Journal o f Radioanalytical and Nuclear Chemistry, Articles, Vol. 100, No. 1 (1986) 15-19
T R A C E E L E M E N T S IN T H E A T M O S P H E R E O F A N K A R A * M. SABUNCU, H. N. ERTEN, N. K. ARAS
Department o f Chemistry, Middle East Technical University, Ankara (Turkey) (Received August 5, 1985) Atmospheric particulate material collected in Ankara was analyzed by instrumental neutron activation analysis. The results are interpreted with respect to trace element concentrations of the earth's crust. Volatile elements such as As, Sb, Zn, Br and Hg are highly enriched suggesting noncrustal origin. Enrichment factors increase with decreasing particle size.
Introduction Polluted air contaminated with chemicals and foreign substances resulting from the activities of man affects all living things. These substances include gases, dust, smoke, fly ash, particulate matter and trace elements. Toxic effect of even very small concentrations Of some of the trace elements make their characterization and quantification particularly important. Neutron activation techniques have become very powerful tools in the determination of trace element concentrations in the environmental samples, 1-4 In this work the concentration of some trace elements in the atmosphere of Ankara has been determined using INAA and 7-ray spectroscopy.
Experimental Sample collection The ambient particulate samples were collected outing 1975. The collecting stations were all located at the Middle East Technical University, about 10 km west of Ankara. Air was pumped through Whatman 41 or Delbag polystyrene filters. In order to minimize contamination from pump motors, filter holders were suspended 2 m above the pumps. They were connected to the high volume hurricane pumps by polyurethane tubes~ Particulates from 1000-2000 m s of air were collected on each filter paper at a 2 mS/rain rate.SA *Supported in part by the Scientific and Technical Research Council (T~BITAK) of Turkey.
Elsevier Sequoia S. A., Lausanne Akad~miai Kiad6, Budapest
M. SABUNCUet al.: TRACE ELEMENTS IN THE ATMOSPHERE
Irradiation The filter papers and the blanks were cut i n t o several pieces and pelletized. They were then sealed in polyethylene vials and irradiated along with standards at the T R - 1 Research Reactor in Istanbul at a flux of 1.5 9 1013 n " cm -2" s -~ for about two hours.
Counting Gamma rays emitted by the irradiated samples were counted with a 30 crna Ge(Li) detector having a FWI-IM for the 1332.5 keV photopeak of 6~ of 2.6 keV, coupled to a 4096 channel analyzer. Suitable irradiation, cooling and counting times were selected to optimize various trace element activities. Since counting was carried out in Ankara, only the long half-life ( > 15 h) isotopes could be studied.
Results and discussion
Ankara is a city with a serious air pollution problem, especially in winter. The seasonal variation of elemental concentrations in the atmospheric particulate matter of Ankara is given in Table 1. It is seen that some elements show significant seasonal
Table 1 Seasonal elemental concentrations of atmospheric particulate material in Ankara Concentration, n g / m 3 Element Spring
Summer
14 4.6 1.4 6.7 0.02 4.1
26 6.7 1.9 2.4 21
Hf
0.09
0.3
-
Sc
0.2
1.0
1.6
Br As Sb La Hg Cr
Zn
Co Na K Cs Eu Ce Sm Fe 16
32
0.4 83 0.2 0.02 1.4 780
-
1.7 560 230 0.5 0.1 6.3 3600
Fall
60 12 1.7 4.6 0.05 21
-
2.8 2400 0.7 5.6 0.6 2700
Winter
340 140 14 4.3 0.2 32 1.0 31 2.9 4400 1.9 11 0.4 3800
M. SABUNCU et al.: TRACE ELEMENTS IN THE ATMOSPHERE
variations, the concentrations generally being higher in winter. The uncertanties in elemental concentrations arise from errors in standard preparations, from uncertainties in the photopeak areas and from uncertainties in the air flow rate through the filters. The last source of uncertainty can sometimes cause errors of up to 20% in volume measurement. Therefore, only two significant figures are given. &
IO 3 ~-
~
As Sb
102
're W
Zn Hg
10
1
,I
LQ
I
;c, Fe : 1.00
1
10-
P
Element
Fig. I. Enrichment factors o f elements in the atmosphere o f Ankara with respect to crustal abundance. Fe was used as the normalizing element
Rather than discussing absolute concentrations, the results may be evaluated in terms of enrichment factor, 1 EF, with respect to different media. One could better understand the sources and distributions of the trace elements by looking at the EF's. The EF of an element X is defined as
EF =
where
(Cx/Cn), (Cx/Cnh Cx Cn
concentrations of element x in medium 1 and reference medium 2, - concentrations of normalizing element in medium 1 and reference medium 2. The EF's of the elements present in the atmosphere of Ankara were determined with respect to elemental distribution in the earth's crust. The crustal data were taken from WEDEPOHL 7 and iron was used as the normalizing element. Trace elements originating from the earth's crust should have EF values close to unity and" those from other sources should have EF's higher than unity. -
17
M. SABUNCU et al.: TRACE ELEMENTS IN THE ATMOSPHERE
The results of EF calculations are shown in Fig. 1, It is seen that the EF values of the elements, La, Hi', Sc, Co, Cr, Sin, Ce, Eu and Cs are between 0.5 to 3.0. Sources of these elements are probably crustal materials. The EF values of the elements Br, As, Sb, Hg, and Zn are much higher than unity indicating non-crustal sources. The enrichment of Br may be due to the use of leaded gasoline, whereas the source of t
$
10
I
Zn
L
L
I tLtill
10
I
~
I
ILIlIII
Br
102
I
~
LLLR~'L
103 Enrichment factor
Fig. 2. Variation of enrichment factors as a function of mass median diameters
the rest of the enriched elements is probably the combustion of coal which is the main source of heating in Ankara. The trace element content of various types of coal used in the Ankara region support our conclusion, s'8 Particle size distribution of the particulate material and other pollutants determine the extent of their harm to human health. The percentage of particle penetration into the pulmonary air space starts from about 10 #m size particles and reaches a maximum at and below about 1 #m. 9 A plot of mass median diameter (MMD) of an element as a function of EF is shown in Fig. 2. The MMD values were taken from References lO-12. It is seen from the figure that generally EF values increase with decreasing particle size; a result which is expected from gravitational force considerations. In monitoring or assessing the suspended particulate material in the atmosphere, we believe that besides trace element concentrations, determination of their particle size is of utmost importance.
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M. SABUNCUet al.: TRACE ELEMENTS IN THE ATMOSPHERE References 1. W. H. ZOLLER, G. E. GORDON, Anal. Chem., 42 (1970) 257. 2. P. SCHUTYSER,A. GOVAERTS, R. DAMS, J. HOSTE, J. Radional. Chem., 37 (1977) 651. 3. D. KURT, Y. SARIKAYA, J. Radioanal. Chem., 62 (1981) 161. 4. A. ALIAN, B. SANSONI, J. Radioanal. Chem., 89 (1985) 191. 5. I. OLMEZ, N. K. ARAS, J. Radioanal. Chem., 37 (1977) 671. 6. N. K. ARAS, W. H. ZOLLER, G. E. GORDON, G. J. LUTZ, Anal Chem., 45 (1973) 1481. 7. K. H. WEDEPOHL, Origin and Distribution of the Elements, L. H. AHRENS (Ed.), Pergamon, London, 1968, p. 999. 8. S. AK~ETIN, E. AY(~A, J. HOSTE, Radiochem. Radioanal. Lett., 15 (1973) 13. 9. T. F. HATCH, P. GROSS, Pulmonary Deposition and Retention of In'haled Aerosols, Academic Press, New York, 1964. 10. R. E. JARVIS, J. J. PACIGA, A. CHATTOPADHYAY, Prec. Intern. Symp. on the Development of Nuclear-Based Techniques for the Measurement, Detection and Control of Environmental Pollutants, IAEA-SM-206/9, Vienna, 1976. 11. R. E. LEE, Jr., C. F. SMITH, Environ. Sci. Teehnol., 6 (1972) 926. 12. N. SOMER, Techn. J., 5 (1978) 146.
2.
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