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

• Published in: Environmental science & technology 2024-08, Vol.58 (33), p.14698-14708
• Main Authors: Li, Haoshuai, Lin, Deju, Zhang, Haiyang, Wang, Nan, Zhou, Yang, Wu, Weifeng, Liu, Jingyu, Che, Yangli, Xia, Cuimei, Zhu, Longhai, Peng, Chuanzhao, Liu, Qian, He, Qian, Bao, Rui
• Format: Article
• Language: English
• Subjects: Aquatic environment; Biogeochemical Cycling; Carbon; Carbon - chemistry; Carbon 14; China; Continental shelves; Fractions; Geologic Sediments - chemistry; Grain size; Hydrodynamics; Iron; Iron - chemistry; Isotopes; Ocean floor; Oceans and Seas; Organic carbon; Particle size; Preservation; Pyrolysis; Sediments
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.4c01727

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 13C and 14C 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 (f OC‑Fe) 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. In addition, Δ14COC‑Fe values fall within the range of from −358.73 to −64.03‰, and both Δ14COC‑Fe values and ancient OC-Fe% exhibit strong positive linear relationships with f OC‑Fe. This emphasized that the hydrodynamic processes may cause the ancient OC to be tightly associated with Fe, accompanying OC-Fe aging. Our findings shed new light on the preservation of OC-Fe in marginal seas to advance the recognition of carbon “rusty sinks” in seafloor sediments.