Export of dissolved organic carbon and acidity from peatlands

Abstract

Because of the vast areal extent and high rates of organic matter production of peatlands, such ecosystems have a significant but poorly quantified impact on large numbers of lakes. This study reports the export of dissolved organic carbon (DOC) and acidity from two bogs and one fen in north central North America. Rates of export of DOC are high for all three peatlands (8–40 g m−2 yr−1), and variations are largely dependent on water yield. Dissolved organic matter from all sites exhibits a charge density between 7 and 24 μeq (mg DOC)−1, and rates of acidity export from all three sites are similar (100–200 meq m−2 yr−1). Variation in elemental composition of dissolved organic matter suggests a seasonal change in relative proportions of organic matter fractions and indicates direct incorporation of microbially reduced sulfur into organic matter. Current definitions and measurement techniques for alkalinity are inappropriate for such high DOC waters, and fixed end point titration to p H 4 is suggested as an alternative.