Structural and metal binding study of Laurentian fulvic acid

Two organic extracts of the Laurentian soil have been studied. The organic extracts are Laurentian fulvic acid (LFA) and Laurentian humic acid (LHA). These two samples were analysed by cross polarisation magic angle spinning (C-MAS) {dollar}rmsp{lcub}13{rcub}C{dollar} NMR, while LFA was also characterised by fluorescence spectroscopy.; A new CP-MAS {dollar}rmsp{lcub}13{rcub}C{dollar} NMR method was developed, which combined ramped amplitude CP (Ramp-CP), high sample spinning rates, and high field strength (7 T). It is shown both theoretically and experimentally that Ramp-CP gives significantly better qualitative and quantitative spectra than does single amplitude CP (SACP).; The characterisation of LFA and LHA revealed that in terms of size LFA is a more heterogeneous mixture of fragments than LHA. In terms of functionality, it was found that LFA had the majority of its functionality located on its carbohydrate moieties, while LHA had the majority of its functionality located on its aromatic moieties. Based on these findings mesostructures for both LFA and LHA are proposed.; Metal binding by LFA was also investigated by both fluorescence and NMR techniques. From the results it was concluded that the strongest metal binding sites of LFA are predominantly on the carbohydrate moieties, and that the aliphatic moieties are also involved in metal binding via aggregation. These findings also suggest that the majority of luminescence observed for LFA involves Foster resonance or donor/acceptor complexes. The metal binding results also indicate that cellulose may be an important fragment in LFA.; This study leads to a reconceptualisation of LFA in terms of the functionally greater importance of the carbohydrate moieties than the aromatic moieties, and the importance of aggregation and conformation.