Examination of spatial and temporal patterns in the molecular weight distribution of dissolved organic carbon in Precambrian Shield streams with high-performance size exclusion chromatography

High performance size exclusion chromatography (HPSEC) was used to establish spatial and temporal patterns in molecular weight distribution (MWD) of dissolved organic carbon (DOC) in a Precambrian shield stream. The method was designed to provide good resolution of DOC in natural waters. The spatial MWD of DOC was observed to shift towards a lower distribution with increasing distance from a large headwater swamp, with the greatest alteration to both the quantity and MWD observed at a beaver pond. Evidence is presented that not all streams behave in a similar fashion, since the molecular weight fractions from a neighboring stream system were found to maintain a consistent spatial concentration and relative percent composition. Temporal patterns were observed to maintain a similar MWD over the course of the seven-month study period, however some alterations to the structure of DOC occurred as a result of a drought and the autumn leaf fall.