An Instrumental Method for the Simultaneous Determination of Organic Carbon, Elemental Carbon, Inorganic Nitrogen, and Organic Nitrogen in Aerosol Samples

Abstract

Carbonaceous and nitrogenous materials are major components of atmospheric aerosols. Their measurements are fundamental for quantifying the crucial roles of aerosols in air quality, climate, ecosystems, and human health. We present the first instrumental method capable of simultaneous quantification of organic carbon (OC), elemental carbon (EC), inorganic nitrogen (IN), and organic nitrogen (ON) in aerosol samples. By integrating thermal evolution (TE) with multivariate curve resolution (MCR) data analysis, this method effectively resolves overlapping TE signals of OC, EC, IN, and ON, circumventing limitations of traditional analytical methods that lack MCR capabilities. Validation against established reference methods showed strong agreement across all components. In comparison with OC and IN, EC and ON exhibited greater variability due to their typical lower proportions in total carbon and total nitrogen, respectively, as well as inherent ambiguities in MCR analysis. The instrumental method was applied to 161 aerosol samples collected from six sites in China during the winter of 2023–2024. The average mass concentrations of IN, ON, OC, and EC were 10.5 ± 6.7, 2.4 ± 1.5, 14.1 ± 7.3, and 4.4 ± 3.2 μg/m³, respectively, with an atomic OC/ON ratio of 7.5 ± 1.9. This ratio, unavailable in past aerosol characterization studies, provides new insights into the validation of various biogenic and anthropogenic sources. Importantly, it can serve as a valuable constraint for atmospheric models, improving simulations of carbonaceous and nitrogenous aerosol sources and transformations. The ability to simultaneously quantify OC, EC, IN, and ON represents a significant advancement in aerosol characterization, offering a powerful new tool for atmospheric research.