SEGH Articles

Dust Deposition in snow from NorthEast Antarctica: mineralogical, morphological and chemical characterization

05 October 2014
Aubry Vanderstraeten is a PhD student and won the runner-up prize for best student poster at SEGH 2014.

 

Mineral dusts are a major source of micronutrients (e.g. Fe) that limit phytoplankton growth in the open ocean, in particular in the so-called “High Nutrient Low Chlorophyll” (HNLC) oceanic zones. The southern Ocean is by far the largest of all HNLC regions and thus has the potential to greatly enhance the biological CO2 pump at the global scale. As the aerosol fluxes and sources in the southern Ocean are not well constrained and the potential impact of anthropogenic airborne particles may be larger than expected, a multidisciplinary study is being carried out on dust-bearing snow samples collected in NE Antarctica. Our goals are multiple: (i) determine the mineralogy, morphology and chemical composition of these dusts and, (ii) quantify, by using heavy stable isotopic signatures, the origin and the relative contribution of desert-derived, volcanic and anthropogenic particles in the dust, (iii) estimate the bioavailable fraction of bio-essential elements such as Fe through chemical extraction.

Snow samples were collected at four sites: two a few kilometres from the sea, at the summit of the Derwael Ice Rise (about 200km North of the Belgian Princess Elisabeth Station) and two other locations in a continental area (~225km inland) around the Princess Elisabeth station in the Sør Rondane Mountains. Three litres of snow from each site were melted and filtrated on 0.2 µm poresize NucleporeÓ polycarbonate filters in an ISO 5-class clean room. Subsequently, a series of single particle analyses were performed by (i) FEG-SEM (Field Emission Gun-Scanning Electron Microscopy) to determine particles-size distribution of dust; (ii) automated-SEM-EDS (Energy Dispersive Spectroscopy) to estimate the chemical composition of individual dust particles; (iii) TEM-SAED analysis (Transmission Electron Microscopy Selected Area Electron Diffraction) to identify the minerals present. In addition, trace element compositions of the bulk samples were analyzed by high-resolution ICP-MS.

Preliminary data in elemental composition and mineralogy indicate similarities between dust samples and the rock-forming minerals from the Sør Rondane Mountains suggesting a local dust source. However, major distinctions can be made between coastal and inland dust samples: (i) mineralogical distributions are very distinct; (ii) a large proportion of the quartz and feldspath dust particles exhibit surprisingly enrichment in iron (less than 20% of particles for inland samples and up to 80% for coastal samples), which is probably due to surface Fe-rich coating/aggregates; (iii) coastal samples are heavily enriched (vs. upper continental crust reference values) in Pb and Ni. These Fe, Pb and Ni enrichment trends tend to suggest an external and distal source of dust at the coast, potentially impacted by anthropogenic activities.

To complement those preliminary results, new sampling campaign will take place in December 2014 at the same locations to acquire large quantity of snow. In addition, passive dust collectors will be placed for a period of one year along a transect connecting the Sør Rondane Mountains and the Derwael Ice Rise. The perspectives of this new sampling campaign aim to fulfil our analysis plan through isotopic analyses and chemical extractions.

This in-depth characterisation study will improve our knowledge and understanding of dusts reaching the coast of NE-Antarctica, which represent a proxy of the dust materials supplied to the Southern Ocean. 

by Aubry Vanderstraeten, PhD student

Keep up to date

SEGH Events

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Status, source identification, and health risks of potentially toxic element concentrations in road dust in a medium-sized city in a developing country 2017-09-19

    Abstract

    This study aims to determine the status of potentially toxic element concentrations of road dust in a medium-sized city (Rawang, Malaysia). This study adopts source identification via enrichment factor, Pearson correlation analysis, and Fourier spectral analysis to identify sources of potentially toxic element concentrations in road dust in Rawang City, Malaysia. Health risk assessment was conducted to determine potential health risks (carcinogenic and non-carcinogenic risks) among adults and children via multiple pathways (i.e., ingestion, dermal contact, and inhalation). Mean of potentially toxic element concentrations were found in the order of Pb > Zn > Cr(IV) > Cu > Ni > Cd > As > Co. Source identification revealed that Cu, Cd, Pb, Zn, Ni, and Cr(IV) are associated with anthropogenic sources in industrial and highly populated areas in northern and southern Rawang, cement factories in southern Rawang, as well as the rapid development and population growth in northwestern Rawang, which have resulted in high traffic congestion. Cobalt, Fe, and As are related to geological background and lithologies in Rawang. Pathway orders for both carcinogenic and non-carcinogenic risks are ingestion, dermal contact, and inhalation, involving adults and children. Non-carcinogenic health risks in adults were attributed to Cr(IV), Pb, and Cd, whereas Cu, Cd, Cr(IV), Pb, and Zn were found to have non-carcinogenic health risks for children. Cd, Cr(IV), Pb, and As may induce carcinogenic risks in adults and children, and the total lifetime cancer risk values exceeded incremental lifetime.

  • Erratum to: Preliminary assessment of surface soil lead concentrations in Melbourne, Australia 2017-09-11
  • In vivo uptake of iodine from a Fucus serratus Linnaeus seaweed bath: does volatile iodine contribute? 2017-09-02

    Abstract

    Seaweed baths containing Fucus serratus Linnaeus are a rich source of iodine which has the potential to increase the urinary iodide concentration (UIC) of the bather. In this study, the range of total iodine concentration in seawater (22–105 µg L−1) and seaweed baths (808–13,734 µg L−1) was measured over 1 year. The seasonal trend shows minimum levels in summer (May–July) and maximum in winter (November–January). The bathwater pH was found to be acidic, average pH 5.9 ± 0.3. An in vivo study with 30 volunteers was undertaken to measure the UIC of 15 bathers immersed in the bath and 15 non-bathers sitting adjacent to the bath. Their UIC was analysed pre- and post-seaweed bath and corrected for creatinine concentration. The corrected UIC of the population shows an increase following the seaweed bath from a pre-treatment median of 76 µg L−1 to a post-treatment median of 95 µg L−1. The pre-treatment UIC for both groups did not indicate significant difference (p = 0.479); however, the post-treatment UIC for both did (p = 0.015) where the median bather test UIC was 86 µg L−1 and the non-bather UIC test was 105 µg L−1. Results indicate the bath has the potential to increase the UIC by a significant amount and that inhalation of volatile iodine is a more significant contributor to UIC than previously documented.