Chemical impurity distribtion (Na, Mg, Sr) in the EPICA Dome C ice core bags 1065 and 3092 and Talos Dome ice core bag 375-B1 obtained from 2D imaging with LA-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers micron-resolution 2D chemical imaging, which has been adapted recently to ice core analysis. Measurements were performed in 2020 at the Ca'Foscari University of Venice, in order to investigate the localization of impurities in the ice samples. Here images are presented from applying LA-ICP-MS elemental imaging to a samples of the EPICA Dome C ice core and the Talos Dome ice core from Antarctica. Lateral resolution is 35 microns both along and perpendicular to the scan direction. Considered as analytes are Na, Mg and Sr. Background and drift correction as well as image construction were performed using the software HDIP (Teledyne Photon Machines, Bozeman, MT, USA). Impurity images are acquired as a pattern of lines, without overlap in the direction perpendicular to that of the scan, and without any further spatial interpolation. Each pixel in an ice core chemical image has a size of 35 μm x 35 μm. For each chemical element the datasets comprise a numerical matrix which contains rows and columns according to the physical size of the image: an image of 7 mm x 35 mm in size has 200 rows and 1000 columns. The numerical entries in this matrix refer to the recorded intensity (e.g. in counts). Values lower than the detection limit are set to zero. Due to the careful synchronization, the individual pixels of the different chemical channels can be considered to be almost perfectly spatially aligned. In contrast, the mosaic of visual images obtained from the laser camera is not a-priori aligned with the chemical images. The visual images are generally characterized by air bubbles (dark blobs), grain boundaries (dark lines) and occasional sub-grain boundaries (thin dark lines).激光剥蚀电感耦合等离子体质谱法（LA-ICP-MS）可实现微米级分辨率的二维化学成像，近年来该技术已被应用于冰芯分析领域。本次实验于2020年在威尼斯卡福斯卡里大学（Ca'Foscari University of Venice）开展，旨在探究冰样品中杂质的空间分布特征。本数据集展示了针对南极EPICA Dome C冰芯与Talos Dome冰芯样品开展LA-ICP-MS元素成像所得到的图像。横向分辨率沿扫描方向及其垂直方向均为35微米。本次分析的目标分析物为钠（Na）、镁（Mg）与锶（Sr）。背景校正与信号漂移校正以及图像构建均通过HDIP软件（美国蒙大拿州博兹曼市Teledyne Photon Machines公司开发）完成。杂质图像以线阵模式采集，在扫描方向的垂直方向上无重叠，且未进行任何额外的空间插值处理。冰芯化学成像中的每个像素尺寸为35 μm × 35 μm。针对每种化学元素，数据集均包含数值矩阵，矩阵的行列数与图像物理尺寸对应：例如尺寸为7 mm × 35 mm的图像对应200行与1000列的矩阵。矩阵中的数值代表记录的信号强度（例如以计数为单位），低于检测限的数值将被置零。由于经过精确的同步校准，不同化学通道的单个像素可视为几乎完全空间对齐。与之相对，激光相机采集的视觉图像拼接图未预先与化学图像完成对齐。视觉图像通常呈现出气泡（暗色团块）、晶界（暗色线条）以及偶尔出现的亚晶界（细暗色线条）的特征。