Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, toxic contaminants that are released to the environment from various petrogenic and pyrogenic sources. In an effort to more clearly identify and trace sources of PAHs in the environment, purification and compound specific isotope analysis methods were developed to accurately measure the stable carbon isotope ratio of individual PAHs. Development of the method included improving accuracy and precision of the isotopic measurement by producing highly pure extracts using various chromatographic techniques. The method was refined by improving compound separations using purification techniques and high resolution chromatographic columns. The purification method consists of alumina/silica gel column chromatography, gel permeation chromatography and thin layer chromatography. The mean recovery of PAHs after the purification procedure was approximately 80 %. Sample purities after purification were verified by GC/FID and full scan mass spectrometry. To better resolve peaks and provide more accurate stable carbon isotope measurements, various gas chromatographic conditions were evaluated. The precision of the method ranged between 0.08 and 0.43 . The analytical protocols were evaluated to confirm compositional and stable isotopic integrity during purification and stable isotopic analysis. To confirm the utility of the purification and isotope analysis methods, various environmental samples from marine, land and lacustrine environments were analyzed. The isolates were analyzed for the composition and the stable carbon isotope ratios of PAHs. The stable carbon isotope ratio was measured by GC/IRMS and the results, along with quantitative compound compositions, were used to characterize and identify the contaminant sources. The sources of the PAHs in the study areas were differentiated by PAH molecular ratios and confirmed by stable carbon isotope ratios. This study confirms that compound specific isotope analysis of pollutants by GC/IRMS can be used to identify PAH sources in environmental samples. The study also confirms that the purification and stable carbon isotope analysis methods that were developed can be used to accurately measure the stable carbon isotope ratios of PAHs in environmental samples for the purpose of source identification. GC/IRMS measurement of stable isotopic compositions can be an effective fingerprinting method when used in conjunction with traditional molecular composition methods.

Periodic flooding has been widely believed to serve an important role in maintaining water levels and productivity of aquatic basins in floodplain landscapes. Here, I analyze four basins of contrasting flood frequencies (one through-flow, one pulse-flooded, two non-flooded) and two adjacent river sites in the PAD were sampled during the open-water season of 2007 and spring of 2008 to characterize linkages between hydrological processes (using O and H stable isotopes) and limnological conditions, and to assess how these linkages affect trophic interactions involving the aquatic flora and fauna (using C and N stable isotopes). The water balance and water chemistry of the through-flow basin was dominated at all times by the input of river water which reduced concentrations of nutrients and ions. In contrast, evaporation played an important role in the water balance and concentrated nutrients and ions in the non-flooded basins. Surprisingly, pulse-flood events had short-lived effects on the water balance and carbon stable isotopic signatures of biota. Hydrological and limnological conditions in the pulse-flooded basin were similar to those of the river water shortly after spring flooding. After flooding, evaporation caused rapid increase of δ18O of the water comparable to patterns observed in the non-flooded basins, but recovery of water chemistry variables was delayed. In the non-flooded and pulse-flooded basins, δ13CDIC declined due to atmospheric CO2 invasion under conditions of high primary productivity and pH that generated strong kinetic fractionation. This decline in δ13CDIC values produced the opposite effect compared to when photosynthesis occurs under non-limiting carbon conditions, as occurred in the through-flow basin. This feature provides important new knowledge to improve paleolimnological interpretation of δ13C values of organic matter in sediment cores to track past changes in flooding regimes. Importantly, this study shows that pulse floods exert short-lived transient (~1-2 months) effects of the water balance and carbon dynamics of aquatic food-webs and do not elevate aquatic production, but exert longer lasting (at least an entire open-water season) on water chemistry conditions. This contrasts with previous beliefs that the effects of pulse flooding are more profound and longer lasting.

Nearly 550 samples of fine grained carbonates, collected every 0.5 to 1.0 m from the Bloom Member of the Snaky Canyon Formation at Gallagher Peak, Idaho, were analyzed to determine the high-resolution carbon isotope stratigraphy. To constrain for diagenesis, thin sections were petrographically analyzed and viewed using cathodoluminescence microscopy. Chemical analyses were performed using an electron microprobe. Average delta18O and delta13C values from the Bloom Member are -4.5% +/- 1.6% (1 sigma) and 2.1% +/- 1.1%, respectively. Maximum delta13C values are about 1% higher for the Desmoinesian and Missourian than the Morrowan and Atokan, similar to results from the Yukon Territory. delta18O and delta13C values are lowest for crystalline mosaic limestones and siltstones, moderate for packstones, wackestones, and mudstones, and highest for boundstones and grainstones. The delta13C profile from Gallagher Peak consists of high frequency 1% oscillations with several larger excursions. No large delta13C increase at the base of the section suggests the Mid-Carboniferous boundary is in the underlying Bluebird Mountain formation. delta13C of Gallagher Peak and Arrow Canyon, NV, correlate well from 318 to 310 Ma, but correlation becomes more difficult around 310 Ma. This may result from increased restriction of the Snaky Canyon platform beginning in the Desmoinesian. Most of the short term (<1 Ma) isotopic excursions are the result of diagenesis. Two of the largest negative excursions at Gallagher Peak correlate with two large negative excursions at Big Hatchet Peak, NM, possibly due to sea level lowstands of the Desmoinesian. Phylloid algal mounds at Gallagher Peak are associated with positive excursions because of original aragonite composition and increased open marine influence. Positive excursions related to other facies characteristics also result from increased marine influence. The delta13C curve for the upper half of Gallagher Peak contains three repeated cycles of increasing delta13C over 1-1.5 Ma, which are possibly related to long-term sea level fluctuations. Given the complexity of each local environment, without detailed biostratigraphy, detailed rock descriptions, and analysis of the various rock components, delta13C stratigraphy of whole rocks can be misinterpreted.

第22回名古屋大学年代測定総合研究センターシンポジウム平成21(2009)年度報告

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, toxic contaminants that are released to the environment from various petrogenic and pyrogenic sources. In an effort to more clearly identify and trace sources of PAHs in the environment, purification and compound specific isotope analysis methods were developed to accurately measure the stable carbon isotope ratio of individual PAHs. Development of the method included improving accuracy and precision of the isotopic measurement by producing highly pure extracts using various chromatographic techniques. The method was refined by improving compound separations using purification techniques and high resolution chromatographic columns. The purification method consists of alumina/silica gel column chromatography, gel permeation chromatography and thin layer chromatography. The mean recovery of PAHs after the purification procedure was approximately 80 %. Sample purities after purification were verified by GC/FID and full scan mass spectrometry. To better resolve peaks and provide more accurate stable carbon isotope measurements, various gas chromatographic conditions were evaluated. The precision of the method ranged between 0.08 and 0.43 . The analytical protocols were evaluated to confirm compositional and stable isotopic integrity during purification and stable isotopic analysis. To confirm the utility of the purification and isotope analysis methods, various environmental samples from marine, land and lacustrine environments were analyzed. The isolates were analyzed for the composition and the stable carbon isotope ratios of PAHs. The stable carbon isotope ratio was measured by GC/IRMS and the results, along with quantitative compound compositions, were used to characterize and identify the contaminant sources. The sources of the PAHs in the study areas were differentiated by PAH molecular ratios and confirmed by stable carbon isotope ratios. This study confirms that compound specific isotope analysis of pollutants by GC/IRMS can be used to identify PAH sources in environmental samples. The study also confirms that the purification and stable carbon isotope analysis methods that were developed can be used to accurately measure the stable carbon isotope ratios of PAHs in environmental samples for the purpose of source identification. GC/IRMS measurement of stable isotopic compositions can be an effective fingerprinting method when used in conjunction with traditional molecular composition methods.

ABSTRACT The sedimentary deposits of the Hadar Formation at Dikika and the Mount Galili Formation at Galili preserve a wealth of paleoenvironmental and paleoclimatic records spanning the last 5.29 Ma. Stable carbon and oxygen isotopic compositions of herbivore tooth enamel were analyzed for more than 600 specimens of 15 different taxa from 10 stratigraphic intervals. The application of carbon and oxygen isotopes here aims principally at reconstructing shifts in the relative abundance of C4 grasses, and its implications for climate indicators including temperature, aridity, and seasonality. The full range of δ13Cenamel values throughout the Plio-Pleistocene signifies a wide range of foraging strategies by the fauna, which in turn reflects the mosaic of vegetation at Dikika and Galili. Estimates of ecosystem carbon isotope composition (δ13Cecosystem , which is given by average δ13Cenamel of each large vertebrate taxon weighted by the respective faunal abundance and the estimated daily biomass consumption) is used to asses shifts in the ecosystem-scale proportion of C3 and C4 vegetation. In the Plio-Pleistocene, the general paleoenvironmental conditions varied from wooded grassland to grasslands with the total amount of C4 grass cover on the landscape varying between 35% and 91%. Likewise, the paleohabitat reconstructions indicate the presence of grassland, wooded grassland, woodland habitats throughout the Pliocene and in Middle Pleistocene but the relative proportion of the habitats has changed substantially with time. Although this result agrees with the general trend towards more open grassland since the Late Miocene, a rebound of closed habitats and C3 resources from closed canopy woodlands or forests is evident in the middle Pliocene between 3.42 Ma and 3.24 Ma. These changes in the proportion of habitats could have affected the distribution and availability of preferred food resources and has an implication on the interaction of the animals on the paleolandscape and competition for resources. 18Oenamel values also show a wide range of variation within each stratigraphic member and through time. Temporal variation of δ13Cenamel values within a given taxon, as well as differences among sympatric taxa, document different aspects of the environment and climate, including changes in drinking water source, seasonality, and periods of strong evaporation. Estimated δ13Cmeteoric water based on the most 18O-depleted hippo tooth enamel, displays values of -1.94 / (VSMOW) and -5.24 / (VSMOW) in the Middle Pleistocene of Asbole and middle Pliocene of Galili, respectively. A major shift in the isotopic composition of water at ~ 3.0 Ma was accompanied by a 6.0 / increase from middle Pliocene to the present. While a +3.8 / shift from early to middle Pliocene was documented. The isotopic composition of meteoric water between 4.6 Ma and 4.38 Ma was most 18O-enriched compared to the rest of the Pliocene estimates. Likewise, an increase in the estimated δ13Cmeteoric water values was documented in the Awash Valley and elsewhere in East Africa, which indicate a regional climate change since the early Pliocene. An increase in the aridity, which is expressed as mean annual water deficit (i.e., the difference between potential evapotranspiration and mean annual precipitation) is also evident since the early Pliocene. These changes during the Pliocene in the region may in part be attributed to a regional decrease in the amount of precipitation and changes in the moisture source superimposed on global climate changes.

Periodic flooding has been widely believed to serve an important role in maintaining water levels and productivity of aquatic basins in floodplain landscapes. Here, I analyze four basins of contrasting flood frequencies (one through-flow, one pulse-flooded, two non-flooded) and two adjacent river sites in the PAD were sampled during the open-water season of 2007 and spring of 2008 to characterize linkages between hydrological processes (using O and H stable isotopes) and limnological conditions, and to assess how these linkages affect trophic interactions involving the aquatic flora and fauna (using C and N stable isotopes). The water balance and water chemistry of the through-flow basin was dominated at all times by the input of river water which reduced concentrations of nutrients and ions. In contrast, evaporation played an important role in the water balance and concentrated nutrients and ions in the non-flooded basins. Surprisingly, pulse-flood events had short-lived effects on the water balance and carbon stable isotopic signatures of biota. Hydrological and limnological conditions in the pulse-flooded basin were similar to those of the river water shortly after spring flooding. After flooding, evaporation caused rapid increase of δ18O of the water comparable to patterns observed in the non-flooded basins, but recovery of water chemistry variables was delayed. In the non-flooded and pulse-flooded basins, δ13CDIC declined due to atmospheric CO2 invasion under conditions of high primary productivity and pH that generated strong kinetic fractionation. This decline in δ13CDIC values produced the opposite effect compared to when photosynthesis occurs under non-limiting carbon conditions, as occurred in the through-flow basin. This feature provides important new knowledge to improve paleolimnological interpretation of δ13C values of organic matter in sediment cores to track past changes in flooding regimes. Importantly, this study shows that pulse floods exert short-lived transient (~1-2 months) effects of the water balance and carbon dynamics of aquatic food-webs and do not elevate aquatic production, but exert longer lasting (at least an entire open-water season) on water chemistry conditions. This contrasts with previous beliefs that the effects of pulse flooding are more profound and longer lasting.

Feeding experiments were conducted on Atlantic pollock (Pollachius virens) to examine the variability in tissue fatty acid (FA) composition and stable carbon isotope fractionation of FA during digestion, assimilation and mobilization of lipids. The FA profiles and compound-specific carbon isotopes of chylomicrons, liver, muscle and fasted serum were compared to diet. FA analysis demonstrated similarity among tissue groups despite differences in feeding states. The FA results indicate the blood of post-prandial fish may serve as an alternative to tissue biopsies for the estimation of marine fish diets with compound-specific isotope analysis (CSIA). Despite similarity among FA profiles, the carbon isotope discrimination factors of FA varied independently, which suggests that fractionation is influenced by the degree to which individual FA are oxidized. These results provide preliminary information that is necessary in order to use CSIA to estimate the effects of fish diets.

Stable carbon isotope ratios (δ13C) in tree-ring cellulose are modified by environmental conditions occurring during carbon fixation. Researchers have however not reached a consensus as to whether extractives, lignin and/or hemicelluloses, all with specific isotopic signatures, should be removed prior to dendroisotopic analysis. The topic of the first paper dealt with the comparison of Thuja occidentalis L. wood components and their suitability for subsequent dendroisotopic analyses. It was recommended that holocellulose be isolated since an alpha-cellulose yield may be too low for subsequent mass spectrometer analysis, especially when narrow rings are encountered and multiple stable isotope analyses are to be performed per sample. The second paper investigated the associations between the ring-width and δ13C chronologies with climate variables. The δ13C chronology spanned from 1650 to 2006 A.D. and incorporated dead and living T. occidentalis trees selected from two sites in central Manitoba, Canada. Compared to the δ13C values, ring width was more often associated with climate conditions in the year prior to ring formation. However, moisture stress was limiting for both radial growth and carbon assimilation. During the year of ring-formation, ring width was associated with spring and early summer conditions whereas, δ13C was more indicative of overall summer conditions. Nonetheless, each of ring width and δ13C contained individualistic climate information which could be used in tandem for long-term climate reconstruction.

Stable carbon isotope ratios (δ13C) in tree-ring cellulose are modified by environmental conditions occurring during carbon fixation. Researchers have however not reached a consensus as to whether extractives, lignin and/or hemicelluloses, all with specific isotopic signatures, should be removed prior to dendroisotopic analysis. The topic of the first paper dealt with the comparison of Thuja occidentalis L. wood components and their suitability for subsequent dendroisotopic analyses. It was recommended that holocellulose be isolated since an alpha-cellulose yield may be too low for subsequent mass spectrometer analysis, especially when narrow rings are encountered and multiple stable isotope analyses are to be performed per sample. The second paper investigated the associations between the ring-width and δ13C chronologies with climate variables. The δ13C chronology spanned from 1650 to 2006 A.D. and incorporated dead and living T. occidentalis trees selected from two sites in central Manitoba, Canada. Compared to the δ13C values, ring width was more often associated with climate conditions in the year prior to ring formation. However, moisture stress was limiting for both radial growth and carbon assimilation. During the year of ring-formation, ring width was associated with spring and early summer conditions whereas, δ13C was more indicative of overall summer conditions. Nonetheless, each of ring width and δ13C contained individualistic climate information which could be used in tandem for long-term climate reconstruction.