HomeBlogWhat are the main sources of air pollution in Bucharest?

What are the main sources of air pollution in Bucharest?

Airly has been measuring the air quality in Romania since 2018. Airly air quality sensors, as well as the official state measurements show that air quality in Romania, due to high concentrations of particulate matter, is one of the worst in the European Union. Recorded measurements of particulate matter, along with Poland and Bulgaria, are amongst the highest. In the whole of Europe, only the less-developed balkan countries Bosnia and Herzegovina and North Macedonia have significantly worse air pollution.

The highest concentration of pollution in Romania is in Bucharest and its surrounding area, however, Airly’s network density is still not enough to identify all of the pollution hotspots in the country.

Particulate matter (PM) – air pollution levels in Romania 

Our analysis of the particulate matter sensors readings points out that the main source of pollution in Romania is combustion and the second main source is traffic. 

We can conclude this base on:

  • the yearly course of PM concentration – showing clearly that during the heating season the  PM10 values are even 4 times higher than in the summer months
  • the inversely proportional relation between the air temperature and air pollution, as cold facilitates individual combustion. Both the seasonal rhythm and this relation is clearly visible on the graph below. However, low temperature increases the pollution also by the atmosphere effect of winter inversion, when the warmer air ‘traps’ the pollution in the lower parts of the atmosphere. This effect facilitates the location of hotspots of air pollution (connected with individual housing areas)


Table: Air pollution levels compared with the average temperature in Romania in the years 2018/19 and 2019/20.

The second most important source of the PM pollution in Romania is the road traffic. It can be seen on the daily course of pollen concentration graphs, where two peaks: the morning and the evening one are visible, which are caused, among others, by the traffic intensity during the rush hours. During the evening peak, average concentrations of PM10 are about 25% higher than at midday.

What is especially interesting, that during the Covid-19 pandemic and the lockdown, a significant decrease of PM concentrations was observed, which was not related to the atmospheric conditions, which may be explained by the limited traffic at this time.


Gases pollution in Romania

In terms of gases, the most serious problems in Romania are the nitrogen dioxide and ozone – as the situation here is similar to other EU countries. Those two gases are strictly connected to each other and their source is the road traffic. During the morning and the evening, the nitrogen dioxide peaks, due to the traffic intensity, but during midday, due to solar radiation, the nitrogen dioxide is split into nitrogen monoxide and atomic oxygen, which reacts with the molecular oxygen (O2) and forms the ozone (O3). That is why the nitrogen dioxide levels drop at midday, the whole process may be seen at the graph below, which presents average NO2 and O3 concentrations in Bucharest).


Table: Air pollution levels – average daily course of NO2 and O3 in concentrations in Bucharest.

Analyses conducted in Romania showed that there is a direct correlation between the traffic intensity and the NO2 concentration, as well as the correlation between the NO2 concentrations and distance to main roads. Analyses of the lockdown impact on the NO2 concentration showed that depending on the sensor distance to road, and the intensity of traffic before the pandemic, the drop was either relatively small (up to a few %) either extremely high (including 250% drop at the sensors near the most congested roads). Average before and during lockdown NO2 concentrations in Bucharest are shown on the graph below. 

Table: The daily concentrations of NO2 based on air quality map and air quality sensors in Bucharest, before and during the lockdown.


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