Although this study sheds some light on the causes of KOC variability,
there is much that still needs to be done. Although we
found that organic matter–mineral interactions were an important
influence on KOC, we also found that the magnitude of these interactions
did not scale with such a simple measure as soil clay content.
A deeper understanding of the organic matter–mineral
interactions that contribute to KOC variation would need to take
account of variations in soil mineralogy, since clay minerals differ
in their interactions with organic matter. Equally, even the
relatively strong correlation of aryl C content with KOC for the
HF-treated soils leaves 60% of KOC variability unaccounted for. This
may be a reflection of the crudeness of the NMR technique for measuring
of organic matter chemistry