Microgram level radiocarbon (14C) determination on carbonaceous particles in ice

In climate research the interest on carbonaceous particles has increased over the last years because of their influence on the radiation balance of the earth. Nevertheless, there is a paucity of available data regarding their concentrations and sources in the past. Such data would be important for a better understanding of their effects and for estimating their influence on future climate. Here, a technique is described to extract carbonaceous particles from ice core samples with subsequent separation of the two main constituents into organic carbon (OC) and elemental carbon (EC) for analysis of their concentrations in the past. This is combined with further analysis of OC and EC 14C/12C ratios by accelerator mass spectrometry (AMS), what can be used for source apportionment studies of past emissions. We further present how 14C analysis of the OC fraction could be used in the future to date any ice core extracted from a high-elevation glacier. Described sample preparation steps to final analysis include the combustion of micrograms of water–insoluble carbonaceous particles, primary collected by filtration of melted ice samples, the graphitisation of the obtained CO2 to solid AMS target material and final AMS measurements. Possible fractionation processes were investigated for quality assurance. Procedural blanks were reproducible and resulted in carbon masses of 1.3 ± 0.6 μg OC and 0.3 ± 0.1 μg EC per filter. The determined fraction of modern carbon (fM) for the OC blank was 0.61 ± 0.13. The analysis of processed IAEA-C6 and IAEA-C7 reference material resulted in fM = 1.521 ± 0.011 and δ13C = −10.85 ± 0.19‰, and fM = 0.505 ± 0.011 and δ13C = −14.21 ± 0.19‰, respectively, in agreement with consensus values. Initial carbon contents were thereby recovered with an average yield of 93%.

Sensitivity of DF-ICP-MS, PERALS and alpha-spectrometry for the determination of actinides: A comparison

We applied three techniques (DF-ICP-MS, PERALS and alpha-spectrometry) for the determination of minor actinides at environmental levels. For each method the limit of detection and the resolution were estimated in order to study the content and isotopic composition of the actinides. Two international reference materials, IAEA-135 (Irish Sea Sediment) and IAEA-300 (Baltic Sea sediment) were analyzed for activity concentrations of 238Pu, 239Pu, 240Pu, 241Pu and 241Am. The sensitivities of the three determination techniques were compared.

Origin and evolution of reactive and noble gases dissolved in matrix pore water

Reactive and noble gases dissolved in matrix pore water of low permeable crystalline bedrock were successfully extracted and characterized for the fist time based on drillcore samples from the Olkiluoto investigation site (SW Finland). Interaction between matrix pore water and fracture groundwater occurs predominately by diffusion. Changes in the chemical and isotopic composition of gases dissolved in fracture groundwater are transmitted and preserved in the pore water. Absolute concentrations, their ratios and the stable carbon isotope signature of hydrocarbon gases dissolved in pore water give valuable indications about the evolution of these gases in the nearby-flowing fracture groundwaters. Inert noble gases dissolved in matrix pore water and their isotopes combined with their in-situ production and accumulation rates deliver information about the residence time of pore water.

Matrix pore water in low-permeable crystalline bedrock: An archive for the palaeohydrogeological evolution of the Olkiluoto Investigation Site

Matrix pore water in the connected inter- and intragranular pore space of low-permeable crystalline bedrock interacts with flowing fracture groundwater predominately by diffusion. Based on the slow exchange between the two water reservoirs, matrix pore water acts as an archive of past changes in fracture groundwater compositions and thus of the palaeohydrological history of a site. Matrix pore water of crystalline bedrock from the Olkiluoto investigation site (SW Finland) was characterised using the stable water isotopes (δ18O, δ2H), combined with the concentrations of dissolved chloride and bromide as natural tracers. The comparison of tracer concentrations in pore water and present-day fracture groundwater suggest for the pore water the presence of old, dilute meteoric water components that infiltrated into the fractures during various warm climate stages. These different meteoric components can be discerned based on the diffusion distance between the two reservoirs and be brought into context with the palaeohydrological evolution of the site.