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38
National Academy of Sciences of RA
Electronic Journal of
NATURAL SCIENCES
ՀՀ Գիտությունների Ազգային Ակադեմիա
Էլեկտրոնային
ամսագիր
ԲՆԱԿԱՆ ԳԻՏՈՒԹՅՈՒՆՆԵՐ
Национальная Академия наук РА
Электронный журнал
ЕСТЕСТВЕННЫЕ НАУКИ
1(20), 2013
Ecology
Էկոլոգիա
Экология
DUST AND STREAM OF HEAVY METALS IN THE ATMOSPHERE
OF THE CITY OF YEREVAN
A. K. Saghatelyan, L. V. Sahakyan, O. А. Belyaeva, G. H. Tepanosyan, N. R. Maghakyan, M. H. Kafyan
The Center for Ecological-Noosphere Studies of NAS RA, Environmental Geochemistry Department, 68 Abovian, 0025 Yerevan,
Armenia; Phone: (+374 10) 572924; Fax: (+374 10) 572938; e-mail: ecocentr@sci.am
ABSTACT
The goal of this research was assessing dust load, heavy metal load and heavy metal concentrations in the dust of ambient air of
Yerevan. With a view of characterizing geochemical associations in the winter of 2011-2012 a survey of snow cover was done. А
dust load level on the major part of the city’s territory is low, whereas in separate points sharp peaks are recorded, a daily dust load
value averaging to 383 kg/sq.km per day. This agrees with а mean pollution level and a moderate degree of hazard. A total load of
heavy metals in dust varies 0.03 to 2.61, averaged 0.37 kg/sq.km per day. Summary mass fraction of heavy metals in dust varies bet-
ween 0.02 to 2.83 %, averaged 0.20%. The intensity of geochemical anomalies of heavy metals in dust is extremely high. Domina-
ting atmospheric dust pollutants to Yerevan are Mo and Ag. 91-99% out of а summary share of heavy metals in geochemical
anomalies of dust falls on Mo and Ag. MAC-exceeding values were recorded for elements of 1st (Pb, Zn, Cd, As, Hg) and 2nd (Mo,
Cu, Co, Ni) category of hazard.
Key words: urban air pollution, dust, heavy metals, environmental geochemistry, geochemical stream
INTRODUCTION
Air basin is a transit environment for diverse pollutants and particularly heavy metals in which they travel and disperse.
Most airborne metals are associated with dust particles [13, 26], transforming thus dust from a pollutant to a pollutant
holding environment. Abundant researches have been done which prove the harmful effect of dust and heavy metals on
human organism. Airborne dust is known to pose an inhalation hazard (IDA) and depending on the size of particles, it
may cause a scope of respiratory diseases (pneumoconiosis, silicosis, asthma and finally lung cancer) and cardio-
vascular, renal, hepatic dysfunctions. Through contact with the skin dust may trigger allergic reactions up to severe skin
eruptions [4, 27]. Depending of doses and ways of exposure, chemical forms as well as of a man’s age, gender, social
status, genetics, diet and many other factors, heavy metals after entering into the human organism may exert neurotoxic,
immunotoxic, nephrotoxic, fetotoxic and teratogenic effects and may also have a direct impact upon behavior of
humans and kids in particular, provoke mental and neural dysfunctions, induce attention deficit syndrome, autism, and
so on. Concluding, one should note that US Environmental Protection Agency and the Agency for Research on Cancer
have labeled heavy metals as carcinogenic (known or possible) elements [5-8, 11, 12, 24].
Air-migration stream is a significant factor in origination of man-made anomalies of heavy metals on urban sites. As
indicated, a high level of dust load in cities in combination with high concentrations of heavy metals is a risk factor to
public health [3, 24, 25]. A dust and heavy metal load issue needs to be investigated in respect to almost all urban sites,
and it is the fact which underpins selection of different research methods. Commonly, airborne dust and metals are
monitored on special stations equipped with automated dust sampling instruments [10]. Automated air sampling
methods are widely accepted nonetheless, they have a number of limitations: the equipment is expensive; maintenance
and running of such stations are labor-intensive and expensive, too. Consequently, the number of such stations is very
limited, making thus unrealistic the arrangement of a regular sampling grid. Monitoring stations are stationary, so they
cannot reflect the dynamics of anomalies under temporal and spatial changes in urban areas. That is why in atmospheric
investigations indirect alternative research methods are often more preferable.
One of alternative methods of airborne dust and metals investigations is surveying snow cover. Due to its good sorption
properties, snow absorbs the major part of dust from the ambient air [13, 17, 18].
So, the goal of this research was assessing dust load, heavy metal load and heavy metal concentrations in the dust of
ambient air of Yerevan through snow cover surveys (2011-2012).
Yerevan – the capital city of Armenia – covers an area of 227 sq. km. The natural landscape of the city’s territory is
mainly semi-desert, arid steppe and steppe. The climate is continental with rather a broad amplitude of temperature
(summer temperature: from +22 to +26oC; winter – from -20 to -30oC), precipitation 300-350 mm. The relief is rather
diverse and is represented by plains, plateaus, foothills, River Hrazdan canyon. A geological composition of the ter-
39
ritory is dominated by volcanic lavas, tuffs and Quaternary sediments characterized by close-to-clarke1 contents of
heavy metals. A natural geochemical association in Yerevan’s soils is characterized by a weak intensive series: Zn(9,4) –
Cu(2,9) – Co(1,8)
2. The soil (mostly brown semi-desert) profile is rich in carbonates, to the lower horizon a presence of
gypsum is common, this evidencing a lack of chemical element washout and creating a good environment for heavy
metals accumulation on soil profiles [20].
Yerevan has long been not only the administrative and industrial center which comprises the impressive amount of
active industrial enterprises and produces some 43% of total industrial output of the country, but also an essential trans-
port junction of the country. Major industrial branches developed in Yerevan are food (adding beverage) production,
jewelry, chemical and metalworking industries. A large share in industrial production falls on processing industries and
particularly on food production, manufacture of finished metal items, press and printing activities, chemical and tobacco
production [9]. The city homes over 34% of total population of Armenia [14].
As result of such density of population, industries and transport a persistent stream of heavy metals has originated with
qualitative and quantitative alternations, which creates a specific man-made geochemical status of the territory of the
city, quite different from natural. So, owing to natural and man-made specificities, the pronounced geochemical anoma-
lies of heavy metals in diverse environmental compartments of Yerevan are of man-made origin [20-22].
MATERIALS AND METHODS
Snow was sampled from a defined area, fixed long-term monitoring sites (Fig. 1). The snow was sampled taking pre-
cautions against sample contamination with underlying soils. Total 24 samples were collected which were then placed
in clean plastic containers and transported to the lab [17, 18].
In order to study dust load and chemical composition of dust absorbed by snow, collected samples were melted at a
room temperature. Then the melted water was filtered using standard, weighted, ash free filters. As most methods of
analysis are designated for liquid samples, so filters with dry residue were dissolved in concentrated nitric acid. The
generated liquid was filtered; the volume of filtrate gauged to 100 ml with distilled water and then filtrate was analyzed
for concentrations of eleven elements (Hg, Cd, As, Pb, Cr, Ni, Co, Zn, Cu, Ag and Mo) on AAS PE AAnalist 800 [2].
The dust load (P) was calculated by a formula (1):
P = P0 / S · t (1),
where P0 is the mass of filtered substance, S – a sampling site area, t – a fell snow layer formation time (in the
considered case – 1 day) [17, 18]. The dust load level was assessed with help of a 4-grade scale suggested by N.S.
Kasimov [13].
The load of elements (P element) is a product of P and Ci:
Pelement = Ci · P (2).
Additive sum of Pelement is a total load of heavy metals in dust [13, 18, 17].
To characterize quality and quantity indices of heavy metals anomalies in dust, arranged were ranked geochemical
series of heavy metals contents in soils graded by concentration coefficients (3):
Kc = Ci / Cb
(3),
here Ci is the contents of i metal in dust, Cb – its background contents in soils [13, 18, 17].
As an integral characteristic of pollution, the Summary Index of Concentration was calculated, as well (Zc):
)1(
1
−−= ∑
=
nKZ
n
i
cc
(4),
where n is number of element with Kc > 1 [13, 18, 17]. This parameter characterizes only the geochemical features with
no regard for the toxicity of elements. So, to provide a sanitary and hygienic assessment, concentrations of heavy metals
in dust were collated with MAC values for soils accepted in Armenia.
KMAC = Ci / CMAC (5),
where Ci is the contents of i metal in dust, CMAC – its Maximum Acceptable Concentration in soils [15, 16].
With a goal to identify heavy metals anomalies in dust, geochemical and sanitary and hygienic series of heavy metals
were calculated and ranked according to Kc and KMAC values [18, 17].
The maps were produced applying GIS technologies through the IDW method (ArcGIS).
RESULTS AND DISCUSSION
1 Clarke number is the average content of a chemical element in lithosphere [17,18, 23].
2 In brackets clarke-exceeding values are given.
40
According to snow cover survey data, the major part of the territory displays low levels of dust load (less than
250 kg/sq.km per day). However, against the background of a low dust load level, 21% of the studied samples displayed
high dust load (varying 450-800 kg/sq.km per day), those values corresponding to a high level of hazard. And finally
8% of samples displayed a very high dust load level (over 800 kg/sq.km per day), which corresponds to an extremely
high level of hazard (Fig. 2). In the study period, daily dust load averaged 383 kg/sq.km¸ this corresponding to a mean
dust load and a medium level of hazard.
Fig. 2. Dust load levels according to snow survey data for Yerevan territory (2011-2012).
Heavy metal total load (HM load) in dust varies from 0.03 to 2.61 and averages to 0.37 kg/sq.km per day (Fig. 3a).
Commonly, the value a total load of heavy metals is directly proportional to that of dust load; the two parameters show
moderate positive correlation (Fig. 3b).
The mass fraction of heavy metals in airborne dust displays two orders of magnitude (Fig. 4a): 0.02-2.83% (on average,
0.20%), however no significant correlation was established of a total load and mass fraction of heavy metals in dust
(Fig. 4b). Unprecedentedly high mass fraction of heavy metals is detected on a sampling point № 6 in the vicinities of
two huge operating plants “Makoor Yerkat (Pure Iron)” and “Armenian Molybdenum Production”.
41
a b
Fig. 3: a) dust load and total load of heavy metals; b) correlation of dust load and total load of heavy metals.
a b
Fig. 4.: a) mass fraction of heavy metals in the atmospheric dust of Yerevan and total load of heavy metals;
b) correlation between mass fraction and total load of heavy metals.
It is noteworthy that on the average 95.3% of mass fraction of heavy metals in dust is made by five elements only,
which include elements of 1st category of hazard – Pb and Zn and 2nd category of hazard – Cu, Mo and Ni (Fig. 5). 4.7%
of the mass fraction of metals falls on Cr, Co, Ag and three toxic elements: Hg, Cd and As.
Qualitative and quantitative characteristics of atmospheric dust are clearly expressed in a geochemical series (Table 1).
As seen from data (Table 1), the main pollutants of airborne dust in the studied period are Mo and Ag, which hold the
first position of series. Mo sources in Yerevan are molybdenum processing plants, whereas major sources of Ag are
jeweler’s workshops. The established geochemical anomalies in the dust of Yerevan are characterized by high intensity,
a summary share of Mo and Ag in the intensity of geochemical anomalies making 90.6-99.8%.
Next positions in the geochemical series are held by Cu and Zn. It should be noted, that in maximal and averaged series
Pb is present, which – despite the fact that the use of ethylated gasoline was banned in 2001 – has been the major
pollutant of atmospheric dust on Yerevan’s territory.
Table 1. Geochemical series of heavy metals in atmospheric dust of Yerevan and
Summary Index of Concentrations (Zc).
Geochemical series [a] Zc
Minimum Mo
(
7.4
)
– Ag
(
5.8
)
13.2
Maximum Mo
(
21759.6
)
>> Ag
(
909.3
)
> Co
(
34.2
)
– Cu
(
30.9
)
–Pb
(
21.9
)
> Zn
(
7.5
)
– Ni, As
(
2.5
)
22768.4
Average Mo
(
959
,
0
)
– Ag
(
138
,
8
)
>> Cu
(
6
,
4
)
– Zn
(
2
,
7
)
– Pb
(
2
,
2
)
– Co
(
1
,
5
)
1112.4
[a] in brackets excesses vs. geochemical background are given.
Wholly, for 38% of samples (9 samples) we established low values of Zc < 64, for 25% (6 samples) values of Zc
ranging 64 to 128, corresponding to a mean pollution level, for 13% (3 samples) – Zc values vary between 128 and 256,
this corresponding to a high pollution level, and finally for 25% of samples (6 samples) Zc > 256, which corresponds to
the extremely high level of pollution. As seen from a map of summary heavy metal pollution in dust (Fig. 6) a major
portion of the city is characterized by an extremely high level of summary pollution field. The highest values of Zc are
42
established for the southern – industrial – part of the city, whereas its central and northern sections display a high to
mean summary level of heavy metal pollution in snow dust.
Fig. 6. A schematic map of summary heavy metal pollution in snow dust.
With a goal of providing a sanitary and hygienic assessment, concentrations of heavy metals in dust were collated with
Maximum Acceptable Concentrations (MAC) for soils established for Armenia [2, 16]. MAC-exceeding values were
recorded for elements of 1st (Pb, Zn, Cd, As, Hg) and 2nd (Mo, Cu, Co, Ni) category of hazard. The sanitary and
hygienic series of heavy metals are visualized in Table 2. Maximal and averaged series are led by Mo. The averaged
and maximal sanitary-hygienic series are characterized by high intensity. Maximal excesses against MAC values for
heavy metal contents in snow dust were detected on the southern part of the city in the surroundings of the two metal
concentrate processing plants “Makoor Yerkat (Pure Iron)” and “Armenian Molybdenum Production”.
Table 2. Sanitary and hygienic series of heavy metals in atmospheric dust of Yerevan and their total intensity.
Sanitary and hygienic series [a] Total intensity
Minimum – –
Maximum Mo
(
197
,
8
)
> Co
(
68
,
5
)
– Cd
(
28
,
5
)
– Cu
(
14
,
0
)
– Pb
(
13
,
5
)
> Zn
(
3
,
4
)
– As
(
2
,
5
)
– Ni
(
1
,
1
)
– Hg
(
1
,
0
)
303.3
Averaged Mo
(
8
,
7
)
– Cd
(
4
,
4
)
– Co
(
3
,
7
)
– Cu
(
2
,
9
)
– Pb
(
1
,
5
)
– Zn
(
1
,
3
)
22.5
[a] in brackets excesses vs. MAC are given
Generalizing the obtain research results, one may conclude that the southern part of the city is characterized by low and
mean levels of dust load and a large mass fraction of heavy metals in dust, whereas in respect to its northern part one
may observe quite a different picture: heavy dust load is accompanied by low values of mass fraction of heavy metals.
Works aimed at identification of sources of dust and those of heavy metal pollution in dust, are in progress.
43
CONCLUSIONS
The performed investigations support the following conclusion.
The major part of Yerevan displays low values of dust load: against such a background sharp peaks are recorded which
correspond to a high and extremely high level of hazard, as the studies advanced, on the average we detected moderate
dust loads all over the city. A total load of heavy metals (HM load) in dust varies from 0.03 to 2.61, averaged
0.37 kg/sq.km per day. The mass fraction of heavy metals in dust varies 0.02 to 2.83%, averaged 0.20%. A major
portion of Yerevan territory exhibits a high intensity of geochemical anomalies of Mo and Ag in dust, this conditioning
an exclusively high level of summary pollution with heavy metals in dust there. MAC-exceeding values were recorded
for elements of 1st (Pb, Zn, Cd, As, Hg) and 2nd (Mo, Cu, Co, Ni) categories of hazard. The southern part of the city is
characterized by low dust loads and a large mass fraction of heavy metals in dust, whereas in the northern part heavy
dust loads are accompanied by low values of mass fraction of heavy metals.
ACKNOWLEDGEMENT
This study was performed within the frame of a research “Investigations of geochemical stream of elements in the
atmosphere of the city of Yerevan” through a grant awarded by a State Committee of Science of the RA Ministry of
Education and Science.
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