Impact/Purpose:

This project proposes to estimate various source contributions to the global methane budget by making atmospheric observations of the mean methane isotopic signature and relating these isotopic signals to sources using mass balance.

This project proposes to estimate various source contributions to the global methane budget by making atmospheric observations of the mean methane isotopic signature and relating these isotopic signals to sources using mass balance.

Description:

The magnitudes of the sources and sinks of greenhouse gases like methane need to be better understood to accurately measure changes in emissions and ensure international compliance with global environmental policies such as the Kyoto Protocol.

Record Details:

Record Type:PROJECT( ABSTRACT )

Start Date:08/01/2000

Completion Date:08/01/2003

Record ID: 85286

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Related Organizations:

Role :OWNER

Organization Name :UNIVERSITY OF COLORADO - BOULDER

Mailing Address :Campus Box 17

Citation :Boulder

State :CO

Zip Code :80309

Project Information:

Approach :

An infrared absorption spectrometer will be developed that will have sufficient sensitivity to resolve spatial and temporal trends in both ¹³C/¹²C and D/H stable isotopic ratios. To date, measurements of atmospheric methane ¹³C/¹²C and D/H values have been performed almost exclusively by isotope ratio mass spectrometry. However, because ¹³CH4 and ¹²CH3D have the same isotopic mass, their measurement requires extensive procedures to convert the CH4 to CO2 and H2. Infrared absorption spectroscopy offers a simple, nondestructive way to simultaneously measure the methane, carbon, and hydrogen isotopic compositions. Samples will be obtained from a global air-sampling network to provide a good spatial distribution of sites from which to collect methane variability data and deduce source and sink information. The spectrometer employs periodically poled lithium niobate (PPLN) to generate different frequency radiation from two near infrared diode lasers (one at 811 nm and the other at 1066 nm). This technique yields ~10 microwatts of single mode, tunable radiation that probes the v3 rotational-vibrational absorption band at 3.4 microns. The radiation is passed through a multipass absorption cell with a path length of 36 meters and a volume of 0.3 liter. Second harmonic wavelength modulation is utilized to reduce spectrometer noise. The current detection limit is 2 ppb of methane. Because the tropospheric mixing ratio of ¹²CH3D is ~1 ppb and is comparable to the instrument detection limit, a procedure to concentrate methane samples is required before isotopic analysis. Methane is

Cost :$79,280.00

Research Component :Fellowship - Atmospheric Chemistry

Approach :

An infrared absorption spectrometer will be developed that will have sufficient sensitivity to resolve spatial and temporal trends in both ¹³C/¹²C and D/H stable isotopic ratios. To date, measurements of atmospheric methane ¹³C/¹²C and D/H values have been performed almost exclusively by isotope ratio mass spectrometry. However, because ¹³CH4 and ¹²CH3D have the same isotopic mass, their measurement requires extensive procedures to convert the CH4 to CO2 and H2. Infrared absorption spectroscopy offers a simple, nondestructive way to simultaneously measure the methane, carbon, and hydrogen isotopic compositions. Samples will be obtained from a global air-sampling network to provide a good spatial distribution of sites from which to collect methane variability data and deduce source and sink information. The spectrometer employs periodically poled lithium niobate (PPLN) to generate different frequency radiation from two near infrared diode lasers (one at 811 nm and the other at 1066 nm). This technique yields ~10 microwatts of single mode, tunable radiation that probes the v3 rotational-vibrational absorption band at 3.4 microns. The radiation is passed through a multipass absorption cell with a path length of 36 meters and a volume of 0.3 liter. Second harmonic wavelength modulation is utilized to reduce spectrometer noise. The current detection limit is 2 ppb of methane. Because the tropospheric mixing ratio of ¹²CH3D is ~1 ppb and is comparable to the instrument detection limit, a procedure to concentrate methane samples is required before isotopic analysis. Methane is

Cost :$79,280.00

Research Component :Air Quality and Air Toxics

Approach :

An infrared absorption spectrometer will be developed that will have sufficient sensitivity to resolve spatial and temporal trends in both ¹³C/¹²C and D/H stable isotopic ratios. To date, measurements of atmospheric methane ¹³C/¹²C and D/H values have been performed almost exclusively by isotope ratio mass spectrometry. However, because ¹³CH4 and ¹²CH3D have the same isotopic mass, their measurement requires extensive procedures to convert the CH4 to CO2 and H2. Infrared absorption spectroscopy offers a simple, nondestructive way to simultaneously measure the methane, carbon, and hydrogen isotopic compositions. Samples will be obtained from a global air-sampling network to provide a good spatial distribution of sites from which to collect methane variability data and deduce source and sink information. The spectrometer employs periodically poled lithium niobate (PPLN) to generate different frequency radiation from two near infrared diode lasers (one at 811 nm and the other at 1066 nm). This technique yields ~10 microwatts of single mode, tunable radiation that probes the v3 rotational-vibrational absorption band at 3.4 microns. The radiation is passed through a multipass absorption cell with a path length of 36 meters and a volume of 0.3 liter. Second harmonic wavelength modulation is utilized to reduce spectrometer noise. The current detection limit is 2 ppb of methane. Because the tropospheric mixing ratio of ¹²CH3D is ~1 ppb and is comparable to the instrument detection limit, a procedure to concentrate methane samples is required before isotopic analysis. Methane is

Cost :$79,280.00

Research Component :Academic Fellowships

Project IDs:

ID Code :U915835

Project type :Fellowship