Large variability of trace element mass fractions determined by ICP-SFMS in ice core samples from worldwide high altitude glaciers

• Published in: Applied geochemistry 2014-08, Vol.47, p.109-121
• Main Authors: Uglietti, Chiara, Gabrielli, Paolo, Olesik, John W., Lutton, Anthony, Thompson, Lonnie G.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; Pollution, environment geology
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2014.05.019

•Between 20% and 90% of the total trace element concentration is determined in ice cores by ICP-SFMS.•These mass fractions depend on the mineralogical content and storage time after sample acidification.•These effects are unlikely to cause changes in the discrimination of the crustal/non-crustal sources of trace elements.•These effects can produce a severe underestimation of trace element mass fluxes to glaciers.•Mass fractions determined in fresh waters that are rich in micro-particles might be also lower than 100%. We quantified leaching and mass fractions of trace elements in melted acidified ice core samples measured by Inductively Coupled Plasma Sector Field Mass Spectrometry (ICP-SFMS). This assessment was conducted using nine ice core sections retrieved from various high-altitude drilling sites in South America, Africa, Asia and Europe. Twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V and Zn) were determined. During a 1½ month acid leaching period our assessment shows distinct increases in the concentration of various trace elements (10% for Cd; 30% for Pb; 50–80% for As, Cu, Mo, Mn, Tl and U; 80–90% for Bi, Rb, Sb, Sn and Zn; 100–160% for Al, Cr, Co, Ti and V; 200% for Fe). The exception is Ag, which shows a 50% decrease. We found that the observed relative increases in trace element concentrations are: (i) independent of the absolute trace element concentrations and micro-particle levels/size of the samples, and (ii) unlikely to affect reconstructions of the crustal/non-crustal origin of trace elements based on the use of the crustal enrichment factor. After 1½months of leaching, the measured trace element concentrations were found to be only a fraction of the estimated total concentration and that the mass fractions determined vary largely from element to element (on average 80–90% for As and Mn; 50–70% for U, Fe, Ti and Tl; 20–50% for Al, Cd, Co, Cr, Cu, Mo, Pb, Rb, V and Zn; 15% for Bi and 2% for Ag). These observations imply: (i) a significant underestimation of the mass fluxes of these trace elements to high altitude glaciers and (ii) a likely dependency of the mass fractions on the typical crystallographic position of each trace element within the micro-particles contained in the ice core samples.