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: hdehghani@tums.ac.ir

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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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