Mineral Dust Samples: Analysing Strontium (Sr), Strontium-Neodymium-Hafnium (Sr-Nd-Hf) and Lead (Pb) Isotopes
Mineral dust plays a major role in controlling the global radiation budget and is an actively changing component of the biogeochemical and hydrological cycles. The concentration, composition and circulation of dust in the atmosphere can have significant implications for the earth’s climate and can also be used to track variability in weather patterns. For example, higher quantities of atmospheric dust landing in the cryosphere leads to faster spring melt of snow surfaces due to reduced albedo. Furthermore, higher quantities of dust have been correlated with the ocean-atmosphere coupled phenomena (e.g. El Niño). Given the importance of atmospheric dust, the analysis of dust composition is an important field of inquiry to investigate dust sources and movement through space and time.
The origin and movement of atmospheric dust can be estimated by analysing the geochemistry of dust collected directly from the atmosphere or from the dust layers found within ice cores or lacustrine and ocean sediment cores.
Strontium isotopes (Sr) are commonly analysed to interpret the likely source of dust through the investigation of 87Sr/86Sr ratios. This technique can be utilised on many scales – from global to regional. Carling et al. (2020) traced the movement of dust from a recently exposed drying lake in Salt Lake City (northern Utah) to nearby snowpacks on the Wasatch Mountains and an urban center along the Wasatch Front. (Read more about the Applications of Strontium Isotopes)
Strontium-Neodymium-Hafnium isotopes (Sr-Nd-Hf) are inherent in many geological settings, and thus have been used to track the origin of sediments and dust. These isotopes can be used in tandem as they are coupled during crustal processes that lead to the development of igneous and clastic rocks and are not significantly altered by other processes (e.g. weathering, transportation, deposition). By tracking the composition of dust based on these isotopes, it is possible to pinpoint the likely originating geological setting. Sharifi et al. (2018) demonstrated that dust sources changed over the Iranian Plateau at the start of the Holocene following the Younger Dryas due to the exposure of land during glacial melt and changes to prevailing atmospheric circulation regimes. (Read more about Applications of Sr-Nd-Hf)
UPDATE: Isobar Science discontinued the Sr-Nd-Hf service starting January 2024.
Lead isotopes (Pb) can complement the Sr-Nd-Hf systematic for provenance study of dust. It can also be analysed to identify atmospheric dust with anthropogenic pollution sources, including mining, industrial and vehicle emissions. Kristensen et al. (2015) were able to track the contamination of lead (Pb) into the environment from uncovered wagons operating along a train line (1888 – 1970) by tracking Pb dispersion patterns in the surrounding soil horizons. (Read more about Applications of Lead Isotopes)
Analysing sources of atmospheric dust can be challenging due to various scenarios which lead to the obscurity of the isotopic signal. For example, atmospheric dust from a specific source can be diluted or altered in composition after travelling vast distances through mixing with other dust sources (e.g. anthropogenic industrial emissions, volcanic eruptions and wildfire emissions). As a result, a strong understanding of the dynamics that are present at the dust source and deposition sites as well as through the transportation path are vital to allow for accurate interpretations of the isotopic results.
If you would like to send dust samples for analysis, the minimum sample size is 30-50 mg of prepared dust for all isotopic services. To prepare your samples, they should be collected on filter paper, and must be ashed (to remove organics) entirely prior to submission. If you wish to measure isotopes only on siliciclastic fractions, all carbonate fractions must be removed. Contact us today to discuss your project.
References
Carling, G.T., Fernandez, D.P., Rey, K.A., Hale, C.A., Goodman, M.M. and Nelson, S.T., (2020). Using strontium isotopes to trace dust from a drying Great Salt Lake to adjacent urban areas and mountain snowpack. Environmental Research Letters, 15(11), p.114035. DOI: 10.1088/1748-9326/abbfc4
Kristensen, L.J., Taylor, M.P. and Morrison, A.L., (2015). Lead and zinc dust depositions from ore trains characterised using lead isotopic compositions. Environmental Science: Processes & Impacts, 17(3), pp.631-637. DOI: 10.1039/C4EM00572D
Sharifi, A., Murphy, L.N., Pourmand, A., Clement, A.C., Canuel, E.A., Beni, A.N., Lahijani, H.A., Delanghe, D. and Ahmady-Birgani, H., (2018). Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia. Earth and Planetary Science Letters, 481, pp.30-40. DOI: 10.1016/j.epsl.2017.10.001
Image references
Atmospheric dust (NOAA): https://www.nesdis.noaa.gov/news/the-dirt-atmospheric-dust