Bagsy the Air Samples: Life on the aircraft for the isotope bag sampling

James France and his sack of bags

James France and his sack of bags

Unlike quite a lot of the science on board the FAAM aircraft, the high precision carbon isotopes in methane have to be done back at the lab at Royal Holloway. To make this happen, we have to collect bags of air mid-flight as we pass over areas of interest, trying to capture the range of sources in the flight plan. However, it does mean that our role can look at little bit budget compared to the needs of a complex and expensive instrument rack measuring species in real-time during the flights.

The life of the isotope sampling team depends on your point of view… The instrument scientist who has to turn up 4 hours before take-off sees the isotope sampler swanning onto the aircraft at the last minute, switching on a pump and a laptop and writing some sticky labels. The logistics team who despair after each flight as we hand over a massive sack containing around 20 bags of air and ask them to find somewhere to store them and then ship them back home. The crew who just hear calls on the radio from the less technically named “bags”. Suggested nicknames which have fortunately not gained traction include “Team Bags”, “Dr Bag” and “Bag Man”…

I prefer to think us more of an Ngolo Kante or Anders Herrera (Ed – can we have a football reference in a science blog?). It’s not altogether obvious what we contribute until all the data is looked at, well after the campaign is done.

Collecting the air

It really is a simple as it sounds. The FAAM aircraft is fitted a large air inlet line which directs air from outside the aircraft to the various instruments, and the bag sampler has a pump which allows air from the outside to be directed in to the bags. The bags are made by SKC, and have been demonstrated in the laboratory to hold the methane without any leaks for months at a time, which gives us plenty of time to do the analysis. To show the full complexity of it, I agreed to do a special with plenty of detail for an upcoming edition of the Barometer podcast run by the University of Manchester.

In order for us to get useful data to identify the source we need to collect a suite of samples at as large a range of concentrations of methane as possible, fortunately the aircraft is well equipped and can measure atmospheric methane concentration in real-time. We use this information to try to sample the air into the bags at the most scientifically useful points.

Why are we interested?

As I’m sure you’ve read on many other posts on this blog and others, methane is rising globally and we’re not entirely sure why… One of the possible reasons is an increase in emissions from tropical wetlands, so we’re on this campaign to try and gather information needed such as the isotopic source signature and the flux of methane being emitted from tropical methane sources. There’s a lovely new paper (shameless plug) which has just been accepted which looks at the impact of methane globally “Very strong atmospheric methane growth in the four years 2014 – 2017: Implications for the Paris Agreement” which will be available in the journal Global Biogeochemical Cycles soon…

We’ll keep the blog updated with something later in the year, once the laboratory analysis has started to take shape.

by James France

On the aircraft, “Team Bags” is James France, Rebecca Fisher and Dave Lowry of Royal Holloway University Earth Science Department.

On the ground, a separate but co-ordinated with the aircraft, sampling campaign is ongoing with Tim Broderick, Trish Broderick and Dave Lowry.

Meanwhile, back in the lab

Wednesday 30th January

While FAAM and the ZWAMPS team head on to Zambia, I have returned home from a busy week of air sampling in Uganda. This week I’m back in the greenhouse gas lab at Royal Holloway. Soon we will have a lab full of Ugandan and Zambian air in Flexfoil bags and WAS cases, so we need to make some space.

Once the air samples return to Royal Holloway we will first measure methane and carbon dioxide mole fraction in each sample using a Picarro cavity ringdown spectrometer, and we will check the measurements against those made by the onboard FGGA. Then it’s over to the mass spectrometer for methane isotopic analysis. We use continuous flow isotope ratio mass spectrometry to measure δ13C in methane in permil (‰). Each sample takes around an hour to analyse, and with more than 500 air samples expected from the MOYA and ZWAMPS campaigns that will mean a lot of time spent in the lab over the coming weeks.

Analysing methane δ13C in bags of air by isotope ratio mass spectrometry at Royal Holloway

Analysing methane δ13C in bags of air by isotope ratio mass spectrometry at Royal Holloway

Methane in background ambient air has an isotopic composition of around -47 ‰. Methane from biogenic sources such as wetlands is more depleted in 13C, making the isotopic composition more negative. Methane from fires is relatively enriched in 13C, making the isotopic composition less negative. This paper by Rebecca Brownlow provides some of the isotopic signatures we have measured from tropical methane sources in previous ground campaigns: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GB005689

Isotopic analysis of the samples collected onboard the aircraft will help distinguish the proportion of methane from fires and from wetlands in methane elevations seen over wide areas of tropical Africa.

By Rebecca Fisher

The MOYA podcast has landed

MOYA has teamed up with the Barometer podcast to produce some special podcasts from the field.

In this introductory episode, Joe Pitt (instrument scientist and mission scientist on MOYA) has a chat with Grant Allen, the Manchester lead on MOYA. They talk about the scope of the project, including some of the challenges we face in doing such ambitious field work in a country that FAAM has not previously worked in.

Listen to this first episode here: https://thebarometer.podbean.com/e/moya-project-introduction-with-joe-pitt-and-grant-allen/

Into the fires

Tuesday 29 January
Fire map from NASA https://firms.modaps.eosdis.nasa.gov/

Fire map from NASA on 29 January 2019 https://firms.modaps.eosdis.nasa.gov/

Today’s morning fires survey team are just on their way back from the airport. Yesterday’s flight was great (apart from the fiery temperatures in the cockpit and a very bumpy ride with the strong daytime turbulence/thermals). We sampled a mix of mile-wide flaming and smouldering fire lines in the north of Uganda with varying CH4/CO2/CO ratios and some interesting fire tracers reported from other instruments, sampled by flying along-wind and across-wind at heights between 1000 ft and 6000 ft above ground. We were joined by a couple of flocks of black and white birds at 3000 ft that passed the window rather fast… Much like the Senegal surveys, there was a thick regional haze from the fires and a faint smell of smoke for the whole flight.

Flight track from the north Uganda fire survey

Flight track from the north Uganda fire survey

We collected bag samples on each pass through the plumes for isotopic analysis and much of the material burning was low-level scrub and papyrus. The land was very dry (much drier than this time last year) and there were many tens of small and large fires in view from the horizon at 3000 ft, most of which appeared to be managed land clearance. The data collected on these flights will improve the knowledge of the isotopic signatures of biomass burning from these plant types in this region, which will better refine models that use isotope measurements as constraints on emission source regions and source types.

By Grant Allen

 

And I was just getting into the swing of things…

Saturday 26 January
Flight C129 - Lake Wamala survey and sampling the plume downwind of Kampala

Flight C129 – Lake Wamala survey and sampling the plume downwind of Kampala

This morning, the aircraft did a repeat of yesterday’s flight plan over Lake Wamala and downwind of Kampala. This gives us another chance to examine the methane emissions from the lake and surrounding swamps (which I think are papyrus swamps like the ones we saw at the nearby airfield the other day), which also might have been polluted by some small fires dotted about the place, and to look at a more complex mix of pollutants coming from the capital city. The FAAM aircraft has done flights like this downwind of cities like London and Lagos, so it will be interesting to see what we find here. Everyone I spoke to seemed very happy with how the flight went, as collecting good data is what we are all here for!

I wasn’t on board, as I’m going back to the UK tonight after nearly a week here. It’s a shame I only got to do one flight, but this is not that surprising given how uncertain it is doing field work in a country that we have never worked in before. You need to build in a lot of contingency for these things, and me having only one flight is not even close to being a factor in our plans. I came along to help with the heavy workload of planning and flying during an intense campaign, so hopefully the others who are staying for another week or more will have been able to pace themselves a bit more than they would otherwise. You can’t really have scientists working long days every day for weeks on end – it’s not healthy even if it’s just for a short time in the field. It also helps to have extra people on hand in case of illness. We have been putting 3 mission scientists on the crew list but flying just 2 of them. This means that if one of us feels even a little ill, they can stay on the ground without any problem with having the right passes sorted out for the airport in advance. This is working really well, as it’s fairly common to get a tummy ache on campaign in tropical regions, and nobody wants to be on an aircraft when that happens!

The operations centre for the field campaign

Just resting our eyes in the operations centre for the field campaign

I’ll miss the excitement of the field campaign when I go back to the UK, as you don’t get the same insight into every aspect of the work from afar – like discussing options for upcoming flights based on how the weather forecast is developing over breakfast, finding out the latest instrument issues or breakthroughs at lunch, or mapping out that future Nature paper over a Nile Special lager and curry in the evening. There is so much value to be gained from going on a campaign that I am extremely grateful I was able to take part. I will continue to send in forecast maps that I have set up with the Met Office for the campaign to help with the flight planning, and keep tabs on what’s going on, but I will really miss the random chats I won’t have with all the great people working on this project. The campaign hasn’t even finished, and I can’t wait until the next project meeting comes along!

 

A swamp and a city

Friday 25 January

Part 1

On board the FAAM aircraft for flight C128

On board the FAAM aircraft for flight C128

I am on the bus to Entebbe Airport for my first and only MOYA flight. We have planned a flight over the nearby Lake Wamala, which is a lot smaller than Lake Victoria (which is like a sea really) or Lake Kyoga,  where they flew to yesterday. I am “mission scientist 1” for this flight, and James Lee from University of York, who will be mission 2, led the flight planning. This means that I sit in the cockpit with the pilots, and James sits at the back of the aircraft with more access to the live data as it comes in from the instrumentation. You get a fantastic view from the cockpit, with the flip side that it’s quite uncomfortable. Definitely worth it though!

We aim to see methane emissions from the lake, and mission 2 is critical in feeding information about the measurements to mission 1, who spends more time liaising with the pilots.

After Lake Wamala, we want to fly downwind of Kampala to measure the emissions from the city. Hopefully we can take off on time and get back before dark, otherwise we may have to modify our flight plan to avoid birds that come out at dusk. And judging by the dense clouds of flies I’ve seen over the lake after dark, maybe they are an issue too!

Part 2

Happy instrument scientists Dominika and Pat

Happy instrument scientists Dominika and Pat

What a great flight! After all the planning and working on the instruments on the aircraft, it feels like the campaign has got off to a great start. Firstly, it appears that ALL the key instruments worked. This might sound rather basic, but the aircraft is a very hostile environment for instrumentation. Lasers are easily misaligned, overheating can be a problem, changes to air pressure are a constant issue for some instruments. Congratulations to all the instrument scientists who have been working in the heat on the ground to get everything working so well.

We got some great measurements of methane downwind of Lake Wamala, Kampala and of some small fires again. I think we are all very happy that everything went to plan, the wind was as forecast, and the layers of methane in the atmosphere was as expected as well. It’s very rewarding and even euphoric when things work well, and it makes the 34C+ cockpit with a burning hot laptop on your lap well worth it!

And we’re off

Thursday 24th January

Today saw the first science flight of MOYA get off the ground. It was so exciting that I completely forgot, and was in the middle of recording a podcast with Pat Barker from Manchester when it happened. I am sure there was a little cheer from everyone paying attention!

The aircraft went up to Lake Kyoga in the middle of the country, where the aim was to sample wetland emissions of methane. They also saw several plumes of smoke coming from fires, and much of the area was not actually wetland but relatively built up.

It was great to get things started and get some samples over this area. It may be more of a challenge to disentangle the signals from the lake and the fires, but that’s what happens in the real world – things are messy!

There will be a flight tomorrow (Friday 25th) if all goes to plan and then we will really get into the swing of things. Forecasts are looking good for a flight over another Lake and to sample the city of Kampala so I am really looking forward to that one – it’s got a bit of everything!

The Botanical Gardens Redux

Sampling cows at the botanical gardens

 

On Wednesday, we came back to the Botanical Garden in Entebbe to take some more air bags from termite mounds and cows methane emissions. Even though a thunderstorm was coming (and probably this is why all the meteorologists stayed in the hotel), we managed to get a great range of samples. Thanks to our guide, Peter, we even found some termites and got very close to the local cows.

The Garden is also a great place for bird spotting – part of our group turned into ornithologists. We have seen monkeys, which escaped from the zoo and local dogs too.

So far, the ground work is very successful and we hope, that we will get some great samples from the aircraft as well!

By Dominika Pasternak

Papyrus: a methane emitter and natural wind vane

The papyrus swamp measurements team
Tue 22 January 2019
Part 1

Having planned out the next few days flights – to lakes/wetlands as well as fires – and with no point refining the plans based on the weather forecast because we don’t know exactly when we will be able to start flying, I’ve joined Rebecca again to do some air sampling. This time with intent, and with a full rucksack containing anything I might need (unlike yesterday).

We are currently in a taxi out to see a contact, Steve Forsyth, who works at Mission Aviation Fellowship – Uganda, and is based at an airfield by a papyrus swamp. MAF is an organisation that operates small aircraft to transport refugees from nearby countries like the Democratic Republic of Congo or Sudan. The swamp will be a source of methane and so will be a good opportunity to work out the carbon-13 fingerprint of such an ecosystem. The principal investigator of this project, Euan Nisbet, has sampled here before, so it will be good to find out whether the fraction of carbon-13 varies over time or is very consistent.

Getting out of the conference room is a good chance to stop obsessing over ever evolving weather forecasts and see some of Uganda. And I can make myself useful by taking photos of the sampling location at very least.

Part 2

We are on the way back from the airfield now. It was completely surrounded by papyrus swamp, which meant we could access it quite easily. We were escorted around the airfield by Ivan, who was essential in helping us not get our feet wet (we were not keen to lose a trainer in the swamp!) while getting as close to the swamp as possible.

The papyrus plants were extremely tall in places – close to 4m probably. Some areas were cut down to the stem, and they grow back in about a month according to Ivan. The stems themselves are very strong, and are excellent wind vanes of you ever are in need of one. Which I did, as I was taking wind measurements to accompany the air samples.

In all, we took 13 samples from locations close to the surface of the water up to about 2m high, all around the edge of the swamp, plus one background sample further away from it. This will allow us to find out the carbon-13 fingerprint of this papyrus swamp, where there were the highest methane concentrations. For example, the papyrus that was cut down to ground level may emit more or less methane than the fully grown area and maybe the measurements will give us an indication of that.

 

Serendipitous sampling

Monday 21 January 2019
Termite mound

Taking an air sample beside a termite mound (Steve Andrews, Rebecca Fisher and our very understanding tour guide)

Today was another down day, with access to the aircraft for instrument scientists. We are fairly well prepared for the flights, as we originally wanted to start flying today, but hold-ups with permissions mean that we will be lucky to fly tomorrow. So we have got several flight plans fully prepared, and we are just keeping an eye on the weather forecasts and waiting for the all clear.

Instead of obsessing over the weather, some of us went to buy local SIM cards and have lunch. So far, so uneventful. We then decided to walk back to the hotel via the botanical gardens, and this is where the day turned up some unexpected excitement. Rebecca Fisher from Royal Holloway, a seasoned and clearly very dedicated field scientist, had come prepared with three air sampling bags and a pump. So when we saw termite mounds in the botanical gardens, Rebecca and I were grinning with glee, as termites are one of the more unusual sources of methane, and one which we hadn’t measured before! The down side of our enthusiasm was that the termites weren’t terribly pleased and one bit me. I admit that termites weren’t on the risk assessment as we had no idea we would see any.

After learning some more about indigenous and non-indigenous plants in the gardens, and spotting various birds (kingfisher, ibis, cormorant, egret and a few more unidentified ones) and a troop of monkeys, we found some cows hanging out with some egrets. And of course, took another sample, cows being a favourite methane source to measure.

Cows and egrets in the Botanical Garden, Entebbe

Cows and egrets in the Botanical Garden, Entebbe

One final sample on the beachfront later, and we were done with the sampling. Rebecca will analyse the air back in the UK to see how much carbon-12 and carbon-13 there is in the methane. Sampling close to a source (e.g. a termite mound) is a way to identify that source’s signature amount of carbon-13 relative to carbon-12. The better we know this from a range of different sources, the better we can work out the origin of a methane measurement far away from the source, by matching up this so-called isotopic fingerprint.

For more about this kind of isotopic fingerprinting, see this blog from our previous campaign about methane in the Arctic.

sampling a cow

A cow shows Shona Wilde and Rebecca Fisher what she thinks of their air sampling!