Assessment of air quality using diffusive samplers and ADMS-Urban

Abstract

The main sources of inorganic pollutants are emissions from facilities of the energy sector and transport exhaust emissions. Nitrogen dioxide (NO₂) as one of the most important inorganic air pollutants forms during the combustion process, especially in motor vehicles. Passive diffusive samplers used to measure NO₂ become more popular because of their simplicity, low cost and possibility to measure in large areas, including cities, regions or even different countries. The aim of this paper is to compare the data on air quality assessment obtained by means of indicative measurements and modelling based on the data from Žirmūnai district, Vilnius city, Lithuania. Nitrogen dioxide was measured with diffusive samplers in 25 points in the district. Samplers were attached to the street light poles. Diffusive samplers consisted of stainless steel mesh discs coated with triethanolamine. Higher concentrations of nitrogen dioxide were measured near intensive traffic streets: Kareivių and Žirmūnų. The average NO₂ concentration was up to 39.0 µg/m³ at the measurement points located near these streets. 2.2 times lower concentrations (17.7 µg/m³ ) of nitrogen dioxide were measured at the measurement points located in the yards of apartment houses further from the heavy traffic streets. The air quality of Žirmūnai district was also assessed by modelling dispersion of nitrogen dioxide from motor exhaust emissions with the ADMS-Urban program. The highest concentrations of nitrogen dioxide calculated using simulation were in the north-western part of Žirmūnai district: intersection of Kareivių, Kalvarijų and Ozo streets. NO₂ concentration at this crossroad was up to 60.0 µg/m³. The lowest concentration of NO₂ (14.0–16.0 µg/m³ ) was recorded at the measurement points located further from road traffic as the main source of pollution. Nitrogen dioxide concentrations in ambient air of Žirmūnai district measured with diffusive samplers were compared with the results obtained using the ADMS-Urban program. The error between two methods ranged from 2.5 to 35.8%. The concentrations measured with diffusive samples differed by 13.9% on average from the concentrations modelled with ADMS-Urban. Simulation data was within the 30% uncertainty of nitrogen dioxide permitted in the Directive 2008/50/EC.