Atmospheric sources of anthropogenic and geogenic trace metals in Australian lichen and fungi

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Trace metals in archived lichen and fungi samples, dating back over 158 years, were measured to ascertain their potential to record temporal shifts in atmospheric source inputs, starting from the onset of industrial activity in Australia to the present. Lichen (Cladonia n = 85; Usnea n = 47) and fungi (Trametes n = 40) samples from the greater Sydney and Melbourne areas were analysed for their total aluminium (Al), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), titanium (Ti) and zinc (Zn) concentrations using inductively coupled mass-spectrometry. We determined enrichment factors (EFs) of each metal, normalised using Al concentration. All metal concentrations were input to the United States Environmental Protection Agency’s Positive Matrix Factorisation (PMF) model to determine the probable contributing sources, with Sydney (n = 81) and Melbourne (n = 91) samples considered separately. Elevated EFs for Cd, Cu, Pb and Zn (14–1211) suggest that anthropogenic inputs have influenced lichen and fungi concentrations, whilst low EFs for Fe and Ti (1–4) imply geogenic source inputs. Elevated EFs for Pb in samples from 1932 to 2002 correspond with the 70-year period of leaded petrol emissions. PMF modelling determined four distinct source factors: Factor 1 – Cr, Co, Fe, Ni, Zn (19.8 % of the total recovered mass) corresponding to metalliferous industries; Factor 2 – Cd, Cu, Zn (5.3 %) typical of smelting, mining and coal combustion emissions; Factor 3 – Pb (6.6 %) dominated by leaded petrol emissions; Factor 4 – Al, Fe and Ti (68.2 %) relating to geogenic sources. The data show that archived Australian lichen and fungi samples provide effective biomarker proxies for atmospheric trace metal contamination. These new data, extending back to the mid-1800s, provide a more nuanced understanding of anthropogenic atmospheric pollution sources since the onset of post European industrialisation on the Australian continent.