A comprehensive study on atmospheric pollution over Ploiesti, Romania

The accumulation of both particulate matter (PM₁₀, PM_2.5) and gaseous species (NO₂, CO, SO₂, O₃) in the atmosphere in urban agglomerations can cause a significant degradation of air quality. The additional impact on human health, visibility, cultural heritage and urban climate has been recognized in studies worldwide. This study represents an air quality assessment in the urban agglomeration of Ploiesti, which is located north of Bucharest (the highest polluted city of Romania), in the central-northern part of Romanian Plain. In Ploiesti operates some of the most important refineries of the country. The city also represents an important link between Bucharest and south of Romania and the northern and western parts of the country.

The study is focused on major air pollutants, particulate matter (PM₁₀, PM_2.5), and also gaseous species (NO₂, CO, SO₂, O₃) at six monitoring sites (traffic, industrial and background). To highlight temporal and spatial variations, a synthetic database covering a four-year period (2018-2021) consisting of time series of hourly and daily values of major air pollutants mass concentrations were statistically investigated. To analyze the influence of meteorological conditions on the air quality in Ploiesti area meteorological observations was constructed.

Present research shows that although Ploiesti is significantly smaller than Bucharest, the anthropogenic activity in Ploiesti strongly affects atmospheric pollution levels on daily timescales (multiannual mean ratio PM_2.5/PM₁₀ = 0.71) at almost same level that in Bucharest area. Additionally, we found the central area impact on surroundings is major, as significant differences were not identified.

We identified both local and regional pollution episodes, but also episodes strongly influenced by the long-range transport of dust pollution.

PM₁₀ pollution roses showed the dominance of local pollution sources in most of the time. On shorter timescale, the long-range transport of fine particulate matter coming from desert dust (Saharan or from Middle East deserts) contributed supplementary to increased pollution as we identified in 13 episodes (during 2018-2021). It has been shown that the atmospheric stability has an important role in the accumulation of PM₁₀ at the scale of Ploiesti urban agglomeration. Trend analysis of annual pollutant mass concentrations for all air quality stations was performed using a larger dataset, since 2008 (first monitoring year) to present (end of 2021), using Mann-Kendal and Sen’slope analysis. Diurnal profile of particulate matter PM₁₀ and the influence of the lockdown restrictions in spring 2020 on PM₁₀ levels were also quantified.

Acknowledgment

The research leading to these results has received funding from the NO Grants 2014-2021, under Project contract no. 31/2020, EEA-RO-NO-2019-0423 project. Data regarding ground-level air pollution and local meteorology by site was extracted from the public available Romanian National Air Quality Database, www.calitateaer.ro, last accessed in December 2022. Meteorological data were extracted from Copernicus Climate Change Service (C3S) Climate Data Store (CDS) ERA5 hourly data on single levels and pressure levels from 1959 to present https://cds.climate.copernicus.eu (last accessed in December 2022).