Design, Performance tests and Application of Melting System for Trace Element Analysis in a Shallow Firn Cores

Abstract

The melting system of ice core samples has been a useful decontamination device. However, it should be very cautious to remove some pollutants caused by ice core drilling in the outer surface of firn cores with typical melting system due to percolation effect of melted samples. In this study, as a major improvement, the melting head of the melting system was constructed with fluorinated ethylene propylene (FEP) coated Cu divided into two zones due to the physical characteristics of firn core and performance tests such as decontamination efficiency and procedural blanks were systematically conducted with the artificial ice core samples (a cross section of 3.2 cm x 3.2 cm, ~10 cm long). Quality of the measurement data was confirmed by analyzing a certified reference material (SLRS5, 1643e for elements) and - 52.3 ~ 27.5 % of relative errors. Ice core samples were efficiently decontaminated by the melting system, which was verified by the signal intensity ratio (S.I.R.) of melting samples from two zones of melting head. Especially, procedural blank tests indicated that the concentrations of elements in melted samples from inner zone of melting head were very comparable with those of elements in system blanks except for Cu. The melting system was rinsed with 0.1% HNO3 (total 10 ml) in order to remove memory effects of elements between ice core samples melted in series. The inter-comparisons of conventional mechanical chiseling method and melting system using NEEM firn core (#144, #155) agreed well with experimental results except for Cu. Finally, this technique was applied for the measurement of elements in firn core samples (68.675 ~ 71.425 m) drilled at the NEEM site located at the north-western part in Greenland (77.45° N, 51.06° W, surface elevation 2450 m, mean annual temperature 29 °C, accumulation 0.22m ice equivalent per year).