Yingyue Wei

The contribution of non-exhaust emissions (NEEs) to particle number concentration (PNC) remains insufficiently quantified, particularly across different urban environments. In this study, we address this gap by quantifying the contribution of NEEs to airborne nanoparticles in urban areas. Using positive matrix factorisation (PMF), conditional probability function analysis, Pearson correlation, and source identification, we identified five source factors contributing to PNC at two sites in London: a traffic site and a background site. Five source factors were resolved at both sites: Aitken-mode traffic exhaust particles, nucleation-mode exhaust emission, secondary aerosol, non-exhaust emission, and regional background accumulation. Interestingly, the contribution of NEEs differed between the two sites. At the traffic site, NEEs contributed 14.9%, while at the background site, their contribution was higher at 28.5%, likely due to the favourable summer dispersion conditions. However, the contribution of nucleation-mode exhaust emission also showed significant differences: 26.6% at the traffic site and only 9.9% at the background site. Based on these findings, we propose that air quality policies should integrate NEEs into regulations, improve road maintenance, and use PNC-based along with metal tracers to identify and control PNC. This study offers valuable insights for developing strategies to manage urban nanoparticle pollution.

With the electrification of road vehicles leading to a reduction in tailpipe emissions, the relative contribution of non-exhaust emissions (NEEs) has become increasingly prominent. NEEs, particularly nanoparticles smaller than 100 nm in aerodynamic diameter (PM0.1), present significant health and environmental risks. A comprehensive understanding and strategic management of these emissions are urgently required to mitigate their impact. This article reviews existing studies and reveals that nanoparticles in NEEs are generated from brake and tyre wear under critical temperature conditions, while road wear and resuspension do not directly produce nanoparticles but contribute to larger particles. Common methodologies in studying these emissions include laboratory experiments (with brake dynamometers, tyre dynamometers, chassis dynamometers, and simulators), field tests (tunnel and real road emission tests), and source apportionments. The emission rate of PM0.1, calculated based on particle number concentration, ranges from 1.2% to 98.9%, depending on driving conditions. Extreme driving conditions result in high nanoparticle generation. Emission inventories reveal that PM0.1 emission levels have remained stable since 2020, without an observable reduction. Moreover, emissions attributable to brake wear are found to surpass those from tyre wear. Current mitigation strategies focus on material improvements for brake pads and tyres, better road maintenance, and regulatory measures. Mitigating the environmental and health impacts of nanoscale particulate matter requires additional research and regulations to control it at the source.

Large passenger ships are characterised as enclosed and crowded indoor spaces with frequent interactions between travellers, providing conditions that facilitate disease transmission. This study aims to provide an indoor ship CO2 dataset for inferring thermal comfort, ventilation and infectious disease transmission risk evaluation. Indoor air quality (IAQ) monitoring was conducted in nine environments (three cabins, buffet, gym, bar, restaurant, pub and theatre), on board a cruise ship voyaging across the UK and EU, with the study conducted in the framework of the EU HEALTHY SAILING project. CO2 concentrations, temperature and relative humidity (RH) were simultaneously monitored to investigate thermal characteristics and effectiveness of ventilation performance. Results show a slightly higher RH of 68.2 ± 5.3 % aboard compared to ASHRAE and ISO recommended targets, with temperature recorded at 22.3 ± 1.4 °C. Generally, good IAQ (20 L s−1 person−1) were highly over-ventilated. Dining areas including the pub and restaurant recorded high CO2 concentrations (>2000 ppm) potentially due to higher footfall (0.6 person/m−2 and 0.4 person/m−2) and limited ACH (2.3 h−1 and 0.8 h−1), indicating a potential risk of infection; these areas should be prioritised for improvement. The IAQ and probability of infection indicate there is an opportunity for energy saving by lowering hotel load for the theatre and cabins and achieving the minimum acceptable VR (10 L s−1 person−1) for occupants' comfort and disease control. Our study produced a first-time dataset from a sailing cruise ship's ventilated areas and provided evidence that can inform guidelines about the optimisation of ventilation operations in large passenger ships, contributing to respiratory health, infection control and energy efficiency aboard.