A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord
<p>We report weekly observations of volatile organic iodocarbons (CH<sub>3</sub>I, CH<sub>2</sub>ClI and CH<sub>2</sub>I<sub>2</sub>) over the time period May 2015 to December 2017 from four depths in Bedford Basin, a coastal fjord (70&thi...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-11-01
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| Series: | Ocean Science |
| Online Access: | https://www.ocean-sci.net/14/1385/2018/os-14-1385-2018.pdf |
| _version_ | 1818478463023054848 |
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| author | Q. Shi D. Wallace |
| author_facet | Q. Shi D. Wallace |
| author_sort | Q. Shi |
| collection | DOAJ |
| description | <p>We report weekly observations of volatile organic iodocarbons
(CH<sub>3</sub>I, CH<sub>2</sub>ClI and CH<sub>2</sub>I<sub>2</sub>) over the
time period May 2015 to December 2017 from four depths in Bedford Basin, a
coastal fjord (70 m deep) on the Atlantic coast of Canada. The fjord is
subject to wintertime mixing, seasonal stratification and bloom dynamics,
subsurface oxygen depletion, local input of freshwater, and occasional
intrusions of higher-density water from the adjacent continental shelf.
Near-surface concentrations showed strong seasonal and sub-seasonal
variability, which is compared with other coastal time series. The vertical
variation of CH<sub>2</sub>I<sub>2</sub> and CH<sub>2</sub>ClI within the upper 10 m is
consistent with rapid photolysis of CH<sub>2</sub>I<sub>2</sub>. Average annual
sea-to-air fluxes (46.7 nmol m<sup>−2</sup> day<sup>−1</sup>) of total volatile
organic iodine were similar to those observed in other coastal and shelf
time series, and polyiodinated compounds contributed 80 % of the total flux.
Fluxes were subject to strong interannual variability (a factor of 2)
mainly due to wind speed variability. Near-surface net production of
CH<sub>3</sub>I averaged 1 pmol L<sup>−1</sup> day<sup>−1</sup> and was similar to
rates in the English Channel but an order of magnitude higher than in shallow
waters of the Kiel Fjord, Germany, possibly due to higher microbial
degradation in the latter. The near-bottom (60 m) time series showed
evidence of CH<sub>3</sub>I production associated with organic matter
degradation and a possible <q>switch</q> from the production of CH<sub>3</sub>I via
an alkylation pathway to the production of CH<sub>2</sub>I<sub>2</sub> by a haloform-type
reaction. Near-bottom CH<sub>3</sub>I production varied strongly between years
but was generally ca. 20 times lower than near-surface production.</p> |
| first_indexed | 2024-12-10T09:48:37Z |
| format | Article |
| id | doaj.art-6945cd70ba5849b38f6709fcf189558f |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-12-10T09:48:37Z |
| publishDate | 2018-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-6945cd70ba5849b38f6709fcf189558f2022-12-22T01:53:44ZengCopernicus PublicationsOcean Science1812-07841812-07922018-11-01141385140310.5194/os-14-1385-2018A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjordQ. Shi0D. Wallace1Department of Oceanography, Dalhousie University, Halifax, CanadaDepartment of Oceanography, Dalhousie University, Halifax, Canada<p>We report weekly observations of volatile organic iodocarbons (CH<sub>3</sub>I, CH<sub>2</sub>ClI and CH<sub>2</sub>I<sub>2</sub>) over the time period May 2015 to December 2017 from four depths in Bedford Basin, a coastal fjord (70 m deep) on the Atlantic coast of Canada. The fjord is subject to wintertime mixing, seasonal stratification and bloom dynamics, subsurface oxygen depletion, local input of freshwater, and occasional intrusions of higher-density water from the adjacent continental shelf. Near-surface concentrations showed strong seasonal and sub-seasonal variability, which is compared with other coastal time series. The vertical variation of CH<sub>2</sub>I<sub>2</sub> and CH<sub>2</sub>ClI within the upper 10 m is consistent with rapid photolysis of CH<sub>2</sub>I<sub>2</sub>. Average annual sea-to-air fluxes (46.7 nmol m<sup>−2</sup> day<sup>−1</sup>) of total volatile organic iodine were similar to those observed in other coastal and shelf time series, and polyiodinated compounds contributed 80 % of the total flux. Fluxes were subject to strong interannual variability (a factor of 2) mainly due to wind speed variability. Near-surface net production of CH<sub>3</sub>I averaged 1 pmol L<sup>−1</sup> day<sup>−1</sup> and was similar to rates in the English Channel but an order of magnitude higher than in shallow waters of the Kiel Fjord, Germany, possibly due to higher microbial degradation in the latter. The near-bottom (60 m) time series showed evidence of CH<sub>3</sub>I production associated with organic matter degradation and a possible <q>switch</q> from the production of CH<sub>3</sub>I via an alkylation pathway to the production of CH<sub>2</sub>I<sub>2</sub> by a haloform-type reaction. Near-bottom CH<sub>3</sub>I production varied strongly between years but was generally ca. 20 times lower than near-surface production.</p>https://www.ocean-sci.net/14/1385/2018/os-14-1385-2018.pdf |
| spellingShingle | Q. Shi D. Wallace A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord Ocean Science |
| title | A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord |
| title_full | A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord |
| title_fullStr | A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord |
| title_full_unstemmed | A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord |
| title_short | A 3-year time series of volatile organic iodocarbons in Bedford Basin, Nova Scotia: a northwestern Atlantic fjord |
| title_sort | 3 year time series of volatile organic iodocarbons in bedford basin nova scotia a northwestern atlantic fjord |
| url | https://www.ocean-sci.net/14/1385/2018/os-14-1385-2018.pdf |
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