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Enormous quantities of greenhouse gases (GHG) exist within Arctic ice and frozen soils, so with the threat of global warming, a clear understanding of the relationship between GHG in the atmosphere and in the ice/soil is vital, because melting of permafrost could cause a dangerous climate tipping point.
There can be few more challenging environments for monitoring gases, but PhD researcher Martin Brummell from the University of Saskatchewan has successfully employed a sophisticated gas analyser to do so in the High Arctic of Canada.
Dr Andrew Hobson from Quantitech explains.
The ability to operate in field conditions creates extra demands for analytical equipment. The extreme weather conditions of the High Arctic, however, impose a new level of capability that is rarely available as standard.
Field work in such conditions must be simple, flexible and fast, but most importantly, “The equipment must also be extremely reliable because you do not have the luxury of a local engineer,” Martin Brummell said.
“The equipment used was also the ideal choice because, as an FTIR analyser, it is able to monitor almost any gas, which is normally a feature of mains powered laboratory instruments, but the model used is portable and powered by a small generator, so it is ideal for monitoring in remote locations.”
Sampling and analysis in the Arctic
A set of simple, perforated steel tubes were driven in to the soil, to the point of the permafrost threshold. Inside these tubes gases within the soil were allowed to reach equilibrium via diffusion over 24 hours. This allowed Brummell to analyse gas concentrations to a depth of 1 metre.
The procedure was simple and therefore reliably repeatable. Furthermore, measurement of gas concentrations at different depths enabled direct comparison with soil analysis.
Using FTIR
FTIR stands for Fourier Transform Infrared, the preferred method for infrared spectroscopy.
Analysis by infrared spectroscopy involves the passing of IR radiation through a sample of gaseous molecules. Some of this radiation is absorbed by the sample and the remainder is transmitted. This produces an infrared spectrum, or ‘molecular fingerprint’.
A unique infrared spectrum is generated because each molecular structure has a unique combination of atoms. As a result, both qualitative and quantitative analysis of the gas is possible.
An FTIR spectrometer obtains infrared spectra by first collecting an ‘interferogram’ of a sample signal with an interferometer, which measures all infrared frequencies simultaneously to produce a spectrum. Sample identification is possible because chemical functional groups absorb light at specific frequencies.
In addition, through calibration of the spectrometer, it is possible to determine the intensity of the absorption (relative to the component concentration).
The Gasmet FTIR gas analyser can measure any gas, with the exception of the following:
• Noble (or Inert) gases • Homonuclear diatomic gases (e.g. N2, Cl2, H2 or F2) • H2S (detection limit too high)
As a multicomponent gas analyser, the Gasmet FTIR is ideal for anyone that needs to:
• Analyse several components • Analyse hot/wet gas (e.g. hot humid applications for HCN, NH3 or HCl) • Analyse any gas in complicated gas mixtures
In comparison with many gas analysers, this analyser is extremely easy to operate. Zero point calibration with Nitrogen (background) just takes a few minutes and is required once a day. Water vapour calibration must be performed after every major maintenance operation and at least once per year. Under normal circumstances no other calibration is required which saves a great deal of time, effort and money.
Absorptivity is a physical constant specific to each gas, and the reference spectra (or calibrations) can be transferred from analyser to analyser. As a consequence it is possible to add measurement parameters to existing systems as and when required.
The Gasmet library of reference spectra consists of reference files of gas spectra measured to date with different Gasmet gas analysers. The library contains hundreds of spectra and each reference spectrum contains both quantitative and qualitative information about the component.
An important advantage of the equipment used over other gas detection methods is its ability to provide retrospective analysis of gases that were previously not required. For example, if at any point in the future the user decides that it is necessary to study a specific new parameter, it is possible to analyse the stored spectra from previous analyses and to determine the values for the new parameter.
High levels of accuracy and low levels of maintenance are achieved as a result of continuous calibration with a He-Ne laser, which provides a stable wavenumber scale. In addition, high spectral signal to noise ratio and high wavenumber precision are characteristic of the FTIR method. This yields high analytical sensitivity, accuracy and precision.
The instrument used is a portable FTIR gas analyser for ambient air analysis. A fourier-transform function is applied by the interferometer to obtain the absorption spectrum as a function of frequency or wavelength. Consequently, it is able to simultaneously analyse up to 50 gas compounds. The analyser is typically set up to measure a variety of different gases, including GHGs, VOCs, acids, aldehydes, and inorganic compounds such as CO, CO2, and N2O.
It is operated using a laptop computer running CalcmetTM software, a programme that not only controls the analyser but also undertakes the analysis. CalcmetTM software is capable of simultaneous detection, identification and quantification of ambient gases, which gives the analyser its ability to simultaneously analyse multiple gases in near real time.
The FTIR’s many beneficial traits, such as reliability, precision and flexibility make it a vital piece of analytical equipment in a very wide variety of applications including industrial emissions monitoring, occupational safety surveys, engine exhaust testing, process monitoring, leak detection, emergency response, chemical spill and fire investigations, and many others.
Brummell’s use of this device on his most recent research expedition investigating the soils in the polar deserts of the High Arctic, highlights the model’s capabilities in the field. Carried out on Ellesmere Island in the Baffin Region of Nunavut, Canada, it had to perform reliably in extreme environmental conditions.
The analyser was used to monitor the production, consumption and atmospheric exchange of the greenhouse gases Carbon Dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O); all three being major components of natural biogeochemical cycles. These gases are each released and up-taken by soil microbes in the Arctic.
Both the flux of gases from the soil surface and the concentration profiles of gases in the soil’s active layer above the permafrost were also examined. In doing so the FTIR provides raw data consisting of gas concentrations in parts-per-million (ppm).
Martin Brummell highlighted some of the analyser’s key advantages: “The real-time nature of the analyser allows me to see results within minutes of setting up in the field. This permits me to make changes to the experimental design and further investigate unexpected results while in the field.
“This contrasts with traditional methods of soil gas analysis, which employ lab-based gas chromatography systems and collection of samples ‘blind’ in the field.”
Results
Surprisingly, the work revealed areas of strong CO2 and CH4 production immediately above the permafrost. Brummell believed this was the result of the relative disparity in carbon distribution in Arctic soils in comparison with warmer climes. Carbon accumulates far lower in Arctic soils due to a process known as cryoturbation; the constant mixing and burying of organic matter, which fuels microbial activity at a deeper level.
Comparisons between the surface flux and the soil profile for each of the greenhouse gases was a key objective within Brummell’s investigation. Most notably, Brummell observed a negative surface flux for NO2, but no significant regions of consumption were identified. The location of the NO2 sink is not yet clear, nor the organisms and biogeochemical processes responsible.
Conclusions
Martin Brummell’s research provided a new but complex insight into the production, consumption and exchange of greenhouse gases and soil microbe pathways in the Arctic. His work highlighted the importance of reliability, ruggedness, flexibility and accuracy in the equipment which is employed in such work. The ability of the analyser he used to provide simultaneous measurement of multiple gases in near real time, however, was a major advantage.
In comparison with all of the equipment that is necessary for research in Arctic conditions, one might imagine that a highly sensitive analytical instrument would be the most likely to be adversely affected. Martin Brummell found this not to be the case, however. He said: “In contrast to other field equipment I have used in the High Arctic, including self-destructing sledgehammers, unreliable generators and broken fibre-optic cables, this instrument has never failed even in the most difficult field conditions.
“It has happily survived air transport, inconsistent electrical supply, low temperatures, rain, snow, mud and all other insults, and always gives me accurate, precise measurements of gas concentrations.” ?
Author
Dr Hobson has worked in both the commercial and R&D fields of gas analysis and detection for more than 15 years. Currently specialising in the use of FTIR for a wide variety of applications, his other fields of interest include contaminated land analysis, greenhouse gas monitoring and hazardous waste process emissions.
Dr Hobson has a BSc (Hons) in Environmental Science and a PhD in Biochemistry, achieved through the study of greenhouse gas emissions from waste treatment processes. His current role at Quantitech includes technical support for FTIR and other gas detection technologies in a wide variety of applications, including process emissions, occupational exposure, ambient monitoring, military applications, research, chemical warfare agent and toxic industrial chemical detection and homeland security. Martin Brummell is a Research Assistant at University of Saskatchewan who studied Ecology and Evolutionary Biology at Simon Fraser University.
About Quantitech
Quantitech Ltd specialises in the provision of the world’s leading environmental monitoring and occupational hygiene testing equipment. The company’s success is built upon the world leading products and customised systems that it is able to offer, coupled with outstanding levels of service and technical support.
Established in 1983, the company provides world class environmental testing and monitoring instrumentation for use both in the field and in the laboratory.
The company’s three directors (who have more than 75 years of experience in analytical instrumentation between them) are dedicated to the delivery of the best possible products from around the world to meet specific application requirements – something that only an independent, owner-managed company can achieve. Quantitech is the exclusive distributor in the UK and Ireland for Gasmet Technologies and has supplied more than 100 FTIR monitoring systems in these markets for a wide variety of applications, including stack emissions, process monitoring, chemical spill, security, forensic investigation, occupational health, anaesthetic gases, research and many others.
About Gasmet
Gasmet Technologies develops and manufactures the Gasmet™ line of gas analysers and monitoring systems. The company’s goal is to provide clients with innovative, customer-driven solutions for industrial gas measurement and monitoring applications. Gasmet™ products are reliable, user-friendly and provide consistently accurate results.
Gasmet Technologies has certified its Quality Management System according to ISO 9001. Gasmet™ CEMS has received TÜV (17th Implementing Order) and MCERTS certificates. Gasmet™ FTIR gas analysers are also compliant with the US EPA 40 CFR part 60 Appendix b Performance Specification 15.
Gasmet™ analysers are sold and supported through a global distributor network that covers all continents. Gasmet Technologies Oy´s headquarters are located in Helsinki, the capital of Finland. The group has two fully owned subsidiaries: Gasmet Technologies (Asia) Ltd coordinates the marketing and sales activities of Gasmet analysers in the Asia – Pacific region and provides technical service in the region. Gasmet Technologies Inc provides sales and after sales support for the North American market.
Further information on Gasmet FTIR is available at www.quantitech.co.uk +44 (0) 1908 227722 [email protected] www.gasmet.fi/
Published: 10th Dec 2011 in AWE International
