Recovery of organic matter from mineral-rich sediment and soils for stable isotope analyses using static dense media

Abstract

Light stable isotopes in organic matter (e.g., d13C, d15N, d18O, dD, d34S) enable a breadth of investigations in the environmental sciences.1–3 However, organic matter is often highly dispersed in mineral-rich sediment and soils, and is thus difficult to reliably isolate for analysis. Moreover, both aquatic and terrestrial sediments contain abundant resistant polymers such as cellulose, keratin, and chitin which can be potentially recovered for multi-isotope proxy measurements for use in investigating past environmental change. Isolation of organic material without mineral contamination for further chemical purification would thus be beneficial, particularly for dD and d18O, where minerals may serve as contaminants during measurement by pyrolysis. In soils, modelling the carbon and nitrogen cycling of soil organic matter (SOM) requires the separation and apportioning of the organic matter to appropriate soil pools of differing residence time with minimal sample loss or cross-mixing.