Isotopic fingerprinting of atmospheric nitrogen and sulfur using lichens (Cladia retipora) in Tasmania, Australia
Hogan, CM and Proemse, BC and Barmuta, LA, Isotopic fingerprinting of atmospheric nitrogen and sulfur using lichens (Cladia retipora) in Tasmania, Australia, Applied Geochemistry, 84 pp. 126-132. ISSN 0883-2927 (2017) [Refereed Article]
Increases in global anthropogenic emissions are far reaching, and are a concern even in remote areas. Tasmania, Australia is an island state that hosts the only Southern Hemisphere premier Baseline Air Pollution Station as part of the World Meteorological Organization-Global Atmosphere Watch network. Despite Tasmania's importance as a baseline location, little is known about atmospheric nitrogen (N) and sulfur (S) deposition and sources across the state. Here we investigate total N and S content and isotopic compositions (δ15N, δ34S) in the lichen Cladia retipora as a bio-indicator to identify whether atmospheric N and S deposition in Tasmania is affected by anthropogenic pollution. Both TN and TS were extremely low in all 66 samples collected across the state, averaging 0.29 ± 0.28% and 0.03 ± 0.05%, respectively. The average δ15N value was −2.8 ± 1.9‰ and there was no correlation with TN, but values were highest towards the denser populated SE of Tasmania. Lichens collected from sites within 500 m of salt marshes revealed a strong local source of microbially-reduced S as indicated by δ34S values as low as −21.9‰. All other lichen samples had a mean value of δ34S value of 13.7 ± 2.2‰, indicating mixing of marine biogenic S and anthropogenic S. This study represents the first baseline study of atmospheric N and S in C. retipora across Tasmania, and demonstrates the suitability of lichen bio-monitoring for future studies in this region.