayama, central Japan) for which exact location of the origin is ambiguous or absent. The sulfur isotopic data were evaluated by comparison with the revised database for the spatial distribution of δ34S values of operative sulfur mines throughout the Japanese archipelagos. With a few exceptions, the commodity sulfur was transported through short-distance marketing systems within close proximity to Nagasaki and Nirayama.

Unique photosynthetic phenotypes in Portulaca (Portulacaceae): C3-C4 intermediates and NAD-ME C4 species with Pilosoid-type Kranz anatomy.
Journal of experimental botany (2016)
Elena V Voznesenskaya, Nuria K Koteyeva, Gerald E Edwards, Gilberto Ocampo

Portulacaceae is a family that has considerable diversity in photosynthetic phenotypes. It is one of 19 families of terrestrial plants where species having C4 photosynthesis have been found. Most species in Portulaca are in the alternate-leaved (AL) lineage, which includes one clade (Cryptopetala) with taxa lacking C4 photosynthesis and three clades having C4 species (Oleracea, Umbraticola and Pilosa). All three species in the Cryptopetala clade lack Kranz anatomy, the leaves have C3-like carbon isotope composition and they have low levels of C4 cycle enzymes. Anatomical, biochemical and physiological analyses show they are all C3-C4 intermediates. They have intermediate CO2 compensation points, enrichment of organelles in the centripetal position in bundle sheath (BS) cells, with selective localization of glycine decarboxylase in BS mitochondria. In the three C4 clades there are differences in Kranz anatomy types and form of malic enzyme (ME) reported to function in C4 (NAD-ME versus NADP-ME): Oleracea (Atriplicoid, NAD-ME), Umbraticola (Atriplicoid, NADP-ME) and Pilosa (Pilosoid, NADP-ME). Structural and biochemical analyses were performed on Pilosa clade representatives having Pilosoid-type leaf anatomy with Kranz tissue enclosing individual peripheral vascular bundles and water storage in the center of the leaf. In this clade, all species except P. elatior are NADP-ME-type C4 species with grana-deficient BS chloroplasts and grana-enriched M chloroplasts. Surprisingly, P. elatior has BS chloroplasts enriched in grana and NAD-ME-type photosynthesis. The results suggest photosynthetic phenotypes were probably derived from an ancestor with NADP-ME-type C4, with two independent switches to NAD-ME type.
Schlagworte: carbon , nitrogen , soil , elem

Marginal Calluna populations are more resistant to climate change, but not under high-nitrogen loads
Plant Ecology (2016)
Maren Meyer-Grünefeldt, Kristina Belz, Leonor Calvo, Elena Marcos, Goddert von Oheimb, Werner Härdtle

The dominant plant species of European heathlands Calluna vulgaris is considered vulnerable to drought and enhanced nitrogen (N) loads. However, impacts may vary across the distribution range of Calluna heathlands. We tested the hypothesis that Calluna of southern and eastern marginal populations (MP) are more resistant to drought events than plants of central populations (CP), and that this is mainly due to trait differences such as biomass allocation patterns. Furthermore, we hypothesised that N fertilisation can offset differences in drought susceptibility between CP and MP. We conducted a full-factorial 2-year greenhouse experiment with Calluna plants of CP and MP and quantified growth responses in terms of biomass production, allocation and tissue δ13C signatures. Biomass production, shoot–root ratios and tissue δ13C values of 1-year-old plants were higher for CP than for MP, indicating a higher drought susceptibility of CP. These trait differences were not observed for 2-year-old plants. N fertilisation increased shoot–root ratios of 1- and 2-year-old plants and across populations due to a stimulation of the aboveground biomass allocation. As a consequence, population-related differences in drought susceptibility were offset for N-fertilised plants. We concluded that Calluna plants originating from different populations developed adaptive traits to local climates, which determined their drought sensitivity. However, the higher drought resistance of MP can be attenuated by an N-induced increase in shoot–root ratios. This suggests that analyses on plant growth responses to global change should include multi-factor approaches with a focus on different populations throughout a species’ distribution range.
Schlagworte: carbon , nitrogen , soil , ecol , clim , elem

Environmental assessment of freshwater ecosystems of the Sava River watershed and Cerkniško Lake, Slovenia, using the bioindicator species Fontinalis antipyretica : insights from stable isotopes and selected elements
Isotopes in Environmental and Health Studies (2016)
Špela Mechora, Tjaša Kanduč

Ten locations in the Notranjska region, Slovenia, with different land use in the catchment (town, village and agricultural areas), including reference points with different geological composition considered as unpolluted sites, were sampled for water and aquatic moss to evaluate environmental assessment in fresh water systems of the Sava River watershed. Samples of fresh water and Fontinalis antipyretica were taken in all four seasons during the years 2010 and 2012. The water chemistry of the investigated locations was dominated by , while concentrations of seasonally ranged from 2.1 to 6.4 mg L−1 and at one of the reference sites did not exceed 1.3 mg L−1. δ13CDIC values seasonally ranged from −13.3 to −8.1 ‰ and indicated waters dominated by degradation of organic matter and dissolution of carbonates. δ13Cplant values of F. antipyretica seasonally ranged from −45 to −32.9 ‰ and of δ15Nplant from −0.2 to 6.5 ‰. The higher δ15N value of 6.5 ‰ found in F. antipyretica was related to agricultural activity i...
Schlagworte: carbon , ecol , poll , gashead