NMR Spectroscopy has been proven to be indispensable in the study of organics in soil and water.¹³ The technique provides both identification (structural) information and quantitative information regarding the individual species contained in a DOC mixed sample. Additionally, NMR experiments can be performed which follow reaction rates of the DOC materials. An overall advantage of the technique lies in its ability to provide qualitative and quantitative information about the DOC systems unperturbed so that the investigators can be confident that they are examining the system as it appears in the environment. Many other experimental techniques are known to cause chemical alteration in the systems of interest. This is one reason NMR spectroscopy is highly valued in the study of environmental samples when sample integrity is of utmost importance.

For these activities studies, USGS collaborators are collecting samples from 13 representative agricultural and Delta channel sites 5 times per year, corresponding to important events in the hydrologic cycle. This sampling strategy is designed to capture both seasonal and source related differences in DOC composition. The locations to be sampled include agricultural drains, Delta channels, and export channels as well as other locations. The overall objective is the correlation of DOC components largely involved in trihalocarbon formation with specific environmental sources and conditions. Sample characterization is being performed using a variety of well established ¹³C CP-MAS (Cross polarization Magic Angle Spinning) NMR techniques.

The experiments for this activity are currently under design and involve insitu kinetic experiments.