Application of Passive Sampler for Ammonia Gas in Soil
2018
Fukae, Kengo | Takenaka, Norimichi
The emissions of ammonia (NH₃) from soil have accelerated rapidly and have affected both vegetation and the atmosphere. It is thus necessary to investigate not only the amounts of NH₃ gas released from the soil surface but also the dynamics of NH₃ gas in the soil. Active sampling and diffusive sampling have been adopted to measure the components of soil air. However, gas aspiration for active sampling inevitably collects a wide range of soil gases. We examined the application of passive sampling to NH₃ gas measurements in soil and compared the outcome to active sampling results. In laboratory experiments, the performance of the present passive sampler in moist soil was investigated. When immersed in solution, the passive sampler collected gas released from the solution, depending on the vapor pressure of the volatile substance. In laboratory experiments measuring NH₃ gas in soil, there were no significant differences among the values measured by passive sampler at each measurement point. Thus, we concluded that the passive sampler can accurately measure NH₃ gas in soil. In field experiments, the average NH₃ gas concentrations were 43 ppb in urea-added soil and 1 ppb in control soil. The relative standard deviation of NH₃ concentrations in urea-added soil was large. This result is expected because soil characteristics can change under the influence of ambient environmental factors such as wind, rain, and temperature. In other words, the spatial differences in NH₃ emissions were reflected in the passive sampler measurements.
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