17:15 〜 18:30
[ACC26-P02] Seasonal changes in concentration, metal composition and size distribution of mineral particles in recent snow at EGRIP, Greenland
キーワード：グリーンランド、積雪、鉱物ダスト
Changes in meteorological and ground surface conditions can cause changes in mineral particle supply to the Greenland ice sheet and thus influence the particle concentration in snow. To reveal the factor causing the changes of the particle supply and concentration, an understanding of their source areas is required. Metal composition and size distribution of the particles should be able to estimate source areas of the particles. To clarify recent seasonal changes in the concentration of mineral particles in snow and their source area, we analyzed the total concentration of metals and particle distribution in snow pit samples obtained from EGRIP (East Greenland Ice Core Project).
In summer 2017, we dug a 2.01 m snow pit at EGRIP camp. Snow samples were collected at 0.03 m intervals. The snow samples were melted, then fractions of them were analyzed for the particle size distribution (0.52-12μm) with a Coulter counter (Beckman Coulter: Multisizer 4). Other fractions of the samples were treated with a microwave acid digestion method to decompose particulates. Total concentrations of Al, Ca and Na in samples were measured by inductively coupled plasma mass spectrometry.
Concentrations of total Al (t-Al) and non-sea-salt Ca (nssCa) increased in winter to spring layers. This indicates that mineral particle concentration in the snow at EGRIP increased in the periods. In addition, volume fractions of fine particles (<4 μm) tended to be relatively high in the layers. This suggests that fine mineral particles from remote source areas were predominantly deposited on the snow at that time. Additionally, nssCa/t-Al ratios tended to be relatively high in those layers, having 2-3 times higher than the crustal average of Ca/Al ratio in some of the layers. Thus, it is suggested that mineral particles originated from remote desert areas were supplied to EGRIP in the periods. In contrast, in summer to autumn layers, the nssCa/t-Al ratios and volume fractions tended to be relatively low. This suggests the supplies from soil areas having Ca-poor compositions near Greenland in the periods.
In summer 2017, we dug a 2.01 m snow pit at EGRIP camp. Snow samples were collected at 0.03 m intervals. The snow samples were melted, then fractions of them were analyzed for the particle size distribution (0.52-12μm) with a Coulter counter (Beckman Coulter: Multisizer 4). Other fractions of the samples were treated with a microwave acid digestion method to decompose particulates. Total concentrations of Al, Ca and Na in samples were measured by inductively coupled plasma mass spectrometry.
Concentrations of total Al (t-Al) and non-sea-salt Ca (nssCa) increased in winter to spring layers. This indicates that mineral particle concentration in the snow at EGRIP increased in the periods. In addition, volume fractions of fine particles (<4 μm) tended to be relatively high in the layers. This suggests that fine mineral particles from remote source areas were predominantly deposited on the snow at that time. Additionally, nssCa/t-Al ratios tended to be relatively high in those layers, having 2-3 times higher than the crustal average of Ca/Al ratio in some of the layers. Thus, it is suggested that mineral particles originated from remote desert areas were supplied to EGRIP in the periods. In contrast, in summer to autumn layers, the nssCa/t-Al ratios and volume fractions tended to be relatively low. This suggests the supplies from soil areas having Ca-poor compositions near Greenland in the periods.