MEMO2: MEthane goes MObile – MEsurements and MOdelling

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Mila Stanisavljevic – The isotopic signature of methane from coal mines facilities

The advantage of doing a PhD within a MSCA network is to have the opportunity of changing laboratories for some time, to e.g. work with different equipment as available at the host institutions or learn different techniques. It can also be fruitful to get to know other types of work/organization. In June 2019 I had the opportunity to visit the Institute for Marine an Atmospheric Research Utrecht (IMAU) during my secondment to the University of Utrecht (UU).
Part of my PhD is to investigate methane isotopes: δ13 CH4 and δD from coal mining. Coal mines are one type of source, but the isotopic composition can vary within this source category or even one facilities (Kotarba et al., 2001; Zazzeri et al.,2016). Basically I am investigating the isotopic methane composition from underground coal mines in Poland.
At my host institution we can measured samples on δ13CH4 ( in a term of isotopic composition ) only if the methane concentration is above 4 ppm due to the capability of our equipment. Quite high concentrations, but we also need to test samples below 4 ppm of CH4.

As a first step for the secondment in Utrecht we collected bag samples of air containing methane by using our Picarro G2201-i instrument (Fig. 1). The Picarro was installed inside a van. Two days of driving and collecting samples around Poland was sufficient for the planned work in Utrecht.

Fig 1: Picarro G2201-i analyser installed inside a van (left side), ready for mobile measurement around coal mine ventilation shafts (right side)

Two boxes with 35 samples in total (Fig. 2) had been prepared for shipping. In my lab I measured 1.08kg for both boxes … Interestingly, the shipping company had other ways of measurement. They came up with about 108 kg of air. Still we do not know how it is possible to pack 108 kg of air into those two boxes. But the boxes arrived on the time, so we could start our measurements.

Fig. 2: Boxes full with samples (transparent and aluminium bags, left side) are ready for the shipping (right side)

Thanks to Malika from Utrecht University, who showed me the lab and the equipment (continuous flow isotope mass spectrometer CF-IRMS or just IRMS) we were able to prepare and test my samples. As some of samples were so high concentrated, we had to dilute them before the measurements (Fig. 3) to get a concentration of methane laying in the operational range of the IRMS.

Fig. 3: Bag samples diluted and ready for isotopic measurements

Unfortunately, or in my case luckily, the source of the IRMS has stopped working during the second week of my secondment. Carina, THE lab engineer decided to clean the source and showed us how to do it (Fi. 4). Luckily, because it was on of those learning moments which do not happen that often – cleaning the source is no lab routine!

Fig. 4: The ion source of the IRMS, ready to be cleaned

However, after installing the ion source the measurements still did not run smoothly. This time the dryer needed to be changed. But as this was part of the regular system maintenance, the IRMS equipment was ready for measurements within an hour.

I was not only lucky with the IRMS. During my stay in June the  group got new equipment. An engineer from the ThermoFisher Scientific company  was around for the installation and was open for answering questions. I had the great opportunity to attend and learn about typical problems and possible solutions when using IRMS.

But, not only measuring samples or learning new methods are part of secondments. During these 2 weeks in another lab I had opportunity to join the group meetings and present my own research, see how students from different groups are cooperating, being a part of activates after lab work. Thank Malika we met other international PhD students, had coffee breaks with them, exchanged ideas… At the end, we had also time to enjoy the nice Netherland summer afternoons.

References:

  1. Maciej J. Kotarba: Composition and origin of coalbed gases in the Upper Silesian and Lublin Basins, Poland, Organic Geochemistry 32(1):163-180, (2001)

  2. Zazzeri, G et al. : Carbon isotopic signature of coal-derived methane emissions to the atmosphere: from coalification to alteration, Atmos. Chem. Phys., 16, 13669-13680, (2016)