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Mercury in an Australian Sclerophyll Eucalyptus Forest and Emissions from Fuel Reduction Prescribed Burning

James Taylor , Larissa Schneider , ANNE HELENE FOSTIER , Heather Keith , Fei Cao, Peter Davies, Geoff Cary, Simon Haberle, Susan Lawrence

Abstract

Rationale Research on mercury in Australian soils and litter is sparse. This study aims to address this knowledge gap by investigating mercury pools in soil and litter in a Victorian Eucalypt forest. Methodology We analysed total mercury concentrations in O and A horizon soils, and twig, bark, and leaf litter. Soil samples were collected from an area affected by a prescribed burn, and unburnt areas. Additionally, soil samples from the base of tree stems were taken in unburnt areas. The organic matter content of all soil samples was also assessed. Results In unburnt soils, mean mercury concentrations at the base of tree stems, in the O-horizon, and A horizon was 143 ± 61 ng g⁻¹, 112 ± 71 ng g⁻¹, and 56 ± 30 ng g⁻¹ respectively. In burnt soils, mean mercury concentrations in the O and A horizons were 91 ± 63 ng g⁻¹ and 46 ± 19 ng g⁻¹ respectively. Mercury concentrations in leaf, bark and twig litter averaged 71 ± 11 ng g⁻¹, 21 ± 13 ng g⁻¹, and 8 ± 4 ng g⁻¹ respectively. The emission factor was estimated as 0.247 g Hg ha-1. Discussion The study site serves as a significant mercury reservoir. Burning did not significantly alter the mercury burden in soil; however, emissions of mercury from litter did occur. This finding underscores the need for more comprehensive research into mercury cycling in Australia and suggests that prescribed burning practices should consider potential impacts on mercury emissions.

EN24087  Accepted 02 December 2024

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