Our Changing World: Playing ‘I-spy’ with urban emissions

If you've spotted a white van cruising around Wellington or the Hutt Valley with strange instruments sticking out of its roof, you might have seen New Zealand's newest tool in tackling our urban emissions.

Follow Our Changing World on Apple, Spotify, iHeartRadio or wherever you listen to your podcasts

Lab on wheels

The 'CarbonWatch - Urban mobile greenhouse gas measurement lab' is designed to detect gases in real time. Outfitted with high-tech equipment, the van monitors carbon dioxide, methane, carbon monoxide and black carbon on the move.

The choice of an electric vehicle is deliberate: researchers didn't want the van's own tailpipe emissions skewing results.

Squeezing all the instruments in - as well as the pumps to suck in air, drying traps to remove moisture, and batteries to keep everything running - took several months, and a bit of Kiwi ingenuity says Earth Sciences New Zealand's Dr Jocelyn Turnbull.

I-Spy carbon

Emissions are detected in real time, appearing as a peak on a computer readout as the van cruises past a source. Methane, for example, often spikes near wastewater plants or leaking gas pipes, while a carbon monoxide peak can point to an older car without a functioning catalytic converter passing by.

The goal of the lab is to 'ground-truth' greenhouse gas measurements, says Jocelyn. As a lead author for a chapter in the IPCC special report on climate change and cities, she is particularly interested in the urban sources and sinks of these gases. Does urban greening have a measurable impact on soaking up carbon, thereby offsetting some emissions? What are the emission profiles or our cities, and what are the main sources? And at what times and seasons do these emissions peak?

Identifying the carbon source

Alongside this on-the-move real-time monitoring, the team are also collecting samples of air for radiocarbon analysis.

At the National Isotope Centre in Petone, a complex lab set-up allows them to figure out the ratios of different forms of carbon isotopes (carbon with ever so slightly different weights) in their samples.

The goal of this analysis is to distinguish between natural carbon dioxide from plants and soil, and carbon dioxide from fossil fuel emissions. Results from air samples collected in urban environments will also be compared to those from Baring Head Atmospheric Research Station, which is the site of the longest running carbon dioxide measurements in the southern hemisphere.

The van has been on the road since June and over the next three years it will travel the country across different seasons, both mapping emissions and engaging with local communities.

Sign up to the Our Changing World monthly newsletter for episode backstories, science analysis and more.