Ubiquitous Presence of Fe(II) in Aquatic Colloids and Its Association with Organic Carbon

Citation:

von der Heyden, BP, EJ Hauser, B Mishra, GA Martinez, AR Bowie, TTyliszczak, TN Mtshali, AN Roychoudhury, and SCB Myneni. 2014. “Ubiquitous Presence of Fe(II) in Aquatic Colloids and Its Association with Organic Carbon.” Environmental Science & Technology Letters 1: 387-392.

Abstract:

Despite being thermodynamically less stable, small ferrous colloids (60 nm to 3 μm in diameter) remain an important component of the biogeochemical cycle at the Earth’s surface, yet their composition and structure and the reasons for their persistence are still poorly understood. Here we use X-ray-based Fe L-edge and carbon K-edge spectromicroscopy to address the speciation and organic–mineral associations of ferrous, ferric, and Fe-poor particles collected from sampling sites in both marine and freshwater environments. We show that Fe(II)-rich phases are prevalent throughout different aquatic regimes yet exhibit a high degree of chemical heterogeneity. Furthermore, we show that Fe-rich particles show strong associations with organic carbon. The observed association of Fe(II) particles with carboxamide functional groups suggests a possible microbial role in the preservation of Fe(II). These finding have significant implications for the behavior of Fe(II) colloids in oxygenated waters, and their role in different aquatic biogeochemical processes.

DOI