Control of carbon mineralization to CH4 and CO2 in anaerobic,Sphagnum-derived peat from Big Run Bog, West Virginia

Abstract

The mineralization of organic carbon to CH4 and CO2 inSphagnum-derived peat from Big Run Bog, West Virginia, was measured at 4 times in the year (February, May, September, and November) using anaerobic, peat-slurry incubations. Rates of both CH4 production and CO2 production changed seasonally in surface peat (0–25 cm depth), but were the same on each collection date in deep peat (30–45 cm depth). Methane production in surface peat ranged from 0.2 to 18.8 μmol mol(C)−1 hr−1 (or 0.07 to 10.4 μg(CH4) g−1 hr−1) between the February and September collections, respectively, and was approximately 1 μmol mol(C)−1 hr−1 in deep peat. Carbon dioxide production in surface peat ranged from 3.2 to 20 μmol mol(C)−1 hr−1 (or 4.8 to 30.3 μg(CO2) g−1 hr−1) between the February and September collections, respectively, and was about 4 μmol mol(C)−1 hr−1 in deep peat. In surface peat, temperature the master variable controlling the seasonal pattern in CO2 production, but the rate of CH4 production still had the lowest values in the February collection even when the peat was incubated at 19°C. The addition of glucose, acetate, and H2 to the peat-slurry did not stimulate CH4 production in surface peat, indicating that CH4 production in the winter was limited by factors other than glucose degradation products. The low rate of carbon mineralization in deep peat was due, in part, to poor chemical quality of the peat, because adding glucose and hydrogen directly stimulated CH4 production, and CO2 production to a lesser extent. Acetate was utilized in the peat by methanogens, but became a toxin at low pH values. The addition of SO42− to the peat-slurry inhibited CH4 production in surface peat, as expected, but surprisingly increased carbon mineralization through CH4 production in deep peat. Carbon mineralization under anaerobic conditions is of sufficient magnitude to have a major influence on peat accumulation and helps to explain the thin ( 13,000 yr) peat deposit found in Big Run Bog.