Spatial concentration distributions of sulfur dioxide and nitrogen oxides in Patras, Greece, in a winter period

Abstract

An economic and quick methodology for performing a preliminary spatial assessment of a city air quality with the purpose to identify locations and zones susceptible to high pollution levels is proposed. A Patras case-study is selected, regarding the air pollutants of sulfur dioxide (SO(2)) and oxides of nitrogen (NO(x)). A total number of 451 samples of short duration, of which 225 were randomly picked in morning rush hours and 226 within evening rush hours, were collected from 50 locations of the major Patras area during a year period, when peaks of primary air pollutants usually occur. Concentration measurements at prescribed locations used to statistically calculate spatial average concentrations approximating 1-h mean values with mean probable errors less than 25.9% for SO(2), NO and NO(x) and less than 15.5% for NO(2). Then iso-concentration contour diagrams plotted indicate high pollution zones and possibly appropriate locations for continuous or random monitoring according to the European Community (EC) Directives. The 1-h mean concentrations were in good correlation to the corresponding traffic rates and useful relationships are given (0.54 <or= r <or= 0.63). In addition, comparisons with data available for other cities, as well as with the limit and guide values provided by the EC and the World Health Organization (WHO) were given. The present data could be useful for the design and optimization of a city network of stations for monitoring air quality, for environmental impact assessments, future reference and comparisons due to city development needs, as well as for validating dispersion models.

Quick and Economic Spatial Assessment of Urban Air Quality

“…The mean probable error made for each final grid matrix of average concentrations can be calculated and tabulated. As we can see in Chapter 3, the maximum values of mean probable errors were around 25% and they depend on the parameter measured (Yannopoulos, 2007a). The ratio of peak to mean concentrations at the ground level depends on the stability of the atmosphere and the type of terrain that the pollutant is passing over.…”

“…Alternatively, Teflon bags and sampling accessories are more inert than Tedlar, but they are more expensive and sensitive to punch and they need more care. Teflon bags can be used for air pollutant sampling and transport for analysis, in conjunction with all possible precautions taken to eliminate any potential errors in pollutant concentrations due to chemical transformations and wall sinks during the time lag in the sampling bags (Yannopoulos, 2007a;Kim et al, 2006).…”

“…Having the possible recovery rate or the maximum rate of losses measured, the maximum allowed time lag for a smaller bag size may be estimated according to the following procedure (Yannopoulos, 2007a). It is considered that the wall losses are proportional to the internal wall surface of the sampling bag, S, or alternatively, the time lag is proportional to the air-sample height, h, defined as h = V S -1 , where V is the air volume sampled in the bag.…”

“…For examined Patras locations, the maxima for 3-415 minutes and for morning or evening period averaging time that is roughly 1 h are given in Table 8 with respect to the location measured. Calculating again C t /C 3 ±σ n-1 , it is found to be 0.542 regarding the morning and evening SO 2 concentrations, while is 0.588±0.0562 based on an average value regarding SO 2 , NO and NO 2 concentrations (Yannopoulos 2007a * The locations where the peak value was observed are given in parentheses. Table 8.…”

“…This chapter describes an economic and quick methodology, which combines the determination of the spatial concentration distribution of air pollutants with suitable model predictions leading to source contribution for several urban receptors. For the determination of spatial concentration distribution, the bag sampling technique is used in conjunction with laboratory measurements performed by pertinent analysers (Yannopoulos, 2007a). The data obtained are then statistically analysed to get approximately spatial distribution of 1-h mean concentrations of specific air pollutants.…”