Non-exhaust particulate matter (PM) emissions from road vehicles, generated by brake wear, tire wear, road surface abrasion, and the resuspension of dust, are becoming an increasingly significant source of urban air pollution, particularly in light of the ongoing reduction in tailpipe emissions driven by vehicle electrification. Despite their growing relevance, these emissions remain poorly characterized, especially under real-world driving conditions, where it is challenging to separate the contributions of individual sources. This study presents a controlled field experiment aimed at quantifying and comparing non-exhaust PM₁₀ emissions from three vehicle types with different powertrain configurations: a fully electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), and an internal combustion engine vehicle (ICEV). Measurements were carried out on an outdoor closed test track, using two complementary approaches: gravimetric sampling and real-time monitoring with MODULAIR-PM sensors. Source apportionment was conducted through both model-based techniques and chemical tracer analysis. Results show that regenerative braking significantly reduces brake wear emissions, with the EV recording the lowest value (3.1 mg/v·km), followed by the PHEV (5.0 mg/v·km) and the ICEV (12.3 mg/v·km). Contrary to expectations based solely on vehicle mass, total PM₁₀ emissions did not correlate linearly with weight: gravimetric results showed the highest emission factor for the ICEV (108 mg/v·km), followed by the EV (82.3 mg/v·km) and the PHEV (63.4 mg/v·km). These findings suggest that regenerative braking, partial electrification, and dynamic operation may outweigh the influence of mass alone. Resuspension emissions, estimated via calcium tracers, followed an unexpected pattern: the EV, despite being the heaviest, recorded the lowest factor (11.1 mg/v·km), likely due to its smoother underbody design. The ICEV showed the highest value (48.1 mg/v·km), while the PHEV (17.9 mg/v·km) fell in between. This suggests smoother vehicle geometries may reduce particle re-entrainment, independently of mass. The study also identified several methodological limitations, including the absence of key tracers (e.g., aluminium, zinc, total carbon) in EV samples, reliance on simplified assumptions for tracer quantification, and the poor performance of the solver-based model. These issues highlight the need for more chemically resolved datasets and improved analytical frameworks. Overall, this study adds new empirical evidence to the currently limited body of field-based research on non-exhaust vehicle emissions. The findings underscore the complex interplay between powertrain type, vehicle mass, and design features, and emphasize the urgency of developing more refined analytical methods to accurately assess the environmental impact of emerging vehicle technologies.
Le emissioni di particolato (PM) non da scarico degli autoveicoli (generate da usura dei freni, usura degli pneumatici, abrasione del manto stradale e risospensione delle polveri), stanno diventando una fonte sempre più rilevante di inquinamento atmosferico urbano, soprattutto in considerazione della progressiva riduzione delle emissioni allo scarico dovuta all’elettrificazione del parco veicoli. Nonostante la loro crescente importanza, queste emissioni rimangono poco caratterizzate, in particolare in condizioni di guida reali, dove risulta difficile distinguere i contributi dei singoli processi emissivi. Questo studio presenta un esperimento in campo controllato finalizzato a quantificare e confrontare le emissioni di PM₁₀ non da scarico di tre veicoli con diverse configurazioni di trazione: un veicolo completamente elettrico (EV), un veicolo ibrido plug-in (PHEV) e un veicolo con motore a combustione interna (ICEV). Le misure sono state effettuate su una pista di prova all’aperto, utilizzando due approcci complementari: campionamento gravimetrico e monitoraggio in tempo reale tramite sensori MODULAIR-PM. L’attribuzione delle sorgenti è stata effettuata sia tramite tecniche modellistiche sia mediante analisi di traccianti chimici. I risultati mostrano che la frenata rigenerativa riduce significativamente le emissioni da usura dei freni: l’EV ha registrato il valore più basso (3,1 mg/v·km), seguito dal PHEV (5,0 mg/v·km) e dall’ICEV (12,3 mg/v·km). Contrariamente a quanto ci si potrebbe aspettare considerando unicamente la massa del veicolo, le emissioni totali di PM₁₀ non mostrano una correlazione lineare con il peso: i risultati gravimetrici indicano il valore più elevato per l’ICEV (108 mg/v·km), seguito dall’EV (82,3 mg/v·km) e dal PHEV (63,4 mg/v·km). Ciò suggerisce che la frenata rigenerativa, l’elettrificazione parziale e il comportamento dinamico possano avere un’influenza maggiore rispetto alla sola massa. Le emissioni da risospensione, stimate attraverso traccianti di calcio, hanno seguito un andamento inaspettato: l’EV, pur essendo il veicolo più pesante, ha fatto registrare il valore più basso (11,1 mg/v·km), probabilmente grazie a un design del sottoscocca più aerodinamico. L’ICEV ha mostrato il valore più alto (48,1 mg/v·km), mentre il PHEV si è collocato in una posizione intermedia (17,9 mg/v·km). Questo risultato suggerisce che geometrie veicolari più regolari possano ridurre il rientro in sospensione delle particelle, indipendentemente dalla massa. Lo studio ha inoltre evidenziato alcune limitazioni metodologiche, tra cui l’assenza di traccianti chiave (ad esempio alluminio, zinco e carbonio totale) nei campioni dell’EV, l’adozione di ipotesi semplificate nella quantificazione tramite traccianti e la scarsa efficacia del modello risolutivo utilizzato. Tali criticità sottolineano la necessità di disporre di dataset chimicamente più risolti e di strumenti analitici più robusti. Nel complesso, questo lavoro fornisce nuove evidenze sperimentali in un ambito ancora poco esplorato a livello di misure sul campo: le emissioni non da scarico dei veicoli. I risultati mettono in luce la complessa interazione tra tipo di trazione, massa veicolare e caratteristiche progettuali, e confermano l’urgenza di sviluppare metodi analitici più avanzati per valutare con precisione l’impatto ambientale delle tecnologie veicolari emergenti.
Experimental assessment of non-exhaust particle emissions for an electric vehicle and its gasoline and plug-in counteparts
BERTI, CAMILLA
2024/2025
Abstract
Non-exhaust particulate matter (PM) emissions from road vehicles, generated by brake wear, tire wear, road surface abrasion, and the resuspension of dust, are becoming an increasingly significant source of urban air pollution, particularly in light of the ongoing reduction in tailpipe emissions driven by vehicle electrification. Despite their growing relevance, these emissions remain poorly characterized, especially under real-world driving conditions, where it is challenging to separate the contributions of individual sources. This study presents a controlled field experiment aimed at quantifying and comparing non-exhaust PM₁₀ emissions from three vehicle types with different powertrain configurations: a fully electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), and an internal combustion engine vehicle (ICEV). Measurements were carried out on an outdoor closed test track, using two complementary approaches: gravimetric sampling and real-time monitoring with MODULAIR-PM sensors. Source apportionment was conducted through both model-based techniques and chemical tracer analysis. Results show that regenerative braking significantly reduces brake wear emissions, with the EV recording the lowest value (3.1 mg/v·km), followed by the PHEV (5.0 mg/v·km) and the ICEV (12.3 mg/v·km). Contrary to expectations based solely on vehicle mass, total PM₁₀ emissions did not correlate linearly with weight: gravimetric results showed the highest emission factor for the ICEV (108 mg/v·km), followed by the EV (82.3 mg/v·km) and the PHEV (63.4 mg/v·km). These findings suggest that regenerative braking, partial electrification, and dynamic operation may outweigh the influence of mass alone. Resuspension emissions, estimated via calcium tracers, followed an unexpected pattern: the EV, despite being the heaviest, recorded the lowest factor (11.1 mg/v·km), likely due to its smoother underbody design. The ICEV showed the highest value (48.1 mg/v·km), while the PHEV (17.9 mg/v·km) fell in between. This suggests smoother vehicle geometries may reduce particle re-entrainment, independently of mass. The study also identified several methodological limitations, including the absence of key tracers (e.g., aluminium, zinc, total carbon) in EV samples, reliance on simplified assumptions for tracer quantification, and the poor performance of the solver-based model. These issues highlight the need for more chemically resolved datasets and improved analytical frameworks. Overall, this study adds new empirical evidence to the currently limited body of field-based research on non-exhaust vehicle emissions. The findings underscore the complex interplay between powertrain type, vehicle mass, and design features, and emphasize the urgency of developing more refined analytical methods to accurately assess the environmental impact of emerging vehicle technologies.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/243457