Isotopic fingerprinting of atmospheric nitrogen and sulfur using lichens (Cladia retipora) in Tasmania, Australia

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 (delta N-15, delta S-34) 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 delta N-15 value was - 2.8 +/- 1.9 parts per thousand 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 delta S-34 values as low as - 21.9 parts per thousand. All other lichen samples had a mean value of delta S-34 value of 13.7 +/- 2.2 parts per thousand, 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. (C) 2017 Elsevier Ltd. All rights reserved.