Sunset-calc: An R Shiny Application for Processing Thermo-Optical Analysis Data from Atmospheric Aerosol Measurements

Atmospheric aerosols are harmful to human health and affect the climate. We use radiocarbon for the source apportionment of carbonaceous aerosols to unequivocally separate fossil form non-fossil sources. We use thermal-optical analysis (TOA) for radiocarbon measurement of the organic carbon (OC) and elemental carbon (EC) fractions, which requires physical OC/EC separation. TOA relies on the changes in the optical behaviour of carbon when OC is thermally separated from EC. Thermal-optical OC/EC separation leads to partial EC-loss and the conversion of some OC to EC (charring). EC-loss and charring are artifacts which falsify the results of the quantification and must be corrected for. Furthermore, quantifications with custom TOA protocols are not supported with the provided device software. These calculations were previously performed with various spreadsheet style templates and other tools. With Sunset-calc, we aimed to bundle the data processing and develop an extendable and simple web application. With R Shiny, we found a powerful and simple language also for people with little prior programming skills to build rich web applications. We have deployed Sunset-calc on an on-premises R server (14c.unibe.ch/sunsetcalc), which is publicly accessible and particularly useful for our collaborators outside of the University. Sunset-calc is available on GitHub (github.com/martin-rauber/sunset-calc).