EAPSI:Investigating Sulfur Sources and Sulfate Oxidation Chemistry in New Zealand Aerosols

Katzman Tanya L, West Lafayette IN

Investigators

Abstract

Sulfate aerosols are a critical part of climate change, the water cycle, and significantly impact human health, yet we do not completely understand the sources of sulfur, nor how it is oxidized into sulfate in the atmosphere. In order to study the impact of sulfur in the environment, researchers in collaboration with the Institute of Geological and Nuclear Science (GNS) will collect aerosols at Baring Head, located on the southern tip of the North Island of New Zealand. In contrast to the Northern Hemisphere, where man-made sulfur dominates, the majority of Southern Hemisphere sulfur is from natural sources and of marine origin. Many Baring Head aerosols are of marine origin, which allows researchers to assess marine sulfur chemistry without terrestrial influences. In addition to the unique sampling location, GNS possesses the experience, expertise, and analytical capability required for evaluating the sulfur chemistry in this project. To assess sulfur chemistry, researchers will utilize the stable isotope concentrations of sulfur (d34S) and oxygen (d17O, d18O, D17O) to evaluate sources and oxidation pathways. Sulfur isotopes allow for the differentiation of sulfur sources (low d34S for land sources; elevated d34S for marine sources), as the value of d34S is retained during oxidation. Oxygen isotopes provide insight to the oxidation pathways (gas phase oxidation, D17O = 0; aqueous phase oxidation, D17O > 0) that form sulfate. Additionally, by collecting size segregated aerosols, researchers will be able to analyze gas and aqueous phase oxidation of a comparable air mass. Coarser aerosols are more likely to undergo aqueous phase oxidation than the finer fraction, as sea water in this region is slightly more alkaline thus promoting aqueous oxidation. Once combined, the analyses preformed will create a robust data set that will compliment future modeling projects and enhance the understanding of the impact sulfate aerosols have on climate change, the water cycle, and human health worldwide. This award is funded in collaboration with the Royal Society of New Zealand.