GasmetTM FTIR application note Greenhouse Gas Soil Flux Analysis KEY WORDS        Greenhouse gas Soil flux Nitrous Oxide (N2O) Climate Change Chamber Soil probe Field measurements DX4015 Portable FTIR Gas Analyzer OVERVIEW Measurement of greenhouse gases released from soil and water surface forms an important part of climate change study. It is essential to know the contribution of soil ecosystems on climate change, as well as how the ecosystem reacts to the changes in atmospheric conditions. There are two ways to measure the activity in the soil: either the samples are collected for the laboratory analysis or a portable analyzer is brought to the measurement site. Figure 1. Gasmet DX4015 multicomponent portable FTIR gas analyzer for trace gas analysis. The most widely used analyzer in the laboratory is a gas chromatography (GC), which uses different types of detectors sensitive only to specific gas components. The samples are usually collected using syringes to extract the gas from chambers or soil probes, and injected into an airtight container for transportation from field to the laboratory for destructive analysis of GC. Copyright Gasmet Technologies Oy

Gasmet Microbial activity in the soil and, for instance, the melting of permafrost releases greenhouse gases such as methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) into the atmosphere. A field-deployable, nondestructive FTIR analyzer is capable of rapid measurements for several gases simultaneously on-site (see Figure 1). There are several advantages provided by the field-based FTIR analyzer, such as the ability to follow the real-time gas concentration changes, and the ability to analyze and study the results as soon as they are collected. With access to online results, the operator...

MEASUREMENT TECHNIQUE There have been multiple measurement campaigns in demanding field conditions in the Canadian High Arctic areas, where Gasmet DX4015 analyzer have been tested in conjunction with soil probes and chambers. The soil probes were used for below-ground in situ measurements of gas concentrations within soil pore spaces, in which probes were buried into the soil to a set depth. Each probe consisted of a ring having 12 tiny holes (2 mm i.d.) around the circumference of the tube at different depths (Figure 2), allowing to do measurements up to 500 mm below the surface. Several probes...

Before starting the measurements of internal gases the analyzer was turned on, allowed to reach the operating temperature (50 ⁰C) and zero calibrated. Then a quick-disconnect in one of the tubes between probe and bottle was disconnected and those ends were connected to the analyzer, creating a closed loop system in which the gas was recirculated between these three components (Figure 2). The measurement interval was adjusted to 180 s and the gas flow rate was 5 L/min. After a 3-min measurement the analyzer was disconnected from the probe and it was flushed with ambient air for at least 120 s...

atmosphere is very sensitive even to small disturbances and pressure changes caused by the chamber installation, thus the initial data points were not representative. The changes in gas concentrations were measured over 10 min periods, and after the stabilization of soil circumstances (2 minutes) the accumulation of GHG fluxes was clearly observed. Figure 4. Measurement campaign in the Canadian High Arctic in which DX4015 was used to sample several home-made chambers. The weather-sealed case of the analyzer protected the instrument for any damage during the measurements, and a laptop running...

RESULTS A reference measurement was performed, in which instead of using DX4015 gas analyzer, the samples were collected by syringes and sent to the laboratory for concentration analyses determined by GC. The experiment showed that the results obtained with the FTIR analyzer, integrated with a non-steady state aluminum chamber, corresponds well with the results achieved by the traditional static chamber method where GC was used for concentration analyses. The pressure inside the cell of DX4015 is maintained at ambient pressure and the temperature is controlled to 50 ⁰C, which facilitated the...