Alkalinity and acidity cycling and fluxes in an intermediate fen peatland in northern Ontario

Abstract

Peatlands are important to global carbon (C) sequestration and surface water acid-base status, both of which are affected by peatland alkalinity and acidity cycling. Relationships among sulfate (SO 4 2-), nitrate (NO 3 -), organic acids (OA -), base cations (i.e., Ca 2? , Mg 2? , K ? , and Na ? ), proton (H ? ) acidity, and bicarbonate (HCO 3 -) alkalinity were investigated in an intermediate fen peatland in northern Ontario during 2004 (an average precipitation year) and 2005 (a dry summer). Potential evapotranspiration was higher and the water table, groundwater input from the uplands, and runoff were lower during 2005. Net inputs of base cations, HCO 3 -, SO 4 2-, and OA -, and to a lesser degree NO 3 -, were lower during the drier year, mainly due to lower groundwater transfer to the fen. Fen porewater HCO 3 -concentration and net output were also lower in the drier year, whereas Ca 2? , Mg 2? , and SO 4 2-concentrations and net output were higher. During the climatically average year, N immobilization, carbonic acid (H 2 CO 3 ) dissociation, and OA dissociation were equally important H ? -producing reactions. Peat cation exchange accounted for 50% of the H ? sink, while SO 4 2-reduction and denitrification accounted for an additional 20 and 25% of the H ? sink, respectively. During the dry year, S oxidation accounted for 55% of the H ? net production, while that for H 2 CO 3 dissociation was 70% lower than that during the climatically average year. Peat cation exchange consumed three times the acidity, and accounted for 92% of the H ? consumption during the dry year compared to the climatically average year. This was consistent with a three-fold higher net base cation export from the fen during the dry year. Based on the study results, a conceptual model was developed that describes the role of acidity formation and its implications to intermediate fen acidification.

Peatland Stream Lipid Biogeochemistry Features in an Intermediate Fen Peatland, Ontario Canada

“…Similar to others in North America, the intermediate fen peatland examined in this study is characterized by calcareous deposits, resulting in circumneutral groundwater (Siegel et al 2006;McLaughlin and Webster 2010). As a result, acidity generated by OM decomposition or oxidative processes are readily neutralized by groundwater discharge to the peat surface and nearby stream.…”

“…Abundance was calculated using DAPI staining and enumeration under a fluorescence microscope nitrification and S oxidation, producing H + that can exchange with base cations (Siegel et al 2006;McLaughlin and Webster 2010). The base cations can then be exported from the peatland by binding with NO 3 − , SO 4 2− , and organic acids (McLaughlin and Webster 2010).…”

Peat decomposition records in three pristine ombrotrophic bogs in southern Patagonia

“…After deposition, alkali loss is a typical phenomenon due to glass alteration of the tephra (Kilian et al, 2003 and references therein). An input of electron acceptors, such as sulfate, could further lead to alkalinity production during reduction under anaerobic conditions (McLaughlin and Webster, 2010), resulting in higher pH and a faster decomposition.…”

Annual emissions of CH<sub>4</sub> and N<sub>2</sub>O, and ecosystem respiration, from eight organic soils in Western Denmark managed by agriculture

“…Fig. 3), allowing for acidifying processes such as nitrification and possibly Fe(II) oxidation in the drained peat (Lüdecke et al, 2010;McLaughlin and Webster, 2010). Following a rise in water is present (Madsen and Jensen, 1988;Jørgensen et al, 2009).…”