Environmental iodine speciation quantification in seawater and snow using ion exchange chromatography and UV spectrophotometric detection

Jones, Matthew R.; Chance, Rosie; Dadić, Ruzica; Hannula, Henna-Reetta; May, Rebecca; Ward, Martyn W.; Carpenter, Lucy J.

doi:10.1016/j.aca.2022.340700

Cited by 9 publications

(3 citation statements)

References 78 publications

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“…However, DOI concentrations in seawater are generally much lower than iodate, and typically range from 10 to 40 nmol L -1 (Wong and Cheng, 1998;Truesdale et al, 2001). We checked the DOI levels in samples collected at three depths in Bedford Basin in both November 2022 and April 2023, using the three-step procedure of Jones et al (2023) which involves addition of Ca(ClO) 2 , Na 2 SO 3 and NH 2 OH-HCl. These samples covered seasons with both high (April 2023) and low (November 2022) oxygen concentrations.…”

Section: Analytical Methods For Iodine Analysismentioning

confidence: 99%

Speciation of dissolved inorganic iodine in a coastal fjord: a time-series study from Bedford Basin, Nova Scotia, Canada

2023

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We report a long-term (4.5 year) time-series with weekly resolution of iodide and iodate measurements made at 4 depths within the Bedford Basin: a 70 m deep, seasonally stratified, coastal fjord located near Halifax, Nova Scotia, Canada. The subsurface data (60 m) reveal strong inverse correlations of both iodide and total dissolved iodine (TDI) with dissolved oxygen and indicate that there is in-situ reduction of iodate in subsurface waters (in the presence of oxygen) as well as an additional external source of iodide from the remineralization of sinking organic matter, a flux from sediments, or both. Surface water (<10 m) iodide concentrations increase gradually from spring (70 nmol L-1) through fall (120-150 nmol L-1) and are not well represented by the current empirical parameterizations used to predict surface water iodide levels globally. The vertical gradient of iodide between subsurface and surface waters increases over the summer as a result of subsurface processes and, together with diapycnal mixing, may contribute to the seasonal accumulation of iodide in surface water. Examination of a global surface water iodide data compilation reveals an inverse relationship with subsurface oxygen concentrations which suggests that subsurface remineralization and sediment-water fluxes coupled with vertical mixing may also contribute to surface water iodide variability on a global scale.

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Section: Analytical Methods For Iodine Analysismentioning

confidence: 99%

Speciation of dissolved inorganic iodine in a coastal fjord: a time-series study from Bedford Basin, Nova Scotia, Canada

2023

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“…Importantly, we acknowledge that the spectrophotometric IO 3 measurement is highly prone to interferences (Truesdale, 1978;Luther et al, 1988). Seawater background measurements at 350 nm have the potential to correct these interferences (Hepach et al, 2020;Jones et al, 2023). Note that the controls with addition of SOD and MnCl 2 (meant to test the potential to stop Ioxidation via scrubbing of superoxide or added preferred electron donor) were only relevant if Ioxidation was observed in other controls, so are not considered further.…”

Section: Iodine Measurements From Incubationsmentioning

confidence: 99%

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

Schnur,

Sutherland,

Hansel

et al. 2024

Front. Mar. Sci.

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The distribution of iodine in the surface ocean – of which iodide-iodine is a large destructor of tropospheric ozone (O3) – can be attributed to both in situ (i.e., biological) and ex situ (i.e., mixing) drivers. Currently, uncertainty regarding the rates and mechanisms of iodide (I-) oxidation render it difficult to distinguish the importance of in situ reactions vs ex situ mixing 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 a 129I- tracer (t1/2 ~15.7 Myr) added to all incubations, and 129I/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 that ex situ processes, such as vertical mixing, may play an important role in broader iodine species’ distribution in this and similar regions.

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“…Iodide concentrations in the reservoir and the waste stream were directly quantified using UV-vis spectrophotometry at 226 nM following ion exchange chromatography (IC) (Jones et al, 2023). The IC used a Dionex IonPac AS23 guard and analytical column (4 x 250 mm), with a mobile phase eluent of 0.4 M NaCl flowing at 0.64 ml min −1 .…”

Section: Measurement Of Aqueous Iodidementioning

confidence: 99%

Negligible Temperature Dependence of the Ozone-Iodide Reaction and Implications for Oceanic Emissions of Iodine

Brown,

Pound,

Ives

et al. 2023

Preprint

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Abstract. The reaction between ozone and iodide is one of the main drivers of tropospheric ozone deposition to the ocean, due to the ubiquitous presence of iodide in the ocean surface and its rapid reaction with ozone. Despite the importance of this sea surface reaction for tropospheric ozone deposition, and also as the major source of atmospheric iodine, there is uncertainty in its rate and dependence on aqueous phase temperature. In this work, the kinetics of the heterogeneous second order reaction between ozone and iodide were investigated using conditions applicable to coupled ocean-atmosphere systems (1 × 10−7 – 1 × 10−5 M [iodide], 40 ppb ozone, 288 – 303 K, 15.0 psi). The Arrhenius parameters determined of A = 1.0 ± 4.6 ×1011 M−1 s−1 and Ea = 8.5 ± 10.9 kJ mol−1 show that the reaction has a negligible positive temperature dependence, which could be weakly negative within errors. This is in contrast to a previous study that found a strong positive activation energy and a pre-exponential factor many orders of magnitude greater than determined here. The re-measured kinetics of ozone and iodide were used to constrain a state-of-the-art sea surface microlayer (SML) model. The model replicated results from a previous laboratory study of the temperature dependence of hypoiodous acid (HOI) and molecular iodine (I2) emissions from an ozoneoxidised iodide solution. This work has significance for global modelling of dry deposition of ozone to the ocean and the subsequent emissions of iodine-containing species, thus improving understanding of the feedbacks between natural halogens, air quality, and climate change.

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Environmental iodine speciation quantification in seawater and snow using ion exchange chromatography and UV spectrophotometric detection

Cited by 9 publications

References 78 publications

Speciation of dissolved inorganic iodine in a coastal fjord: a time-series study from Bedford Basin, Nova Scotia, Canada

Speciation of dissolved inorganic iodine in a coastal fjord: a time-series study from Bedford Basin, Nova Scotia, Canada

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

Negligible Temperature Dependence of the Ozone-Iodide Reaction and Implications for Oceanic Emissions of Iodine

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