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Professor Junshi XU  許駿什 助理教授

Assistant Professor

Room 10.15

391 03254

junshixu@hku.hk

HKU Scholar Hub
Junshi-Xu_edited.png

Junshi Xu is a tenure-track Assistant Professor in the Department of Geography at The University of Hong Kong (HKU). Prior to joining HKU, Professor Xu worked as a Research Associate at the University of Toronto’s Department of Civil & Mineral Engineering, where he earned his Ph.D. in Transportation Engineering in 2020. He also served as the Director of Positive Zero Transport Futures, a living lab initiative evaluating transport decarbonization innovations with positive societal impacts.

At HKU, Professor Xu leads the PEACE (People-oriented, Equitable, Accessible, Community-focused, and Environmental) urban mobility research group, focusing on addressing complex urban transport and environmental challenges. His multidisciplinary research bridges data science, engineering, and social sciences to investigate the interactions between transportation, air quality, climate change, public health, and socioeconomics.

Professor Xu's recent work explores urban air quality and population exposure, particularly concerning emerging and unregulated air pollutants. He leverages machine learning modelling and deep learning applications to investigate environmental justice issues, especially for marginalized individuals facing transport and social challenges. His research aims to achieve thriving, equitable, and sustainable cities through diverse collaborations with academia, government, industry, and communities.

Research Interests

  • Transportation Decarbonization and Air Quality

  • Environmental Monitoring and Population Exposure

  • Machine Learning and Deep Learning Applications in Environmental Science

  • Sustainability, Equity, and Justice in Urban Mobility

  • Urban Transport and City Dynamics

Courses

Profile

GEOG2018

Transport Geography

6

credits

Annual; 2nd Semester

Profile

GEOG2120

Introductory Spatial Analysis #

6

credits

Annual; 1st Semester

Selected Publications

  2024  

  • Xu, J., Saeedi, M., Zalzal, J., Zhang, M., Ganji, A., Mallinen, K., Wang, A., Lloyd, M., Venuta, A., Simon, L., Weichenthal, S., Hatzopoulou, M, 2024. Exploring the triple burden of social disadvantage, mobility poverty, and exposure to traffic-related air pollution. Science of The Total Environment, 170947. https://doi.org/10.1016/j.scitotenv.2024.170947
     

  • Xu, J., E. Farrar, C. Jeong, W. Jaafar, D. Anwar, I. Nielsen, M. Tamura, G. Evans, M. Hatzopoulou, 2024. Aircraft activities and ultrafine particle exposures near a city airport: insights from a measurement campaign in Toronto, Canada. Environmental Science & Technology Air. https://doi.org/10.1021/acsestair.3c00114
     

  • Venuta A., M. Lloyd, A. Ganji, J. Xu, L. Simon, M. Zhang, M. Saeedi, S. Yamanouchi, E. Lavigne, M. Hatzopoulou, S. Weichenthal, 2024. Predicting within-city spatiotemporal variations in daily median outdoor ultrafine particle number concentrations and size in Montreal and Toronto, Canada. Environmental Epidemiology, 8(4). https://doi.org/10.1097/EE9.0000000000000323
     

  • Lloyd M., Olaniyan T., Ganji A., J. Xu, Venuta A., Simon L., Zhang M., Saeedi M., Yamanouchi S., Wang A., Schmidt A., Hong K., Chen H., Villeneuve P., Apte J., Lavigne E., Burnett R., Tjepkema M., Hatzopoulou M., Weichenthal S, 2024. Airborne Nanoparticle Concentrations Are Associated with Increased Mortality Risk in Canada’s Two Largest Cities. American Journal of Respiratory and Critical Care Medicine, https://doi.org/10.1164/rccm.202311-2013OC
     

  • Torbatian S., M. Saleh, J.Xu, L. Minet, S. Mahagammulla Gamage, D. Yazgi, S. Yamanouchi, M. Roorda, M. Hatzopoulou, 2024. Societal co-benefits of zero-emission vehicles in the freight industry. Environmental Science and Technology, 58 (18), 7814-7825. https://doi.org/10.1021/acs.est.3c08867
     

  • Weaam J., J. Xu, E. Farrar, C. Jeong, A. Ganji, G. Evans, M. Hatzopoulou, 2024. Challenges and opportunities of low-cost sensors in capturing the impacts of construction activities on neighborhood air quality. Building and Environment, 111363. https://doi.org/10.1016/j.buildenv.2024.111363
     

  • Ganji A., M. Saeedi, M. Lloyd , J. Xu, S. Weichenthal, M. Hatzopoulou, 2024. Air pollution prediction and backcasting through a combination of mobile monitoring and historical on-road traffic emission inventories. Science of The Total Environment, 170075. https://doi.org/10.1016/j.scitotenv.2024.170075

  2023  

  • Lloyd, M., A. Ganji, J. Xu, A. Venuta, L. Simon, M. Zhang, M. Saeedi, S. Yamanouchi, J. Apte, K. Hong, M. Hatzopoulou, S. Weichenthal. Predicting spatial variations in annual average outdoor ultrafine particle concentrations in Montreal and Toronto, Canada: Integrating land use regression and deep learning models. 2023. Environment International, 178, 108106. https://doi.org/10.1016/j.envint.2023.108106
     

  • Ganji, A., O. Youssefi, J. Xu, K. Mallinen, M. Lloyd, A. Wang, A. Bakhtari, S. Weichenthal, M. Hatzopoulou. 2023. Design, calibration, and testing of a mobile sensor system for air pollution and built environment data collection: The Urban Scanner platform. Environmental Pollution, 120720. https://doi.org/10.1016/j.envpol.2022.120720
     

  • Z. Zhai, J. Xu, M. Zhang, A. Wang, M. Hatzopoulou. Quantifying start emissions and impact of reducing cold and warm starts for gasoline and hybrid vehicles. 2023. Atmospheric Pollution Research, 101646. https://doi.org/10.1016/j.apr.2022.101646

  2022  

  • Xu, J., M. Zhang, A. Ganji, K. Mallinen, A. Wang, M. Lloyd, A. Venuta, L. Simon, J. Kang, J. Gong, Y. Zamel, S. Weichenthal, M. Hatzopoulou. 2022. Prediction of short-term ultrafine particle exposures using real-time street-level images paired with air quality measurements. Environmental Science & Technology, 56, 12886 - 12897. https://doi.org/10.1021/acs.est.2c03193
     

  • Ahmed, U., R. Tu, J. Xu, G. Amirjamshidi, M. Hatzopoulou, M. J. Roorda. 2023. GPS-based traffic conditions classification using machine learning approaches. Transportation Research Record, 036119812211113. https://doi.org/10.1177/03611981221111370
     

  • Zhai Z., J. Xu, G. Song, M. Hatzopoulou. Comparative analysis of drive-cycles, speed limit violations, and emissions in two cities: Toronto and Beijing. 2022. Science of the Total Environment, 811 (x), 152323. https://doi.org/10.1016/j.scitotenv.2021.152323
     

  • Tu, R., J. Xu, T. Li, H. Chen. 2022. Effective and acceptable eco-driving guidance for human-driving vehicles: a review. International Journal of Environmental Research and Public Health, 19 (12). https://doi.org/10.3390/ijerph19127310
     

  • Tu, R., J. Xu, A. Wang, M. Zhang, Z. Zhai, M. Hatzopoulou. 2022. Real-world emissions and fuel consumption of gasoline and hybrid light duty vehicles under local and regulatory drive cycles. Science of the Total Environment, 805, 150407. https://doi.org/10.1016/j.scitotenv.2021.150407
     

  • Wang, A., J. Xu, M. Zhang, Z. Zhai, G. Song, M. Hatzopoulou. 2022. Emissions and fuel consumption of a hybrid electric vehicle in real-world metropolitan traffic conditions. Applied Energy, 306 (PB), 118077. https://doi.org/10.1016/j.apenergy.2021.118077

  2021  

  • Xu, J., R. Tu, U. Ahmed, G. Amirjamshidi, M. Hatzopoulou, M. J. Roorda. 2021. An eco-score system incorporating driving behavior, vehicle characteristics, and traffic conditions. Transportation Research Part D, 95: 102866. https://doi.org/10.1016/j.trd.2021.102866
     

  • Wang, A., R. Tu, J. Xu, Z. Zhai, M. Hatzopoulou. 2021. A novel model emission modelling approach and its application with on-road emission measurements. Applied Energy, 306 (PA), 117967. https://doi.org/10.1016/j.apenergy.2021.117967
     

  • Talaat, H., J. Xu, M. Hatzopoulou, H. Abdelgawad. 2021. Mobile monitoring and spatial prediction of black carbon in Cairo, Egypt. Environmental Monitoring and Assessment, 193 (9). https://doi.org/10.1007/s10661-021-09351-0
     

  • Wang, A., J. Xu, R. Tu, M. Zhang, M. Adams, M. Hatzopoulou. 2021. Near-road air quality modelling that incorporates input variability and model uncertainty. Environmental Pollution, 284: 117145. DOI: 10.1016/j.envpol.2021.117145
     

  • Tu, R., J. Xu, A. Wang, Z. Zhai, M. Hatzopoulou. 2021. Effects of ambient temperature and cold starts on excess NOx emissions in a gasoline direct injection vehicle. Science of The Total Environment, 143402. https://doi.org/10.1016/j.scitotenv.2020.143402

  2020  

  • Xu, J., A. Wang, N. Schmidt, M. Adams, M. Hatzopoulou. 2020. A gradient boost approach for predicting near-road ultrafine particle concentrations using detailed traffic characterization. Environmental Pollution, 265: 114777. https://doi.org/10.1016/j.envpol.2020.114777
     

  • Xu, J., R. Tu, A. Wang, Z. Zhai, M. Hatzopoulou. 2020. Generation of spikes in ultrafine particle emissions from a gasoline direct injection vehicle during on-road emission tests. Environmental Pollution, 267: 115695. https://doi.org/10.1016/j.envpol.2020.115695
     

  • Wang, A., J. Xu, R. Tu, M. Saleh, M. Hatzopoulou. 2020. Potential of machine learning for prediction of traffic related air pollution. Transportation Research Part D, 88: 102599. https://doi.org/10.1016/j.trd.2020.102599
     

  • Zhai, Z., R. Tu, J. Xu, A. Wang, M. Hatzopoulou. 2020. Capturing the variability in instantaneous vehicle emissions based on field test data. Atmosphere (Basel), 11. https://doi.org/10.3390/atmos11070765
     

  • Xu, J., M. Saleh, M. Hatzopoulou. 2020. A machine learning approach capturing the effects of driving behaviour and driver characteristics on trip-level emissions. Atmospheric Environment, 224: 117311. https://doi.org/10.1016/j.atmosenv.2020.117311

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