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

Selected Ion Flow Tube Mass Spectrometry

^a Department of Chemistry, University of Canterbury, Christchurch, New Zealand
^b Soil, Plant and Ecological Sciences Division, P.O. Box 84, Lincoln University, Canterbury, New Zealand

View larger version (27K): [in a new window]   Fig. 1. A schematic diagram of the flowing afterglow–selected ion flow tube mass spectrometry (FA–SIFT) apparatus at the University of Canterbury.

View larger version (7K): [in a new window]   Fig. 2. Gas sampling sequences showing the linear increase of NO headspace concentration with collection time during a 5-min collection time. The symbols represent experiments with different urea soil concentrations and NO emission rates.

View larger version (16K): [in a new window]   Fig. 3. A plot of the headspace NH3 concentrations and flux vs. time since urine application. Planted treatments incorporated four to eight mature grass plants. Both planted and unplanted treatments received 0.04 L of the synthetic urine. Data points are means of four replicates and error bars represent 95% confidence intervals.

View larger version (13K): [in a new window]   Fig. 4. A plot of headspace NH3 concentrations and fluxes from soil samples prepared with three different rates of synthetic urine. Points are means of two replicates with error bars showing 95% confidence intervals.

View larger version (20K): [in a new window]   Fig. 5. Flux of NO gas over time, following the application of synthetic urine. The samples with or without grass plants partially dried out at Day 45 to simulate summer drought, and were not fully rehydrated until Day 65. A third treatment, unplanted, remained wet throughout. Points are means of four replicates with error bars showing 95% confidence intervals.

View larger version (18K): [in a new window]   Fig. 6. A sample mass spectrum, generated in mass scanning mode. The primary ion is O+2 (32 amu). This sample was emitting NH3 and had been treated with pyridine and dimethylamine. Consequently, peaks from these species (17 amu-NH3, 44 and 45 amu-dimethylamine, and 79 amu-pyridine) are also present, demonstrating that multiple emissions can be readily analyzed.