Isolation of Methane from Ambient Water and Preparation for Source-Diagnostic Natural Abundance Radiocarbon Analysis.

A key challenge in climate change research is apportioning the greenhouse gas methane (CH) between various natural and anthropogenic sources. Isotopic source fingerprinting of CH releases, particularly with radiocarbon analysis, is a promising approach. Here, we establish an analytical protocol for preparing CH from seawater and other aqueous matrices for high-precision natural abundance radiocarbon measurement.

Black carbon aerosols over Indian Ocean have unique source fingerprint and optical characteristics during monsoon season.

Effects of aerosols such as black carbon (BC) on climate and buildup of the monsoon over the Indian Ocean are insufficiently quantified. Uncertain contributions from various natural and anthropogenic sources impede our understanding. Here, we use observations over 5 y of BC and its isotopes at a remote island observatory in northern Indian Ocean to constrain loadings and sources during little-studied monsoon season.

Observational Evidence of Large Contribution from Primary Sources for Carbon Monoxide in the South Asian Outflow.

South Asian air is among the most polluted in the world, causing premature death of millions and asserting a strong perturbation of the regional climate. A central component is carbon monoxide (CO), which is a key modulator of the oxidizing capacity of the atmosphere and a potent indirect greenhouse gas. While CO concentrations are declining elsewhere, South Asia exhibits an increasing trend for unresolved reasons.

Source apportionment of methane escaping the subsea permafrost system in the outer Eurasian Arctic Shelf.

The East Siberian Arctic Shelf holds large amounts of inundated carbon and methane (CH). Holocene warming by overlying seawater, recently fortified by anthropogenic warming, has caused thawing of the underlying subsea permafrost. Despite extensive observations of elevated seawater CH in the past decades, relative contributions from different subsea compartments such as early diagenesis, subsea permafrost, methane hydrates, and underlying thermogenic/ free gas to these methane releases remain elusive.

Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach.

A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity.