Spatial variation and species transformation of 129 I and 127 I in the Central Arctic Ocean

• Published in: Earth and Planetary Science Letters
• Main Authors: Zhang, Luyuan, Hou, Xiaolin, Gwynn, Justin P., Karcher, Michael, Chen, Ning, Fan, Yukun, Liu, Qi
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Speciation transformation; 129I; 127I; Marine redox environment; Geochemical cycling of iodine; /dk/atira/pure/sustainabledevelopmentgoals/climate_action; name=SDG 13 - Climate Action; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Arctic; Arctic Ocean; Climate change
• Online Access: https://orbit.dtu.dk/en/publications/0519cc51-cbf3-4e1e-845c-2b4b3174198a; https://doi.org/10.1016/j.epsl.2023.118165; https://backend.orbit.dtu.dk/ws/files/319040218/1_s2.0_S0012821X23001784_main.pdf

The spatial distributions of anthropogenic 129 I and natural 127 I in iodide (I − ) and iodate (IO 3 - ) of anthropogenic 129 I and natural 127 I were investigated in the upper central Arctic Ocean. The results show that the molecular ratios of reductive iodide (I − ) to oxidative iodate (IO 3 - ) ranged from 0.228 to 0.560 for 127 I and 0.383 to 0.827 for 129 I in the Polar Mixed Layer (PML). Greater 127 I − concentrations and markedly higher I − /IO 3 - ratios for both 129 I and 127 I were found in the PML over the Lomonosov and Alpha Ridges. This suggests that the in-situ formation of I − occurs as a result of enhanced reductive environments at these locations due to bacterial-mediated decomposition of dissolved organic matter (DOM) that likely originates from the inflow of river water into the central Arctic Ocean. Ratios of 129 I − / 129 IO 3 - and 127 I − / 127 IO 3 - decrease gradually along the main transport pathway of the Atlantic water, revealing that I − is gradually oxidized back to IO 3 - at a slow net rate within the Atlantic Water Layer. Our study provides insights into the marine geochemical cycling of iodine and raises the potential for iodine species, notably of 129 I, to be used as indicators of changes in the redox condition of surface water in the Arctic Ocean, which may occur due to the predicted impacts of climate change.