Single-Particle Analysis of Vienna Traffic Emissions

The SciX Conference this year is set to take place from October 4–9, 2026, in Sparks, Nevada.¹ The conference returns to the Nugget Casino Resort, the venue that hosted the 2023 SciX Conference as well as this year.¹

At the upcoming conference, there will be numerous talks dedicated to the role that spectroscopy is playing in advancing environmental analysis. One of these talks, which will be delivered by Esther S. Breuninger, a postdoctoral researcher at the University of Vienna, is titled, “The Chemistry Behind Urban Air Pollution: Source Apportionment at the Single Particle Level,” and it will highlight a new study conducted by researchers at the University of Vienna that employed single-particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) to examine brake wear particles pulled from 49 in-use tire rims around the Austrian capital.²

What will the SciX 2026 talk focus on?

Breuninger’s talk at SciX will highlight new analysis of nearly 1.6 million individual particles collected from vehicle brakes in Vienna, calling into question a set of chemical markers that air-quality scientists have long relied on to trace urban particulate pollution back to its source.²

Breuninger will highlight the core finding of her team’s study, which is that iron, copper, barium and antimony rarely appear together within the same individual particle.² This finding is significant because all four of these elements are treated by bulk analytical methods as co-occurring “fingerprints” of brake wear for source apportionment.² They rarely appear together within the same individual particle. Instead, the data set is dominated by particles composed of pure iron, with iron-tin combinations forming the next most common pattern.²

Why does this distinction matter?

The distinction matters because source apportionment, which is defined as determining how much of the particulate matter in urban air comes from vehicle brakes versus tires, road dust, industrial activity or other sources, supports regulatory and public health efforts to target air pollution. Bulk methods measure aggregate samples and infer source contributions from average elemental ratios.² According to Breuninger, when those averages are built from populations of chemically distinct particles, the technique can produce misleading associations that don’t reflect what is actually happening at the particle level.²

How does spICP-TOFMS solve this limitation?

The researchers used spICP-TOFMS to analyze particles individually rather than in aggregate. By using this technique, they detected 21 relevant elements simultaneously across the particle set, which is a level of simultaneous, particle-by-particle detection that conventional bulk or size-based measurements cannot achieve.²

Next, the research team grouped the particles into two compositional groups. They did this with a process known as unsupervised clustering. The first was a brake-related population defined by iron alongside variable copper, tin and chromium.² The second group a separate, environmentally influenced population enriched in silicon and aluminum, likely reflecting road dust and mineral background rather than brake wear itself.²

Because the particles were collected directly from in-use rims rather than generated on a dynamometer or other laboratory rig, the results are intended to reflect accumulated, real-world emissions rather than simplified surrogates.²

Breuninger’s talk will also describe her team’s early work pairing this particle-resolved compositional fingerprinting with speciation analysis, aimed at identifying which chemical forms are released from specific particle populations under environmentally relevant conditions.² That direction would extend the technique beyond source identification toward questions of bioavailability and environmental fate.² The hope was that the team would learn more about how particles behave and what they release, once airborne or deposited.

What should attendees take away from this upcoming talk?

Breuninger’s talk is expected to show that there are tradeoffs between throughput and dimensionality. As her team’s study demonstrates, spICP-TOFMS can characterize dozens of elements across large particle populations at a scale bulk methods cannot match, but the resulting high-dimensional data sets bring their own data-analysis challenges, which Breuninger’s talk will also address.²

References

(1) Wetzel, W.; Spectroscopy Staff. Previewing the Upcoming 2026 SciX Conference. Spectroscopy Online, 2026. https://www.spectroscopyonline.com/view/previewing-the-upcoming-2026-scix-conference (accessed September 2, 2026).

(2) Breuninger, E. S. The Chemistry Behind Urban Air Pollution: Source Apportionment at the Single Particle Level. Presented at the SciX 2026 Conference, Sparks, Nevada, October 5, 2026. Available at: https://www.scixconference.org/onlineprogram