ICMGP 2022 – On-Demand / Poster Presentation

Abstract Information :

Mercury is a pollutant of global concern, however studies assessing the long-term Hg deposition record in Southeast Asia (SEA) are scarce. As we enter a new age of unprecedented climate change, it is imperative that we develop our knowledge of the Hg cycle in SEA to anticipate pollution issues and take appropriate measures. Using a multi-proxy framework, including pollen, charcoal, and high-resolution geochemistry records, we investigate the response of atmospheric Hg deposition to shifts in climate (between ~16.2 and 1 cal Kyrs BP) in Lake Lantoa, south Sulawesi, Indonesia. This period encompasses the B?lling-Aller?d (BA) warming and Younger Dryas (YD) cooling events, providing new insight into the effects of global climatic transitions on atmospheric Hg deposition in SEA. Mercury deposition was mostly stable throughout the sediment core. The few Hg variations throughout the record were most closely related to charcoal patterns, suggesting that changes in the Hg profile of Lake Lantoa were primarily driven by changes in fire regimes. To our knowledge, no other studies report a stable Hg profile with no significant responses to climate change in SEA. At ~14.35 cal Kyrs BP the pollen record indicates an increase in humid conditions, as shown by a decrease in fire tolerant taxa (Casuarinaceae, Poaceae, and Cyperaceae) and an increase in a humid rainforest taxon (Dipterocarpaseae). The pollen record suggests that by ~12 cal Kyrs BP a permanent rainforest had been established. Long-term vegetation cover on Sulawesi allows constant year-round Hg uptake from local flora. The Hg profile is stable overall and indicates constant atmospheric deposition throughout the core. These records indicate that Sulawesian soils have been acting as long-term Hg sinks. Our results demonstrate the need to study the Hg profile of tropical SEA soils, as deforestation and fire activities in the region can result in remobilising sequestered Hg.