AMBIENT VOLATILE ORGANIC COMPOUND (VOC) CONCENTRATIONS AROUND A

PETROCHEMICAL PLANT

by

Eylem ÇETİN

July, 2002

İZMİR

ABSTRACT

Volatile organic compounds (VOCs) make up a major class of air pollutants.

Petrochemical industries and petroleum refineries are large industrial installations

emitting significant amounts of VOCs. Air samples were collected between

September 2000 and September 2001 in Izmir at three sampling sites located around

a petrochemical industry and an oil refinery to measure ambient concentrations of

VOCs, sulfur dioxide and mercaptans.

Total volatile organic compound concentrations (average±SD) were 165.3±188.5,

114.3±153.6, and 91.7±91.2 µg/m3 for Site 1, Site 2, and Site 3, respectively. Site 1

had the highest average concentration because during most of the sampling program

it was affected by petrochemical plant and refinery emissions (when the wind was

from NE). At all sites all hydrocarbon groups showed seasonal variation. VOC

concentrations generally increased with temperature. However, temperature

accounted only 3-30% for the variability in ambient concentrations of VOCs. When

wind speed was ≥5 m/s, concentrations were higher for all sites and all VOC groups

compared to those measured at lower wind speeds. VOC concentrations measured in

this study around the petrochemical plant and oil refinery were 5-20 times lower than

those measured in urban Izmir sites and they were 3-20 times higher than the

concentrations measured in Buca suburban site. Benzene, toluene, ethyl benzene, and

xylene concentrations measured in this study were 2-5 times higher than those

measured around an oil refinery in Greece. Concentrations of all VOCs for all

sampling sites were much lower than the limit values given in Turkish Air Quality

Protection Regulation.

Sulfur dioxide concentrations measured in this study were ranged from 1 to 934

µg/m3 (average±SD, 87±133 µg/m3). The highest sulfur dioxide concentrations at all

sites were measured when the wind direction was NE indicating the effect of

petrochemical plant and refinery emissions. Average SO2 concentrations for all

sampling sites were below the long-term ambient air limit value for industrial

regions.

Mercaptan concentrations ranged between 65 and 1462 µg/m3. Butanethiol was

the most abundant mercaptan followed by methanethiol. Mercaptan concentrations

measured at all sampling sites were significantly higher than the limit values.

ÖZET

Uçucu organik bileşikler (VOC), hava kirleticilerinin önemli bir sınıfını

oluşturmaktadırlar. Petrokimya endüstrileri ve petrol rafinerileri önemli miktarlarda

hidrokarbon emisyonları yayınlayan büyük endüstriyel kuruluşlardır. Uçucu organik

bileşikler, kükürtdioksit ve merkaptanların havadaki konsantrasyonlarını ölçmek için

Eylül 2000 ile Eylül 2001 tarihleri arasında İzmir yakınlarındaki bir petrokimya

endüstrisi ve petrol rafinerisi etrafındaki üç noktada hava örnekleri toplanmıştır.

Sırasıyla 1 no’lu, 2 no’lu, 3 no’lu örnekleme noktaları için toplam uçucu organik

bileşik konsantrasyonları (Ortalama±SS) 165.3±188.5, 114.3±153.6, ve 91.7±91.2

µg/m3’dır. 1 no’lu örnekleme noktasında en yüksek ortalama konsantrasyon

bulunmasının nedeni örnekleme programı boyunca çoğunlukla petrokimya tesisi ve

petrol rafinerisinden etkilenmesidir (rüzgar NE yönünden estiğinde). Bütün ölçüm

noktalarında bütün hidrokarbon grupları mevsimsel değişim göstermektedir. Bunun

nedeni yüksek sıcaklıklarda buharlaşma nedeniyle VOC konsantrasyonlarının

artması olabilir. Sıcaklık, VOC konsantrasyonlarındaki degişimin %3-30’unu

açıklayabilmektedir. Bütün örnekleme noktalarında rüzgar hızı ≥5 m/s olduğu

durumlarda bütün VOC gruplarının konsantrasyonlarının düşük rüzgar

hızlarındakilere kıyasla yüksek olduğu bulunmuştur. Bu çalışmada petrokimya tesisi

ve petrol rafinerisi etrafında ölçülen VOC konsantrasyonları, İzmir’de kentiçi

ölçümlerinde bulunan değerlerden 5-20 kat daha azdır, Buca’da ölçülen değerlerden

ise 3-20 kat daha fazladır. Bu çalışmada bulunan benzen, toluen, etil benzen ve

ksilen konsantrasyonları, Yunanistan’da bulunan bir petrol rafinerisi etrafında

ölçülen değerlerden 2-5 kat daha fazladır. Bütün ölçüm noktalarında bulunan bütün

VOC konsantrasyonları Hava Kalitesi Korunması Yönetmeliği’nde verilen sınır

değerlerden daha düşüktür.

Bu çalışmada ölçülen SO2 konsantrasyonları 1 ile 934 µg/m3 (ortalama±SS,

87±133 µg/m3) değerleri arasında değişmiştir. Rüzgar yönünün NE olduğu

durumlarda petrokimya endüstrisi ve petrol rafinerisinin etkisi nedeniyle bütün

ölçüm noktalarında en yüksek kükürt dioksit konsantrasyonu bulunmuştur. Bütün

ölçüm noktaları için bulunan ortalama SO2 konsantrasyonları endüstri bölgeleri için

verilen uzun vadeli hava kalitesi sınır değerinin altındadır.

Merkaptan konsantrasyonları 65 ile 1462 µg/m3 değerleri arasında değişmiştir.

Konsantrasyonu en yüksek olan bileşik butil merkaptandır, bunu metil merkaptan

izlemiştir. Bütün ölçüm noktalarında bulunan merkaptan konsantrasyonları sınır

değerlerin çok üzerindedir.

1. Introduction

Petroleum refineries and petrochemical industries are generally large industrial

installations. Their operation is associated with the emission of various organic

compounds into the atmosphere, mainly originating from the production processes,

the storage tanks and the waste areas (Kalabokas et al., 2001). The province of the

petrochemical industry is production of chemicals from petroleum feedstocks

(Barnes et al., 1984). Most of the organic compounds are derived from petroleum

fractions, and actually from only a few basic hydrocarbons including methane,

ethane, propane, benzene, toluene, and xylene (Crosby, 1998). Petroleum refining is

the physical, thermal, and chemical separation of crude oil into its major distillation

fractions. The primary products of the industry fall into three major categories (EPA,

1995): fuels (motor gasoline, diesel and distillate fuel oil, liquefied petroleum gas, jet

fuel, residual fuel oil, kerosene, and coke), finished non-fuel products (solvents,

lubricating oils, greases, petroleum wax, petroleum jelly, asphalt, and coke),

chemical industry feed stocks (naphtha, ethane, propane, butane, ethylene, propylene,

butylenes, butadiene, benzene, toluene, and xylene). Air emissions from refineries

include fugitive emissions, emissions from the burning of fuels in process heaters,

and emissions from the various refinery processes (EPA, 1995).

Although some VOCs are emitted from large sources, most are emitted from

small sources. The variety of sources is quite large (Nevers, 1995). Some VOCs are

powerful infrared absorbers and thus contribute to the greenhouse problem. Some are

known to be toxic or carcinogenic (Nevers, 1995). VOCs are recognized to be

important precursors of tropospheric ozone, as well as other oxidants and organic

aerosols (WMO, 2001). Since they are associated with many adverse effects in the

atmosphere VOC emissions should be controlled. Some of control options can be

used for VOC emissions are (Nevers, 1995): substitution, leakage control, adsorption

and recycling, incineration, condensation, process modification. Volatile organic

compound concentrations have been determined in urban, suburban, and industrial

areas throughout the world.

The major sources of atmospheric sulfur dioxide can be divided into two

categories: stationary and mobile sources. Stationary sources include residential

heating, industries, power and heat generation, incineration and open fires. Mobile

sources are the motor vehicle engines (Bagıroz, 2002). The sources for sulfur dioxide

in the atmosphere also include the sea, volcanic activity, and biomass decay

processes (WMO, 2001). Sulfur dioxide also plays a significant role in producing

acid deposition by forming sulfate particles.

Mercaptans are organic sulfur containing odorous substances that are emitted

from industrial or biogenic sources. Most of the odorous substances derived from

anaerobic decomposition of organic matter contain sulfur and nitrogen (Buonicore

and Davis, 1992). In the literature related to environmental evaluations around

industries, kraft pulp and paper mills, rayon and other artificial fiber plants have the

priority (Muezzinoglu, 2002). Petroleum refineries also emit significant amounts of

mercaptans (Buonicore and Davis, 1992).

The objectives of this work were: to measure VOC, sulfur dioxide, and mercaptan

concentrations around a petrochemical industry and a petroleum refinery; to

investigate the effect of meteorological parameters (wind speed, wind direction and

temperature) on the measured concentrations; and to compare the measured

concentrations with the regulated and literature values.

Ambient air samples were collected between September 2000 and September

2001. The air sampling was carried out at three selected sites around the

petrochemical industry and the oil refinery. Figure 1 shows the study area. Sampling

site 1 was located at the dock of the petrochemical plant at the geographical

coordinates (X, Y) 493512 m, 4292186 m. Since the prevailing wind direction in the

area was NE and followed by SW, this site located at SW of the petrochemical plant

and the oil refinery was selected to investigate the effect of both plants on the

ambient VOC concentrations. When the wind direction is SW, this site is expected to

represent the background levels that are not effected by the petrochemical complex.

Site 2 was located between the petrochemical industry and the petroleum refinery at

the geographical coordinates (X, Y) 494961 m, 4294151 m (Figure 1). When wind is

from NE, Site 2 is affected by the refinery emissions, and when the wind is from SW

this site is affected by petrochemical plant emissions. Site 3 was selected at the

housing area of the petrochemical plant located at the south of the petrochemical

complex at the geographical coordinates (X, Y) 494702 m, 4292363 m. This site was

selected to investigate the impacts of the industries on the housing area when the

wind blew from northerly directions. Geographical coordinate measurements were

performed by means of GPS 12 (Garmin). During the sampling program 26 VOC

samples were collected for each sampling site. A total number of 78 VOC samples,

64 sulfur dioxide samples, and 7 mercaptan samples were collected. Mercaptan

samples were collected when the wind was from NE to determine the effect of the

refinery on the ambient levels of these compounds. All samples were collected

during daytime when there was no rain or threat of rain. Elevation of the sample inlet

was 1.5 m from the ground level. The meteorological measurements were performed

using an anemometer (Testo 451) equipped with humidity and temperature sensors at

the beginning of each sampling. The ambient air concentrations of the following

volatile organic compounds were measured: benzene, toluene, p,m,o-xylenes, ethyl

benzene, 1,2,3-trimethyl benzene, isopropyl benzene, n-hexane, ethylene dichloride,

ethyl alcohol, n-butyl alcohol, ethyl acetate, n-butyl acetate, acetone, and isobutyl

methyl ketone.

Figure 1. General layout of the study area

2. Materials and Methods

2.1. Volatile Organic Compounds

An active sampling method with special charcoal tubes was used to collect

airborne VOCs. Sampling and analysis of volatile organic compounds in ambient

samples were conducted in accordance with the NIOSH Method 2549 (NMAM,

1996). Charcoal tubes (Drager-NIOSH) containing 150 mg of activated carbon in

two successive sections were used for sampling. Air samples were drawn through the

tubes using a special vacuum pump with flow control. The ambient VOC samples

were efficiently retained at flow rates between 0.5 to 3.0 L min-1 and sampling time

was ranged between 130 and 1680 min. The caps of the sampling tubes were

removed immediately before sampling. Sampler was attached to the sampling pump

using flexible tubing. A calcium chloride trap was used during the sampling to

remove moisture. A glass suction pipe ending with an inverted glass funnel was used

to prevent precipitation to enter the system.

N

The adsorption tubes after the sampling were labeled and closed with special caps

to avoid contamination and desorption. The samplers were transferred to the

laboratory in cold boxes. The samples were placed into tightly closed special plastic

bags and kept in a freezer until they were processed.

Before analysis, all sample tubes were taken from the freezer, contents of both

sections of the adsorber tubes were emptied into two different vials in which they

were weighed, 0.5 or 1.0 mL carbon disulfide was added as extraction solvent then

they were reweighed. Samples were extracted in an ultrasonic bath for 15 min. Then

they were centrifuged for another 15 min to obtain a clear phase at the top. These

vials were stored in a freezer until they were injected into the GC. For GC injection,

carbon disulfide extracts were drawn into a micro-syringe. The micro-syringe was

washed two times with the sample, washings were discarded successively and finally

3.0 µL of sample extract was injected into the GC. After injection, GC was started.

The peaks were monitored on the computer connected to GC and the peak areas were

calculated using the PCI software. The injector was cleaned with acetone after every

injection. Samples were analyzed for VOCs using a gas chromatograph (Chrompack,

CP 9000) equipped with a FID detector. A capillary GC column (Chrompack WCOT

FUSED SILICA, 50mx0.32 mm ID) was used with an initial oven temperature of

40°C and then raised to 120 °C at a rate of 5 °C min-1. Chromatographic grade pure

hydrogen, and air were used for the FID flame while pure nitrogen was used as the as

carrier gas with a split ratio of 1:5. The GC was connected to a computer to store and

evaluate the output data.

The calibration was performed using different levels of standard solutions in

carbon disulfide. Liquid-phase standards were prepared by placing known volumes

of chromatographic grade pure benzene, toluene, p,m,o-xylenes, ethyl benzene,

1,2,3-trimethyl benzene, isopropyl benzene, n-hexane, ethylene dichloride, ethyl

alcohol, n-butyl alcohol, ethyl acetate, n-butyl acetate, acetone, isobutyl methyl

ketone into vials and diluting with carbon disulfide. Three microliters of these

standard solutions were injected into the GC and run at selected conditions. Four

levels of calibration standards (0.006 µL/mL, 0.03 µL/mL, 0.09µL/mL, 0.15µL/mL)

were used to prepare the calibration curves. The concentrations of the analytes in the

calibration solutions were calculated using their densities. The calibration curve was

confirmed daily by analyzing a midrange standard solution. In all cases linear fit was

good with r2> 0.99. VOCs in samples were identified by comparing their retention

times to the ones obtained from the runs of calibration standards under specified

chromatographic conditions. Identified compounds quantified using their peak areas

by the external calibration method. Amounts of VOCs in samples were calculated

using the linear regression equations obtained from calibration curve.

2.2. Mercaptans

Sampling and analysis of mercaptans in ambient samples were conducted in

accordance with the NIOSH Method 2542 (NMAM, 1994). The filters used in

sampling were prepared by immersing 47-mm glass fiber filters (Sartorius AG) in

5% (w/v) aqueous solution of mercuric acetate. Then, the filters were allowed to dry

at room temperature, assembled in two-piece filter cassettes, and sealed with plugs.

The filters were exhibited a yellowish color that does not affect their collection

efficiency (NMAM, 1994). The plugs were removed from the filter cassette

immediately before sampling. The cassette was connected to the sampling pump with

flexible tubing. Silica gel was used during the sampling to protect the pump from

moisture. Samples were efficiently retained at flow rate between 1.4 and to 3.5

L/min. The sampling time ranged between 145 and 220 min and the total volume of

air sampled was between 290 and to 510 L. The plugs were replaced into the filter

cassette immediately after sampling. The samples were stored in the dark.

20 mL of 25% (v/v) hydrochloric acid and 5 mL of 1,2-dichloroethane were

added to a 30 mL separatory funnel. Sample filter was fold and inserted into the neck

of the separatory funnel, without allowing the filter to become wet. The filter was

pushed into the funnel while placing the stopper. Funnel was shaken for 2 min

without venting. It was left to stand at least 5 min, until the phases completely

separated. Then the 1,2-dichloroethane was drained into a vial and sealed using a cap

with a TFE liner. Sample extracts were analyzed with a gas chromatograph equipped

with an FPD-S detector (Muezzinoglu, 2002). Analytical work for mercaptans was

carried out by a Carlo Erba HRGC 5300 Mega series gas chromatograph with FPD-

sulfur and FID detectors using hydrogen as fuel. A fused silica capillary column (50

m, 0.25 mm ID, Permabond lining) was used. Two microliters of the sample extracts

were injected into the GC at 1:10 split ratio. A temperature program of 76 minutes

was set by holding the oven temperature for 5 minutes at 40 °C, 2 °C/min to 150 °C,

holding for 1 minute, and 15°C/min to 240 °C for cleaning the column. Analyses of

mercaptans were conducted at the Stuttgart University, Germany. Gas-phase

standards were prepared by injecting known volumes of chromatographic grade pure

methanethiol, ethanethiol, 2-propanethiol, 2-butanethiol, as well as dimethyl sulfide

and dimethyl disulfide into a quartz gas chamber at successive steps. After each

addition the mixture was heated to evaporate the added chemicals, and obtained gas

mixtures were analyzed with the same procedure. Resulting chromatograms were

studied for the successive retention times as well as for determination of

concentrations of the compounds analyzed. Retention times were also confirmed

using a GC-MS. In this configuration methanethiol, ethanethiol, 2-propanethiol,

dimethyl sulfide, 2-butanethiol and dimethyl disulfide were tested. However,

ethanethiol, 2-propanethiol, dimethyl disulfide were not detected in samples. The

samples were also analyzed using a GC (HP 5890) equipped with a chemilumiscence

detector to find additional organic sulfur compounds (2-propanethiol, 2-methyl-2-

propanethiol, thiophene, diethylsulfide, 2-methylthiophene, diphenylsulfide). Among

them only 2-propanethiol could be detected in the samples.

2.3. Sulfur Dioxide

ASTM Method D 2914-78 was used for sampling and analysis of sulfur dioxide

in ambient air (ASTM, 1988). Sulfur dioxide (SO2) was sampled by drawing a

measured volume of air through a tetrachloromercurate (TCM) solution, resulting in

the formation of a dichlorosulfitomercurate complex. The temperature of the

impinging solution should be maintained below 25 °C during sampling, transporting

to the laboratory, and storage prior to analysis, to avoid loss of SO2. 100 mL of TCM

solution was added to a midget impinger and it was inserted into the sampling

system. The sample was efficiently retained at flow rate between 0.4 and to 3.0 L

min-1 and the sampling time ranged between 133 and 1680 min. The absorbing

reagent was shielded from direct sunlight during and after sampling by covering the

impinger to prevent deterioration. After the sampling, the impinger was removed and

stoppered. The temperature of the samples was kept below 25 °C using refrigerated

shipping containers to transport them from the field. Solutions of

dichlorosulfitomercurate are relatively stable. When stored at 5 °C for 30 days, no

detectable losses of SO2 occur.

For each set of determinations, a reagent blank was prepared by adding 10 mL of

the absorbing reagent to a 25 mL volumetric flask. To each flask containing 10 mL

of the sample, 1 mL of 0.6% sulfamic acid was added and allowed to react for 10

min to destroy the nitrite from oxides of nitrogen. Two milliliters of 0.2%

formaldehyde, then 5 mL of pararosaniline reagent were added and mixed well. A

laboratory timer that has been set for 30 min was started. All flasks were brought to

volume with distilled water. After 30 min, the absorbance of the sample and the

blank were determined at 548 nm. Water was used in the reference cell. The

concentration of the SO2 in the sample was determined from the calibration curve.

Graduated amounts of the dilute standard sulfite solution were pipeted into a serious

of volumetric flasks (1, 5, 10, and, 20 mL). Sufficient TCM solutions were added to

bring each flask to about 10 mL. The remaining reagents were added as described

above. The absorbances against the corresponding SO2 concentrations (0.1, 0.5, 1.0,

and 2.0 mg/mL) were plotted. In all cases linear fit was good (r2>0.99). Ambient

concentrations (C, µg/m3) of the compounds analyzed in this study were calculated

as follows:

C (µg/m3) = m/V

where m is the mass of the analyte (µg) in the sample and V (m3) is the sampled air

volume.

2.4. Quality Control

A midrange calibration standard containing 0.03 µL/mL of VOCs was analyzed

everyday to confirm the system performance. If the percent difference of response

factor of any compounds was greater than 20%, the initial calibration was assumed to

be invalid, and system was recalibrated. Identification of individual VOCs was based

on their retention times obtained from calibration runs. If the percent difference of

the retention time of any compound was greater than 5%, the compound could not be

identified.

Extraction solvent (carbon disulfide) was analyzed to determine if there was any

contamination in CS2. None of the compounds analyzed in this study were detected

in CS2. Blank activated carbon tubes were also extracted and analyzed as process

blanks to determine if there was any contamination in the activated carbon tubes. No

contamination was found in the process blanks. Recently, recovery efficiencies of

various VOCs were determined for the analytical method used in the current study

(Cetin, 1999). Average desorption efficiency was determined as 71%, 85%, 86%,

99% for isobutyl methyl ketone, xylene, benzene, and hexane, respectively. Since the

recoveries were found high, no recovery correction was made for samples.

Back-up sections of adsorbent tubes used in sampling were also extracted and

analyzed. VOC amounts in the back-up sections were below the detection limit.

Some of the samples were analyzed in duplicate. The differences in duplicate

samples were less than 5%.

For mercaptan analyses, a suitable number of unexposed filters that were brought

to the field, as well as unused reagent blanks were also analyzed. None of the

compounds analyzed were detected in field and reagent blanks.

3. Results and Discussion

3.1. Spatial and Temporal Variation of VOC

Total VOCs refer to sum of 16 compounds analyzed in this study. Total volatile

organic compound concentrations (average±SD) were 165.3±188.5, 114.3±153.6,

and 91.7±91.2 µg/m3 for Site 1, Site 2, and Site 3, respectively (Table 1). The

prevailing wind direction during the sampling program was NE and it was followed

by SW (Figure 2). The highest total VOC concentration was measured at Site1

followed by Site 2. Site 1 had the highest average concentration because during most

of the sampling program it was affected by petrochemical plant and refinery

emissions (when the wind was from NE) (Figure 2 and Figure 3). However, Site 2,

having the second highest average total VOC concentration was affected either by

petrochemical plant emissions (when the wind was from SW) or refinery emissions

(when the wind was from NE or NW). The highest concentrations at Sites 1 and 2

were observed for northerly wind directions. Concentration at Site 3 was relatively

lower than other sites as expected. Site 3 was located at SE of the sources

investigated and the other sampling sites. Therefore, Site 3 was affected relatively

less from petrochemical plant and refinery emissions since the wind was mostly from

NE or SW during the sampling program. The highest concentrations at Site 3 were

measured when the wind direction was NW (Figure 3). The total VOC

concentrations measured at Sites 1 and 3 when the wind was from SE were probably

due to the emissions from the highway located at the south of these sites.

Table 1. Summary of total VOC concentrations at the sampling sites (µg/m3)

Sites Average SD Max Min Median Number of Samples

Site1 165.3 188.5 736.9 28.5 85.9 25

Site2 114.3 153.6 680.1 1.1 47.2 26

Site3 91.6 91.2 359.7 6.6 64.4 26

Figure 2. Rose diagram of wind direction (%) for the sampling program

N

↑

Figure 3. Rose diagrams of total VOC concentration (µg/m3) for the sampling

sites

Since o-xylene, m-xylene and isopropyl benzene were co-eluted from the

chromatographic column used in this study, their concentrations were reported as the

• Site 1

• Site 3

• Site 2

Petroleum Refinery

Petrochemical Plant

0

100

200

300N

NE

E

SE

S

SW

W

NW

0100200300

N

NE

E

SE

S

SW

W

NW

0

100200

300N

NE

E

SE

S

SW

W

NW

0

10

20

30

40N

NE

E

SE

S

SW

W

NW

sum of these three compounds. Figure 4 shows the average concentrations of

individual VOCs. Ethylene dichloride was the most abundant volatile organic

compound followed by ethyl alcohol and acetone (Figure 4). High ethylene

dichloride and ethyl alcohol concentrations were probably due to the fugitive

emissions from ethylene process used in the petrochemical plant.

Figure 4. Concentrations of individual VOCs. Error bars represent 1 SD.

The VOCs measured in this study were classified into four different categories

for a more detailed examination of their observed concentrations: aromatics

(benzene, toluene, m,o,p-xylenes, ethyl benzene, 1,2,3-trimethyl benzene, and

isopropyl benzene), oxygenated VOCs (ethyl alcohol, acetone, ethyl acetate, n-butyl

alcohol, isobutyl methyl ketone, and butyl acetate), saturated hydrocarbons (hexane),

and chlorinated hydrocarbons (ethylene dichloride). This classification can be

justified by their common physico-chemical properties and their different origin in

the atmosphere (Kalabokas et al., 2001). Aromatic hydrocarbon concentrations

ranged from 0.44 to 251.1 µg/m3, (average±SD, 43.5±58.1 µg/m3), oxygenated

hydrocarbon concentrations ranged from 0.49 to 438.4 µg/m3 (53.0±69.9 µg/m3).

Oxygenated hydrocarbons were the most abundant hydrocarbon group followed by

aromatic hydrocarbons and ethylene dichloride (Figure 5). Aromatic hydrocarbon

concentration was the highest at Site1 and followed by Site 2, probably due to the

predominant wind direction (NE) carrying the emissions from the petrochemical

0

20

40

60

80

100

120

Benz To

l

p-X

E Be

nz

1,2,

3-TM

B

m-X

o-X

IPB

EDC

E A

lc

Ace

tone Hxn

E A

ct

B A

lc

IBM

K

B A

ct

Conc

entra

tion

(µg/

m3 )

plant and refinery. Concentration of oxygenated hydrocarbons was the highest at Site

2 followed by Site 1 and Site 3 (Figure 6).

Figure 5. Concentrations of VOC groups (µg/m3). Error bars represent 1 SD.

Figure 6. Concentrations of VOC groups at the sampling sites (µg/m3). Error

bars represent 1 SD.

Concentration of ethylene dichloride was the highest at Site 1 followed by Site 3.

Ethylene dichloride is mainly emitted from petrochemical industry. Therefore,

concentrations at Site 1 and Site 3 were higher than those measured at Site 2 (Figure

7). At all sites all hydrocarbon groups showed seasonal variation. Concentrations of

aromatic hydrocarbons, oxygenated hydrocarbons, and ethylene dichloride, were the

highest in summer followed by autumn. However hexane showed a different pattern.

The highest average hexane concentrations were measured in winter at Site 1 and in

0153045607590

105120

Aromatic EDC n-Hexane Oxygenated

Con

cent

ratio

n (µ

g/m

3 ) n=71 n=53

n=55

n=77

0153045607590

105120135150

Aromatic EDC n-Hexane Oxygenated

Con

cent

ratio

n (µ

g/m

3 ) Site1 Site2 Site3

n=25, 23, 23 n=24, 10, 19 n=19, 17, 19 n=25, 26, 26

autumn at Sites 2 and 3. Higher concentrations measured in summer and autumn may

be in part due to the increased evaporation as a result of higher temperatures.

Figure 7. Seasonal variation of VOC concentrations at the sampling sites

Site1

0

50

100

150

200

250

300

Wınter Spring Summer Autumn

Con

cent

ratio

n (µ

g/m

3 )

Aromatic HydrocarbonsEthylene Dichloriden-HexaneOxygenated Hydrocarbons

Site2

0

50

100

150

200

250

300

Wınter Spring Summer Autumn

Con

cent

ratio

n (µ

g/m

3 )

Aromatic Hydrocarbons

Ethylene Dichloride

n-Hexane

Oxygenated Hydrocarbons

Site3

0

20

40

60

80

100

120

140

Wınter Spring Summer Autumn

Con

cent

ratio

n (µ

g/m

3 )

Aromatic HydrocarbonsEthylene Dichloriden-HexaneOxygenated Hydrocarbons

n=8, 8, 6, 8 n=7, 7, 5, 7 n=4, 3, 3, 4 n=6, 6, 5, 6

n=8, 0, 2, 9 n=7, 3, 6, 7 n=3, 3, 4, 4 n=5, 4, 5, 6

n=7, 4, 4, 9 n=7, 7, 7, 7 n=4, 4, 4, 4 n=5, 4, 4, 6

3.2. Effect of Temperature and Wind Speed

The relationship between temperature and VOC concentrations was investigated

using linear regression analysis. The average total VOC concentration for the three

sampling sites was positively correlated with the temperature (r2=0.21) (Figure 8)

indicating that the measured VOC concentration increased with temperature. The

correlation coefficients for separate plots of VOC concentration vs. temperature were

0.12, 0.04, and 0.30 for the Sites 1, 2, and 3 respectively. The relationship between

temperature and the concentrations of VOC groups measured at different sites was

also investigated. VOC concentrations generally increased with temperature.

However, temperature accounted only 3-30% for the variability in ambient

concentrations of VOCs. These results indicated that the VOC emissions may

increase as a result of evaporation during the periods with relatively higher

temperatures.

Figure 8. Relationship between the total VOC concentration and temperature

The relationship between wind speed and VOC concentrations was also

investigated by separating the measurements on the basis of wind speed (Figure 9).

Wind velocities equal or higher than the 5 m/s were classified as strong winds while

wind speeds smaller than 5m/s were characterized as weak winds. High wind speeds

generally result in higher dispersion conditions. Therefore, a decrease in VOC

y = 6.7 x - 10.2R2 = 0.21

0

100

200

300

400

500

600

700

800

5 10 15 20 25 30 35

Temperature (°C)

Tota

l VO

C C

once

ntra

tion

(µg/

m3 )

concentrations may be expected during the periods with high wind speeds. However,

when wind speed was ≥5 m/s, concentrations were relatively higher for all sites and

all VOC groups (Figure 9). When the wind speed is high the plume rise and the touch

down distance from the stack is decreased resulting in higher concentrations at close

distances to the source. Therefore, the higher concentrations measured in this study

for the winds ≥5 m/s may be due to the proximity of the sampling sites to the

emission sources.

Figure 9. VOC concentrations at different wind speed ranges for the sampling

sites

Site1

0

50

100

150

200

250

<5 >5Wind Speed (m/s)C

once

ntra

tion

(µg/

m3 )

Aromatic Hydrocarbons

Ethylene Dichloride

n-Hexane

Oxygenated Hydrocarbons

Site2

0

50

100

150

200

250

300

<5 >5Wind Speed (m/s)

Con

cent

ratio

n (µ

g/m

3 ) Aromatic Hydrocarbons

Ethylene Dichloride

n-Hexane

Oxygenated Hydrocarbons

Site3

0

20

40

60

80

100

120

<5 >5Wind Speed (m/s)

Con

cent

ratio

n (µ

g/m

3)

Aromatic HydrocarbonsEthylene Dichloriden-HexaneOxygenated Hydrocarbons

n= 14, 13, 10, 14 n= 11, 11, 9, 11

n= 16, 4, 11, 19 n= 7, 6, 6, 7

n= 20, 16, 16, 22 n= 3, 3, 3, 4

3.3. Comparison of the VOC Concentrations with Urban, Suburban, and

Industrial Site Measurements

A summary of VOC concentrations measured in this study and previously in

urban, suburban, industrial areas, and near an oil-refinery is presented in Table 2.

VOC concentrations measured in this study around the petrochemical plant and oil

refinery were 5-20 times lower than those measured in urban Izmir sites and they

were 3-20 times higher than the concentrations measured in Buca suburban site.

Average hexane concentration in this study (4.1 µg/m3) was similar to the value

measured around a Greek oil refinery (5.1 µg/m3) (Kalabokas et al., 2001). However,

benzene, toluene, ethyl benzene, and xylene concentrations measured in this study

were 2-5 times higher than those reported by Kalabokas et al. (2001). VOC

concentrations measured in this study were comparable to the ones measured at an

industrial site in Korea located near a petrochemical complex (Na et al., 2001).

Measured VOC concentrations were compared with the limit values given in Turkish

Air Quality Protection Regulation (1986). Concentrations of all VOCs for all

sampling sites were much lower than the limit values. The closest concentrations to

the limit values were measured for ethyl benzene (9.3 µg/m3) and 1,2,3-

trimetylbenzene (8.3 µg/m3) at Site 2.

Table 2. Summary of VOC concentrations (µg/m3, average±SD) measured in this study and previous studies

Reference Location Hexane Benzene Toluene Ethyl

Benzene m,p-Xylenes o-Xylene

1,3,5-

Trimethyl

Benzene

Kalabokas et al. (2001) Around an oil refinery, Greece 5.1±15.6 2.6±2.2 6.3±5.4 1.3±1.5 3.1±3.1 2.7±2.9 0.7±1.1

Na et al. (2001) Ulsan industrial site, Korea

Yochon industrial sitea, Korea

12.3±7.4

13.0±8.8

6.7±2.6

6.7±3.2

14.7±3.4

7.5±3.8

3.9±1.3 16.5±9.1 4.8±1.7

5.6±3.9

Eryigit (2000)

Muezzinoglu et al.

(2001)

Aliaga, Izmir

Bornova, Izmir

Basmane, Izmir

28.6±12.0

51.1±5.3

1.0-35.5

37.1±10.2

55.9±8.3

0.4-101.4

100.6±10.9

104.8±10.9

21.3±10.9

37.3±5.2

0.4-122.4

91.6±23.4

82.9±22.1

5.6-28.7

95.1±17.8

84.7±32.6

46.2±8.8

42.2±19.7

This study Buca, Izmir 1.06±0.62 0.96±0.52 1.77±1.74 0.69±0.55 1.02±0.76 0.74±0.55 0.86±0.74d

This study Around a petrocemical plant

and an oil refinery, Aliaga,

Izmir

4.1±5.0 18.2±37.3 19.0±29.7 2.6±2.4 8.8±12.7b 17.8±28.6c 2.3±1.9d

a Reference data from Moon et al. (1997) b p-xylene c o,m-xylene+isopropyl benzene d 1,2,3-trimethyl benzene

3.5. Sulfur Dioxide

A recent study by Elbir (2002) indicated that the fuel oil use in Aliaga is high due

to the petroleum refinery and petrochemical plant, which covers 69% of fuel oil used

in Izmir area. Petroleum refinery and petrochemical plant are the largest sources of

air pollution in the region, for instance, contributing together about 72% to total

industrial SO2 emissions and 66% to overall SO2 emissions (Elbir, 2002). Air

pollution inventories and dispersion model studies by Elbir, (2002) indicated that the

maximum annual average SO2 concentration of approximately 182 µg/m3 during the

year 2000 occurs around the city center. Seventy eight percent of this concentration

is due to the contribution of emissions from industrial plants. Elbir (2002) have

shown that the sulfur dioxide emissions from petrochemical plant and refinery

always maintain an annual average SO2 concentration between 5-10 µg/m3 all over

the city of Izmir (Elbir, 2002). Sulfur dioxide concentrations measured in this study

were ranged from 1 to 934 µg/m3 (average±SD, 87±133 µg/m3) (Table 3). The rose

diagrams of sulfur dioxide concentrations are presented in Figure 10. The highest

sulfur dioxide concentrations at all sites were measured when the wind direction was

NE (Figure 10) indicating the effect of petrochemical plant and refinery emissions.

The lowest concentrations were measured for southerly winds at Site 1 and 3.

However, higher concentrations were observed at Site 2 for southerly winds

indicating the impact of petrochemical plant emissions.

Table 3. Summary of atmospheric measurements of sulfur dioxide (µg/m3)

Site Average SD Max Min n

Site 1 68 83 281 4 22

Site 2 130 199 934 1 22

Site 3 62 68 209 2 20

All sites 87 133 934 1 64

N

↑

Figure 10. Rose diagrams of SO2 concentration (µg/m3) for the sampling sites

The rose diagrams of sulfur dioxide concentrations were generally similar to those

drawn for total VOCs (Figures 3 and 10). The differences may be due to the different

sources and source characteristics (i.e., emission, stack height, plume rise, location).

Sulfur dioxide emissions are mainly from combustion. In addition to combustion

significant amounts of VOCs are emitted from various processes in the plants

studied. Measured sulfur dioxide concentrations were also compared with the limit

values given in Turkish Air Quality Protection Regulation (1986). Long-term

ambient air limit of SO2 for industrial regions is given as 250 µg/m3. Average SO2

concentrations for all sampling sites were below this limit value.

3.6. Mercaptans

Mercaptans are mainly emitted from the petroleum refinery. Mercaptan samples

were collected during the periods when the wind direction was NE to investigate the

• Site 1

• Site 3

• Site 2

Petroleum Refinery

Petrochemical Plant

050

100150

N

NE

E

SE

S

SW

W

NW

0100200300

N

NE

E

SE

S

SW

W

NW

050

100150

N

NE

E

SE

S

SW

W

NW

effect of refinery emissions. Mercaptan concentrations ranged between 65 and 1462

µg/m3. Summary of atmospheric measurements are shown in Table 4. Butanethiol

was the most abundant mercaptan followed by methanethiol. When wind blew from

refinery to petrochemical industry mercaptan concentration was higher at Site 2.

Table 4. Ambient mercaptan concentrations (µg/m3) in the study area

Sample Date Methanethiol Propanethiol Butanethiol

07.05.2001 Site1 226 65 520

07.05.2001 Site2 446 75 732

07.05.2001 Site3 102 414

07.12.2001 Site1 330 77

07.30.2001 Site1 77

07.30.2001 Site2 593 80 1262

07.30.2001 Site3 118 1462

A recent study by Muezzinoglu (2002) using the same sampling method indicated

that mercaptan concentrations ranged between 1800 and 25000 µg/m3 at the

malodorous deltas of the polluted creeks in the city of Izmir. By comparison,

methanethiol concentrations up to 25600 mg/m3 in kraft pulp mill operations were

measured (Bordado & Gomes, 2001). Chi-Wen (2001) measured a propanethiol

concentration of 58 µg/m3 in Taiwan. Ambient air standards for mercaptans around

the petrochemical plants and oil refineries are given as 5 µg/m3 (primary standard)

and 60 µg/m3 (secondary standard) in Turkish Air Quality Protection Regulation

(1986). Mercaptan concentrations measured at all sampling sites were significantly

higher than these limit values.

4. Conclusions

Several effects of volatile organic compounds are recognized, such as their

contribution to stratospheric ozone depletion, tropospheric photochemical ozone

formation, toxic, carcinogenic human health effects, and enhancement of global

greenhouse effect.

A sampling program was conducted between September 2000 and September

2001 in Aliaga, Izmir to measure VOC, sulfur dioxide, and mercaptan concentrations

around a petrochemical industry and a petroleum refinery. Ambient air samples were

collected using activated carbon tubes for VOCs, mercuric acetate impregnated glass

fiber filters for mercaptans, and an absorbing solution (tetrachloromercurate) for

sulfur dioxide. Ambient concentrations obtained from the experimental studies were

evaluated by comparing them to the values reported in the literature and limit values

set by regulations. The relationship between meteorological parameters and VOC

concentrations was also investigated.

Total volatile organic compound concentrations (average±SD) were 165.3±188.5,

114.3±153.6, and 91.7±91.2 µg/m3 for Site 1, Site 2, and Site 3, respectively. The

highest total VOC concentration was measured at Site1 followed by Site 2. Site 1 had

the highest average concentration because during most of the sampling program it

was affected by petrochemical plant and refinery emissions (when the wind was from

NE). However, Site 2, having the second highest average total VOC concentration

was affected either by petrochemical plant emissions or refinery emissions.

Concentration at Site 3 was relatively lower than other sites.

Ethylene dichloride was the most abundant volatile organic compound followed

by ethyl alcohol and acetone. High ethylene dichloride and ethyl alcohol

concentrations were probably due to the fugitive emissions from ethylene process

used in the petrochemical plant.

At all sites all hydrocarbon groups showed seasonal variation. Concentrations of

aromatic hydrocarbons, oxygenated hydrocarbons, and ethylene dichloride, were the

highest in summer followed by autumn probably due to the increased evaporation as

a result of higher temperatures. VOC concentrations generally increased with

temperature. However, temperature accounted only 3-30% for the variability in

ambient concentrations of VOCs.

When wind speed was ≥5 m/s, concentrations were relatively higher for all sites

and all VOC groups.

VOC concentrations measured in this study around the petrochemical plant and

oil refinery were 5-20 times lower than those measured in urban Izmir sites and they

were 3-20 times higher than the concentrations measured in Buca suburban site.

Benzene, toluene, ethyl benzene, and xylene concentrations measured in this study

were 2-5 times higher than those measured around an oil refinery in Greece.

Concentrations of all VOCs for all sampling sites were much lower than the limit

values given in Turkish Air Quality Protection Regulation.

Sulfur dioxide concentrations measured in this study were ranged from 1 to 934

µg/m3 (average±SD, 87±133 µg/m3). The highest sulfur dioxide concentrations at all

sites were measured when the wind direction was NE indicating the effect of

petrochemical plant and refinery emissions.

Average SO2 concentrations for all sampling sites were below the long-term

ambient air limit value for industrial regions.

Mercaptan concentrations ranged between 65 and 1462 µg/m3. Butanethiol was

the most abundant mercaptan followed by methanethiol. Mercaptan concentrations

measured at all sampling sites were significantly higher than the limit values.

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