Bull Environ Contam Toxicol (2014) 92:738–744 DOI 10.1007/s00128-014-1276-8
Physicochemical Characterization of Ambient Air Particulate Matter in Tabriz, Iran Akbar Gholampour • Ramin Nabizadeh • Masud Yunesian • Simin Naseri • Hasan Taghipour • Noushin Rastkari • Shahrokh Nazmara • Amir Hossein Mahvi
Received: 14 August 2013 / Accepted: 8 April 2014 / Published online: 23 April 2014 Ó Springer Science+Business Media New York 2014
Abstract Atmospheric particulate matter (PM) was measured concurrently from September, 2012, to June, 2013, at two sites, urban and industrial suburban, in Tabriz, Iran. The annual average concentration of total suspended particulates (TSP), PM10, PM2.5, and PM1 at the urban site were 142.2 ± 76.3, 85.3 ± 43.9, 39 ± 19.1, and 28.4 ± 14.9 lg/m3 (mean ± SD), respectively. A total of 11 inorganic watersoluble ions in the TSP and PM10 were identified by ion chromatography. In the urban site, concentrations of total water-soluble ions in TSP and PM10 were 20.3 ± 20.8 and 16.0 ± 14.1 lg/m3, respectively. In this sampling site, sec þ ondary inorganic aerosols (i.e., R SO2 4 , NO3 , and NH4 concentrations) were the main measured water-soluble ions, which collectively accounted for 13.9 % of TSP mass and 17.7 % of PM10 mass. Correlations between NHþ 4 with NO3 and SO2 4 indicated that the main source of these ions in PM was the combustion processes. Results of elemental analysis
A. Gholampour H. Taghipour Department of Environmental Health Engineering, School of Public Health, Tabriz University of Medical Sciences, Tabriz, Iran e-mail: [email protected] H. Taghipour e-mail: [email protected] A. Gholampour R. Nabizadeh M. Yunesian S. Naseri S. Nazmara A. H. Mahvi (&) Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] R. Nabizadeh e-mail: [email protected] S. Nazmara e-mail: [email protected]
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in the industrial suburban site showed that natural sources were the dominant source of PM in this area. Keywords Particulate matter Water-soluble ions Source identification Ions correlations It has been shown that heart and respiratory diseases resulting from air pollutants are mainly associated with particulate matter (PM) (Naddafi et al. 2012; Deshmukh et al. 2012).The biological causes of the health effects due to the exposure with PM are not clear; thus, the investigation of both physical and chemical characteristics of PM is important to explain their toxicity. However, ambient PM is a mixture of various chemical constituents with different potentials to cause health effects (Pipalatkar et al. 2012). It has been reported that inorganic ions increase the potential health effects of fine (PM2.5; particles with the
M. Yunesian Center for Air Pollution Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] S. Naseri N. Rastkari Center for Water Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] N. Rastkari e-mail: [email protected] A. H. Mahvi Center for Solid Waste Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
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aerodynamic diameter smaller than 2.5 lm) and coarse particles (PM10; particles with the aerodynamic diameter smaller than 10 lm), reduce atmospheric visibility, and also affect terrestrial and aquatic ecosystems (Galindo et al. 2011). Understanding the responsible constituents and related sources of PM is important, and could potentially lead to more targeted and effective regulations of ambient PM sources (Chang et al. 2006). The present study was carried out to determine the mass levels of total suspended particulates (TSP), PM10, PM2.5, and particles with the aerodynamic diameter smaller than 1 lm (PM1) together with the seasonal variations of watersoluble ionic species associated with TSP and PM10 in Tabriz. Tabriz is one of the largest cities in Iran, the capital of East Azerbaijan province, with a population of approximately 1.7 million in 2012 extending over a surface area of 320 km2.
Materials and Methods Two sites were selected based on their different land-use categories: (1) urban site, which was located near the center of the city in a residential region (38° 30 18.100 N, 46° 190 22.800 E), and (2) industrial suburban site that was located out of the urban border (38° 40 24.000 N, 46° 90 35.500 E). A petroleum refinery, a thermal powerhouse and some other small industrial plants were located adjacent to the industrial sampling site. At the urban site, samples were collected every 6 days throughout the period, and at the industrial suburban site, 3–4 samples were collected every month. Sampling was conducted from September 2012 to June 2013. Total suspended particulates and PM10 samples were collected by two high volume samplers manufactured by Graseby–Andersen (Smyrna, GA, USA) at flow rates of 1.13–1.41 m3/min for 24 h. Both TSP and PM10 were collected on Whatman glass microfiber filters (20.3 9 25.4 cm). All filters (before and after sampling) were maintained first at the condition of 40 % relative humidity (RH) and 25°C over 48 h. Afterward they were left in room condition for 2 h; then were weighed three times using an A&D electronic balance (Model GR-300, San Jose, CA, USA) with the reading precision of 0.1 mg. PM2.5 and PM1.0 were measured by means of two portable HAZ-
DUST EPAM-5000 particulate air monitors (Environmental Devices Corp., Plaistow, NH, USA). One quarter of each filter was placed in a glass vial and 40 mL ultrapure water (with specific resistance C18 X cm) was added. The vials were shaken for 2 h, and subsequently were ultra-sonicated for 30 min. The extracted solutions were filtered through a microporous membrane with the pore size 0.45 lm (Cheng et al. 2008). An ion chromatograph (Metrohm 850 Professional IC, Herisau, CH) with an operating flow rate of 0.7 mL/min was used to analyze watersoluble ions. Field and laboratory blanks and spiked samples were analyzed along with the PM samples that were used for water-soluble ion analysis. The method detection limits (MDLs) were calculated for all ions by adding three standard deviations of the blank readings to the average of five replicates of the blank. The obtained MDLs and the recovery efficiencies for water-soluble ions are presented in Table 1. Linear regression analysis was applied to determine the correlation coefficients among water-soluble ions using Stata12 (Stata Corp, College Station, TX, USA) statistical software (Fig. 1). Meteorological data were obtained from National Climatic Data Center (NCDC 2013) and East Azerbaijan Meteorological Organization. The obtained data were fed into WRPLOT View Freeware 7.0 (http://www.weblakes. com/products/wrplot/?AspxAutoDetectCookieSupport=1) to develop wind-rose plots. Based on the collected data, January was the coldest month with a mean temperature of -3°C, while July was the warmest month with a mean temperature of 38°C. The RH varied from 15 % to 87 %. Seasonal wind-rose plots (Fig. 2) showed that autumn and winter with the mean wind speeds of 3.1 and 3.0 m/s, respectively, were relatively calmer than summer (5.1 m/s) and spring (4.6 m/s). Calm wind (0 m/s) frequencies were 5.3 %, 1.8 %, 11.5 %, and 9.3 % in spring, summer, autumn and winter, respectively.
Results and Discussion The annual average concentrations of TSP, PM10, PM2.5, and PM1 in the urban site were 142.2 ± 76.3, 85.3 ± 43.9, 39 ± 19.1, and 28.4 ± 14.9 lg/m3 (mean ± SD), respectively. As the national standard levels for PM (DOE 2012) are identical
Table 1 Method detection limits (MDLs) and the recovery efficiencies for water-soluble ions Water-soluble ion
Na?
NHþ 4
K?
Mg2?
Ca2?
F
Cl-
NO 2
NO 3
SO2 4
PO2 4
Method detection limits (MDLs) (ng/mL)
95
6.3
4.4
12.5
5.3
3.7
6.5
3.6
52
45
6.1
Recovery efficiencies* (%)
97–103
78–106
101–103
112–133
109–122
105–107
99–103
100–117
98–104
102–104
95–106
* Based on 3r blank filters (n = 5)
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740 Fig. 1 Location of study area and sampling sites
Fig. 2 Seasonal wind rose plots during the study period in Tabriz (2012–2013)
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Bull Environ Contam Toxicol (2014) 92:738–744
Bull Environ Contam Toxicol (2014) 92:738–744 Urban
60
SO4¯ ¯
50
NO3¯
40
NO2¯ PO4¯ ¯
30
Cl¯ 20
F¯
10
Ca++
0
Mg++
(b) 70
Na+ 50 40 30 20 10 0
50 40 30 20 10 0
TSP
NH4+
60
Suburban
60
K+
Concentration (µg/m3)
TSP
Concentration (µg/m3)
(C) 70
(d)
70
Concentration (µg/m3)
Concentration (µg/m 3)
(a) 70
741
60 50 40 30 20 10 0
PM10
PM10
Fig. 3 Monthly average concentration of water-soluble ions in urban [a TSP, b PM10] and in the suburban [c TSP, d PM10] sampling site
to WHO guidelines (Europe 2006) (50 and 10 lg/m3 for PM10 and PM2.5, respectively), the percentage of days that the 24-h mean concentrations of PM10 and PM2.5 exceeded standard were 73 % and 76 %, respectively. It should be mentioned that no standards or allowable limits have been established by the Iranian government for TSP and PM1. The highest mean concentration of PM was observed during winter followed by autumn, and the lowest mean occurred in the spring. The obtained results showed that the maximum diurnal mass concentration of TSP (480.4 lg/ m3) occurred in January. In addition, the maximum daily mass concentration of PM10 (197.0 lg/m3) was detected in October, while for PM2.5 (96.6 lg/m3) and PM1 (72.2 lg/m3) the maximum occurred in February. Sometimes, local dust accrued in the area of the urban and suburban sampling sites, but dust storms were not observed during the study period. At the industrial suburban site, the overall average of TSP, PM10, PM2.5, and PM1 mass concentrations were 178.7 ± 52.7, 109.9 ± 30.2, 40.0 ± 10.9, and 31.4 ± 9.1 lg/m3 (mean ± SD), respectively. Because of the Iranian New Year holidays in March and the subsequent decline in industrial activity, as well as increased rainfall, PM concentrations exhibited a considerable decrease at this time. The monthly averages for water-soluble ion concentrations in TSP and PM10 collected from the urban site are given in Fig. 3a, b. Total measured water-soluble ions in TSP were 20.3 ± 20.8 lg/m3 (20.8 % ± 10.0 % of total TSP mass); in
PM10, they were 16.0 ± 14.1 lg/m3 (23.9 ± 12.3 of total PM10 mass). Higher concentrations of ions during winter could be attributed to vehicular traffic and increased use of fuel for heating homes, combined with dry and cold weather. At the suburban site, the concentration for total water-soluble ions in the TSP sample was 37.1 ± 16.5 lg/m3 (23.2 % ± 9.7 % of total TSP mass), while in PM10 it was 24.9 ± 19.3 lg/m3 (26.5 % ± 12.5 % of total PM10 mass). As shown in Table 2, NO 3 was the most dominant ion, 2? , Ca and Na? (36.1, 26.6, 11.1, and followed by SO2 4 3 8.4 lg/m for TSP and 24.5, 21.5, 7.2, and 5.6 lg/m3 for PM10, respectively). These results are in good agreement with studies from other countries that noted SO2 4 , NO3 2? and Ca as three main ions measured in PM (Wang and Shooter 2001; Klejnowski et al. 2012). It is clear that the 2 main sources of NO in the urban ambient 3 and SO4 atmosphere are the oxidation of their gaseous precursors (NOx and SO2) emitted from various anthropogenic activ ities (Guo et al. 2011). In TSP, SO2 4 and NO3 together account for about 60 % and 54 % of the total measured ionic mass at both urban and suburban site, while in PM10 they account for 61 % and 59 %, respectively. Nitrate exhibits high seasonality, with much higher concentrations during cold seasons (13.2 ± 9 lg/m3 for TSP and 8.6 ± 5.9 lg/m3 for PM10) and lower
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Table 2 Ion concentrations (lg/m3) in TSP and PM10 samples from the urban site (n = 45) Species
Min
Percentile 25th
50th
75th
Max
Mean
SD
TSP (PM10)
26.5 (14.9)
77.0 (42.4)
127.5 (82.3)
179.8 (106.4)
480.0 (197.1)
142.2 (85.2)
76.3 (43.9)
Naþ
35 (0.32)
1.01 (0.87)
2.13 (1.99)
3.43 (3.32)
8.43 (5.58)
2.44 (2.14)
1.79 (1.46)
NHþ 4
08 (0.03)
0.33 (0.22)
0.82 (0.59)
1.62 (1.52)
3.31 (2.94)
1.07 (0.95)
0.87 (1.09)
K
0.01 (0.01)
0.16 (0.05)
0.31 (0.21)
0.50 (0.39)
1.47 (0.93)
0.38 (0.25)
0.33 (0.22)
03 (0.02)
0.13 (0.08)
0.18 (0.12)
0.24 (0.15)
0.44 (0.35)
0.19 (0.12)
0.10 (0.07)
Ca
1.14 (0.41)
2.50 (1.24)
4.01 (2.38)
5.40 (3.46)
11.13 (7.25)
4.23 (2.63)
2.36 (1.62)
F-
00 (0.00)
0.03 (0.02)
0.07 (0.05)
0.14 (0.06)
0.30 (0.28)
0.09 (0.05)
0.08 (0.05)
Cl-
17 (0.13)
0.69 (0.38)
1.26 (1.12)
3.23 (1.71)
11.00 (5.13)
2.37 (1.48)
2.59 (1.38)
NO 2
00 (0.00)
0.01 (0.01)
0.02 (0.01)
0.03 (0.02)
0.05 (0.03)
0.03 (0.02)
0.01 (0.01)
NO 3
0.82 (0.66)
2.80 (2.05)
5.33 (4.33)
10.90 (6.18)
36.18 (24.49)
8.47 (5.81)
8.48 (5.97)
SO2 4
19 (1.18)
3.80 (2.47)
6.77 (4.94)
12.20 (10.67)
26.61 (21.47)
8.34 (6.78)
6.06 (5.58)
PO2 4
0.01 (0.00)
0.03 (0.03)
0.04 (0.03)
0.05 (0.04)
0.06 (0.05)
0.03 (0.02)
0.01 (0.02)
Mg2þ 2
700
(b) 700
600
Total Anions ( neq m-3)
• TSP : y = 0.91x
• TSP : y = 0.92x R² = 0.93 PM10 : y = 0.97x R² = 0.92
Total Anions (neq m-3)
(a)
500 400 300
Urban
200
R² = 0.88 PM10 : y = 0.94x R² = 0.91
600 500 400 300
Suburban
200
100
100 0
0 0
100
200
300
400
500
600
700
Total Cations ( neq m-3)
0
100
200
300
400
500
Total Cations (neq
600
700
m-3)
Fig. 4 Ionic balance between total anions and cations for TSP (solid line) and PM10 (dashed line) fractions from a urban and b suburban sites
concentrations (1.7 ± 0.7 lg/m3 for TSP and 3 1.0 ± 0.2 lg/m for PM10) in warm seasons, in the urban sampling site. The partition of NO 3 , in the ambient air, between the gas and particle phases depends mainly on temperature, RH, and concentration of NH3 (Ho et al. 2006). The lower temperature during winter favors the shift from gas phase of nitric acid to the particle phase of NO 3, which may have led to the high concentration of NO 3 in PM during winter. Conversely, lower concentrations of NO 3 during summer might be due to the volatilization of NH4NO3, which increased with the increased temperature and decreased RH (Mouli et al. 2006). According to Table 2 and Fig. 3a, secondary inorganic aerosols (sum of þ the SO2 4 , NO3 and NH4 concentrations) were the main water-soluble ions in the urban ambient air, which accounted for 13.9 % of TSP mass and 17.7 % of PM10
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mass. These results confirm that the smaller particles have higher mass percentages of secondary inorganic aerosols (Fattore et al. 2011). Ionic balance relationships are often employed to determine the possible presence of ions that were not ? measured, such as CO 3 and H . Plots of total cation versus total anion equivalents (neq/m3) are presented in Fig. 4a, b. The slope of the regression line for PM indicated a value smaller than unity (slope = 0.92, r = 0.93 for TSP and slope = 0.97, r = 0.0.92 for PM10), which may have been due to CO 3 , which was not analyzed. Using Na? as a tracer element of sea salt, excess sulfate (as non-sea-salt sulfates, nss-SO2 4 can be calculated as (Ho et al. 2006): 2 ½Naþ 0:2516 nss SO2 4 ¼ SO4
Bull Environ Contam Toxicol (2014) 92:738–744
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slope = 0.93) that revealed almost complete formation of ðNH4 Þ2 SO4 in the PM2.5 aerosols. The existence of higher portions of other nss-SO2 4 complexes in TSP and PM10 than NHþ complex, in addition to the NHþ 4 4 complex alone may be responsible for the weaker relationship. Concentrations of Naþ and Cl at the suburban site were 3.8 and 5.3 lg/m3 for TSP and 3.4 and 3.1 lg/m3 for PM10, respectively, which were higher than those ion concentrations at the urban site, 2.4 and 2.3 lg/m3 for TSP and 2.1 and 1.5 lg/m3 for PM10, respectively. Based on the study of Eimanifar et al. (2007), Na?, K?, Ca2?, Li? and Mg2? were reported as the main cations in the water of Urmia lake, while Cl-, SO2 4 and HCO3 were the main anions. Urmia lake is a hypersaline lake, and the concentrations of Na? and Cl- were roughly four times the concentration of natural seawater (Eimanifar and Mohebbi 2007). Therefore, it can be concluded that the Urmia lake bed creates abundant marine aerosols. Whereas Urmia Lake was at one time much larger and included the suburban sampling site within its boundaries, the higher concentrations of Na? and Cl- at this site may be explained on the basis of the former extent of this hypersaline lake. Ion correlation matrices were calculated using Stata software to quantify the relationships between elemental concentrations (Table 3). The number of significant correlations of elements in PM10 is higher and also stronger than for TSP. Yatkin and Bayram (2007) reported that
200
• TSP : y = 0.32x
R² = 0.50
PM10 : y = 0.29x R² = 0.58
NH4+(neq m-3)
150
100
50
0 0
100
200
300
nss-SO4(neq m-3) þ Fig. 5 Relationship between nss-SO2 4 with NH4 for TSP (solid line) and PM10 (dashed line) at urban sampling site
þ The daily averages of nss-SO2 4 .and NH4 at the urban site 3 were 5.6 and 2.1 lg/m for TSP and 4.6 and 1.8 lg/m3 for PM10, respectively. It could be concluded that the daily þ average concentrations of nss-SO2 4 .and NH4 decreased slightly in the order of TSP and PM10. Also, Fig. 5 shows þ that the relationship between nss-SO2 4 .and NH4 in both 2 TSP and PM10 is weak (R = 0.5–0.58) and the slope of this relation is about 0.3. On the other hand, the relationship between nss-SO2 and NHþ 4 4 in the study of Karthikeyan (2006) showed a high correlation (R2 = 0.88 and
Table 3 Correlation matrices for ions in the TSP and PM10 samples for the urban site
Na?
NHþ 4
K?
Mg2?
Ca2?
F
Cl-
NO 2
NO 3
TSP NHþ 4
0.66**
K?
0.52**
0.57**
2þ
0.52**
0.41*
0.60**
Ca2?
0.70**
0.55**
0.59**
0.87**
F
0.49*
0.35
0.39*
0.40*
0.48*
Cl
0.89**
0.56**
0.57**
0.46*
0.67**
NO 2 NO 3 SO2 4
0.12
0.53*
-0.37
-0.08
0.25
0.20
0.57**
0.75**
0.38
0.26
0.47**
0.43*
0.62**
0.82**
0.65**
0.78**
0.19
0.33
0.75**
0.48*
0.66**
0.78**
NHþ 4
0.77**
K?
0.63**
0.78**
0.55**
0.66**
Ca
0.56**
0.69**
0.61**
0.91**
F
0.61**
0.81**
0.49*
0.80**
0.77**
Cl
0.87**
0.72**
0.72**
0.58**
0.62**
0.55**
NO 2
0.75**
0.81**
0.24
0.64**
0.59**
0.87**
0.65**
NO 3 SO2 4
0.75**
0.91**
0.79**
0.74**
0.74**
0.71**
0.72**
0.54*
0.78**
0.86**
0.75**
0.82**
0.86**
0.72**
0.77**
0.56**
Mg
-0.01
0.62**
0.81**
PM10
Mg
2þ
2?
Bold numbers represented the significant correlation ** p \ 0.01; * p \ 0.05
0.61**
0.83*
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744
element correlations in PM2.5 were much higher than in PM10. Therefore, it could be concluded that with decreasing the size of PM, the ion correlations increased, possibly indicating that the number of different sources emitting smaller PM was more limited than for larger PM. High correlations between the terrestrial elements in TSP and PM10 were obtained. For example, the correlation between Ca2? and Mg2? was 0.88 in TSP and 0.91 in PM10 (p \ 0.01). These results suggest that the sources of the terrestrial elements were most probably soil, soil-related activities, and anthropogenic sources. Also the correlations between Na?, Ca2?, Mg2? and K? indicate that a portion of the PM originated from marine salt. Correlations between 2 NHþ 4 with NO3 and SO4 were 0.75 and 0.78 in TSP and 0.91 and 0.86 for PM10, respectively (p \ 0.01). It was determined that the main source of these elements in PM of urban was combustion processes, especially as secondary ions. The average Cl-/Na?.mass ratio for the whole study period in the urban samples ranged from 0.41 in warm seasons to 1.07 in cold seasons for TSP, and from 0.42 in warm seasons to 0.78 in cold seasons for PM10. These results reveal that a massive loss of particulate Cl- occurs during the warm seasons. This may be caused by the formation of gaseous HCL from NaCL and acidic gases (Galindo et al.). Based on the present study, it can be concluded that the main sources of PM in the urban site were various anthropogenic activities together with resuspension of polluted soil; but in the suburban site, natural sources, especially Urmia lake bed, were the dominant source of PM. Further analyses using more sophisticated methods (i.e., Chemical Mass Balance Modeling or Positive Matrix Factorization) are required for more accurate source apportionment estimation. The results will be used for further source apportionment studies. Acknowledgments The authors would like to acknowledge the Health Faculty of Tabriz Medical Science University and Tabriz Petrochemical Plant for providing us with sampling locations. This work was funded by the Institute for Environmental Research (IER), Tehran University of Medical Sciences (grant number 92-01-46-21257).
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Physicochemical Characterization of Ambient Air Particulate Matter in Tabriz, Iran Akbar Gholampour • Ramin Nabizadeh • Masud Yunesian • Simin Naseri • Hasan Taghipour • Noushin Rastkari • Shahrokh Nazmara • Amir Hossein Mahvi
Received: 14 August 2013 / Accepted: 8 April 2014 / Published online: 23 April 2014 Ó Springer Science+Business Media New York 2014
Abstract Atmospheric particulate matter (PM) was measured concurrently from September, 2012, to June, 2013, at two sites, urban and industrial suburban, in Tabriz, Iran. The annual average concentration of total suspended particulates (TSP), PM10, PM2.5, and PM1 at the urban site were 142.2 ± 76.3, 85.3 ± 43.9, 39 ± 19.1, and 28.4 ± 14.9 lg/m3 (mean ± SD), respectively. A total of 11 inorganic watersoluble ions in the TSP and PM10 were identified by ion chromatography. In the urban site, concentrations of total water-soluble ions in TSP and PM10 were 20.3 ± 20.8 and 16.0 ± 14.1 lg/m3, respectively. In this sampling site, sec þ ondary inorganic aerosols (i.e., R SO2 4 , NO3 , and NH4 concentrations) were the main measured water-soluble ions, which collectively accounted for 13.9 % of TSP mass and 17.7 % of PM10 mass. Correlations between NHþ 4 with NO3 and SO2 4 indicated that the main source of these ions in PM was the combustion processes. Results of elemental analysis
A. Gholampour H. Taghipour Department of Environmental Health Engineering, School of Public Health, Tabriz University of Medical Sciences, Tabriz, Iran e-mail: [email protected] H. Taghipour e-mail: [email protected] A. Gholampour R. Nabizadeh M. Yunesian S. Naseri S. Nazmara A. H. Mahvi (&) Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] R. Nabizadeh e-mail: [email protected] S. Nazmara e-mail: [email protected]
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in the industrial suburban site showed that natural sources were the dominant source of PM in this area. Keywords Particulate matter Water-soluble ions Source identification Ions correlations It has been shown that heart and respiratory diseases resulting from air pollutants are mainly associated with particulate matter (PM) (Naddafi et al. 2012; Deshmukh et al. 2012).The biological causes of the health effects due to the exposure with PM are not clear; thus, the investigation of both physical and chemical characteristics of PM is important to explain their toxicity. However, ambient PM is a mixture of various chemical constituents with different potentials to cause health effects (Pipalatkar et al. 2012). It has been reported that inorganic ions increase the potential health effects of fine (PM2.5; particles with the
M. Yunesian Center for Air Pollution Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] S. Naseri N. Rastkari Center for Water Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] N. Rastkari e-mail: [email protected] A. H. Mahvi Center for Solid Waste Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
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aerodynamic diameter smaller than 2.5 lm) and coarse particles (PM10; particles with the aerodynamic diameter smaller than 10 lm), reduce atmospheric visibility, and also affect terrestrial and aquatic ecosystems (Galindo et al. 2011). Understanding the responsible constituents and related sources of PM is important, and could potentially lead to more targeted and effective regulations of ambient PM sources (Chang et al. 2006). The present study was carried out to determine the mass levels of total suspended particulates (TSP), PM10, PM2.5, and particles with the aerodynamic diameter smaller than 1 lm (PM1) together with the seasonal variations of watersoluble ionic species associated with TSP and PM10 in Tabriz. Tabriz is one of the largest cities in Iran, the capital of East Azerbaijan province, with a population of approximately 1.7 million in 2012 extending over a surface area of 320 km2.
Materials and Methods Two sites were selected based on their different land-use categories: (1) urban site, which was located near the center of the city in a residential region (38° 30 18.100 N, 46° 190 22.800 E), and (2) industrial suburban site that was located out of the urban border (38° 40 24.000 N, 46° 90 35.500 E). A petroleum refinery, a thermal powerhouse and some other small industrial plants were located adjacent to the industrial sampling site. At the urban site, samples were collected every 6 days throughout the period, and at the industrial suburban site, 3–4 samples were collected every month. Sampling was conducted from September 2012 to June 2013. Total suspended particulates and PM10 samples were collected by two high volume samplers manufactured by Graseby–Andersen (Smyrna, GA, USA) at flow rates of 1.13–1.41 m3/min for 24 h. Both TSP and PM10 were collected on Whatman glass microfiber filters (20.3 9 25.4 cm). All filters (before and after sampling) were maintained first at the condition of 40 % relative humidity (RH) and 25°C over 48 h. Afterward they were left in room condition for 2 h; then were weighed three times using an A&D electronic balance (Model GR-300, San Jose, CA, USA) with the reading precision of 0.1 mg. PM2.5 and PM1.0 were measured by means of two portable HAZ-
DUST EPAM-5000 particulate air monitors (Environmental Devices Corp., Plaistow, NH, USA). One quarter of each filter was placed in a glass vial and 40 mL ultrapure water (with specific resistance C18 X cm) was added. The vials were shaken for 2 h, and subsequently were ultra-sonicated for 30 min. The extracted solutions were filtered through a microporous membrane with the pore size 0.45 lm (Cheng et al. 2008). An ion chromatograph (Metrohm 850 Professional IC, Herisau, CH) with an operating flow rate of 0.7 mL/min was used to analyze watersoluble ions. Field and laboratory blanks and spiked samples were analyzed along with the PM samples that were used for water-soluble ion analysis. The method detection limits (MDLs) were calculated for all ions by adding three standard deviations of the blank readings to the average of five replicates of the blank. The obtained MDLs and the recovery efficiencies for water-soluble ions are presented in Table 1. Linear regression analysis was applied to determine the correlation coefficients among water-soluble ions using Stata12 (Stata Corp, College Station, TX, USA) statistical software (Fig. 1). Meteorological data were obtained from National Climatic Data Center (NCDC 2013) and East Azerbaijan Meteorological Organization. The obtained data were fed into WRPLOT View Freeware 7.0 (http://www.weblakes. com/products/wrplot/?AspxAutoDetectCookieSupport=1) to develop wind-rose plots. Based on the collected data, January was the coldest month with a mean temperature of -3°C, while July was the warmest month with a mean temperature of 38°C. The RH varied from 15 % to 87 %. Seasonal wind-rose plots (Fig. 2) showed that autumn and winter with the mean wind speeds of 3.1 and 3.0 m/s, respectively, were relatively calmer than summer (5.1 m/s) and spring (4.6 m/s). Calm wind (0 m/s) frequencies were 5.3 %, 1.8 %, 11.5 %, and 9.3 % in spring, summer, autumn and winter, respectively.
Results and Discussion The annual average concentrations of TSP, PM10, PM2.5, and PM1 in the urban site were 142.2 ± 76.3, 85.3 ± 43.9, 39 ± 19.1, and 28.4 ± 14.9 lg/m3 (mean ± SD), respectively. As the national standard levels for PM (DOE 2012) are identical
Table 1 Method detection limits (MDLs) and the recovery efficiencies for water-soluble ions Water-soluble ion
Na?
NHþ 4
K?
Mg2?
Ca2?
F
Cl-
NO 2
NO 3
SO2 4
PO2 4
Method detection limits (MDLs) (ng/mL)
95
6.3
4.4
12.5
5.3
3.7
6.5
3.6
52
45
6.1
Recovery efficiencies* (%)
97–103
78–106
101–103
112–133
109–122
105–107
99–103
100–117
98–104
102–104
95–106
* Based on 3r blank filters (n = 5)
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740 Fig. 1 Location of study area and sampling sites
Fig. 2 Seasonal wind rose plots during the study period in Tabriz (2012–2013)
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Bull Environ Contam Toxicol (2014) 92:738–744
Bull Environ Contam Toxicol (2014) 92:738–744 Urban
60
SO4¯ ¯
50
NO3¯
40
NO2¯ PO4¯ ¯
30
Cl¯ 20
F¯
10
Ca++
0
Mg++
(b) 70
Na+ 50 40 30 20 10 0
50 40 30 20 10 0
TSP
NH4+
60
Suburban
60
K+
Concentration (µg/m3)
TSP
Concentration (µg/m3)
(C) 70
(d)
70
Concentration (µg/m3)
Concentration (µg/m 3)
(a) 70
741
60 50 40 30 20 10 0
PM10
PM10
Fig. 3 Monthly average concentration of water-soluble ions in urban [a TSP, b PM10] and in the suburban [c TSP, d PM10] sampling site
to WHO guidelines (Europe 2006) (50 and 10 lg/m3 for PM10 and PM2.5, respectively), the percentage of days that the 24-h mean concentrations of PM10 and PM2.5 exceeded standard were 73 % and 76 %, respectively. It should be mentioned that no standards or allowable limits have been established by the Iranian government for TSP and PM1. The highest mean concentration of PM was observed during winter followed by autumn, and the lowest mean occurred in the spring. The obtained results showed that the maximum diurnal mass concentration of TSP (480.4 lg/ m3) occurred in January. In addition, the maximum daily mass concentration of PM10 (197.0 lg/m3) was detected in October, while for PM2.5 (96.6 lg/m3) and PM1 (72.2 lg/m3) the maximum occurred in February. Sometimes, local dust accrued in the area of the urban and suburban sampling sites, but dust storms were not observed during the study period. At the industrial suburban site, the overall average of TSP, PM10, PM2.5, and PM1 mass concentrations were 178.7 ± 52.7, 109.9 ± 30.2, 40.0 ± 10.9, and 31.4 ± 9.1 lg/m3 (mean ± SD), respectively. Because of the Iranian New Year holidays in March and the subsequent decline in industrial activity, as well as increased rainfall, PM concentrations exhibited a considerable decrease at this time. The monthly averages for water-soluble ion concentrations in TSP and PM10 collected from the urban site are given in Fig. 3a, b. Total measured water-soluble ions in TSP were 20.3 ± 20.8 lg/m3 (20.8 % ± 10.0 % of total TSP mass); in
PM10, they were 16.0 ± 14.1 lg/m3 (23.9 ± 12.3 of total PM10 mass). Higher concentrations of ions during winter could be attributed to vehicular traffic and increased use of fuel for heating homes, combined with dry and cold weather. At the suburban site, the concentration for total water-soluble ions in the TSP sample was 37.1 ± 16.5 lg/m3 (23.2 % ± 9.7 % of total TSP mass), while in PM10 it was 24.9 ± 19.3 lg/m3 (26.5 % ± 12.5 % of total PM10 mass). As shown in Table 2, NO 3 was the most dominant ion, 2? , Ca and Na? (36.1, 26.6, 11.1, and followed by SO2 4 3 8.4 lg/m for TSP and 24.5, 21.5, 7.2, and 5.6 lg/m3 for PM10, respectively). These results are in good agreement with studies from other countries that noted SO2 4 , NO3 2? and Ca as three main ions measured in PM (Wang and Shooter 2001; Klejnowski et al. 2012). It is clear that the 2 main sources of NO in the urban ambient 3 and SO4 atmosphere are the oxidation of their gaseous precursors (NOx and SO2) emitted from various anthropogenic activ ities (Guo et al. 2011). In TSP, SO2 4 and NO3 together account for about 60 % and 54 % of the total measured ionic mass at both urban and suburban site, while in PM10 they account for 61 % and 59 %, respectively. Nitrate exhibits high seasonality, with much higher concentrations during cold seasons (13.2 ± 9 lg/m3 for TSP and 8.6 ± 5.9 lg/m3 for PM10) and lower
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Table 2 Ion concentrations (lg/m3) in TSP and PM10 samples from the urban site (n = 45) Species
Min
Percentile 25th
50th
75th
Max
Mean
SD
TSP (PM10)
26.5 (14.9)
77.0 (42.4)
127.5 (82.3)
179.8 (106.4)
480.0 (197.1)
142.2 (85.2)
76.3 (43.9)
Naþ
35 (0.32)
1.01 (0.87)
2.13 (1.99)
3.43 (3.32)
8.43 (5.58)
2.44 (2.14)
1.79 (1.46)
NHþ 4
08 (0.03)
0.33 (0.22)
0.82 (0.59)
1.62 (1.52)
3.31 (2.94)
1.07 (0.95)
0.87 (1.09)
K
0.01 (0.01)
0.16 (0.05)
0.31 (0.21)
0.50 (0.39)
1.47 (0.93)
0.38 (0.25)
0.33 (0.22)
03 (0.02)
0.13 (0.08)
0.18 (0.12)
0.24 (0.15)
0.44 (0.35)
0.19 (0.12)
0.10 (0.07)
Ca
1.14 (0.41)
2.50 (1.24)
4.01 (2.38)
5.40 (3.46)
11.13 (7.25)
4.23 (2.63)
2.36 (1.62)
F-
00 (0.00)
0.03 (0.02)
0.07 (0.05)
0.14 (0.06)
0.30 (0.28)
0.09 (0.05)
0.08 (0.05)
Cl-
17 (0.13)
0.69 (0.38)
1.26 (1.12)
3.23 (1.71)
11.00 (5.13)
2.37 (1.48)
2.59 (1.38)
NO 2
00 (0.00)
0.01 (0.01)
0.02 (0.01)
0.03 (0.02)
0.05 (0.03)
0.03 (0.02)
0.01 (0.01)
NO 3
0.82 (0.66)
2.80 (2.05)
5.33 (4.33)
10.90 (6.18)
36.18 (24.49)
8.47 (5.81)
8.48 (5.97)
SO2 4
19 (1.18)
3.80 (2.47)
6.77 (4.94)
12.20 (10.67)
26.61 (21.47)
8.34 (6.78)
6.06 (5.58)
PO2 4
0.01 (0.00)
0.03 (0.03)
0.04 (0.03)
0.05 (0.04)
0.06 (0.05)
0.03 (0.02)
0.01 (0.02)
Mg2þ 2
700
(b) 700
600
Total Anions ( neq m-3)
• TSP : y = 0.91x
• TSP : y = 0.92x R² = 0.93 PM10 : y = 0.97x R² = 0.92
Total Anions (neq m-3)
(a)
500 400 300
Urban
200
R² = 0.88 PM10 : y = 0.94x R² = 0.91
600 500 400 300
Suburban
200
100
100 0
0 0
100
200
300
400
500
600
700
Total Cations ( neq m-3)
0
100
200
300
400
500
Total Cations (neq
600
700
m-3)
Fig. 4 Ionic balance between total anions and cations for TSP (solid line) and PM10 (dashed line) fractions from a urban and b suburban sites
concentrations (1.7 ± 0.7 lg/m3 for TSP and 3 1.0 ± 0.2 lg/m for PM10) in warm seasons, in the urban sampling site. The partition of NO 3 , in the ambient air, between the gas and particle phases depends mainly on temperature, RH, and concentration of NH3 (Ho et al. 2006). The lower temperature during winter favors the shift from gas phase of nitric acid to the particle phase of NO 3, which may have led to the high concentration of NO 3 in PM during winter. Conversely, lower concentrations of NO 3 during summer might be due to the volatilization of NH4NO3, which increased with the increased temperature and decreased RH (Mouli et al. 2006). According to Table 2 and Fig. 3a, secondary inorganic aerosols (sum of þ the SO2 4 , NO3 and NH4 concentrations) were the main water-soluble ions in the urban ambient air, which accounted for 13.9 % of TSP mass and 17.7 % of PM10
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mass. These results confirm that the smaller particles have higher mass percentages of secondary inorganic aerosols (Fattore et al. 2011). Ionic balance relationships are often employed to determine the possible presence of ions that were not ? measured, such as CO 3 and H . Plots of total cation versus total anion equivalents (neq/m3) are presented in Fig. 4a, b. The slope of the regression line for PM indicated a value smaller than unity (slope = 0.92, r = 0.93 for TSP and slope = 0.97, r = 0.0.92 for PM10), which may have been due to CO 3 , which was not analyzed. Using Na? as a tracer element of sea salt, excess sulfate (as non-sea-salt sulfates, nss-SO2 4 can be calculated as (Ho et al. 2006): 2 ½Naþ 0:2516 nss SO2 4 ¼ SO4
Bull Environ Contam Toxicol (2014) 92:738–744
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slope = 0.93) that revealed almost complete formation of ðNH4 Þ2 SO4 in the PM2.5 aerosols. The existence of higher portions of other nss-SO2 4 complexes in TSP and PM10 than NHþ complex, in addition to the NHþ 4 4 complex alone may be responsible for the weaker relationship. Concentrations of Naþ and Cl at the suburban site were 3.8 and 5.3 lg/m3 for TSP and 3.4 and 3.1 lg/m3 for PM10, respectively, which were higher than those ion concentrations at the urban site, 2.4 and 2.3 lg/m3 for TSP and 2.1 and 1.5 lg/m3 for PM10, respectively. Based on the study of Eimanifar et al. (2007), Na?, K?, Ca2?, Li? and Mg2? were reported as the main cations in the water of Urmia lake, while Cl-, SO2 4 and HCO3 were the main anions. Urmia lake is a hypersaline lake, and the concentrations of Na? and Cl- were roughly four times the concentration of natural seawater (Eimanifar and Mohebbi 2007). Therefore, it can be concluded that the Urmia lake bed creates abundant marine aerosols. Whereas Urmia Lake was at one time much larger and included the suburban sampling site within its boundaries, the higher concentrations of Na? and Cl- at this site may be explained on the basis of the former extent of this hypersaline lake. Ion correlation matrices were calculated using Stata software to quantify the relationships between elemental concentrations (Table 3). The number of significant correlations of elements in PM10 is higher and also stronger than for TSP. Yatkin and Bayram (2007) reported that
200
• TSP : y = 0.32x
R² = 0.50
PM10 : y = 0.29x R² = 0.58
NH4+(neq m-3)
150
100
50
0 0
100
200
300
nss-SO4(neq m-3) þ Fig. 5 Relationship between nss-SO2 4 with NH4 for TSP (solid line) and PM10 (dashed line) at urban sampling site
þ The daily averages of nss-SO2 4 .and NH4 at the urban site 3 were 5.6 and 2.1 lg/m for TSP and 4.6 and 1.8 lg/m3 for PM10, respectively. It could be concluded that the daily þ average concentrations of nss-SO2 4 .and NH4 decreased slightly in the order of TSP and PM10. Also, Fig. 5 shows þ that the relationship between nss-SO2 4 .and NH4 in both 2 TSP and PM10 is weak (R = 0.5–0.58) and the slope of this relation is about 0.3. On the other hand, the relationship between nss-SO2 and NHþ 4 4 in the study of Karthikeyan (2006) showed a high correlation (R2 = 0.88 and
Table 3 Correlation matrices for ions in the TSP and PM10 samples for the urban site
Na?
NHþ 4
K?
Mg2?
Ca2?
F
Cl-
NO 2
NO 3
TSP NHþ 4
0.66**
K?
0.52**
0.57**
2þ
0.52**
0.41*
0.60**
Ca2?
0.70**
0.55**
0.59**
0.87**
F
0.49*
0.35
0.39*
0.40*
0.48*
Cl
0.89**
0.56**
0.57**
0.46*
0.67**
NO 2 NO 3 SO2 4
0.12
0.53*
-0.37
-0.08
0.25
0.20
0.57**
0.75**
0.38
0.26
0.47**
0.43*
0.62**
0.82**
0.65**
0.78**
0.19
0.33
0.75**
0.48*
0.66**
0.78**
NHþ 4
0.77**
K?
0.63**
0.78**
0.55**
0.66**
Ca
0.56**
0.69**
0.61**
0.91**
F
0.61**
0.81**
0.49*
0.80**
0.77**
Cl
0.87**
0.72**
0.72**
0.58**
0.62**
0.55**
NO 2
0.75**
0.81**
0.24
0.64**
0.59**
0.87**
0.65**
NO 3 SO2 4
0.75**
0.91**
0.79**
0.74**
0.74**
0.71**
0.72**
0.54*
0.78**
0.86**
0.75**
0.82**
0.86**
0.72**
0.77**
0.56**
Mg
-0.01
0.62**
0.81**
PM10
Mg
2þ
2?
Bold numbers represented the significant correlation ** p \ 0.01; * p \ 0.05
0.61**
0.83*
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744
element correlations in PM2.5 were much higher than in PM10. Therefore, it could be concluded that with decreasing the size of PM, the ion correlations increased, possibly indicating that the number of different sources emitting smaller PM was more limited than for larger PM. High correlations between the terrestrial elements in TSP and PM10 were obtained. For example, the correlation between Ca2? and Mg2? was 0.88 in TSP and 0.91 in PM10 (p \ 0.01). These results suggest that the sources of the terrestrial elements were most probably soil, soil-related activities, and anthropogenic sources. Also the correlations between Na?, Ca2?, Mg2? and K? indicate that a portion of the PM originated from marine salt. Correlations between 2 NHþ 4 with NO3 and SO4 were 0.75 and 0.78 in TSP and 0.91 and 0.86 for PM10, respectively (p \ 0.01). It was determined that the main source of these elements in PM of urban was combustion processes, especially as secondary ions. The average Cl-/Na?.mass ratio for the whole study period in the urban samples ranged from 0.41 in warm seasons to 1.07 in cold seasons for TSP, and from 0.42 in warm seasons to 0.78 in cold seasons for PM10. These results reveal that a massive loss of particulate Cl- occurs during the warm seasons. This may be caused by the formation of gaseous HCL from NaCL and acidic gases (Galindo et al.). Based on the present study, it can be concluded that the main sources of PM in the urban site were various anthropogenic activities together with resuspension of polluted soil; but in the suburban site, natural sources, especially Urmia lake bed, were the dominant source of PM. Further analyses using more sophisticated methods (i.e., Chemical Mass Balance Modeling or Positive Matrix Factorization) are required for more accurate source apportionment estimation. The results will be used for further source apportionment studies. Acknowledgments The authors would like to acknowledge the Health Faculty of Tabriz Medical Science University and Tabriz Petrochemical Plant for providing us with sampling locations. This work was funded by the Institute for Environmental Research (IER), Tehran University of Medical Sciences (grant number 92-01-46-21257).
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