Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to (12)C to enrich in the released CO2 while (13)C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstr...

Stable isotope ratios are biogeochemical tracers that can be used to determine the source of nutrients and contaminants in avian eggs. However, the interpretation of stable carbon ratios in lipid-rich eggs is complicated because (13)C is depleted in lipids. Variation in (13)C abundance can therefore be obscured by variation in percent lipids. Past attempts to establish an algebraic equation to ...

Hydrogen and carbon isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from C(3), C(4), and Crassulacean acid metabolism (CAM) plants were determined for plants growing within a small area in Val Verde County, Texas. Plants having CAM had distinctly higher deuterium/hydrogen (D/H) ratios than plants having C(3) and C(4) metabolism. When hydrogen isotope ratios are plotte...

Compound-specific carbon isotope ratio analysis is a promising tool to assess the origin and fate of organic contaminants in groundwater. The aim of this study was to develop and evaluate a reliable, fast method to determine carbon isotope ratios of chlorinated methanes, ethanes, and ethenes in aqueous samples. Direct solid-phase microextraction (dSPME) and headspace solid-phase microextraction...

Moderate elevated vertical methane (CH4) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH4 flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH4 flux r...

[1] Two hypotheses have been proposed to explain simultaneous large negative excursions (up to 7% PeeDee belemnite) in bulk carbonate (dCcarb) and organic carbon isotope records (d Corg) from black shales marking the Toarcian oceanic anoxic event (T-OAE). The first explanation envisions recycling of dissolved inorganic carbon (DIC) with a light isotopic signature into the photic zone from the l...

The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which...

Despite the widespread use of carbon stable isotopes to distinguish among potential energy pathways in food webs, their usefulness is limited where potential basal carbon sources are numerous and diverse. We measured carbon isotope values of the major fisheries species, the mostly carnivorous Scylla serrata (giant mud crab), and potential basal, autotrophic sources supporting the food web. Conv...

Time-series stable carbon isotope monitoring of volatile organic compounds (VOCs) atthe Idaho National Engineering and Environmental Laboratory's (INEEL) field site Test Area North (TAN) was conducted during a pilot study to investigate the treatment potential of using lactate to stimulate in situ biologic reductive dechlorination of trichloroethene (TCE). The isotope ratios of TCE and its biod...

The Toarcian oceanic anoxic event (T-OAE; ∼ 183 million y ago) is possibly the most extreme episode of widespread ocean oxygen deficiency in the Phanerozoic, coinciding with rapid atmospheric pCO2 increase and significant loss of biodiversity in marine faunas. The event is a unique past tipping point in the Earth system, where rapid and massive release of isotopically light carbon led to a majo...