A model of mercury cycling and isotopic fractionation in the ocean
<p>Mercury speciation and isotopic fractionation processes have been incorporated into the HAMOCC offline ocean tracer advection code. The model is fast enough to allow a wide exploration of the sensitivity of the Hg cycle in the oceans, and of factors controlling human exposure to monomet...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
|
| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/6297/2018/bg-15-6297-2018.pdf |
| _version_ | 1819039801015271424 |
|---|---|
| author | D. E. Archer J. D. Blum |
| author_facet | D. E. Archer J. D. Blum |
| author_sort | D. E. Archer |
| collection | DOAJ |
| description | <p>Mercury speciation and isotopic fractionation processes
have been incorporated into the HAMOCC offline ocean tracer advection code.
The model is fast enough to allow a wide exploration of the sensitivity of
the Hg cycle in the oceans, and of factors controlling human exposure to
monomethyl-Hg through the consumption of fish. Vertical particle transport
of Hg appears to play a discernable role in setting present-day Hg
distributions, which we surmise by the fact that in simulations without
particle transport, the high present-day Hg deposition rate leads to an Hg
maximum at the sea surface, rather than a subsurface maximum as observed. Hg
particle transport has a relatively small impact on anthropogenic Hg uptake,
but it sequesters Hg deeper in the water column, so that excess Hg is
retained in the model ocean for a longer period of time after anthropogenic
Hg deposition is stopped. Among 10 rate constants in the model, steady-state
Hg concentrations are most sensitive to reactions that are sources or sinks
of Hg(0), the evasion of which to the atmosphere is the dominant sink term
in the surface ocean. Isotopic fractionations in the interconversion
reactions are most strongly expressed, in the isotopic signatures of
dissolved Hg, in reactions that involve the dominant dissolved species,
Hg(II), including mass independent fractionation during Hg photoreduction.
The Δ<sup>199</sup>Hg of MMHg in the model, subject to photoreduction
fractionation, reproduces the Δ<sup>199</sup>Hg of fish in the upper 1000 m of the ocean, while the impact of anthropogenic Hg deposition on Hg
isotope ratios is essentially negligible.</p> |
| first_indexed | 2024-12-21T08:58:58Z |
| format | Article |
| id | doaj.art-eb4c88f546854b7aac2f395673b06eca |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-21T08:58:58Z |
| publishDate | 2018-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-eb4c88f546854b7aac2f395673b06eca2022-12-21T19:09:30ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-10-01156297631310.5194/bg-15-6297-2018A model of mercury cycling and isotopic fractionation in the oceanD. E. Archer0J. D. Blum1Department of the Geophysical Sciences, University of Chicago, Chicago, 60637, USADepartment of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, 48109, USA<p>Mercury speciation and isotopic fractionation processes have been incorporated into the HAMOCC offline ocean tracer advection code. The model is fast enough to allow a wide exploration of the sensitivity of the Hg cycle in the oceans, and of factors controlling human exposure to monomethyl-Hg through the consumption of fish. Vertical particle transport of Hg appears to play a discernable role in setting present-day Hg distributions, which we surmise by the fact that in simulations without particle transport, the high present-day Hg deposition rate leads to an Hg maximum at the sea surface, rather than a subsurface maximum as observed. Hg particle transport has a relatively small impact on anthropogenic Hg uptake, but it sequesters Hg deeper in the water column, so that excess Hg is retained in the model ocean for a longer period of time after anthropogenic Hg deposition is stopped. Among 10 rate constants in the model, steady-state Hg concentrations are most sensitive to reactions that are sources or sinks of Hg(0), the evasion of which to the atmosphere is the dominant sink term in the surface ocean. Isotopic fractionations in the interconversion reactions are most strongly expressed, in the isotopic signatures of dissolved Hg, in reactions that involve the dominant dissolved species, Hg(II), including mass independent fractionation during Hg photoreduction. The Δ<sup>199</sup>Hg of MMHg in the model, subject to photoreduction fractionation, reproduces the Δ<sup>199</sup>Hg of fish in the upper 1000 m of the ocean, while the impact of anthropogenic Hg deposition on Hg isotope ratios is essentially negligible.</p>https://www.biogeosciences.net/15/6297/2018/bg-15-6297-2018.pdf |
| spellingShingle | D. E. Archer J. D. Blum A model of mercury cycling and isotopic fractionation in the ocean Biogeosciences |
| title | A model of mercury cycling and isotopic fractionation in the ocean |
| title_full | A model of mercury cycling and isotopic fractionation in the ocean |
| title_fullStr | A model of mercury cycling and isotopic fractionation in the ocean |
| title_full_unstemmed | A model of mercury cycling and isotopic fractionation in the ocean |
| title_short | A model of mercury cycling and isotopic fractionation in the ocean |
| title_sort | model of mercury cycling and isotopic fractionation in the ocean |
| url | https://www.biogeosciences.net/15/6297/2018/bg-15-6297-2018.pdf |
| work_keys_str_mv | AT dearcher amodelofmercurycyclingandisotopicfractionationintheocean AT jdblum amodelofmercurycyclingandisotopicfractionationintheocean AT dearcher modelofmercurycyclingandisotopicfractionationintheocean AT jdblum modelofmercurycyclingandisotopicfractionationintheocean |