Characterisation of Dissolved Organic Matter Fractions Released from Scottish Peatlands

A high concentration of dissolved organic matter is intimately related to the chemistry and ecology of water environments linked to peatlands. To understand the variations in the chemical characteristics of peat derived dissolved organic matter, those in drainage water from natural vegetation and an area containing Sitka spruce (Picea sitchensis), surface water (dubh lochans), and stream water associated with a peatland in central Scotland were analyzed after fractionation into two fulvic acids that were desorbed from an XAD-8 column with water (FAs(H₂O)) and 0.1 M NaOH (FAs(NaOH)), humic acids, and dissolved non-humic substances. The elemental composition and the carbon composition as estimated by ¹³C cross polarisation/magic angle spinning nuclear magnetic resonance did not differ significantly between the FAs(H₂O) and FAs(NaOH), whilst the FAs(H₂O) were differentiated from the FAs(NaOH) by the greater proportion of carboxy groups with a low pK_a at approximately 2. The carboxy group content and the distribution of carboxy groups with respect to the pK_a of dissolved non-humic substances were similar to those of FAs(H₂O), suggesting their importance as a metal carrier in water systems associated with peatland.