Using nitrogen isotope fractionation to assess redox reactions of substituted aromatic amines and N-alkylamines

Compound-specific isotope analysis (CSIA) is a very promising tool for the qualitative and quantitative assessment of organic contaminant transformation in the environment. For a specific element (e.g., H, C, N, O) present in an organic compound of interest, CSIA can be used to detect changes in its bulk isotopic composition occurring during a particular transformation reaction. In many cases, these changes can be expressed quantitatively in a way that allows for a quantification of contaminant (bio)degradation in complex environments.

While CSIA of the elements C and H has been applied successfully to assess the transformation of a variety of groundwater contaminants including chlorinated solvents, fuel components, its potential for assessing priority contaminants such as pesticides, dyes, antibiotics, and explosives, exhibiting nitrogen-containing functional groups is largely unexplored. On the basis of our newly developed analytical methods for studying N isotope fractionation in organic compounds, we will investigate redox reactions of important contaminants under environmental conditions typical for soils and aquifers. The type of reactions to be investigated include the reduction of aromatic nitro and azo groups by reduced iron species, the surface catalyzed oxidation of aromatic amines by manganese oxide, and the enzymatic, oxidative dealkylation of tertiary amines. The interpretation of measured isotope effects will be supported by theoretical work including density functional calculations carried out in collaboration with research groups at the University of Minnesota.

Partners

• William Arnold (University of Minnesota)
• Christopher Cramer (University of Minnesota)