Chemical composition of soluble and insoluble particles around the last termination preserved in the Dome C ice core, inland Antarctica

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Oyabu, Ikumi ; Iizuka, Yoshinori ; Wolff, Eric ; Hansson, Margareta (2016)

Knowing the chemical composition of particles preserved in polar ice sheets is useful for understanding past atmospheric chemistry. Recently, several studies have examined the chemical compositions of soluble salt particles preserved in ice cores from inland and peripheral regions in both Antarctica (Dome Fuji and Talos Dome) and Greenland (NEEM). On the other hand, there is no study that compares salt compositions between different sites in inland Antarctica. This study examines the chemical compositions of soluble salt particles around the last termination in the Dome C ice core, and compares them to those from Dome Fuji. Particles larger than 0.45 μm are obtained from the ice core by an ice sublimation method, and their chemical compositions are analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy. The major soluble salt particles are CaSO<sub>4</sub>, Na<sub>2</sub>SO<sub>4</sub>, and NaCl, which is the same as that from the Dome Fuji ice core. Time-series changes in the composition of these salts are similar to those for the Dome Fuji ice core. Specifically, from 25 to 18 ka, the ratio of NaCl to Na<sub>2</sub>SO<sub>4</sub> is variable, but generally the CaSO<sub>4</sub> and NaCl fractions are high and the Na<sub>2</sub>SO<sub>4</sub> fraction is low. Between 18 and 17 ka, the CaSO<sub>4</sub> and NaCl fractions decrease and the Na<sub>2</sub>SO<sub>4</sub> fraction increases. Between 16 and 6.8 ka, the CaSO<sub>4</sub> and NaCl fractions are low and Na<sub>2</sub>SO<sub>4</sub> fraction is high. However, the sulfatization rate of NaCl at Dome C is higher than that at Dome Fuji. We argue that this higher rate arises because at Dome C more SO<sub>4</sub><sup>2&minus;</sup> is available for NaCl to form Na<sub>2</sub>SO<sub>4</sub> due to a lower concentration of Ca<sup>2+</sup>.
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