6:15 PM - 7:30 PM
[ACC28-P02] Dependence of the size distribution of BC in snow on thawing temperature
Keywords:snow, BC, size distribution, SP2, thawing temperature
We are measuring the size distribution of BC mass concentration in snow with the incandensence method (MacConel et al. 2007). Before the measurement, snow samples are melted and are aerosolized by a nebulizer. In these procedures, there are some factors to reduce the accuracy or precision. One of them is the influence of the thawing temperature of snow samples on the size distribution of BC in the thawing snow. Many researchers (e.g. Brandt et al., 2011) heated to thaw out snow faster. However, Schwarz et al.(2012) suggested that the size distribution of BC in the thawed snow could be varied with the thawing temperature significantly. In this paper, we present the experiment to examine the thawing temperature influence on the measurement of BC in snow by the incandensence method and the results.
We adopted two snow samples obtained at Hakusan and Shirouma in 2013 for this experiment. The snow samples are well uniformed with a mixer and are divided into 9 bottles, respectively. 3 bottle samples were melted at 70℃,20℃ and 5℃, respectively, using a water bass. Then, we measured the size distribution of BC mass concentration in the melted snow in each bottle with the SP2 instrument.
The mass concentration of BC in the lower thawing temperature samples was higher than those in the higher temperature samples. Their ratio between samples melted at 5℃ and 70℃ was 40.8% for the Hakusan snow case, and 11% for Shirouma snow case. Smaller size of BC was more sensitive to the thawing temperature. These result showed that the thawing temperature has a significant influence on the mass concentration and size distribution of BC in thawing snow, and that lower thawing temperature is better for the measurement of size distribution of BC mass concentration in snow. Because not only the temperature but also thawing/preserve time may affect the size distribution of BC in the thawing snow BC, we are planning of next experiment to examine the time influence.