Comparison of methods for the quantification of carbonate carbon in atmospheric PM10 aerosol samples

Abstract

Carbonate carbon (CC) represents an important fraction of atmospheric PM10 along with organic carbon (OC) and elemental carbon (EC), if specific sources (e.g. street abrasion, construction sites, desert dust) contribute to its composition. However, analytical methods for an easy and unambiguous determination of CC in atmospheric aerosols collected on filter matrices are scarce. We propose here a method for the determination of CC based on a heating pretreatment of the sample to remove OC and EC, followed by a total carbon determination to measure CC. This procedure is used for the correction of EC also determined by a heating pretreatment (Cachier, H., Bremond, M.P., Buat-Ménard, P., 1989. Determination of atmospheric soot carbon with a simple thermal method. Tellus 41B, 379–390) but without previous HCl fumigation, as proposed. Comparison of the carbon remaining after the proposed thermal treatment at 460 °C for 60 min in an oxygen stream showed good correlation for the carbonate carbon derived by calculation from the ionic balance for ambient air and street dust samples. Using the “three step” combustion technique it is now possible to determine OC, EC and CC by the use of a TC analyser in the concentration range of 2–200 μg carbon per sample aliquot, with good precision (3–5% RSD for TC and 5–10% for CC) and accuracy. In ambient air samples from a sampling site in Vienna with elevated PM10 levels (“Liesing”) CC values as high as 25% of TC and 27% CO 3 2−; for street dust samples 32% of TC and 25% CO 3 2− of total PM10 mass were observed.