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Journal of Atmospheric Pollution, 2014, Vol. 2, No. 1, 12-16
Available online at http://pubs.sciepub.com/jap/2/1/3
© Science and Education Publishing
DOI:10.12691/jap-2-1-3
Studying Atmospheric Dust and Heavy Metals on Urban
Sites through Synchronous Use of Different Methods
Armen Saghatelyan, Lilit Sahakyan, Olga Belyaeva*, Nairuhi Maghakyan
Environmental Geochemistry Department, Center for Ecological-Noosphere Studies of NAS RA, Yerevan, Armenia
*Corresponding author: olgabel80@gmail.com
Received July 30, 2014; Revised August 11, 2014; Accepted August 14, 2014
Abstract Outdoor dust as a pollutant is also a transit environment for different pollutants emphasizing heavy
metals. Commonly, it is urban population, who is exposed to the maximal adverse impact of dust and associated
pollutants. In most cases, urban atmosphere researches are implemented on a few permanent monitoring stations.
Data obtained from these stations cannot be sufficient enough to provide a real picture of atmospheric pollution. The
most detailed information is obtained from synchronous instrumental sampling (aspiration) and studies of indicator
environments (snow cover, leaves). This research pursued assessment of levels of dust and heavy metal pollution of
near-surface air through different methods on the example of city of Yerevan (Armenia). The city area comprises a
complex mosaic of natural and man-made sources of dust and heavy metals. So, for many years Yerevan has been
exposed to high dust and associated heavy metals pollution levels. The research was implemented in 2011 through
2012 and included spatially coherent snow and tree leaf sampling, and instrumental sampling of dust and allowed
assessing dust and heavy metal load and contents on the entire territory of Yerevan, identifying pollution sources,
contouring ecologically unfavorable sites and finally identifying risk groups among the population.
Keywords: urban air pollution, dust, heavy metals, alternative research methods
Cite This Article: Armen Saghatelyan, Lilit Sahakyan, Olga Belyaeva, and Nairuhi Maghakyan, “Studying
Atmospheric Dust and Heavy Metals on Urban Sites through Synchronous Use of Different Methods.” Journal of
Atmospheric Pollution, vol. 2, no. 1 (2014): 12-16. doi: 10.12691/jap-2-1-3.
1. Introduction
It is known that outdoor dust is not only an
environmental pollutant, but also a transit medium for
different environmental pollutants and heavy metals (HM)
in particular [16]. Today, it is urban population, who is
most exposed to adverse impacts of dust and dust-
associated pollutants [15] as a modern city combines a
variety of economic activities with numerous pollution
sources and high density of population [4].
Commonly, dust and HM pollution researches on urban
sites are implemented on a few permanent monitoring
stations [3]. Automated air sampling methods are used
widely, however they have a number of limitations such as
expensive equipment, labour-intensive and expensive
maintenance and service, and so on. So, it is obvious that
the number of such stations is too limited. This makes the
setting up of a regular sampling grid unrealistic.
Such disadvantages may be compensated by alternative
research methods with application of indicator mediums.
The latter allows setting up a regular grid of sampling
throughout urban areas, whereas localization of sampling
sites may vary depending on research tasks so as to assure
representativeness of data obtained. One of major result of
this indicator medium research is the generated set of
complementary informative air pollution parameters
[4,9,14], the analysis of which allows assessing both dust
and HM load, contour ecologically unfavorable sites
throughout a city, identify risk groups among the
population, assess health risks [2,10] and finally develop
appropriate risk reduction measures.
This research was aimed at assessment of near-surface
air pollution levels with dust and HM through different
methods on the example of city of Yerevan (Armenia).
Yerevan – Armenia’s capital city – covers an area of
227sq.km. It is situated in north-east of Ararat valley in
the canyon of River Hrazdan. The relief is sufficiently
diverse and is shaped as plains, plateaus, foothills,
canyons.
The climate is continental with rather broad
temperature daily and seasonal amplitude. Summers are
hot, dry and long-lasting, winters are cold and short. Mean
annual temperature varies from +8.80 to +11.60, with
summer mean +22°C, winter mean –20°C, snow cover is
not common for every year: The temperature regime of
the city is strongly impacted by slope aspect and large
altitudinal variations (850-1420 m a.s.l.). Mean air
temperature of the lower central and upper suburban parts
of the city varies 1.5 to 2.0°C. The annual norm of
precipitation varies from 300 to 350 mm. Main
precipitations occur in the spring and autumn.
The natural landscape of the city area is mainly semi-
desert (predominant) and arid steppe.
The geological structure of the area is dominated by
volcanic lavas, tuffs and Quaternary sediments
characterized by close-to-Clarke contents of HM (Zn(9,4)–
Journal of Atmospheric Pollution 13
Cu(2,9)–Co(1,8)). The soil is mostly of brown semi-desert
type, soil profile is rich in carbonates and the lower
horizon presence of gypsum is common, this providing a
favorable environment for HM accumulation on soil
profiles [11].
For years Yerevan was distinguished by high levels of
dust pollution of atmospheric air and intense geochemical
anomalies of HM in transit and depositing mediums
[12,13]. The city houses the major part of Armenia’s
industrial enterprises (42%) and population (34%); heavy
traffic loads, too, are common to Yerevan. Major
industrial branches are food production, jewelry, chemical
and metalworking industries. Most of industrial enterprises
are located in the south, in the so-called industrial part of
the city. Another peculiarity of Yerevan is that it
comprises 39 active deposits and mines of tuff and basalt,
sand and gypsum which add to the dust load on the city.
2. Materials and Methods
This dust research was done through two different
methods: indication environment and direct instrumental
sampling. Indicator environments allow assessing both
dust and HM load throughout the city, disclosing
geochemical peculiarities of HM anomalies in dust, while
instrumental measurements are aimed at assessment dust
content and spatial distribution of dust throughout urban
areas. A picture of dust load distribution reflects pollution
with coarse dust which deposits under the effect of gravity
whereas airborne dust represents a mass of fine suspended
particles.
The different aspects of atmospheric air pollution with
dust may be assessed through different methods, the
concurrent use of which allows obtaining comprehensive
data about different aspects of pollution. Finally, this will
serve as a basis for assessment of population health risks.
Investigations were carried out on a seasonal basis in
2011 through 2012 in the Center for Ecological-
Noosphere Studies of NAS RA (CENS). Due to its
sorption properties snow is a temporal depositing medium
and provides information about short-term pollution [9],
[14]. In summer similar indicator medium are leaves of
arboreous plants [7].
Because of a limited budget, coherent sampling points
(Figure 1) were selected from numerous mobile long-term
monitoring sites (over 100) of CENS. Selection was based
on 1) research data obtained earlier, 2) presence of
probable pollution sources, 3) presence of persistent snow
cover in winter months and its integrity within a sampling
day, 4) presence of tree species required for carrying out
sampling in summer, 5) maximal proximity of sampling
points to residential sites.
Snow was sampled in compliance with the appropriate
methods [9,14]. Snow samples were collected from plots
with a defined area, placed into plastic containers and
transported to the lab where the snow samples were
melted at a room temperature and filtered; dry residue was
then weighed. Dust and HM load in winter (Pw and PHM_w)
was determined by formulas (1) and (2) [9]:
/
w dust
P m St= ⋅
(1)
__HM w i snow w
P CP= ⋅
(2)
where mdust is the sample dust weight; S – area of a
sampling plot; t –a time interval between formation of a
stable snow cover and sampling; Ci_snow – concentration of
an element in snow dust.
Figure 1. A map of location of sampling sites in Yerevan
Selection of plant species was done with regard for dust
accumulation properties and prevalence in Yerevan area.
The studied tree species were white elm (Ulmus laevis),
Chinese elm (U. parvifolia), Persian walnut (Juglans
regia), eastern plane (Platanus orientalis), and common
lilac (Syringa vulgaris). Leaves were gathered at a max.
height of 2 m above the ground, placed into paper bags
and transported to the lab. Dust from leaf surfaces was
washed out by distilled water, the generated liquid was
filtered. A residue was dried are weighed. Dust and HM
load in summer (Ps and PHM_s) was determined by
formulas (3) and (4) [17]:
( 0.35 ) /
s dust dust
P m m St=−⋅
(3)
__HM s i leaf s
P CP= ⋅
(4)
With a goal to assess HM contents in dust, dry residue
was dissolved in nitric acid, then the acid was evaporated,
and finally, to the residual solution de-ionized water was
added until 20 ml was achieved. After that, the obtained
solution was analyzed for concentrations of 11 chemical
elements Hg, Cd, As, Pb, Cr, Ni, Co, Zn, Cu, Ag, Mo
(ISO 9001) on AAS AAnalyst 800 [1].
A dust load level and a hazard degree of dust pollution
of atmospheric air in winter and summer are assessed
according to the N.S. Kasimov four-step scale provided in
Table 1 [4].
Table 1. A four-step scale of dust load levels assessment [4]
Dust load level,
kg/sq.km daily
Pollution level and degree of hazard
< 250 Low
250 – 450 Moderate, moderately hazardous
450 – 800 High, hazardous
> 800 Very high, extremely hazardous
14 Journal of Atmospheric Pollution
A sanitary and hygienic assessment of the sites was
done through collation between concentrations of
chemical elements and their Maximum Acceptable
Concentrations (MAC) in soils [5], as no MAC values for
deposited dust have ever been developed. A level and
degree of hazard of poly-element pollution of dust with
HM was assessed based on the value of summary index of
pollution (SIP) – an additive sum of excesses of actual
concentrations of HM in dust vs. MAC (unit less),
formulas (5) and (6) [5]:
_/
i snow
SIP C MAC=
∑
(5)
_/
i leaf
SIP C MAC=
∑
(6)
The levels of poly-element dust pollution with HM was
assessed according to a five-step scale accepted in
Armenia [5]
Table 2. A five-step scale of assessment of levels of poly-element dust
pollution with HM [5]
SIP value
Pollution level and degree of hazard
< 8
Permissible
8 – 16
Low
16 – 32
Moderate, moderately hazardous
32 – 128
High, hazardous
> 128
Very high, extremely hazardous
Instrumental sampling of dust was done consistent with
methods accepted in the RA [8] and using a portable
aspirator АВА-1-120-02А. A certain volume of air was
pumped through an AFA standard filter (a cotton fiber
filter), then the filtrates were placed into paper bags and
transported to the lab. Dust content was determined by
weighing. Then collation was done between the obtained
data and atmospheric dust standards accepted in the RA [6].
A set of relevant maps has been produced employing
IDW methods and GIS ArcView software.
3. Results and Discussion
According to snow cover survey data, in winter the
major part of the territory displays low levels of dust load
(less than 250 kg/sq.km daily). However, against the
background of a low dust load level, 21% of the studied
samples displayed high level of dust load (varying 450-
800 kg/sq.km daily). And finally 8% of samples displayed
an extremely high dust load level (over 800 kg/sq.km
daily). In the studied period, daily dust load averaged to
383.382 kg/sq.km (Table 3), this corresponding to a
moderate degree of hazard.
Table 3. Descriptive statistics of dust load, dust content, HM total in
winter and summer
Parameter Valid N Mean Median Min Max SD
Dust load in
winter,
kg/sq.km
24 383.38 211.94 38.33 2072.3 473,82
Dust load in
summer,
kg/sq.km
25 471.37 491.81 110.28 912.89 227,53
Dust content
in summer,
mg/cub.m
24 0.175 0.143 0.003 0.518 0,12
HM load in
winter,
kg/sq.km
24 0.368 0.175 0.030 2.610 0.60
HM load in
summer,
kg/sq.km
25 0.972 0.340 0.090 14.940 2.92
In summer, a low level of dust load was established for
20, medium – for 32, high – for 44% of samples, whereas
4% of samples exhibited an extremely high level of dust
load. In summer daily dust load averaged to 471.365
kg/sq.km daily (Table 3), that corresponds to a high
degree of hazard.
As seen from provided data, dust load levels in winter
vs. summer vary in a far more broader range, so a standard
deviation in winter is almost twofold higher against a
summer index (Table3).
Quite a different picture is observed in respect of
summary load of HM. A range and standard deviation of
this parameter is higher in summer (Table 3).
Figure 2. Dust load levels and dust contents in Yerevan atmosphere
As indicated by the research, in winter a mosaic-like
distribution of dust load is common to the city (Figure 2). The highest dust load level in winter is detected in the
north and northwest of the city. Its central part is
Journal of Atmospheric Pollution 15
characterized by a high level, in the southwest - by a low
level of dust load. In summer vs. winter dust distribution
throughout the city is of a more even character. Maximal
values were established in the north of Yerevan (Figure 2).
In the southern and central parts of the city dust content
is low and does not exceed MAC (0.15 mg/cub. m), while
in the north, northeast and southwest the dust contents are
high. Maximal peaks of dust were recorded in the
northwest of the city. Mean dust content in Yerevan is
0.175 mg/cub. m (Table 3), exceeding the MAC 1.16
times.
In multifunctional cities such as Yerevan stationary
dust sources are located rather dense, so it is hard to
identify a dominant one. Nonetheless, considering
distribution of man-made dust sources (including deposits
noted above), directions of dominant winds (Figure 3) and
frequently detected temperature inversions one may
conclude that presumably, high dust contents in the north
and northeast districts of the city and in near-earth layer
originate under the impact of active deposits.
A mosaic character of dust load distribution in winter is
determined by frequent calm weather (Figure 3). In
summer, winds are more frequent, air movement is more
intense. Consequently, this brings to a relative increase in
dust load throughout the city.
Figure 3. Frequency of wind directions and calm weather in Yerevan
Dust load distribution reflects pollution with coarse
dust which deposits under the effect of gravity whereas
dust content represents a mass of fine suspended particles.
It is a cause, for which dust content and dust load in the
city area do not correlate (r = –0.134; p = 0.541). Yet, a
significant correlation is detected between dust loads in
winter and summer (r = 0.435; p = 0.038).
Both in winter and in summer in most parts of the city
the HM load is low; the highest value of this parameter is
detected in the south, housing three operating
metalworking plants.
Generalizing the obtained research results, one may
conclude that the southern part of the city is characterized
by low and medium levels of dust load and high level of
HM load in dust, whereas an opposite picture is observed
in respect of the northern part of Yerevan: heavy dust load
is accompanied by low load of HM. Central part of the
city is characterized by high level of dust load (Figure 2)
and medium level of HM load in both seasons.
One should note that partially, Yerevan dust is of
natural origin. However, extremely high dust load levels
and dust contents detected in the north and northeast of the
city are formed presumably under man-made impacts
emphasizing those produced by active tuff, basalt, clay
and sand deposits. Heavy metals in atmospheric dust are
of manmade origin.
The major share (over 50%) in a total load of HM falls
on Zn and Cu in both seasons. In winter a sum mass
fraction of Mo, Pb and Ni is also high. In summer Co and
Cr deposition is more intense per unit area, their shares
increasing at the expense of Pb, Ni and Mo. The level of
load of most HM except Pb increases in summer. From
the ecological viewpoint it is noteworthy, that in summer,
Cd load and contents in dust increase (Figure 4).
Figure 4. HM load in Yerevan
Figure 5. Levels of HM pollution
16 Journal of Atmospheric Pollution
In winter, the major part of the city area is characterized
by permissible and low levels of HM pollution (Fig. 5).
The most intense pollution zone forms in the south of the
city. Dominating pollutants in winter period are Pb and Cd,
Mo being in the zone of extremely high pollution level.
Commonly, in summer pollution levels are high
throughout Yerevan, a dominant summer pollutant being
Cd. The obtained results prove that a number of
metalworking plants located in the south of the city are a
powerful source of HM and particularly of Mo, Hg and Cu.
So, a concurrent application of indicator mediums and
instrumental measurements allows to mutually
compensating disadvantages of separate atmospheric air
research methods (Figure 6). This helps cover the most
essential research aspects to obtain best informative
parameters of eco-geochemical status of near-surface layer
of urban air basins.
Figure 6. A conceptual scheme of a concurrent application of alternative and instrumental methods of investigation of atmospheric dust and associated
pollutants on urban sites
4. Conclusions
Using alternative indicators allows assessing dust and
HM load, deriving a picture of a spatial distribution of
pollutants, providing eco-geochemical and sanitary and
hygienic assessment of air pollution with dust and HM.
Using instrumental methods of research allows
assessing dust content in the atmosphere and obtaining a
picture of spatial distribution of dust.
A concurrent use of alternative and instrumental
methods allows compensating disadvantages of separate
methods and therefore obtaining the best comprehensive
picture of pollution of near-surface layer of urban air,
identifying pollution sources, contouring ecologically
unfavorable sites, revealing risk groups among the
population and assessing environmental and health risks.
Acknowledgements
This research was implemented in the frames of a grant
№11-1e054 “Investigations of geochemical stream of
elements in the atmosphere of the city of Yerevan” under
support of State Education Committee to the Ministry of
Education and Science RA.
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