Evaluation of formaldehyde concentration in the ambient air of a most
populated Iranian city, Tehran.
Mohammad Hadi Dehghani1,2*, Mehdi Salari1, Kazem Naddafi1,3, Shahrokh Nazmara1,
Ehsan Ahmadi1,4, Prashant Kumar5,6
1- Department of Environmental Health Engineering, School of Public Health, Tehran
University of Medical Sciences, Tehran, Iran.
2- Center for Solid Waste Research, Institute for Environmental Research, Tehran University of
Medical Sciences, Tehran, Iran.
3- Center for Air Pollution Research, Institute for Environmental Research, Tehran University of
Medical Sciences, Tehran, Iran.
4- Department of Environmental Health, School of Health, Kashan University of Medical
Sciences, Kashan, Iran.
5- Department of Civil and Environmental Engineering, Faculty of Engineering and Physical
Sciences (FEPS), University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom.
6- Environmental Flow Research Centre, FEPS, University of Surrey, Guildford GU2 7XH,
Surrey, United Kingdom.
*Corresponding author. Tel. +98 21 42933227; Fax: +98 21 66419984; Email: [email protected]
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Abstract
Exposure to high levels of formaldehyde is known as both acute and chronic health problems,
but the studies analyzing ambient concentrations of formaldehyde, especially in Middle East
cities such as Tehran, are still rare. The aim of this study is to survey the variations in the
concentration of formaldehyde in several areas with a high traffic volume of Tehran city during
different seasons. The other objectives include understanding the influence of carbon monoxide,
ozone and nitrogen dioxide concentrations, ambient temperature, relative humidity, and air
pressure on the variation of formaldehyde concentration. Measurements were carried out during
the period of 6 months between 2013 (December 22 to February 14) and 2014 (April 27 to June
20 at five different locations within the city, together with a background site. One hundred and
eight samples, each averaged over 3 hours from 11 AM to 2PM, were taken from the sampling
locations. The average concentration of formaldehyde in the spring (22.7±5.3 ppb) was found
about 1.31 times higher than winter (17.3±4.2ppb). Formaldehyde concentrations demonstrated a
significant correlation with the changes in air temperature (in the range of 0.46 to 0.66 for
different locations) but not having any strong correlation with humidity and pressure. Carbon
monoxide and nitrogen dioxide showed a significant coefficient of determination with
formaldehyde concentrations with R2 as 0.80 and 0.67 during the winter, respectively, whereas
the corresponding R2 values during spring were 0.39 and 0.41. Ozone showed a significant
correlation with formaldehyde (R2=0.64) during the spring and has not such the significant
correlation during the season winter (R2=0.23). Overall, it concluded that Road vehicles were
recognized as main contributor of formaldehyde production during both the seasons, especially
in the winter, also photochemical oxidation was another important and considerable contributor
producing formaldehyde during the spring.
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Keywords: Formaldehyde concentration; Air Pollutants; Ambient air; Tehran city.
1. Introduction
Air pollution and especially outdoor air pollution is a critical global health problem (Huang et
al. 2015; Zhu et al. 2015) and it consists of exposure to pollutants like ozone (O3), nitrogen
oxides (NOX), carbon monoxide (CO), sulfur dioxide (SO2), volatile organic compounds
(VOCs), particulate matters and other emerging pollutants (Kumar et al. 2011; Kumar et al.
2014; Lovera-Leroux et al. 2015; Motesaddi Zarandi et al. 2015; Xie et al. 2015). Long-term
exposure to air pollution can result in many adverse health outcomes including respiratory,
neurological, cardiovascular, developmental, etc. (Bertazzon et al. 2015; Khoder 2006; Leili et
al. 2008; Shahsavani et al. 2012). Meanwhile, formaldehyde (FA) is one of the major indoor and
outdoor organic pollutants that has been considered as one of the important precursors of free
radicals in the atmosphere (Salthammer 2013; Szulejko and Kim 2016; Zheng et al. 2013). This
carcinogenic compound is formed naturally in the troposphere during the oxidation of
hydrocarbons. In the ambient air, FA exists in low concentration due to its presence in the
methane cycle (Rovira et al. 2016). This pollutant is considered as an important compound for its
oxidation capacity in the atmosphere and has a half-life of a few hours (Possanzini et al. 2002;
Wagner et al. 2002). Major sources of FA emission in the atmosphere are directly from vehicles,
industrial processes and combustion of biomass (Lei et al. 2009; Wang et al. 2009). It is also
produced by photochemical oxidation of organic compounds, which are released from natural
and anthropogenic sources (alkanes, alkenes, isoprene, volatile organic compounds, VOCs)
(Moussa et al. 2006; Polkowska et al. 2006). The background concentration of FA without
interference of man-made sources in ambient air is typically less than 1 μg.m-3 (IARC 1995).
According to regional condition of urban atmosphere, annual average concentrations in urban
environments can vary in the 1-20 μg.m-3 range, but these levels can reach up to 100 μg.m-3 in
heavy traffic or during severe inversion conditions (IARC 1995; WHO 1989). Short-term effects
of this toxic aldehyde include tumor in the nose, irritation of eyes, respiratory and skin
(Hasanbeiki et al. 2014; Rovira et al. 2016; Wang et al. 2009). Long-term exposure to FA
includes chronic effects such as liver toxicity, neurotoxicity, reproductive impairment, and
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abortion in women. International Agency for Research of Cancer (IARC) and US National
Toxicology Organization introduced FA as an agent of Leukemia (Zhang et al. 2013). Several
studies have measured the concentration of FA in urban areas, with diurnal and seasonal changes
leading to variations from about 1 to 36 ppb (Andreini et al. 2000; Bono et al. 2010; Cerón-
Bretón et al. 2015; Miguel et al. 1995; Zheng et al. 2013). Nevertheless, the studies analyzing
formaldehyde concentrations, especially in Middle Eastern cities, are still rare. Moreover, this
study focuses to fill some other existing research gaps in the literature including the correlation
among other pollutants with FA concentration, and the impacts of meteorological conditions.
The other aims include understanding the diurnal and seasonal changes in FA concentrations for
the urban environment of Tehran, the most populated Iranian cities.
2. Material and Methods
2.1. Site description
This cross-sectional study was performed over the two-year duration (2014-2015) through
sampling at five different high-traffic areas of Tehran. These areas included: (i) Enghelab Square
(A; 35°42'3"N, 51°23'30"E), (ii) Three-way Tehran Pars (B; 35°41'58"N, 51°20'28"E), (iii)
Azadi Square (C; 35°43'25"N, 51°31'23"E), (iv) Tajrish Square (D; 35°48'24"N, 51°25'46"E),
and (v) Shosh Square (E; 35°39'33"N, 51°25'52"E). These locations considered as sampling sites
were reported by Tehran Air Quality Control Company as five regions with extreme pollution
that have a higher air quality index (AQI) in comparison with other regions of the city.
Background sampling was carried out in the center of a park, Laleh (F; 35°42'39"N, 51°23'34"E),
which had a distance of about 526, 233, 336 and 263 m from the streets around. Because of low
concentrations of FA in Laleh Park, only four samples were measured for each season at the
background location. Sampling was performed during both the winter (December 22 to
February 14) and spring (April 27 to June 20) seasons in which 54 samples was taken duration
each season and totally 108 samples were simultaneously collected during the two-season from
11 AM to 2 PM. Also, numbers of the samples in each of the sampling locations and background
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location were 20 and 8 times, respectively. . Figure 1 presents the details of sampling locations
along with potential sources of FA emission
2.2. Sampling and analytical methods
Chromotropic acid method was used to measure FA concentration. Materials including
Sodium bisulfate 39% (NaHSO3), Formalin 37%, Chromotropic acid
((HO)2C10H4(SO3Na)2·2H2O) and Sulfuric acid 97-95% (H2SO4) were purchased from Sigma-
Aldrich. Sampling was carried out by personal sampling pump (SKC, United State of America)
(at height of 1.5 m above ground level and with a distance of 5 m from the main streets of
studied regions), which had a flow rate of 1 lit min-1 and the size of each sample was equal to 180
lit from 3 hour continuous sampling. For the effective absorption of FA, two impingers were
used in series so that each impinger had 20 mL sodium bisulfite (1%). PTFE filters with 3 μm
pore sizes were placed at the entrance of impinger to prevent the particles entering the absorbent.
The samples were then transferred to low-density polyethylene containers for their analysis in
University’s air pollution lab. Four mL of each sample was poured inside 25 mL of Arlon, along
with 0.1 mL of chromotropic acid (1%), as reagent to the sample and was stirred for 1 min.
Further, 6 mL sulfuric acid (95-97%) was added slowly to the sample and gently stirred. The
sample was heated in water bath at 95 °C temperature for 15 min. Eventually; the sample was
kept at a room temperature for 2-3 hours for cooling.
For measuring FA concentrations, PerkinElmer LAMBDA spectrophotometer model of 25
UV/Vis with 1 cm cuvette and 580 nm wavelength was used. Blank samples were employed for
each sampling period in order to determine the actual FA concentrations in the ambient air.
Finally, Eq. (1) was used to measure FA concentrations for each sample.
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C ( μgL )=M f+M b−2MB
V (1)
Where:
Mf, Mb and MB are FA concentrations in µg in the front, back and blank impingers,
respectively. V is the volume of sampled air in liter (Fushimi and Miyake 1980; Sciences 1994).
Eventually, it was mentioned that the lowest concentration that can be detected by chromotropic
acid method, is 7 ppb. Therefore, the concetrations lower than 7 ppb were considered as 3.5 ppb in
order to make it possible for statistical analysis. Meteorological conditions at each of the
sampling periods were measured by Humidity/Barometer/Temp. Meter model PHB318, as
summarized in Table 1. In order to identify the relation between FA with air pollutants' criteria,
hourly mean concentrations of CO, NO2 and O3 pollutants obtained from Tehran Air Quality
Control Company were used. The devices applied to measure of CO, NO2, and O3 concentrations
were Carbon Monoxide Analyzer (model CO12M of Environment SA, France), nitrogen oxides
analyzer (model AC32M of Environment SA, France), and Ozone analyzer (model O342M of
Environment SA, France). The national exposure standard for hourly mean of CO, NO2, and O3
concentrations are 35 ppm, 100 ppb, and 0.12 ppb, respectively.
2.3. Statistical analyses
Kolmogorov-Smirnov method was used to determine for the checking normal distribution
of data, and paired-sample T-test was used to compare average concentrations of FA between
both the seasons. ANOVA-Tukey's multiple range test was used for comparing the average
concentration of FA among sampling locations. Pearson's correlation test was used for
determining the effect of temperature, pressure, and humidity on FA concentration and its
relationship with the variations of carbon monoxide (CO), ozone (O3) and nitrogen dioxide
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(NO2) concentrations. Excel software was applied to draw charts and arrange data into table and
SPSS 16 functions was used to make statistical analysis.
3. Results and discussion
3.1 Trends in FA concentration data variation
The maximum and minimum average concentrations of FA were observed in the A and F
areas, respectively (Table 2). Except at one occasion, the FA concentration in the F area was
7 ppb; the other samples at this location were below the detection limit. The maximum values of
average FA concentrations were measured as 20.2 and 25.5 ppb for winter and spring,
respectively in (A) area. As shown in Figure. 2, it was observed that the average concentration of
FA on Fridays (9 January 2015and 15 May 2015) in comparison to other days in the week had
significant difference (p<0.05). The maximum diurnal concentration of FA during the winter and
spring were observed on 27 January and 2 June 2015, respectively. On January 27, 2015,
ambient temperature decreased to less than 3.5°C while it was 30°C on 2 June (Fig. 2). A
comparison of FA concentrations in A, B, C, D, E, and F areas during winter and spring was
made using ANOVA-Tukey's multiple range test. No significant differences were found between
A, B, C, D and E areas with p-values of 0.061 (for winter) and 1.306 (for spring) while all of the
areas with F area have significant differences with a p-value<0.05 (Table 3). The lowest FA
concentrations were measured in the F area located in the center of Lale Park (3.5ppb) and away
from urban traffic. Moreover, high density of trees in this park acts as a sink for FA. Kondo et al.
(1996) investigated the ability of some tree species in adsorption of atmospheric FA and reported
that FA adsorption mechanism is through the stomata on the leaves with a rapid velocity of
metabolizing (Kondo et al. 1996). On the other hand, Fridays with lower volume of traffic
(Fridays are holiday in Iran which result in decreasing the volume of traffic) in comparison with
other days, have the minimum diurnal average of FA concentration. To support this, trend of
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traffic density was surveyed using of CO chances as a pollutant emitted directly from vehicles. It
is concluded that CO concentration had a large reduction of emission in Fridays than the other
days (p-value<0.05). These results allow concluding that a large amount of FA in the atmosphere
in Tehran arises from direct emissions of vehicles. Viskari et al. (2000) reported that the distance
from FA emission sources and existing buffer zone were the main reseasons for the FA
concentration differences observed in the polluted urban area. Furthermore, Andreini et al.
(2000) stated that differences between concentration of FA during working days to those during
the weekend may be as a result of lighter traffic volume on weekend days (Andreini et al. 2000;
Viskari et al. 2000). Highways, roads, Bus Rapid Transit (BRT) station, terminals and intercity
buses with a large volume of cars (gasoline fuel) and buses (diesel fuel) in the A, B, C, D and E
areas were included as the main sources of FA emissions in the areas; these are similar factors
identified by previous studies (Sagebiel et al. 1996). The majority of the vehicles in these areas
were personal automobiles and public transport, which use gasoline and diesel as a fuel,
respectively. Most of the fuels consumed in these areas contained oxygenated compounds such
as ethanol, methanol and MTBE in order to improve engine combustion processes which lead to
production of FA (Ban-Weiss et al. 2008; Machado Corrêa and Arbilla 2008; Shayan et al.
2012). Moreover, there were no catalysts used to control the exhaust emissions of FA from
vehicles. Previous studies have reported the reduction in FA emissions after the use of catalysts
(López-Aparicio and Hak 2013; Watson et al. 1988). The maximum numbers of vehicles were
found in the C, B, and Areas, respectively, and the minimum numbers were in E area. The area A
was located in the enclosed space in the middle of city center and therefore the average speed of
wind in this area was lower than the other areas. Furthermore, area D located in the northern
Tehran shares boundary with the Tochal Mountains and hence has more buffering space than the
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other areas. In general, slight differences of FA concentrations in the sampling locations can be
due to the differences in traffic density, meteorological and geographical among areas. The daily
average and maximum allowable concentration of formaldehyde in ambient air were proposed by
WHO the values of 28 and 24ppb, respectively. In the regard to the concentration of FA in some
sampling days that exceed than the mentioned exposure limit in ambient air, it is necessary to
employ practical control operations to improve and decrease of FA level in ambient air (WHO
1989).
3.2 Seasonal variation of FA concentrations
Paired sample T-test was used to compare average concentrations in the winter and
spring. Significant differences (p-value <0.05) were observed between average concentrations of
FA during winter and spring with and confidence interval being -6.3 and -4.5, respectively
(Table 4). Average concentration in winter and spring were obtained 17.3±4.2 and 22.7±5.3 ppb,
respectively. These values are comparable to those reported by Possanzini et al. (2002) where
they found that range of concentration in summer and winter as 18±6 and 10±4 ppb,
respectively. The formaldehyde concentrations' difference in Tehran and Rome can come from
different traffics amount and meteorological conditions. Numbeo.com, which is an international
online database, was used for comparing mentioned cities traffics the traffic index for Tehran
and Rome were 260.07 and 201.09, respectively, which is considerably higher for Tehran.
Moreover, annual mean temperature for Tehran was about 1.33 warmer than Rome, which can
contribute for more photochemical FA production in Tehran (Ciobanu et al. 2015)
Photochemical oxidation reaction, which is the secondary source of FA production, can be the
main reason of differences in FA concentration between the two seasons. Photochemical
oxidation is a result of changes in meteorological parameters during the different seasons. For
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example, photochemical reaction can lead to increase FA concentration in the spring more than
the winter. This process requires to HC (gaseous hydrocarbons) and VOCS for FA production,
which vehicles are the main sources of HC emissions into the air (Andreini et al. 2000).
Possanzini et al. (2002) observed a major difference in the concentration of FA due to
photochemical oxidation variation during winter and summer seasons in Rome, Italy, and
photochemical reactions in the summer and winter contributed to about 85 and 35% of FA
production, respectively. Likewise, Sin et al. (2001) measured the maximum concentrations of
FA in the summer (Possanzini et al. 2002; Sin et al. 2001). The differences in FA concentrations
between these two seasons reflect that a major part of FA production in warm seasons is in
association with photochemical reactions. It can be concluded that the main factor in the
production of FA during winter is emissions from vehicles. During the spring, both of the
vehicles and photochemical oxidation reactions are contributing factors.
3.3 Comparative study of carbon monoxide, ozone, and nitrogen dioxide correlations
with formaldehyde
For investigating FA correlation with other pollutants and its concentration along with
comparing the sampling locations and diurnal and seasonal concentrations, the relation between
CO, O3, and NO2 concentration variations with FA were investigated. The data of mentioned
pollutants except FA (which measured as mentioned in analytical method section) were obtained
from Tehran Air Quality Control Company, which works under the Tehran municipality control.
In order to evaluate the correlations between these three pollutants with the FA, coefficients of
determination test (R2) was used. It was observed that CO had R2 equal to 0.805 and 0.389 in
winter and spring, respectively, while the corresponding values were 0.244 and 0.635 for O3,
respectively. Furthermore, statistically significant differences observed between NO2 and FA
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with coefficients of determination of 0.676 and 0.412 for winter and spring, respectively (Figures
3, 4, and 5). The concentrations of all these pollutants (CO, O3, NO2, and FA) on Fridays were
lower than other working days. Coefficients of determination for evaluating CO and NO2 with
FA chances concluded that CO and NO2 had more significant relation with FA in the winter
compared with the spring. In contrast, observing that correlations of determination between O3
and FA had not a high significant relation during the winter, whereas this relation during the
spring was more significant than the winter. Weak correlations between O3 and FA
concentrations in winter against strong correlation of CO and NO2 indicates that in this season
the main source of FA is direct emission from road vehicles (Pang and Mu 2006). Similar results
had been observed by past studies where they reported direct emissions of both the CO and NO2
from automobile sources (Granby et al. 1997). Bahez et al. (2001) measured CO in ambient air
and it was found that CO had strong correlation coefficients with FA as 0.591 and 0.885 for the 8
to 10 AM and 10 to 12 AM, respectively (Báez et al. 2001). Furthermore, Anderson and et al.
(1996) reported that because of stronger correlation between CO and FA (R=0.8) in winter than
summer, especially during daylight (Anderson et al. 1996). With season changing from winter to
spring and consequently an increase in pollutants distribution, it is expected that FA
concentration decrease. However, it was observed that its mean concentration in comparison
with winter was increased. Besides the above observation, the correlation between ozone and FA
was significantly increased. Main sources of ozone production in ambient air are photochemical
reactions particularly in higher temperatures (Zhu et al. 2015). Since this correlation can
demonstrate that both mentioned pollutants has the same production source, which is
photochemical reactions. Our results are comparable with the study of Possanzini et al. (2002)
where they found correlation between ozone and formaldehyde very weak during winter
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(R2=0.12) and rather higher (R2=0.58) during summer. Likewise, Granbly et al. (1997) reported
very high correlations as 0.92 and 0.90 during winter and summer between CO and NO2 in the
month of February, respectively. In April, the correlation between FA with nitrogen dioxide and
ozone were observed as 0.5 and 0.35, respectively, and in June correlation between FA, and CO,
NO2 and O3 observed as 0.54, 0.42 and 0.42, respectively (Granby et al. 1997). Strong
correlation between these pollutants with FA can simplify diagnosis of main FA production in
winter and spring. Therefore, it can be concluded that the main formaldehyde emissions in winter
have similar sources to CO and NO2, and in spring, it is similar to O3, NO2, and CO. For
predicting the formaldehyde's concentration variation by using three mentioned pollutants multi-
variable regression was used and for each season, it calculated separately. As it presented in
Table 5, the models have R2 of 0.935 and 0.733 (p-value<0.05). The remarkable thing in this
model is the determined coefficients of X1 (O3), X2 (CO) and X3 (NO2). In winter, the most
effective coefficients on FA concentration belong to CO, NO2, and O3, respectively, while it is
O3, CO and NO2 for spring. These results confirm the obtained R2 coefficients from Figs 3 and 4.
3.4 Relationship between meteorological parameters and FA concentrations
The effect of ambient temperature, relative humidity and pressure on concentrations
variation of FA were evaluated by using the Pearson's Correlation test. Concentrations of FA
have significant correlation with temperature changes in all of the sampling locations, but such
correlations were not observed with the relative humidity and pressure (Table 6). Relationship of
ambient temperature with the FA concentrations indicate that this parameter has an important
role in the chain of photochemical reactions, which can lead to FA production. Previous study
showed that strong relationship between increase in temperature and FA with correlation
coefficient as 0.58 (Possanzini et al. 2007). In addition, Mahmoud et al. (2002) reported positive
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relationships between temperatures and increasing concentration of carbonyl compounds and the
effect of temperature in increasing concentrations of FA. Likewise, Seo et al. (2011) did not find
relation between FA concentrations and humidity variations. (Mohamed et al. 2002; Seo and
Baek 2011). Granby et al. (1997) reported that an increase in temperature and photochemical
reaction lead to increase concentration of carbonyl compounds such as FA in spring than in
winter. The Highest diurnal concentration of FA in the winter season was obtained on 27 January
(Fig. 2) when inversion conditions persisted and temperature decreased to less than 3.5°C. Thus,
an increase in temperature not only can raise severity of photochemical reaction but also can
cause inversion condition in low temperature. The effect of inversion condition on increasing FA
concentration is observed by many studies. For example, Viskari et al. (2000) observed that the
concentration of FA increase in the inversion condition (Viskari et al. 2000). Nogueira et al.
(2014) studied formaldehyde and acetaldehyde concentrations in urban atmosphere of the
metropolitan area of Sao Paulo and observed a large increase in aldehyde level on November 23,
2012 due to thermal inversion (Nogueira et al. 2014). In addition, Slemr et al. (1996) referred to
influence of temporal inversion in winter that cause to increase of formaldehyde concentration
(Slemr et al. 1996).
4. Summary and conclusions
This study aims to quantify the FA concentration in one of the most polluted Iranian
cities, Tehran, and understand diurnal and seasonal changes in its concentration. Moreover,
influence of meteorological conditions on the concentrations of FA is assessed. The average
concentrations of FA were found to be 17.3±4.2 and 22.7±5.3 ppb during winters and summers,
respectively. These values were about 1.73 and 1.26 times upper than those reported for Rome
Italy in winter and summer, respectively (Possanzini et al. 2002).
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It was observed that the main source of FA in the winter is direct emissions from vehicles and
the important additional sources during the spring being photochemical oxidation. Moreover,
temperature and inversion conditions showed that it is difficult to ignore the importance of
meteorological condition on the variations of FA concentration.
Further studies are recommended investigating and compare the contribution of vehicles with
gasoline and diesel fuels in the direct production of FA by measuring their exhausts emissions.
Moreover, it would be useful if future studies could focus on evaluating FA concentration and its
correlation with other pollutants for the entire year through continuous measurements. Since FA
has adverse health effects and its concentration are found to considerable high in this study,
studies focusing on the evaluation of control measures (e.g. novel technologies or fuels with
better quality, catalysts in vehicle exhausts, etc.) would allow to understand the relative benefits
of these methods in terms of controlling FA emissions at city scale.
5. Acknowledgments
This research has been supported by the Center for Air Pollution Research (CAPR), Institute for
Environmental Research (IER), Tehran University of Medical Sciences (Grant # 94-02-46-30306).
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Table 1. Average temperature (°C), relative humidity (RH, %) and pressure (atm) at sampling
locations in the winter and spring seasons.
Number of sample
Pressure (atm)RH (%)Temperature (°C)SeasonSampling location
100.869348WinterEnghlab Square
100.8751924Spring100.8722610WinterAzadi Square 100.8781727Spring100.8333010WinterTajrish Square 100.8341926Spring100.8832411WinterShosh Square 100.8781728Spring100.860299WinterThree Ways Tehran Pars100.8661826Spring40.871379WinterPark Lale 40.8782321Spring
Table 2. Summary of FA concentrations (ppb) in different sampling locations.
Site A B C D E FWinter
Mean(SD) 20.2(±4.3) 17.4(±4.5) 18.1(±4.35) 15.1(±3.38) 15.8(±3.22) 3.5
Max 30 27 28 20 22 3.5
Min 13 10 11 9 10 3.5Spring
Mean(SD) 25.5(±5.4) 23.3(±4.77) 22.5(±5.99) 20.2(±5.05) 21.9(±4.95) 3.5
Max 33 30 31 27 29 7
Min 14 13 11 10 12 3.5
Note: In this study, lowest concentration that can be detected by chromotropic acid method, was 7
ppb. Therefore, concetrations that were lower than 7 ppb were considered as 3.5 ppb(Vogelgesang
and Hädrich 1998).
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Table 3. ANOVA analysis for comparing average concentration of FA in sampling site.Statistical analysis Season Sampling location F P-Value
One - Way ANOVA
Winter A,B, C, D and E Areas 2.36 0.061
Spring A, B, C, D and E Areas 1.30 0.282
Winter A, B, C, D, E and F Areas 9.50 <0.05
Spring A, B, C, D, E and F Areas 9.55 <0.05
Table 4. Paired T-test for comparing the average concentration of FA in winter and spring
P-Value95% Confidence Interval
of the DifferenceMeans Difference
MeanSpring
MeanWinterStatistical analysis
UpperLower
<0.05-4.5-6.7-5.422.717.3T- test
Table 5. Multi variable regression model for independent variables (O3, CO and NO2) and dependent variable (FA).
Model(winter)
R R2 F Sig0.967 0.935 28.817 0.001
Y=0.092X1+0.688X2+0.309X3-2.707
Model(spring)
R R2 F Sig0.879 0.773 6.793 0.023
Y=0.454X1+0.377X2+0.274X3-15.481
336
337
338
339
340
341342
343
344
Fig. 1. Sampling locations for measuring FA, O3, NO2, and CO concentrations and determining meteorological parameter (air temperature, humidity, and pressure) in Tehran city
345
346347
348
22-D
ec
28-D
ec03
-Jan09
-Jan15
-Jan21
-Jan27
-Jan
02-F
eb
08-F
eb
14-F
eb
27-A
pr
03-M
ay
09-M
ay
15-M
ay
21-M
ay
27-M
ay02
-Jun08
-Jun14
-Jun20
-Jun
05
101520253035
05101520253035
Formaldehyde Temparature
Dayes of Sampling
Form
alde
hyde
(ppb
)
Tem
prat
ure
(C)
22-D
ec
28-D
ec03
-Jan09
-Jan15
-Jan21
-Jan27
-Jan
02-F
eb
08-F
eb
14-F
eb
27-A
pr
03-M
ay
09-M
ay
15-M
ay
21-M
ay
27-M
ay02
-Jun08
-Jun14
-Jun20
-Jun
05
101520253035
0
0.1
0.2
0.3
0.4
0.5
Formaldehyde Humidity
Dayes of Sampling
Form
alde
hyde
(ppb
)
Hum
idity
(%)
22-D
ec
28-D
ec03
-Jan09
-Jan15
-Jan21
-Jan27
-Jan
02-F
eb
08-F
eb
14-F
eb
27-A
pr
03-M
ay
09-M
ay
15-M
ay
21-M
ay
27-M
ay02
-Jun08
-Jun14
-Jun20
-Jun
05
101520253035
0.8580.860.8620.8640.8660.8680.87
Formaldehyde Pressure
Dayes of Sampling
Form
alde
hyde
(ppb
)
Pres
sure
(atm
)
349
350
351
Fig. 2. Diurnal variations of FA concentrations, ambient temperature, pressure and relative humidity.
5.0 10.0 15.0 20.0 25.0 30.0 35.00
10
20
30
40
50
60
051015202530354045
f(x) = 1.23658137278681 x + 1.06987387824399R² = 0.237763069451086
f(x) = 1.06471881606765 x + 18.6648828752643R² = 0.635345440687394
Spring Linear (Spring) Linear (Spring)Winter Linear (Winter) Linear (Winter)
Formaldehyde concentration (ppb)
O3
conc
entr
atio
ns in
spri
ng (p
pb)
O3
conc
entr
atio
ns in
win
er (p
pb)
Fig. 3. Relation between concentration chances of O3 with FA in spring and winter seasons.
5.0 10.0 15.0 20.0 25.0 30.0 35.00
5
10
15
20
25
30
35
40
45
0
10
20
30
40
50
60
70
80
f(x) = 3.29879335435363 x − 8.36014916323065R² = 0.676283347939482f(x) = 0.629682875264271 x + 20.1781987315011
R² = 0.412691356332362
Spring Linear (Spring) Linear (Spring)Winter Linear (Winter)
Formaldehyde concentration (ppb)
NO
2 co
ncen
trat
ions
in sp
ring
(ppb
)
NO
2 co
ncen
trat
ions
in w
iner
(ppb
)
Fig. 4. Relation between concentration chances of NO2 with FA in spring and winter seasons.
352353
354
355
356
357
358
5.0 10.0 15.0 20.0 25.0 30.0 35.00
1
2
3
4
0
1
2
3
4
5
6
7
f(x) = 0.179073490177056 x + 1.24781008974048R² = 0.855019938161445
f(x) = 0.0533209302325581 x + 1.96641488372093R² = 0.389539199311023
Spring Linear (Spring) Linear (Spring)Winter Linear (Winter)
Formaldehyde concentration (ppb)
CO
con
cent
ratio
ns in
spri
ng (p
pb)
CO
con
cent
ratio
ns in
win
er (p
pb)
Fig. 5. Relation between concentration chances of CO with FA in spring and winter seasons.
6. ReferencesPrimary Sources
Secondary Sources
Uncategorized References
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