Mineralogical and Chemical Records of Icelandic Dust Sources Upon Ny-Ålesund (Svalbard Islands)

Beatrice Moroni,Stefano Crocchianti,Olafur Arnalds,David Cappelletti,Riccardo Vivani,Pavla Dagsson-Waldhauserová

doi:10.3389/feart.2018.00187

Abstract

This work aims to identify the geochemical and mineralogical markers of Icelandic dust and to differentiate it from the dust of local origin deposited at the Ny-Alesund station. We characterized representative sediment samples from Iceland and Svalbard and compared them to a set of aerosol samples collected in Ny-Alesund to check the existence and type of the mineralogical markers. The sediment samples were analyzed by X-ray diffraction (XRD) to detect the mineralogical constrain of the geochemical markers. Both aerosol and sediment samples were examined by scanning electron microscopy coupled with EDS microanalysis (SEM-EDS) and image analysis to detect and to provide a morpho-chemical characterization of the mineralogical markers of dust provenance. Comparison between local and Icelandic sediments reveals the metal oxide particles as the most representative and distinguishing mineralogical/phase markers for Iceland dust sources. In particular, we have considered the magnetite-chromite and the magnetite-ulvospinel associations as marker facies of the tholeiitic magmatic series and the presence of volcanic glass as a further indicator of provenance from Iceland. The morphochemical characteristics of the metal oxide particles in the aerosol samples compared to those of the sediment samples have proved to be a powerful tool to separate Icelandic dust from other sources for dust. In particular, the small size, higher grain boundary complexity and lower Fe/Cr ratios suggest the influence of anthropogenic sources, well in accordance with the results of air mass backward trajectories which reveal a main contribution from industrialized areas in Eurasia. This study shows the reliability of the geochemical characterization of the metal oxide particles for the identification of the source regions of dust. In addition it provides an evidence that Icelandic dust can be transported long range to Svalbard confirming the importance of High Latitude Dust sources.

Highlights

The Arctic is experiencing a dramatic impact of the present climate change; an effect referred to as the ‘Arctic amplification’ (Serreze and Francis, 2006)
The Svalbard dust sources comprise both natural sediments suspended from dry riverbeds and anthropogenic sources from coal mines, both activated at the end of the dry summer season (Dörnbrack et al, 2010)
We have characterized representative sediment samples from Iceland and Svalbard and compared them to a set of aerosol samples collected in Ny-Ålesund in 2011 to check the existence and type of the mineralogical markers

Summary

INTRODUCTION

The Arctic is experiencing a dramatic impact of the present climate change; an effect referred to as the ‘Arctic amplification’ (Serreze and Francis, 2006). We have characterized representative sediment samples from Iceland and Svalbard and compared them to a set of aerosol samples collected in Ny-Ålesund in 2011 to check the existence and type of the mineralogical markers. ICE3 refers to Dyngjusandur in NE Iceland, the largest and most active of TABLE 1 | Location of sediment sampling sites by Ny-Ålesund (NyA) and in Iceland (ICE). Results of back-trajectory (BT) analysis identify 23 days in 2011 characterized by air mass circulation passing over Iceland before reaching Ny-Ålesund. Looking to the BT patterns, the contribution from Iceland to the dust load is expected to be high on April 26 when a channeled air flow originating in the Arctic ocean crossed the North American continent at high altitude before experiencing a steep descending motion over Iceland up to the Svalbard archipelago. The weight fraction of the amorphous component of the Icelandic samples was determined by an indirect method using a Rietveld refinement procedure: a weighed amount of fully crystalline internal standard (in this case silicon, about 10% w/w) was FIGURE 3 | Plots of 120 h back trajectories of April 18 (A), 22 (B), 26 (C), and 29 (D), 2011 ending at 1000 m a.g.l. (April 18 and 29) and at 1100 m a.g.l. (April 22 and 26) upon Ny-Ålesund

18 April 22 April 26 April 29 April

RESULTS AND DISCUSSION

CONCLUSION