Results of sorption experiments on dust samples from ephemeral rivers in Namibia - Time series-100 mg dust

Different amounts of dust (5 mg and 100 mg) were added to a mixture (30 mL) of artificial seawater and 13C-labeled Spirulina extract (~500 µM). Water samples were taken at multiple time points (0, 10, 24, 48, 72, 120, and 168 hours) and analyzed for DOC using a carbon analyzer (multiN/C 2100s, Analytik Jena). Dust samples were analyzed for TOC and δ13C-TOC before and after the experiments using isotope ratio mass spectrometry (IRMS) (Delta V Plus, Thermo Scientific, with a ConFlo IV interface to an elemental analyzer), calibrated against the Vienna Pee Dee Belemnite (VPDB) standard with a precision of ±0.35‰. After 72 hours, water samples were also analyzed for δ13C-DIC using isotope ratio infrared spectrometry (IRIS) with a universal reference interface (URI) (Delta Ray, Thermo Scientific), calibrated to the VPDB standard with a precision of ±0.05‰.