Standard Testing and Analysis in Ice Using LA-ICP-MS

This thesis is divided into two parts, each intended for publication in the Journal of Glaciology. The first explores existing methods for creating ice standards for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and tests a novel method. Standardizing ice samples is essential for consistent comparisons over time and across different laboratories, as LA-ICP-MS data outputs intensity values (counts per second, or cps), which can fluctuate daily. In terms of standards, when ice freezes, water molecules form hexagonal crystalline structures that grow outward and collide, creating grain boundaries. Impurities are localized in these areas due to impurities pushing outward from the crystal lattice. These boundaries make it difficult to produce homogeneous ice standards, and their removal in artificially made ice has proven challenging. To address this, we propose soaking cellulose filter paper in standard solutions and freezing the filters to distribute impurities across the filter matrix. The results yield homogenous standards that have strong linearity and low variability. While results are promising, in comparison to real ice standards, intensity values are artificially lower due to a mismatched matrix. This indicates further study is needed on matrix effects in aerosol transport from laser ablation systems. The second paper focuses on LA-ICP-MS iron (56Fe) measurements of ice from Allan Hills, Antarctica and comparisons with water isotope (δ18O) and dust concentration data from continuous flow analysis (CFA) measurements. LA-ICP-MS yields a resolution of ~120 to ~150 microns, depending on methodology, with CFA resolving ~1 cm. By using these two methods in parallel, we gain valuable high-resolution insights into ice core chemistry and past climate change in some of the oldest ice on Earth. We analyze selected sections of Allan Hills ice to assess changes in chemistry during past warm and cold conditions.