A method for carbon stable isotope analysis of methyl halides and chlorofluorocarbons at pptv concentrations

A pre-concentration system has been validated for use with a gas chromatography/mass spectrometry/isotope ratio mass spectrometer (GC/MS/IRMS) to determine ambient air 13C/12C ratios for methyl halides (MeCl and MeBr) and chlorofluorocarbons (CFCs). The isotopic composition of specific compounds can provide useful information on their atmospheric budgets and biogeochemistry that cannot be ascertained from abundance measurements alone. Although pre-concentration systems have been previously used with a GC/MS/IRMS for atmospheric trace gas analysis, this is the first study also to report system validation tests. Validation results indicate that the pre-concentration system and subsequent separation technologies do not significantly alter the stable isotopic ratios of the target methyl halides, CFC-12 (CCl2F2) and CFC-113 (C2Cl3F3). Significant, but consistent, isotopic shifts of -27.5 to -25.6 do occur within the system for CFC-11 (CCl3F), although the shift is correctible. The method presented has the capacity to separate these target halocarbons from more than 50 other compounds in ambient air samples. Separation allows for the determination of stable carbon isotope ratios of five of these six target trace atmospheric constituents within ambient air for large volume samples (10 L). Representative urban air analyses from Belfast City are also presented which give carbon isotope results similar to published values for 13C/12C analysis of MeCl (-39.1) and CFC-113 (-28.1). However, this is the first paper reporting stable carbon isotope signatures for CFC-11 (-29.4) and CFC-12 (-37.0).

Stable isotope analysis of archived roach (Rutilus rutilus) scales for retrospective study of shallow lake responses to nutrient reduction

1. There is increasing interest in the use of stable isotope analysis of archived materials to study the long-term impacts of lake perturbations, including nutrient manipulation or species invasion. We tested the utility of this approach in a shallow productive lake using the zooplanktivorous early life stages of roach ( Rutilus rutilus), a fish species that is widespread throughout Eurasian lakes.

Resolving genetic functions within microbial populations: In situ analyses using rRNA and mRNA stable isotope probing coupled with single-cell raman-fluorescence in situ hybridization

Prokaryotes represent one-half of the living biomass on Earth, with the vast majority remaining elusive to culture and study within the laboratory. As a result, we lack a basic understanding of the functions that many species perform in the natural world. To address this issue, we developed complementary population and single-cell stable isotope (C-13)-linked analyses to determine microbial identity and function in situ. We demonstrated that the use of rRNA/mRNA stable isotope probing (SIP) recovered the key phylogenetic and functional RNAs. This was followed by single-cell physiological analyses of these populations to determine and quantify in situ functions within an aerobic naphthalene-degrading groundwater microbial community. Using these culture-independent approaches, we identified three prokaryote species capable of naphthalene biodegradation within the groundwater system: two taxa were isolated in the laboratory (Pseudomonas fluorescens and Pseudomonas putida), whereas the third eluded culture (an Acidovorax sp.). Using parallel population and single-cell stable isotope technologies, we were able to identify an unculturable Acidovorax sp. which played the key role in naphthalene biodegradation in situ, rather than the culturable naphthalene-biodegrading Pseudomonas sp. isolated from the same groundwater. The Pseudomonas isolates actively degraded naphthalene only at naphthalene concentrations higher than 30 mu M. This study demonstrated that unculturable microorganisms could play important roles in biodegradation in the ecosystem. It also showed that the combined RNA SIP-Raman-fluorescence in situ hybridization approach may be a significant tool in resolving ecology, functionality, and niche specialization within the unculturable fraction of organisms residing in the natural environment.

Lacustrine evidence of Holocene environmental change from three Faroese lakes: a multiproxy XRF and stable isotope study

The vegetation history of the Faroe Islands has been investigated in numerous studies all broadly showing that the early-Holocene vegetation of the islands largely consisted of fellfield with gravely and rocky soils formed under a continental climate which shifted to an oceanic climate around 10,000 cal yr BP when grasses, sedges and finally shrubs began to dominant the islands. Here we present data from three lake sediment cores and show a much more detailed history from geochemical and isotope data. These data show that the Faroe Islands were deglaciated by the end of Younger Dryas (11,700 10,300 cal yr BP), at this time relatively high sedimentation rates with high delta C-13 imply poor soil development. delta C-13, Ti and chi data reveal a much more stable and warm mid-Holocene until 7410 cal yr BP characterised by increasing vegetation cover and build up of organic soils towards the Holocene thermal maximum around 7400 cal yr BP. The final meltdown of the Laurentide ice sheet around 7000 cal yr BP appears to have impacted both ocean and atmospheric circulation towards colder conditions on the Faroe Islands. This is inferred by enhanced weathering and increased deposition of surplus sulphur (sea spray) and erosion in the highland lakes from about 7400 cal yr BP. From 4190 cal yr BP further cooling is believed to have occurred as a consequence for increased soil erosion due to freeze/thaw sequences related to oceanic and atmospheric variability. This cooling trend appears to have advanced further from 3000 cal yr BR A short period around 1800 cal yr BP appears as a short warm and wet phase in between a general cooling characterised by significant soil erosion lasting until 725 cal yr BP. Interestingly, increased soil erosion seems to have begun at 1360 cal yr BP, thus significantly before the arrival of the first settlers on the Faroe Island around 1150 cal yr BP, although additional erosion took place around 1200 cal yr BP possibly as a consequence of human activities. Hence it appears that if humans caused a change in the Faroe landscape in terms of erosion they in fact accelerated a process that had already started. Soil erosion was a dominant landscape factor during the Little Ice Age, but climate related triggers can hardly be distinguished from human activities. (c) 2010 Elsevier Ltd. All rights reserved.

Palaeobiology of an extinct Ice Age mammal: Stable isotope and cementum analysis of giant deer teeth

The extinct giant deer, Megaloceros giganteus, is among the largest and most famous of the cervids. Megaloceros remains have been uncovered across Europe and western Asia. but the highest concentrations come from Irish bogs and caves Although Megaloceros has enjoyed a great deal of attention over the centuries, paleobiological study has focused oil morphometric and distributional work until now. This paper presents quantitative data that have implications for understanding its sudden extirpation in western Europe during a period of global climate change approximately 10.600 C-14 years ago (ca 12,500 calendar years BP). We report here the first stable isotope analysis of giant deer teeth. which we combine with dental cementum accretion in order to document age, diet and life-history seasonality from birth until death Enamel delta C-13 and delta O-18 measured in the second and third molars from seven individual giant deer Suggest a grass and forbbased diet supplemented with browse in a deteriorating. possibly water-stressed, environment, and a season of birth around spring/early summer Cementurm data indicate that the ages of the specimens ranged from 6.5 to 14 years and that they possessed mature antlers by autumn, similar to extant cervids. In addition. the possibility for combining these two techniques in future mammalian paleoccological studies is considered. The data presented in this study imply that Megoloceros would have indeed been vulnerable to extirpation during the terminal Pleistocene in Ireland. and this information is relevant to understanding the broader pattern of its extinction.

Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data

Stable isotopes (delta O-18 and delta C-13) of lacustrine carbonates (Chara spp. algae and Pisidium spp. molluscs) from a lake sedimentary sequence in central Sweden were analysed to infer changes in lake hydrology and climate during the late Holocene. Results from analysis of lake water isotopes (delta O-18 and delta H-2) show that Lake Blektjarnen water isotope composition is responsive to the balance between evaporation and input water (E/l ratio). A high E/l ratio results from a dry and probably warmer climate, decreasing the relative importance of precipitation input. Under such conditions evaporation and atmospheric equilibration probably enrich lake water in O-18 and C-13, respectively, which is reflected in the isotopic composition of the carbonates in the lake. From the relatively positive Chara delta O-18 values we infer that conditions were dry and warm between 4400 and 4000 cal. a BP, whereas more negative values indicate that conditions were wetter and probably cooler between 4000 and 3000 cal. a BP. A drier climate is inferred from more positive values between 2500 and 1000 cal. a BP. However, a successive depletion after ca. 1750 cal. a BP, also detected in several other delta O-18 records (carbonate and diatom), suggest increasingly wetter conditions in Scandinavia after that time, which is probably related to increased strength of the zonal flow.