Air pollution in Hangzhou, China was studied to understand its sources and effects. Particulate matters (PMs) and gaseous pollutants were measured at two locations with different traffic levels. PMs, especially PM1.0 and ultrafine particles (UFP), were found to be major contributors to air pollution, particularly from heavy-duty vehicles. Traffic, especially the type of fuel used, also played a significant role. Weather factors like temperature and wind speed affected air quality, with negative impacts on pollutants. The study suggests that vehicle emissions, particularly from heavy-duty vehicles, are a significant source of air pollution in the city.