Preservation of Organic Carbon Associated with Iron on Continental Shelves Influenced by Hydrodynamic Processes.

Understanding the environmental fate of organic carbon associated with iron (OC-Fe) is critically important for investigating OC preservation in aquatic systems. Here, we first investigate C and C isotopes of OC-Fe within grain size-fractionated sediments retrieved from the East China Sea and estimate their sources and reactivities of OC-Fe through isotope-mixing models and thermal pyrolysis approaches in order to reveal the fate of OC-Fe on continental shelves influenced by hydrodynamic processes. Our results show that the OC-Fe proportion in total OC () in the sortable silt fractions (20-63 μm) is the highest among three grain size fractions, likely suggesting that hydrodynamics may enhance the iron protection on OC.

Influences of oxidation ability on precision in nitrogen isotope measurements of organic reference materials using elemental analysis-isotope ratio mass spectrometry.

Rationale: The precision of the standard measurements of reference materials (RMs) is critical to normalize the raw δ N values of samples to the international scale. Because the measurement configuration is required to moderate the properties of both RMs and samples for obtaining an ideal measurement precision, it is important to determine the appropriate measurement configurations of RMs to achieve accurate nitrogen isotope compositions of samples. Therefore, it is critical to systematically examine RMs for optimizing the configurations and further improve the measurement precision.