This study demonstrates the application of Wavelength-Scanned Cavity Ring-Down Spectroscopy (WS-CRDS) technology which is used to measure the stable isotopic composition of water. This isotopic water analyzer incorporates an evaporator system that allows liquid water as well as water vapor to be measured with high precision. The analyzer can measure H…

A continuous-flow cavity ring-down spectroscopy (CRDS) system integrating a chromatographic separation technique, a catalytic combustor, and an isotopic¹³C/¹²C optical analyzer is described for the isotopic analysis of a mixture of organic compounds. A demonstration of its potential is made for the geochemically important class of short-chain hydrocarbons. The system…

High-accuracy continuous measurements of greenhouse gases (CO₂ and CH₄) during the BARCA (Balanço Atmosférico Regional de Carbono na Amazônia) phase B campaign in Brazil in May 2009 were accomplished using a newly available analyzer based on the cavity ring-down spectroscopy (CRDS) technique. This analyzer was flown without a drying system or any in-flight…

Horizontal drilling and hydraulic fracturing are transforming energy production, but their potential environmental effects remain controversial. We analyzed 141 drinking water wells across the Appalachian Plateaus physiographic province of northeastern Pennsylvania, examining natural gas concentrations and isotopic signatures with proximity to shale gas wells. Methane was detected in 82% of…

The doubly labeled water method provides an objective and accurate measure of total energy expenditure in free-living subjects and is considered the gold-standard method for this measurement. Its use, however, is limited by the need to employ isotope ratio mass spectrometry (IRMS) to obtain the high-precision isotopic abundance analyses needed to optimize the dose of expensive ^18…

The Deepwater Horizon oil spill was unprecedented in total loading of petroleum hydrocarbons accidentally released to a marine ecosystem. Controversial application of chemical dispersants presumably accelerated microbial consumption of oil components, especially in warm Gulf of Mexico surface waters. We employed δ¹³C as a tracer of oil-derived carbon to resolve two periods of…

Methane was the most abundant hydrocarbon released during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. Beyond relevancy to this anthropogenic event, this methane release simulates a rapid and relatively short-term natural release from hydrates into deepwater. Based on methane and oxygen distributions measured at 207 stations throughout the affected region, we find that within…

Bats are one of the most successful mammalian groups, even though their foraging activities are restricted to the hours of twilight and night-time. Some studies suggested that bats became nocturnal because of overheating when flying in daylight. This is because—in contrast to feathered wings of birds—dark and naked wing membranes of bats efficiently absorb short-wave solar radiation. We…

We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios (δD and δ¹⁸O) of…

Direct quantification of fossil fuel CO₂ (CO₂ff) in atmospheric samples can be used to examine several carbon cycle and air quality questions. We collected in situ CO₂, CO, and CH₄ measurements and flask samples in the boundary layer and free troposphere over Sacramento, California, USA, during two aircraft flights over…

Monitoring is essential for the approval and control of geological storage of carbon dioxide and to judge the effectiveness of the technology in mitigating CO₂ emissions and climate change. We present a strategy for monitoring the atmosphere in the vicinity of a geological storage project that is designed to detect and quantify potential emissions. The strategy includes…

CO₂ was injected into a coal fire burning at a depth of 15 m in the subsurface in southwestern Colorado, USA. Measurements were made of the 13CO₂ isotopic signature of gas exhaust from an observation well and two surface fissures. The goal of the test was to determine (1) whether CO₂ with a distinct isotopic signature could be used as a tracer to…

A portable stable carbon isotope ratio analyzer for carbon dioxide, based on wavelength scanned cavity ringdown spectroscopy, has been used to detect, locate, and characterize an intentional leakage of CO₂ from an underground pipeline at the ZERT experimental facility in Bozeman, Montana. Rapid (1 h) walking surveys of the 100 m x 100 m site surrounding the…

The potential of a continuous wave cavity ringdown spectrometer for monitoring the isotope ratio 13CO₂/12CO₂ and the partial pressure pCO₂ of CO₂ dissolved in water was thoroughly analyzed by quantitative measurements. Running calibration gas standards under typical operation conditions, a elative accuracy of D(d13C[CO₂]) = ±0.1‰…