Standard names: *Oxidized Mercury - mole_concentration*

[EDescourvieres]

Proposer's name: Emmanuelle DESCOURVIERES (on behalf of NECCTON and Copernicus Marine Service).

We would like to propose new standard_names for product Mercury. This data is developed in the framework of the NECCTON project as potential new products for Copernicus Marine Service.

Date: 12 January 2026.

Term:

1- mole_concentration_of_oxidized_mercury_in_zooplankton
2- mole_concentration_of_oxidized_mercury_in_fish
3- mole_concentration_of_oxidized_mercury_in_sea_water
4- mole_concentration_of_oxidized_mercury_in_phytoplankton
5- mole_concentration_of_dissolved_oxidized_mercury_in_sea_water
6- mole_concentration_of_dissolved_elemental_mercury_in_sea_water

Description:

As there is no CF definitions for the followings terms yet, I suggest:

• "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂).
• "Dissolved oxidized mercury" refers to mercury ions (Hg²⁺ or Hg⁺) that are oxidized from elemental mercury (Hg⁰) and are present in water in dissolved form, often as free ions or partially dissociated salts (e.g., HgCl₂(aq), HgSO₄(aq)) or as complexes with other dissolved molecules (e.g., mercury bound to dissolved organic matter, Hg–DOM).
• "Dissolved elemental mercury" refers to mercury in its neutral form (Hg⁰) that is present in water in dissolved form, occurring as uncharged Hg atoms or molecules.

1: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂). "Zooplankton" means the total zooplankton population, with components such as mesozooplankton, microzooplankton and miscellaneous zooplankton.

2-3: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂).

4: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂). "Phytoplankton" are algae that grow where there is sufficient light to support photosynthesis

5: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. "Dissolved oxidized mercury" refers to mercury ions (Hg²⁺ or Hg⁺) that are oxidized from elemental mercury (Hg⁰) and are present in water in dissolved form, often as free ions or partially dissociated salts (e.g., HgCl₂(aq), HgSO₄(aq)) or as complexes with other dissolved molecules (e.g., mercury bound to dissolved organic matter, Hg–DOM).

6: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction mole_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. "Dissolved elemental mercury" refers to mercury in its neutral form (Hg⁰) that is present in water in dissolved form, occurring as uncharged Hg atoms or molecules.

Units (If applicable): nmol mg-3

Thank you in advance for you help.

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[JonathanGregory]

My comments on #297 and #298 apply also to these proposals.

[github-actions]

This issue has had no activity in the last 3 weeks. Accordingly:

• If you proposed this issue or have contributed to the
  discussion, please reply to any outstanding concerns.
• If there has been little or no discussion, please comment
  on this issue, to assist with reaching a decision.
• If the proposal seems to have come to a consensus, please
  wait for the moderators to take the next steps towards
  acceptance.

Standard name moderators are also reminded to review @feggleton @japamment

[EDescourvieres]

Hello @JonathanGregory,

Sorry for the delayed response. I will answer in the issues #297 and #298.

Thank you for your reply,

Best regards

Emmanuelle

[eileenhertwig-dkrz]

Hello @EDescourvieres,

I have now added the proposed new standard names to the CF standard name editor. Please check if everything looks fine:

1. mole_concentration_of_oxidized_mercury_in_zooplankton: https://cfeditor.ceda.ac.uk/proposal/5800/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂). "Zooplankton" means the total zooplankton population, with components such as mesozooplankton, microzooplankton and miscellaneous zooplankton.
   Unit: mol m-3

2. mole_concentration_of_oxidized_mercury_in_fish: https://cfeditor.ceda.ac.uk/proposal/5801/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂).
   Unit: mol m-3

3. mole_concentration_of_oxidized_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5802/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂).
   Unit: mol m-3

4. mole_concentration_of_oxidized_mercury_in_phytoplankton: https://cfeditor.ceda.ac.uk/proposal/5803/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized_mercury" refers to mercury in ionic form (Hg²⁺ or Hg⁺), formed by the oxidation of elemental mercury (Hg⁰), typically combined with non-carbon elements such as oxygene (mercury oxyde, HgO), sulfur (mercury sulfide, HgS), chlorine (mercury chloride, HgCl₂). Phytoplankton are algae that grow where there is sufficient light to support photosynthesis.
   Unit: mol m-3

5. mole_concentration_of_dissolved_oxidized_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5804/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Dissolved oxidized mercury" refers to mercury ions (Hg²⁺ or Hg⁺) that are oxidized from elemental mercury (Hg⁰) and are present in water in dissolved form, often as free ions or partially dissociated salts (e.g., HgCl₂(aq), HgSO₄(aq)) or as complexes with other dissolved molecules (e.g., mercury bound to dissolved organic matter, Hg–DOM).
   Unit: mol m-3

6. mole_concentration_of_dissolved_elemental_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5805/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Dissolved elemental mercury" refers to mercury in its neutral form (Hg⁰) that is present in water in dissolved form, occurring as uncharged Hg atoms or molecules.
   Unit: mol m-3

Best regards,
Eileen

[EDescourvieres]

Dear @eileenhertwig-dkrz,
I have contacted the producers regarding the definitions of in_fish, and I will get back to you as soon as I receive their response.
Best regards,
Emmanuelle

[EDescourvieres]

Hello @eileenhertwig-dkrz,
I've had a reply from the producer. Regarding “in fish” the producer explained to me that the values are in g Hg/m3 water plus the amount of fish in g/m3. Because using g Hg/g fish can lead to silly infinit values where fish concentration goes towards zero. The g/m³ approach, on the other hand, would tend towards zero. In the end the user will always need to be cautious to look at both the Hg content and the fish mass to avoid wrong conclusions. We could maybe add a few words about this in the description .

In addition, after discussion with the producer, if possible i would like to modify the definitions as follows

• "Oxidized_mercury" refers to mercury in its ionic form, which may be directly emitted to the environment or formed through the oxidation of elemental mercury.
• "Dissolved oxidized mercury" refers to mercury ions present in water in dissolved form, often as free ions or partially dissociated salts, or as complexes with other dissolved molecules.
• "Dissolved elemental mercury" refers to mercury in its neutral form, a gaseous species that is dissolved in water. It can be measured as dissolved gaseous mercury.

Best regards,

Emmanuelle

[JonathanGregory]

Dear Emmanuelle

Here you write about g m-3 but the quantities concerned are in mol m-3. I'm confused. I think the clarification might refer whether we were talking about a mass ratio of mercury to fish (g of Hg per g of mercury-free fish) or a mass fraction of mercury in fish (g of Hg divided by g of mercury-contaminated fish). By mol m-3 we mean moles of Hg per cubic metre of fish.

Best wishes

Jonathan

[eileenhertwig-dkrz]

Dear @EDescourvieres,

I have updated the descriptions regarding oxidized_mercury, dissolved_oxidized_mercury and dissolved_elemental_mercury. Regarding in_fish I will wait for your answer.

This is the state in the CF standard names editor now:

1. mole_concentration_of_oxidized_mercury_in_zooplankton: https://cfeditor.ceda.ac.uk/proposal/5800/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized mercury" refers to mercury in its ionic form, which may be directly emitted to the environment or formed through the oxidation of elemental mercury. "Zooplankton" means the total zooplankton population, with components such as mesozooplankton, microzooplankton and miscellaneous zooplankton.
   Unit: mol m-3

2. mole_concentration_of_oxidized_mercury_in_fish: https://cfeditor.ceda.ac.uk/proposal/5801/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized mercury" refers to mercury in its ionic form, which may be directly emitted to the environment or formed through the oxidation of elemental mercury.
   Unit: mol m-3

3. mole_concentration_of_oxidized_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5802/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized mercury" refers to mercury in its ionic form, which may be directly emitted to the environment or formed through the oxidation of elemental mercury.
   Unit: mol m-3

4. mole_concentration_of_oxidized_mercury_in_phytoplankton: https://cfeditor.ceda.ac.uk/proposal/5803/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Oxidized mercury" refers to mercury in its ionic form, which may be directly emitted to the environment or formed through the oxidation of elemental mercury. Phytoplankton are algae that grow where there is sufficient light to support photosynthesis.
   Unit: mol m-3

5. mole_concentration_of_dissolved_oxidized_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5804/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Dissolved oxidized mercury" refers to mercury ions present in water in dissolved form, often as free ions or partially dissociated salts, or as complexes with other dissolved molecules.
   Unit: mol m-3

6. mole_concentration_of_dissolved_elemental_mercury_in_sea_water: https://cfeditor.ceda.ac.uk/proposal/5805/
   "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical species or biological group denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "Dissolved elemental mercury" refers to mercury in its neutral form, a gaseous species that is dissolved in water. It can be measured as dissolved gaseous mercury.
   Unit: mol m-3

Best regards,
Eileen

[eileenhertwig-dkrz]

Dear @EDescourvieres,

Do you have an update regarding the description of in_fish?

Best regards,
Eileen