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

Abstract

Methods to radiolabel natural organic matter by reduction with a hydrogen labeled reducing agent, and compositions, are provided.

1 . A method for determining the concentration of fulvic acid (FA) or humic acid (HA) comprising:
 a) contacting solubilized FA or HA with tritiated borohydride (BH 4   − ) to label said solubilized FA or HA with tritium; and   b) measuring the radioactivity of said labeled FA or labeled HA and determining the concentration of said FA or HA.   
     
     
         2 . The method of  claim 1 , wherein said determining further comprises comparing said measured radioactivity against the measured radioactivity of a tritiated FA standard or a tritiated HA standard. 
     
     
         3 . The method according to  claim 1  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. 
     
     
         4 . A hydrogen labeled fulvic acid composition, wherein said label is distributed substantially equally by molecular size in said fulvic acids as measured by size exclusion chromatography. 
     
     
         5 . The labeled fulvic acid composition of  claim 4 , wherein the hydrogen label is tritium. 
     
     
         6 . The labeled fulvic acid composition of  claim 5 , wherein the tritium label does not substantially degrade, as measured by tritium activity, during a period of less than or equal to twenty-one (21) months. 
     
     
         7 . The tritiated fulvic acid composition of  claim 5 , wherein the label does not show substantial chemical degradation during a period of less than or equal to twenty-one (21) months. 
     
     
         8 . The tritiated fulvic acid composition of  claim 5 , wherein the label does not show substantial isotope exchange during a period of less or equal to twenty-one (21) months.