Plateau Marsh Methane Oxidation as affected by Inorganic N

In a series of laboratory incubations using soils of two contrasting sites from a temperate marsh on the QinghaiTibet Plateau,potential methane (CH4) oxidation rates were measured to study the effects of inorganic N inputs on CH4 oxidation. For a drained site,subsurface peat (5-15 cm) at an initial 20 μL CH4 L-1 showed a significantly different (P＜0.05) CH4 oxidation rate compared to other soil depths,with a maximal rate of 20.9 ng CH4 gDW (dry weight)-1h-1; the underlying mineral soil layers (15-30 and 30-50 cm) also had a strong CH4 oxidation capacity at about an initial 2000 μL CH4 L-1. With a waterlogged site,the CH4 oxidation rate in an aerobic incubation was significantly greater (P＜0.05) in the surface soil layer (0-5cm) compared to the 15-30 and 30-50 cm depths. There was generally no or a very weak effect from addition of NO3- on CH4 oxidation. In marked contrast,NH4+ salts,such as (NH4)2SO4,NH4C1 and NH4NO3,exhibited strong inhibitions,which varied as a function of the added salts and the initial CH4 level. Increasing NH4+ usually resulted in greater inhibition and increasing initial CH4 concentrations resulted in less. NH4+ inhibition on CH4 oxidation in natural high-altitude,low-latitude wetlands could be as important as has been reported for agricultural and forest soils. The NH4+ effects on the CH4 oxidation rate need to be further investigated in a wide range of natural wetland soil types.

The specific carbon isotopic compositions of branched and cyclic hydrocarbons from Fushun oil shale

Various branched and cyclic hydrocarbons are isolated from the Fushun oil shale and their carbon isotopes are determined. The analytical results show that the branched and cyclic hydrocarbons are fully separated from n-alkanes by 5 molecular-sieve adduction using long time and cold solvent. The branched and cyclic hydrocarbon frac-tion obtained by this method is able to satisfy the analytic requests of GC-IRMS. The carbon isotopic compositions of these branched and cyclic hydrocarbons obtained from the sample indicate that they are derived from photoautotrophic algae, chemoautotrophic bacteria (-33.4—-39.0) and methanotrophic bacteria (-38.4—-46.3). However the long-chain 2-methyl-branched alkanes indicate that their carbon isotopic compositions reflect biological origin from higher plants. The carbon isotopic composition of C30 4-methyl sterane (-22.1? is the heaviest in all studied ste- ranes, showing that the carbon source or growth condition for its precursor, dinoflagellate, may be different from that of regular steranes. The variation trend of d 13C values between isomers of hopanes shows that 13C-enriched precursors take precedence in process of their epimerization. Methanotro-phic hopanes presented reveal the processes of strong trans-formation of organic matter and cycling of organic carbon in the water column and early diagenesis of oil shale.