Role of Meteorological Parameters in the Diurnal and Seasonal Variation of NO2 in a Romanian Urban Environment.

Mirela Voiculescu,Simona Condurache-Bota,Adrian Roșu,Daniel-Eduard Constantin,Valentina Călmuc,Carmelia Mariana Dragomir Bălănică

doi:10.3390/ijerph17176228

Abstract

The main purpose of this study was to investigate whether meteorological parameters (temperature, relative humidity, direct radiation) play an important role in modifying the NO2 concentration in an urban environment. The diurnal and seasonal variation recorded at a NO2 traffic station was analyzed, based on data collected in situ in a Romanian city, Braila (45.26° N, 27.95° E), during 2009–2014. The NO2 atmospheric content close to the ground had, in general, a summer minimum and a late autumn/winter maximum for most years. Two diurnal peaks were observed, regardless of the season, which were more evident during cold months. Traffic is an important contributor to the NO2 atmospheric pollution during daytime hours. The variability of in situ measurements of NO2 concentration compared relatively well with space-based observations of the NO2 vertical column by the Ozone Monitoring Instrument (OMI) satellite for most of the period under scrutiny. Data for daytime and nighttime (when the traffic is reduced) were analyzed separately, in the attempt to isolate meteorological effects. Meteorological parameters are not fully independent and we used partial correlation analysis to check whether the relationships with one parameter may be induced by another. The correlation between NO2 and temperature was not coherent. Relative humidity and solar radiation seemed to play a role in shaping the NO2 concentration, regardless of the time of day, and these relationships were only partially interconnected.

Highlights

Monitoring atmospheric pollution and the possibility to predict its evolution are of high interest.One major atmospheric pollutant is nitrogen dioxide (NO2 ), which may cause many health problems [1].The NO2 gas has a reddish-brown color, is nonflammable, and has a detectable, pungent odor, perceptible from concentrations of approximately 190 μg/m3 [2]
Meteorological parameters recorded at an hourly rate were used, in order to verify to what extent they are relevant for modulating the nitrogen oxides (NOx) variability by means of correlation analysis
This paper describes the diurnal, monthly, seasonal and annual evolution of the NO2 concentration for 2009–2014, measured in situ by an urban traffic station in southeast Romania

Summary

Introduction

Monitoring atmospheric pollution and the possibility to predict its evolution are of high interest.One major atmospheric pollutant is nitrogen dioxide (NO2 ), which may cause many health problems [1].The NO2 gas has a reddish-brown color, is nonflammable, and has a detectable, pungent odor, perceptible from concentrations of approximately 190 μg/m3 [2]. Monitoring atmospheric pollution and the possibility to predict its evolution are of high interest. One major atmospheric pollutant is nitrogen dioxide (NO2 ), which may cause many health problems [1]. Nitrogen dioxide reacts with the hydroxyl radical (-OH) in the atmosphere, forming the highly-corrosive nitric acid, but it can form toxic organic nitrates. Part of the NO2 molecules in the atmosphere are of primary nature (i.e., directly emitted), while most NO2 results from nitrogen monoxide (NO) [1,3]. The latter is produced via natural and anthropogenic processes. About one-fifth of NOx is released in the atmosphere during

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