Real‐Time, High‐Resolution Quantitative Measurement of Multiple Soil Gas Emissions

Abstract

A new technique is presented for the rapid, high-resolution identification and quantification of multiple trace gases above soils, at concentrations down to 0.01 microL L(-1) (10 ppb). The technique, selected ion flow tube mass spectrometry (SIFT-MS), utilizes chemical ionization reagent ions that react with trace gases but not with the major air components (N2, O2, Ar, CO2). This allows the real-time measurement of multiple trace gases without the need for preconcentration, trapping, or chromatographic separation. The technique is demonstrated by monitoring the emission of ammonia and nitric oxide, and the search for volatile organics, above containerized soil samples treated with synthetic cattle urine. In this model system, NH3 emissions peaked after 24 h at 2000 nmol m(-2) s(-1) and integrated to approximately 7% of the urea N applied, while NO emissions peaked about 25 d after urine addition at approximately 140 nmol m(-2) s(-1) and integrated to approximately 10% of the applied urea N. The monitoring of organics along with NH3 and NO was demonstrated in soils treated with synthetic urine, pyridine, and dimethylamine. No emission of volatile nitrogen organics from the urine treatments was observed at levels >0.01% of the applied nitrogen. The SIFT method allows the simultaneous in situ measurement of multiple gas components with a high spatial resolution of < 10 cm and time resolution <20 s. These capabilities allow, for example, identification of emission hotspots, and measurement of localized and rapid variations above agricultural and contaminated soils, as well as integrated emissions over longer periods.

Alcohol in breath and blood: a selected ion flow tube mass spectrometric study

“…The SIFT instrument used in the current work has been described previously13 as have the modifications necessary for the trace gas analysis mode of operation 8. Breath and/or headspace samples were added to the SIFT flow tube through a heated capillary inlet at the upstream port of the flow tube.…”

“…SIFT‐MS was developed as an analytical technique by Smith and Spanel and these authors have written several reviews on the method 1–3. A similar approach, also based on flow tube technology and chemical ionisation, has also been developed by Lindinger et al 4 The SIFT‐MS technique has been used to quantify both endogenous and exogenous volatile compounds in human breath,1,, 5 gases in the headspace of urine samples,6 emissions from porcine faeces,7 and to measure the release of inorganic volatiles over soil 8…”

Selected ion flow tube mass spectrometry (SIFT‐MS) for on‐line trace gas analysis

“…The detection quadrupole mass spectrometer in current instruments can be scanned up to m/z values of 300. TransSIFT instruments are now in operation in other laboratories, including the Chemistry Department at Canterbury University, New Zealand (their previous articles on SIFT-MS include Senthilmohan et al, 2001;Milligan et al, 2002;Clough et al, 2003) and at the Silsoe Research Institute, England (previously involved in SIFT-MS studies; see Dewhurst et al, 2001). Smaller benchtop instruments operating on SIFT-MS principles are also being developed by Trans Spectra Ltd. (see: www.transspectra.com).…”

Long-term tropospheric formaldehyde concentrations deduced from ground-based fourier transform solar infrared measurements

“…At present, we do not have concurrent measurements of HCHO and NO x to confirm NO x mixing ratios at Lauder. However, Johnston and McKenzie (1984) found using long path spectroscopic absorption that the tropospheric mixing ratio of NO 2 at Lauder was extremely vari- Kingerlee, 1997; Milligan et al, 2002;Veldkamp and Keller, 1997). Between 0.5% (Veldkamp and Keller, 1997) and 10% of the nitrogen applied as fertilizer can be emitted as NO to the atmosphere if the soil is moist.…”