A time series of incubation experiments to examine the production and loss of CH3I in surface seawater

Shi, Qiang; Marandino, Christa; Petrick, Gert; Quack, Birgit; Wallace, Douglas W.R.

doi:10.1002/2014jc010223

Cited by 12 publications

(5 citation statements)

References 46 publications

(92 reference statements)

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“…Shi and Wallace (2018) made the same point, specifically with respect to cycling of iodine. They argued that understanding of iodine cycling could best be advanced through the combination and co-location of: a) comprehensive measurement of various iodine species with high temporal resolution; b) repeated experimentation in the context of the time-series (Shi et al, 2014) and c) biogeochemical modelling. A barrier to this comprehensive approach is the logistical effort required to sustain the three components, over the long term.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…Biological activity plays a role for the production of bromoform (CHBr 3 ), dibromomethane (CH 2 Br 2 ), methyl iodide (CH 3 I), chloroiodomethane (CH 2 ClI) and diiodomethane (CH 2 I 2 ) (Gschwend et al, 1985;Tokarczyk and Moore, 1994;Moore et al, 1996), while CH 3 I also originates from photochemical reactions with dissolved organic matter (DOM) (Moore and Zafiriou, 1994;Bell et al, 2002;Shi et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

et al. 2016

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Abstract. Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH 3 I) of up to 35.4 pmol L −1 , chloroiodomethane (CH 2 ClI) of up to 58.1 pmol L −1 and diiodomethane (CH 2 I 2 ) of up to 32.4 pmol L −1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH 3 I (up to 3.2 ppt), CH 2 ClI (up to 2.5 ppt) and CH 2 I 2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

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“…While different source and sink processes determine the distribution of halocarbons in the oceanic surface water, the underlying mechanisms are largely unresolved. Biological activity plays a role for the production of bromoform (CHBr 3 ), dibromomethane (CH 2 Br 2 ), methyl iodide (CH 3 I), chloroiodomethane (CH 2 ClI) and diiodomethane (CH 2 I 2 ) (Gschwend et al, 1985;Tokarczyk and Moore, 1994;Moore et al, 1996), while CH 3 I also originates from photochemical reactions with dissolved organic matter (DOM) (Moore and Zafiriou, 1994;Bell et al, 2002;Shi et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

Hepach¹,

Quack²,

Tegtmeier³

et al. 2016

Preprint

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Abstract. Halocarbons, halogenated short-chained hydrocarbons, are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling obtained during the M91 cruise onboard the research vessel Meteor in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group as likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L&#8722;1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L&#8722;1 and diiodomethane (CH2I2) of up to 32.4 pmol L&#8722;1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. The enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels.

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A time series of incubation experiments to examine the production and loss of CH₃I in surface seawater

Cited by 12 publications

References 46 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

Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

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