Anthropogenic Impact on Atmospheric Composition over Bucharest, Romania: Insights from Multiple Field Campaigns (2022–2025)

Urban air pollution represents a major environmental and public health issue, particularly in large metropolitan areas. This study presents an analysis of black carbon (BC) and particulate matter with an aerodynamic diameter smaller than 2.5 µm (PM_2.5) concentrations in Bucharest, Romania, over the period 2022–2025, using a combination of on-site and mobile measurements. Field campaigns considered both short-term (about 10 days) and longer-term measurements, up to three months. The short-term field campaign, was carried out using a mobile laboratory that covered more than 1,500 km in August 2024. The city area was divided into three distinct zones—north-west, north-east, and south—with a specific route defined for each zone. Each route was travelled four times: once during night-time and three times during daytime on consecutive days. This data acquisition strategy ensured adequate statistical consistency and enabled the capture of both temporal and spatial variations in atmospheric BC and PM_2.5 concentrations. The temporal variability of atmospheric pollutants was analysed based on data gathered in the long-term campaign performed at a location situated in the western part of the city, an area with high traffic. The results reveal significant spatial-temporal variability in BC and PM_2.5 levels, strongly influenced by road traffic intensity, urban land-use characteristics, and time of day. Areas that exhibit elevated fine particulate pollution were identified within Bucharest. As an example, in 2022, close to the high traffic western area with traffic noise levels ranging from 40 dB (night-time) to about 75 dB (daytime), a mean PM_2.5 concentration of about 35 µg m⁻³, and mean black carbon (BC) concentration of 11.38 ng m⁻³ in the ultrafine particles were measured. No significant changes were detected in PM_2.5 and BC levels over time at that location, indicating a significant people chronic exposure. These elevated long-term concentrations support the role of road traffic as a major urban stressor by the combined exposure to air pollution and noise, both relevant for public health risk. Each field campaign was also meteorological characterized, in order to better understand the variations of PM_2.5 and BC concentrations. During the mobile measurement campaign in summer 2024, the Bucharest area was characterized by a moderately deep atmospheric boundary layer (mean height ~850 m), favouring partial vertical mixing, while prevailing weak-to-moderate south-easterly winds (mean speed 2.6 m s⁻¹) suggest limited horizontal ventilation. Air temperatures ranging between 22 and 32 °C, combined with relatively low to moderate relative humidity (35–55%), indicate warm and generally dry conditions, conducive to thermal stress and potentially reduced dispersion of urban pollutants, especially during night-time stable periods. This is a typical meteorological condition for Bucharest summers.

Present study highlights the importance of integrating fixed and mobile measurements for a detailed assessment of urban atmospheric composition to further assess the population exposure to harmful atmospheric constituents, and provides relevant information to support air quality management strategies in Bucharest.