| Popis: |
Mineral dust (MD) and elemental carbon (EC) deposited on snow surfaces lead to a variety of consequences for the environment. Hence, the determination in snow is of great interest. Thermal-optical analysis (TOA) is routinely used for the determination of EC, while its use for the analysis of carbonate carbon (CC), as possible proxy for MD, is not as common. Within this work the possibility to determine both CC and EC in snow samples within one analytical run is evaluated. Thereby the challenges caused by the optical properties of hematite are considered. During filtration of the liquid sample a slight vacuum has to be applied to avoid leaks. The filter loadings were found to be homogeneous, but a slight enrichment on the outer rim of the filter was observed. Cutting filters and weighing of these aliquots was found to be suitable for partitioning. Adding NH4H2PO4 as coagulant to increase the filter efficiency for EC led to problems regarding the OC / EC split, since the optical correction via the transmittance signal could not be performed. For the removal of CC rinsing of samples with HCl is recommended. Temperature steps attributed to CC were identified by reference substances and real samples containing MD. CC assessed from the thermograms correlated with the calzium concentration, but CC from TOA was higher. A comparison of the change in transmittance due to iron compounds was performed based on reference substances and samples containing defined amounts of MD. |
