Biomarker compounds as source indicators for dissolved fulvic acids in a bog

In order to evaluate the sources of DOC in a subalpine bog, we compare the lignin and carbohydrate compositions of aquatic fulvic acid isolated from the bog (BogWFA) with the fulvic acids isolated from water leachates of two local plants, sedge (sedgeL-FA) and willow leaves (willowL-FA), and of the peat in the bog (peatL-FA). The bogW-FA and peatL-FA have similar biomarker compositions and both differ significantly from either of the fulvic acids from the water leachate of the plants. Thus, the biomarker data strongly suggest that the peat, and not fresh leaffall, provides most of the aquatic fulvic acid to the bog at this time of year (Fall). However, additional sources of lignin- and carbohydrate-depleted fulvic acid to the bog are also needed to quantitatively match the relatively low levels of recognizable biochemicals in the aquatic fulvic acid from the bog. The unusual lignin compositions of both plant leachates suggest that nonstructural lignin phenol producing components, such as lignans, are part of the water-extractable component of plants. These extractable plant products could potentially contribute to aquatic fulvic acids in other environments or at different times of the year.