Methods to radiolabel natural organic matter by reduction with hydrogen labeled reducing agents

1. A method of labeling natural organic matter (NOM) with a hydrogen label comprising:

removing insoluble NOM from solubilized NOM;

contacting said solubilized NOM with a tritiated or deuterated reducing agent to label said solubilized NOM with tritium or deuterium;

aerating the labeled mixture to reoxidize unstable tritiated products; and

removing any destabilized label by complete solution evaporation.

2. The method of claim 1 , wherein NOM is humic acid (HA) or fulvic acid (FA).

3. The method of claim 1 , wherein the tritiated or deuterated reducing agent is borohydride.

4. The method of claim 1 , wherein the label is distributed substantially equally by molecular size.

5. The method according to claim 1 , further comprising aerating the mixture to reoxidize unstable labeled NOM and removing of the destabilized label by complete solution evaporation.

6. A composition comprising tritiated NOM made according to the method of claim 1 .

7. A composition comprising tritiated HA or tritiated FA made according to the method of claim 1 .

8. A method for determining the concentration of natural organic matter (NOM) comprising:

a) labeling said NOM according to the method of claim 1 ; and

b) measuring the radioactivity of said labeled NOM and determining the concentration of said NOM.

9. The method of claim 8 , wherein said determining further comprises comparing said measured radioactivity against the measured radioactivity of a tritiated NOM standard.

10. The method according to claim 8 further comprising c) aerating the mixture formed in step a) to reoxidize unstable tritiated products and removing of the destabilized label by complete solution evaporation.

11. The method according to claim 8 , wherein said NOM comprises solubilized humic acid or solubilized fulvic acid.

12. The method according to claim 8 , wherein said NOM comprises a ketone functionality and/or an aldehyde functionality.