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824 Ergebnisse:

Stable oxygen isotope evidence for mobility in medieval and post-medieval Trondheim, Norway
Journal of Archaeological Science: Reports (2016)
Stian Suppersberger Hamre, Valérie Daux

Immigration and mobility in the medieval and post-medieval periods in Norway have, up until now, mainly been discussed on the basis of historical sources. This paper presents the results of stable oxygen isotope (δ18O) analyses of the 1st and 3rd molars from 95 individuals from medieval and post-medieval Trondheim, as well as new information about the δ18O composition in the precipitation and drinking water in Trondheim. Through these analyses, the authors have attempted to shed light on the age of migrating individuals and directions of migration, to investigate temporal changes with regard to migration, and to make suggestions regarding the proportion of immigrants to locals in the population. The results show that the majority of the immigrants came from areas to the north or east of Trondheim, and some travelled at least 800–1000km to come to Trondheim. It has also been shown that a large proportion of the medieval individuals moved during childhood. Both with regard to child mobility and migration in general, the evidence suggests that the migratory activity decreased from the medieval to the post-medieval period.
Schlagworte: oxygen , arch , aquap

Cross-checking groundwater age by 4He and 14C dating in a granite, Tono area, central Japan
Geochimica et Cosmochimica Acta (2016)
Takuma Hasegawa, Kotaro Nakata, Yuichi Tomioka, Kazuyuki Goto, Kouki Kashiwaya, Katsuhiro Hama, Teruki Iwatsuki, Takanori Kunimaru, Masaki Takeda

Groundwater dating was performed simultaneously by the 4He and 14C methods in granite of the Tono area in central Japan. Groundwater was sampled at 30 packed-off sections of six 1000-m boreholes. 4He concentrations increased and 14C concentrations decreased along a groundwater flow path on a topographic gradient. 4He ages were calculated by using the in situ 4He production rate derived from the porosity, density, and U and Th content of the rock, neglecting external flux. 14C ages were calculated with a noncorrected model in which the initial 14C content was 100 percent of the modern radiocarbon level (Co = 100 pmC), a statistical model using the average 14C content of tritium-bearing samples (Co = 46.4 pmC), and a δ13C model based on the isotopic mass balance. Although the absolute 14C ages calculated by the models were different, the relative 14C ages were almost identical. The relative 14C ages were considered reliable because dissolved inorganic carbon has no significant geochemical reactions in granite. The relation between the 4He ages and the noncorrected 14C ages was [4He age] = 1.15 [14C age] + 7200 (R2 = 0.81), except in the discharge area. The slope of this relation was equivalent to unity, which indicates that the 4He accumulation rate is confirmed by the relative 14C ages. Moreover, the accumulated 3He/4He ratio was equivalent to that derived from the 6Li(α,n)3H reaction in granite. These results show that the accumulated He is of crustal origin, produced in situ without external flux, except in the discharge area. The intercept value of 7200 a implies that the 14C concentrations were diluted due to geochemical reactions. Tritium-bearing samples supported this result. Simultaneous measurements make it feasible to estimate the accumulation rate of 4He and initial dilution of 14C, which cannot be done with a single method. Cross-checking groundwater dating has the potential to provide more reliable groundwater ages. The circulation time of the groundwater flow in the Tono area may be several tens of thousands of years, and the groundwater age calculated from the 4He and 14C ages appears to be consistent with geochemical information such as groundwater types, δD and δ18O.
Schlagworte: hydrogen , oxygen , geol , gashead

Determining the geographical origin of Asian longhorn beetle (Anoplophora glabripennis) specimens using stable isotope and trace element analyses
Pest Management Science (2016)
Katharina Heinrich, Larissa Collins

BACKGROUND An outbreak of EU quarantine listed pest Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambicidae), Asian Longhorn Beetle, in Kent (UK) resulted in environmentally and financially costly eradication action being taken. In this study the potential of using multi-element stable isotope or trace element analyses to determine the geographical origin of individual specimens has been investigated. RESULTS The isotope ratios of A. glabripennis individuals for hydrogen varied within and across 5 locations. Carbonisotope ratios fell within the expected values for C3 plants (trees using the photosynthetic pathway common for moderate climates). Nitrogen isotope ratios indicated separation of UK laboratory from American (New York, Ohio, Massachusetts) beetles; whilst sulfur isotope ratios distinguished beetles from New York against the other 4 locations. Three trace elements (TEs) separated UK laboratory-reared beetles from American beetles (Ohio and New York) with ~ 68% confidence. CONCLUSIONS Stable isotope and TE analyses show potential to differentiate between newly arrived A. glabripennis individuals and those from previously undetected in-country populations, which would be of immediate practical benefit in making appropriate strategic decisions on surveillance and eradication. Analyses of additional samples (i) from the same populations, (ii) different locations and (iii) variety of host trees will enhance the overall picture.
Schlagworte: carbon , nitrogen , ecol , elem

A Spatially Explicit Dual-Isotope Approach to Map Regions of Plant-Plant Interaction after Exotic Plant Invasion
PLOS ONE (2016)
Christine Hellmann, Christiane Werner, Jens Oldeland, MRT Dale, M-J Fortin, WW Hargrove, FM Hoffman, J Kumar, RT Mills, FM Hoffman, WW Hargrove, MP Ward, TE Carpenter, S Brooker, S Clarke, JK Njagi, S Polack, B Mugo, B Estambale, F Tanser, T Bärnighausen,

Understanding interactions between native and invasive plant species in field settings and quantifying the impact of invaders in heterogeneous native ecosystems requires resolving the spatial scale on which these processes take place. Therefore, functional tracers are needed that enable resolving the alterations induced by exotic plant invasion in contrast to natural variation in a spatially explicit way. 15N isoscapes, i.e., spatially referenced representations of stable nitrogen isotopic signatures, have recently provided such a tracer. However, different processes, e.g. water, nitrogen or carbon cycles, may be affected at different spatial scales. Thus multi-isotope studies, by using different functional tracers, can potentially return a more integrated picture of invader impact. This is particularly true when isoscapes are submitted to statistical methods suitable to find homogeneous subgroups in multivariate data such as cluster analysis. Here, we used model-based clustering of spatially explicit foliar δ15N and δ13C isoscapes together with N concentration of a native indicator species, Corema album, to map regions of influence in a Portuguese dune ecosystem invaded by the N2-fixing Acacia longifolia. Cluster analysis identified regions with pronounced alterations in N budget and water use efficiency in the native species, with a more than twofold increase in foliar N, and δ13C and δ15N enrichment of up to 2‰ and 8‰ closer to the invader, respectively. Furthermore, clusters of multiple functional tracers indicated a spatial shift from facilitation through N addition in the proximity of the invader to competition for resources other than N in close contact. Finding homogeneous subgroups in multi-isotope data by means of model-based cluster analysis provided an effective tool for detecting spatial structure in processes affecting plant physiology and performance. The proposed method can give an objective measure of the spatial extent of influence of plant-plant interactions, thus improving our understanding of spatial pattern and interactions in plant communities.
Schlagworte: carbon , nitrogen , soil , elem

Particulate organic matter higher concentrations, terrestrial sources and losses in bottom waters of the turbidity maximum, Delaware Estuary, U.S.A.
Estuarine, Coastal and Shelf Science (2016)
Anna L. Hermes, Elisabeth L. Sikes

The pathway and fate of land-derived suspended particulate organic matter (POM) as it passes through estuaries remains a poorly constrained component of coastal carbon dynamics. The δ13C of bulk POC (particulate organic carbon; δ13C-POC) and n-alkane biomarkers were used to assess the proportion of algal- and land- (vascular plant) derived POM through the Delaware Estuary, on five cruises in 2010–2011. We found that POC was highly correlated with suspended sediment concentrations (SSC). Higher SSC was present in bottom waters, causing bottom waters to have consistently higher concentrations of POC than surface waters, with the bottom waters of the estuarine turbidity maximum (ETM) exhibiting maximum POC concentrations for all seasons and flow regimes. Algal-derived POM seasonally affected the δ13C-POC and n-alkane geochemical signatures of surface waters, whereas bottom waters were dominated by vascular plant-derived POM. δ13C-POC results suggested a gradual loss in vascular plant-derived POM between the riverine and marine endmember stations. In contrast, n-alkane concentrations peaked in bottom waters of the ETM at 2–5 times surface water concentrations. Indices of the relative proportions of n-alkanes and n-alkanes as a proportion of total POC had their levels decrease considerably downstream of the ETM. These biomarker analyses suggest enhanced loss of land-derived material across the ETM and that the ETM acts as a geochemical filter for vascular plant-derived POM in a classic well mixed estuary.
Schlagworte: carbon , soil , elem

Sulfur isotopic characteristics of volcanic products from the September 2014 Mount Ontake eruption, Japan
Earth, Planets and Space (2016)
Kei Ikehata, Teruyuki Maruoka

Components and sulfur isotopic compositions of pyroclastic materials from the 2014 Mt. Ontake eruption were investigated. The volcanic ash samples were found to be composed of altered volcanic fragments, alunite, anhydrite, biotite, cristobalite, gypsum, ilmenite, kaolin minerals, native sulfur, orthopyroxene, plagioclase, potassium feldspar, pyrite, pyrophyllite, quartz, rutile, and smectite, and most of these minerals were likely derived from the acidic alteration zones of Mt. Ontake. The absence of juvenile material in the eruptive products indicates that the eruption was phreatic. The sulfur isotopic compositions of the water-leached sulfate, hydrochloric acid-leached sulfate, acetone-leached native sulfur, and pyrite of the samples indicate that these sulfur species were produced by disproportionation of magmatic SO2 in the hydrothermal system at temperatures of 270–281 °C. This temperature range is consistent with that inferred from the hydrothermal mineral assemblage (e.g., pyrophyllite and rutile) in the 2014 pyroclastic materials (200–300 °C). Except for the sulfur isotopic compositions of anhydrite, which may have been altered by incorporation of sulfate minerals in a fumarolic area with lower sulfur isotopic values into the underground materials during the 1979 eruption, no significant differences in the mineral assemblages and sulfur isotopic compositions of the pyroclastic materials were identified between the products of the 2014 and 1979 Ontake phreatic eruptions, which suggests geochemical similarities in the underlying hydrothermal systems before the 2014 and 1979 eruptions

Multiphase dolomitization of deeply buried Cambrian petroleum reservoirs, Tarim Basin, north-west China
Sedimentology (2016)
Lei Jiang, Chunfang Cai, Richard H. Worden, Stephen F. Crowley, Lianqi Jia, Ke Zhang, Ian J. Duncan

Cambrian dolostone reservoirs in the Tarim Basin, China, have significant potential for future discoveries of petroleum, although exploration and production planning is hampered by limited understanding of the occurrence and distribution of dolomite in such ancient rocks buried to nearly 8 km. The study herein accessed new drill core samples which provide an opportunity to understand the dolomitization process in deep basins and its impact on Cambrian carbonate reservoirs. This study documents the origin of the dolostone reservoirs using a combination of petrology, fluid-inclusion microthermometry, and stable and radiogenic-isotopes of outcrop and core samples. An initial microbial dolomitization event (D1) occurred in restricted lagoon environments and is characterized by depleted δ13C values. Dolomicrite (D2) from lagoonal and sabkha facies, some fabric-retentive dolomite (D3) and fabric-obliterative dolomite (D4) in the peloidal shoal and reef facies show the highest δ18O values. These dolomites represent relatively early reflux dolomitization. The local occurrence of K-feldspar in D2 indicates that some strontium was contributed via terrigenous input. Most fabric-retentive dolomite (D3) may have precipitated from seawater at slightly elevated temperatures, suggested by petrological and isotopic data. Most fabric-obliterative dolomite (D4), and medium to coarse dolomite cement (D5), formed between 90°C and 130°C from marine evaporitic brine. Saddle dolomite (D6) formed by hydrothermal dolomitization at temperatures up to 170°C, and involved the mixing of connate brines with Sr- enriched hydrothermal fluids. Intercrystalline, moldic, and breccia porosities are due to the early stages of dolomitization. Macroscopic, intergranular, vuggy, fracture, and dissolution porosity are due to buial-related dissolution and regional hydrothermal events. This work has shown that old (for example, Cambrian or even Precambrian) sucrosic dolomite with associated anhydrite, buried to as much as 8000 m, can still have a high potential for hosting large hydrocarbon resources and should be globally targeted for future exploration.
Schlagworte: carbon , geol , oilg , gashead

Interactions between biochar and soil organic carbon decomposition: Effects of nitrogen and low molecular weight carbon compound addition
Soil Biology and Biochemistry (2016)
Xinyu Jiang, Michelle L. Haddix, M. Francesca Cotrufo

Conversion of plant residues to biochar is an attractive strategy for atmospheric CO2 emission mitigation and soil carbon (C) storage enhancement. However, our understanding of the factors controlling biochar persistence in soil is still limited, and generally based on biochar chemical recalcitrance. In addition to its chemical properties, biochar C decomposition might be limited by other factors, such as N and low molecular weight C compounds (LMW-C) availability. We presented results from a laboratory incubation experiment, where 4 atom% 13C enriched biochar was added at a rate of 10% by weight to two different soils, with or without N and LMW-C additions. Sucrose was used as the LMW-C, and its 13C natural abundance composition was manipulated, by mixing sucrose from sugar beet (C3) and from sugar cane (C4), to make it equal or dissimilar to the native soil organic carbon (SOC). This approach allowed partitioning the biochar-C from the ‘soil + LMW-C’ in the biochar amendment units and the LMW-C from SOC in the non-biochar amended units. Biochar-C, SOC and LMW-C were traced into CO2 throughout the 112 day incubation and into microbial biomass C (MBC) and dissolved organic C (DOC) at the end of the incubation. Compared to LMW-C addition, N was a more significant factor stimulating biochar-C mineralization and biochar-C incorporation in microbial biomass. Biochar significantly decreased SOC mineralization and this negative effect was not influenced by N and LMW-C additions. Biochar addition promoted formation of SOC derived DOC; however, DOC accumulated in soil rather than being mineralized to CO2. According to our study, biochar was confirmed to be highly resistant to decomposition, and N or LMW-C availability did not affect the overall soil C sequestration potential of biochar. Biochar effects on soil DOC dynamics will need to be farther investigated in the field to better constrain the overall C sequestration potential of biochar.
Schlagworte: carbon , soil , elem

Fluid inclusion and stable isotopic constraints on fluid sources and evolution of the Luojiahe Cu deposit in the southern margin of the North China Craton
Ore Geology Reviews (2016)
Yuhang Jiang, Hecai Niu, Yan Zhao, Zhiwei Bao, Ningbo Li, Qiang Shan

The Luojiahe Cu deposit in the Zhongtiaoshan region is located in the southern margin of the North China Craton. The orebodies are hosted in the mafic volcanic-sedimentary sequences of the metamorphosed (greenschist-facies) Neoarchean Songjiashan Group. The Luojiahe Cu mineralization can be divided into the primary volcanogenic massive sulfide (VMS) mineralization stage (Stage I, banded or stockwork ores) and the subsequent metamorphic remobilization stage (Stage II, coarse-vein ores). Three types of quartz selected for fluid inclusion (FI) studies were collected from the Stage I banded (Q1) and stockwork (Q2) ores and Stage II coarse-vein (Q3) ores. Four types of FIs were identified: (1) liquid-rich FIs (L-type), (2) pure vapor and vapor-rich FIs (V-type), (3) daughter mineral-bearing FIs (S-type), and (4) CH4-H2O FIs (C-type). Systematical microthermometric and H-O isotopic studies show that the Stage I ore-forming fluids consist predominantly of high salinity evolved seawater (125–220°C; 23.9–27.9wt.% NaCl equiv.) and some magmatic-hydrothermal fluids (249–339°C; 34.5–42.2wt.% NaCl equiv.). The two fluid end-members are represented by the L-type FIs in Q1 and the S- and V-type FIs in Q2. The temperature- and salinity variation trends of the L-type FIs in Q1 indicate a mixing process between the hot evolved seawater and cold seawater at Stage I. Furthermore, the V- and S-type FI coexistence in Q2 and their microthermometric data suggest that fluid unmixing has occurred in original magmatic fluids at Stage I. In contrast, the Stage II ore-forming fluids consist of CH4-rich metamorphic fluids (192–350°C; 10.6–43.2wt.% NaCl equiv.). Carbon isotopic analysis of the Stage II calcite (−4.58 to −10.83‰) and graphite (−32.01 to −39.16‰) in the ore-hosting chlorite schist indicates that the metamorphic ore-forming fluids had exchanged carbon isotope with graphite. The generation of CH4 may have resulted from the interaction between H2O (released by metamorphic devolatilization) and graphite. The continuous consumption of H2O in the hydrothermal fluid system may have increased the fluid salinity and triggered fluid unmixing in the CH4-NaCl-H2O system. In addition, the VMS metallogenic environment is generally favorable for microbial communities. It is considered that the graphite at Luojiahe may have been derived from sedimentary organic matter formed in seafloor hydrothermal vent systems, as also supported by carbon isotopic data. We propose that at Stage I, the main mineralization may have been resulted from 1) fluid mixing of hot evolved seawater and cold seawater in the near-surface environment; and 2) fluid unmixing caused by the percolation of magmatic fluids into syn-volcanic faults, forming the stockwork ores. At Stage II, the interaction between H2O and graphite may have resulted in the reduction of ore-forming fluids and Cu precipitation, and fluid unmixing in the CH4-NaCl-H2O system may have further promoted the Cu mineralization.
Schlagworte: hydrogen , oxygen , geol , gashead

Beyond Zar: the use and abuse of classification statistics for otolith chemistry
Journal of Fish Biology (2016)
C. M. Jones, M. Palmer, J. J. Schaffler

Classification method performance was evaluated using otolith chemistry of juvenile Atlantic menhaden Brevoortia tyrannus when assumptions of data normality were met and were violated. Four methods were tested [linear discriminant function analysis (LDFA), quadratic discriminant function analysis (QDFA), random forest (RF) and artificial neural networks (ANN)] using computer simulation to determine their performance when variable-group means ranged from small to large and their performance under conditions of typical skewness to double the amount of skewness typically observed. Using the kappa index, the parametric methods performed best after applying appropriate data transformation, gaining 2% better performance with LDFA performing slightly better than QDFA. RF performed as well as QDFA and showed no difference in performance between raw and transformed data while the performance of ANN was the poorest and worse with raw data. All methods performed well when group differences were large, but parametric methods outperformed machine-learning methods. When data were skewed the performance of all methods declined and worsened with greater skewness, but RF performed consistently as well or better than the other methods in the presence of skewness. The parametric methods were found to be more powerful when assumptions of normality can be met and can be used confidently when skewness and kurtosis are minimized. When these assumptions cannot be minimized, then machine-algorithm methods should also be tried.
Schlagworte: carbon , oxygen , ecol , gashead