Abstract
Abstract. The influence of temperature and time of snow sample melting on the measurement of mass concentration and size distribution of black carbon (BC) in snow was evaluated experimentally. In the experiments, fresh (Shirouma) and aged (Hakusan) snow samples were melted at different temperatures or at different time lengths, and the BC mass concentration and size distribution in the melted snow samples were measured using a nebulizer and a single-particle soot photometer (SP2). In the experiment where melting temperature was varied, the BC mass concentration in the liquid decreased at a melting temperature of 70 °C. This decrease was 8.0 % for the Shirouma sample and 46.4 % for the Hakusan sample and depended on BC particle size, with a significant decrease found at BC diameters less than 350 nm. A similar decrease in BC mass concentration was found when the Hakusan snow sample that had been melted at 5 °C was heated to 70 °C. The experiment in which melting time was varied indicated that BC mass concentration in the liquid did not change for the Shirouma sample but decreased significantly with a longer melting time for the Hakusan sample (38.6 %). These results indicate that melting of snow samples at high temperatures or over long time periods can significantly affect the measurement of BC mass and its size distribution, especially for aged snow samples.
Highlights
Black carbon (BC), commonly referred to as soot, strongly absorbs solar radiation in the atmosphere, leading to significant climate effects
The BC mass concentration values do not show a significant difference between the melting temperatures of 5 and 20 ◦C; the BC mass concentration was systematically smaller at the 70 ◦C melting temperature
To enable a more accurate measurement of the amount of BC in snow, we evaluated the influence of temperature and time during the procedure for melting snow samples
Summary
Black carbon (BC), commonly referred to as soot, strongly absorbs solar radiation in the atmosphere, leading to significant climate effects. Some studies suggest that the heating condition for melting snow/ice samples may significantly affect the BC mass concentration and its size distribution in the melted water, leading to possible uncertainty in the measurement of BC mass in snow/ice. Lim et al (2014) evaluated sample treatment procedures in the SP2 method, including the melting procedure, freezing/melting cycle, and surface area to volume ratio of the sample containers They compared two snow melting procedures, melting at room temperature and melting in a warm bath (30 ◦C), but did not find a significant difference in the measured BC concentration between the two procedures. By comparing the results for the different temperatures and the time lengths, their influence on BC measurement in snow/ice are evaluated
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