Carbon and hydrogen isotopic composition of methane over the last 1000 years
نویسندگان
چکیده
[1] New measurements of the carbon and hydrogen isotopic ratios of methane (dC of CH4 and dD of CH4) over the last millennium are presented from the WAIS Divide, Antarctica, ice core (WDC05A), showing significant changes that likely were the result of human influences prior to the industrial revolution (at least as early as the 16th century of the common era (CE)). The dC of CH4 data corroborate the record from Law Dome, Antarctica, with high fidelity. The new dD of CH4 data set covaries with the d C of CH4 record. Both d C of CH4 and dD of CH4 were relatively stable and close to the present-day values from 1000 to 1500 CE. Both isotopic ratios decreased to minima around 1700 CE, remained low until the late 18th century, and then rose exponentially to present-day values. Our new dD of CH4 data provide an additional independent constraint for evaluating possible CH4 source histories. We searched a broad range of source scenarios using a simple box model to identify histories consistent with the constraints of the CH4 concentration and isotope data from 990–1730 CE. Results typically show a decrease over time in the biomass-burning source (found in 85% of acceptable scenarios) and an increase in the agricultural source (found in 77% of acceptable scenarios), indicating preindustrial human influence on atmospheric methane as proposed in previous studies.
منابع مشابه
Catalytic Decomposition of Methane and Ethylene into the Carbon and Hydrogen
The role of nickel as catalyst on the conversion of methane and ethylene in a gas phase flow reactor in the absence of oxygen is studied. In this study, nickel in its different forms is used as catalyst. The role of pressure, flow rate, and temperature on the conversion of feed gases is investigated. The experiments have been carried out in the presence and absence of the catalysts to measure t...
متن کاملDual Isotopic Composition of Methane in Murchison Meteorite
Introduction: Examining the record contained within the organic matter in meteorites can reveal the nature of the inputs and processes that contributed to the early solar system environment. Specifically, isotopic measurements for individual organic compounds can reveal the reaction mechanisms and possible source environments from which the organic constituents were formed. Hydrogen isotopic me...
متن کاملThe Kinetics of Methanation on Nickel Catalysts
An empirical rate equation was obtained for the methanation kinetics catalyzed by MCR-2X, a commercial catalyst prepared by Haldor-Topsoe. The studies were carried out in a fixed-bed reactor under differential conditions, and in a gradientless recycle reactor (Berry) over a range of total pressures, reactant concentractions (H2/CO ratios), and temperatures. The kinetics of methanation were foun...
متن کاملFinal Report on Pd Catalysts , March , 2001
Zirconia-supported Pd160 and bulk Pd160 were used as methane combustion catalysts for a reaction mixture containing 1% methane and 4% l8Oz in helium. The methane oxidation reaction was performed in pulsed experiments and the distribution of oxygen isotopes among the reaction products was monitored. The “0 content of the catalyst following labeled reaction mixture pulses was determined by cataly...
متن کاملAn Experimental Investigation on Simultaneous Effects of Oxygen Ratio and Flow-Rate in SOFCs Performance Fueled by a Mixture of Methane and Oxygen
Catalytic partial oxidation (CPOX) has recently received particular attention because it is one of the most attractive technologies for the production of syngas and hydrogen in small to medium scales. Current study subjected to partial oxidation reforming which have simultaneously studied the effect of the fuel composition and flow rates of methane-oxygen mixed gas on the SOFCs performances. In...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2009