Fractionation and characterisation of NOM in the Nordic countries

A. Conduct a Nordic intercalibration of dissolved organic carbon (DOC) in natural organic matter (NOM) using high temperature catalytic combustion. B. Study the physiochemical properties of NOM fractions from similar sites that differ in S-loading and climate. (A) There exists to our knowledge no standard operational procedure for the determination of DOC in NOM using high temperature catalytic combustion. This is a problem since different results may emerge depending on how the analysis is conducted on the partly very refractory NOM. Furthermore, there is a lack of documentation of the inter-laboratory analytical merits using the high temperature catalytic combustion method. (B) It is well known that the amount and quality of NOM are strongly influenced by acid rain and seasonal variations in climate. Most conceptually based prediction models for soil/soilwater interactions lack consideration of the organic component. This is mainly due to deficiency of knowledge and understanding of the physiochemical characteristics of NOM as well as its highly inhomogeneous character. Our hypothesis is that the relative fraction of hydrophobic acids (HPO-A) will change due to the decrease in acid rain and change in climate. This is important since HPO-A is a relatively stronger acid and a complex metals more strongly then the other fractions.