Investigating origins of atmospheric dusts through uranium-lead isotopic analysis of individual mineral grains using Nano-SIMS and related microanalytical techniques
EMSL Project ID
47522
Abstract
Human activities of the past several centuries have significantly increased the flux of atmospheric dusts in the global environment, and these dusts generally have negative consequences to human health, ecosystems, climate, and property. Most dusts originate from surface soils and sediments in deserts and arid regions, and these dusts may be transported locally, regionally or even globally. Paramount questions include, "Where does dust come from", and "What is the deposition rate"? Exogenous dusts are detectable through mineralogical evidence, comparison of elemental constituent signatures, and the application of isotope mass balance models. While these bulk methods can place constraints on possible sources, they often cannot pinpoint specific origins. In this proposal, we will develop a novel approach using Nano-SIMS and related techniques utilizing the capabilities at EMSL (Specific Aim 1). We will develop a method to determine uranium-lead and lead-lead signatures in individual zircon particles, and we will compare these signatures to candidate dust source areas. We will focus on very small (< 10 micron) zircon particles that can be transported in the troposphere. We will also investigate the possible use of related microanalytical techniques (XPS, TEM, and He ion microscopy) to characterize elemental or chemical signatures of individual dust particles (Specific Aim 2). The use of Nano-SIMS and related microanalytical techniques will be investigated using bulk samples of pothole dusts from the San Francisco Peaks of northern Arizona (Specific Aim 3), where several types of preliminary analysis of bulk samples demonstrates the presence of considerable exogenous dust. We will also characterize dusts deposited in Kyrgyzstan (Specific Aim 4). We hypothesize that individual airborne zircon grains contain valuable isotopic signature information that is more specifically indicative of origin than is possible through bulk analysis, and that these signatures can be matched to their respective geologic provinces of origin. Further, we hypothesize that the Owens Valley and the Aral Sea, respectively, represent major contributors to dusts deposited at the San Francisco Peaks and in Kyrgystzan, respectively. This project represents, to our best knowledge, a novel approach for provenance of atmospheric dusts, and the new EMSL Nano-SIMS capability offers an excellent opportunity to implement the project.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2012-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members