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Title: Rates and pathways of iodine speciation transformations at the Bermuda Atlantic Time Series

The distribution of iodine in the surface ocean – of which iodide-iodine is a large destructor of tropospheric ozone (O3) – can be attributed to bothin situ(i.e., biological) andex situ(i.e., mixing) drivers. Currently, uncertainty regarding the rates and mechanisms of iodide (I-) oxidation render it difficult to distinguish the importance ofin situreactions vsex situmixing in driving iodine’s distribution, thus leading to uncertainty in climatological ozone atmospheric models. It has been hypothesized that reactive oxygen species (ROS), such as superoxide (O2•−) or hydrogen peroxide (H2O2), may be needed for I-oxidation to occur at the sea surface, but this has yet to be demonstrated in natural marine waters. To test the role of ROS in iodine redox transformations, shipboard isotope tracer incubations were conducted as part of the Bermuda Atlantic Time Series (BATS) in the Sargasso Sea in September of 2018. Incubation trials evaluated the effects of ROS (O2•−, H2O2) on iodine redox transformations over time and at euphotic and sub-photic depths. Rates of I-oxidation were assessed using a129I-tracer (t1/2~15.7 Myr) added to all incubations, and129I/127I ratios of individual iodine species (I-, IO3-). Our results show a lack of I-oxidation to IO3-within the resolution of our tracer approach – i.e., <2.99 nM/day, or <1091.4 nM/yr. In addition, we present new ROS data from BATS and compare our iodine speciation profiles to that from two previous studies conducted at BATS, which demonstrate long-term iodine stability. These results indicate thatex situprocesses, such as vertical mixing, may play an important role in broader iodine species’ distribution in this and similar regions.

 
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Award ID(s):
1829406
PAR ID:
10561133
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Frontiers
Date Published:
Journal Name:
Frontiers in Marine Science
Volume:
10
ISSN:
2296-7745
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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