This project will explore the use of Fe isotope analysis to determine the importance of anthropogenic aerosols as a source of Fe to the oceans. Fe is known to limit primary production in many high-nutrient, low-chlorophyll areas, so it is important to understand where the Fe that is delivered to the oceans originates. Recent work using V/Al abundance ratios has shown that anthropogenic aerosols are a major source of bioavailable Fe in some areas of the ocean, due to their higher solubility as compared to natural aerosols. However, V/Al cannot discriminate between some important anthropogenic and natural sources, and so additional tools are needed. We have discovered distinct variations in the isotopic composition of aerosol Fe that arise from differences between natural and anthropogenic Fe, which provides a foundation for the proposed research. Intellectual Merit: We will measure the Fe isotopic compositions of aerosol particles collected in Bermuda over a period of one year. Bermuda is ideally suited to this investigation because aerosol sources to this region alternate seasonally when summer winds that carry soil dust from the Saharan Desert give way to winter winds that come from the West, bringing anthropogenic aerosols from North America. This change in wind direction will provide us with a large contrast in source material, which we hypothesize will give rise to seasonal variations in Fe isotopes. We will compare results from the Bermuda samples to analyses of key anthropogenic and natural sources of aerosol Fe to the Atlantic Ocean. The source samples we will analyze include dust collected near West Africa, several samples of oil and coal fly ash, and a sample of diesel particulate matter. Existing research suggests that these are likely to be the most important sources of particulate Fe to the Bermuda region. Fe isotope analyses will be paired with elemental analyses, providing an independent way to assess the sources of aerosol Fe. Our recent work has shown that different size fractions carry different isotope signatures that can be attributed to different sources. Therefore, we will employ size-segregated sampling and will also separately analyze the soluble Fe fraction, in contrast to prior studies of Fe isotopes in marine aerosols.
|Effective start/end date||10/1/10 → 9/30/14|
- National Science Foundation (NSF): $225,202.00