THE ECOLOGICAL ASSESSMENT OF SOILS AROUND AGARAK TOWN

Abstract

Mining and smelting industry is developed in the area of the study. This economic sphere is one of the main sources of soil pollution with heavy metals which are considered as dangerous pollutants causing the desertification of soils. As a result of this study the appreciable qualitative changes in contents of some heavy metals were revealed.

Full text

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Փորձարարական և տեսական հոդվածներ
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Экспериментальные и теоретические статьи
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• Experimental and theoretical articles •
Biolog. Journal of Armenia, 1 (65), 2013
THE ECOLOGICAL ASSESSMENT OF SOILS AROUND
AGARAK TOWN
K.A. GHAZARYAN1, H.S. MOVSESYAN1,
N.P. GHAZARYAN2, K.V. GRIGORYAN1
1Yerevan State University, Faculty of Biology, Department of Ecology and
Nature Protection, ghazaryank@mail.ru
2Ministry of Agriculture, Scientific Center for Risks Assessment and Analysis
in Food Safety Area SNCO, Nubarashen
Mining and smelting industry is developed in the area of the study. This economic sphere is one
of the main sources of soil pollution with heavy metals which are considered as dangerous pollutants
causing the desertification of soils. As a result of this study the appreciable qualitative changes in
contents of some heavy metals were revealed.
Soil pollution – heavy metals – mining industry – recultivation of soils – hydroseeding method
Ուսումնասիրման տարածքում զարգացած են արդյունաբերության լեռնամետալուրգիական և
լեռնաարդյունաբերական ճյուղերը: Արդյունաբերության այս ճյուղերը հանդիսանում են հողերի
անապատացման պրոցեսին նպաստող վտանգավոր աղտոտիչներից` ծանր մետաղներով, աղտոտման
հիմնական աղբյուրներից մեկը: Մեր կողմից կատարված ուսումնասիրություններով հայտնաբերվել են
մի շարք ծանր մետաղների պարունակության նկատելի քանակական փոփոխություններ:
Հողերի աղտոտում – ծանր մետաղներ – լեռնարդյունաբերություն –
հողերի ռեկուլտիվացում – հեղուկ սերմնացանի մեթոդ
В районе проводимыx нами исследований (г.Агарак) развиты горнодобывающая и
горнометаллургическая отрасли промышленности. Эти отрасли являются одним из основныx
источников загрязнения почв тяжелыми металлами – наиболее опасными загрязнителями,
способствующими процессу опустынивания почв. Проведенными нами исследованиями
выявлены заметные количественные изменения в содержании ряда тяжелыx металлов.
Загрязнение почв – тяжелые металлы – горнодобывающая промышленность – рекультивация
почв – метод гидропосева
Agarak town is situated in the south-east of Armenia. Mining and smelting industry is
developed in this area. This economic sphere is one of the main sources of soil pollution with
heavy metals (Pb, Cu, Ni, Cd, As, Mo, etc) which are considered as dangerous pollutants causing
the desertification of soils [4, 5, 7, 8, 9, 10].
The lands of the studying area belong to the mountain forest brown soil type. In Armenia,
this soil type is distributed at 500-1700 meters above sea level, and reaches up to 2400 meters in
arid southern slopes. The topology of mountains with forest brown soils is characterized by
various altitudes, such as mountains and dividing ridges, as well as fallings lowering to clefts and
tributaries [1, 3].

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K.A. GHAZARYAN, H.S. MOVSESYAN, N.P. GHAZARYAN, K.V. GRIGORYAN
Materials and methods. Experiments were carried out under field and laboratory conditions. Ten
the most risky regions and one non-polluted region, as a control, were selected for field studies the
sections were dug, and the samples were taken from the horizontal profile. The physicochemical
parameters of soil samples were determined under laboratory conditions [2, 6].
Results and Discussion. Eleven sections were sorted into types and subtypes according
to the results of field study.
The main soil types in studying objects were the mountain forest brown soil type and
its 2 subtypes: (1) the brown carbonate soil of mountain forests, and (2) the brown typical soil
of mountain forests.
Section descriptions and total properties determined during the field study are
presented in tab. 1.
Tab. 1. Total characteristics of sampling areas
Sample
number Soil type and
subtype Basin Surface
gradient Microrelief Soil surface cover Erosion degree (0-4)
1 brown typical
of forest Karchevan
river 30° smooth herbage - 75%,
naked soil - 20%,
stones - 5% 2
2 brown typical
of forest Karchevan
river 25° smooth herbage - 40%,
naked soil - 30%,
stones - 30% 2
3 brown typical
of forest Karchevan
river 30° small mounds herbage - 40%,
naked soil - 20%,
stones - 40% 2
4 brown typical
of forest Karchevan
river 35° smooth
herbage - 70%,
shrubs - 15%,
naked soil - 10%,
stones - 5%
2
5 brown typical
of forest Karchevan
river 0° smooth
herbage - 85%,
shrubs - 12%,
stones - 3% 0
6 brown
carbonate of
forest
Karchevan
river 30° mounds herbage - 50%,
naked soil - 10%,
stones - 40% 2
7 brown
carbonate of
forest
Karchevan
river 0° smooth
herbage - 50%,
naked soil - 50% 0
8 brown
carbonate of
forest
Karchevan
river 10° small mounds herbage - 30%,
naked soil - 20%,
stones - 50% 2
9 brown
carbonate of
forest
Araks
river 5° small mounds
herbage - 20%,
naked soil - 25%,
stones - 55% 3
10 brown
carbonate of
forest
Araks
river 10° smooth herbage - 30%,
naked soil - 45%,
stones - 25% 2
Control brown
carbonate of
forest
Karchevan
river 0° smooth
herbage - 70%,
naked soil - 25%,
stones - 5% 1
According to tab. 1, the soil surface was 10-30% uncovered by plants, except the
section 5, which was fully covered, and the sections 7 and 10, which were nearly half covered.
The main vegetation was presented by herbage. Shrubs were observed only in the areas of
sections 4 and 5. The studied soils were medium and highly eroded, except the 5, 7 and
control sections, where erosion processes almost didn’t occur related to the well-developed
vegetation and the smooth microrelief.
The type and subtype properties of the soil are presented in the paragraphs bellow.

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THE ECOLOGICAL ASSESSMENT OF SOILS AROUND AGARAK TOWN
The first subtype was the brown carbonate soil of mountain forests (sections – 6, 7, 8, 9,
10 and control). This subtype of soil was distributed 700-1000 meters above sea level, on the
gradients of 0-30 degrees, the microrelief was mainly smooth, and the erosion degree was 0-3.
This soil was mainly very rocky, and the carbonates were distributed from top to bottom. This
subtype of soil was not fertile and useful for agricultural purposes, except the 7 and control
samples.
The second subtype of the studied soil was the brown typical soil of mountain forests
(sections – 1, 2, 3, 4, 5). The brown typical soil of mountain forests occupied intermediate
place between the carbonate and limeless subtypes by their geographical position,
morphological and physicochemical characteristics. This type of soil, compared to the
carbonate type, had higher position above sea level, the gradient was 0-35 degrees, the
microrelief was smooth, and the erosion degree was 0-2. The soil of this subtype was not
fertile and useful for agricultural purposes, except the samples 4 and 5.
Data indicate that the soils of all areas were medium eroded, except the 5, 7 and control
samples (tab. 1). The erosion processes were conditioned by natural climatic conditions, high
slope gradients and high anthropogenic impact. Due to high anthropogenic pressure, related to
economic activities and soil pollution (especially with heavy metals), the growth of vegetation
and the formation of strong root system were partially pressed, and the soil became more
vulnerable to erosion processes. General characteristic of studied soil is presented in tab. 2.
The best ratio of physical clay/physical sand was observed in soil samples 2, 4, 5, 7.
These soil samples, according to texture classification, were characterized as good soil. The
worst ratio of physical clay/physical sand was observed in soil samples 8, 9, 10, which were
characterized as moderate bad soil according to the texture classification. Much rockiness was
observed in soil samples 6, 8, 9. Comparatively well-developed root systems were observed in
4, 5 and control soil samples. The 2, 4, 5, 7 and control soil samples had favorable structural
properties. The pH of studying soil samples was slightly alkaline and ranged from 7.43 to
7.75. The content of humus ranged from 1.73 to 4.52% in the upper A horizon. The highest
content of humus was observed in section 5 (4.52%), where the soil was not eroded and was
rich with vegetation. The lowest content of humus was observed in section 9, where
incompletely formed, sandy loam, highly eroded, slight capacity soil types were distributed.
The content (mg/kg) of some metals (including heavy metals) and non-metals in stu-
died soils is presented in tab. 3. As the content of metals and nonmetals in soil is specific and
depends on the compound of rocks producing the soil, and the conditions of soil formation, for
the determination of pollution level the obtained results were compared with control sample
which was considered as a background. The study revealed significant changes in
concentrations of following heavy metals: Mn (samples 4, 6 and 7), Co (1, 4), Ni (4, 8, 9), V
(2, 4), Zn (6), Cr (8, 9), As (2, 3, 6, 7, 9), Cu, Mo, Ag, Cd, Pb (almost all samples). Compared
to the control sample a significant difference (over 15 times) in the content of heavy metals
such as copper and molybdenum was observed which was due to the high content of copper
and molybdenum in ores. Soil samples 2, 3, 4, 6 and 9 were highly polluted, and the soil
sample 10 was non-polluted. It is important to mention that such pollution of soil with heavy
metals in studied area was conditioned by human activities, especially by mining and smelting
industrial activities.

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K.A. GHAZARYAN, H.S. MOVSESYAN, N.P. GHAZARYAN, K.V. GRIGORYAN
Tab. 2. General characteristics of studied soils
Mechanical
consistency
Sample
number Physical
clay
< 0.01, %
Physical
sand
>0.01, %
Texture Texture
classi-
fication
Stones
Quantity
of roots
Structure
pH Humus
content, %
1 30 70
sandy
clay
loam
moderate
bad basically
2-5 mm few granular weak
1-2 mm 7.53 2.87
2 40 60
silty
clay
loam good basically
2-5 mm few
granular mild
1-2 mm - 20%,
2-5 mm - 60%,
> 5 mm - 20%
7.75 1.83
3 20 80
sandy
loam moderate
bad 2-5 mm - 60%,
5-20 mm - 40% very few granular weak
1-2 mm 7.68 2.14
4 40 60
silty
clay
loam good basically
2-5 mm moderate granular mild
1-2 mm - 70%,
2-5 mm - 30% 7.59 3.12
5 40 60
silty
clay
loam good basically
2-5 mm many
granular mild
1-2 mm - 20%,
2-5 mm - 70%,
> 5 mm - 10%
7.43 4.52
6 25 75
sandy
clay
loam
moderate
bad
2-5 mm - 35%,
5-20 mm - 40%.
> 20 mm - 25% few granular weak
1-2 mm 7.62 2.42
7 40 60
silty
clay
loam good basically
2-5 mm few granular mild
1-2 mm - 60%,
2-5 mm - 40% 7.48 3.34
8 15 85
sandy
loam moderate
bad
2-5 mm - 30%,
5-20 mm - 40%,
> 20 mm - 30% very few dusty
up to 1mm 7.74 1.85
9 13 87
sandy
loam moderate
bad
2-5 mm - 15%,
5-20 mm - 50%,
> 20 mm - 35% very few dusty
up to 1mm 7.75 1.73
10 10 90
sandy
loam moderate
bad
2-5 mm - 50%,
5-20 mm - 40%,
> 20 mm - 10% very few granular weak
1-2 mm 7.69 1.90
Control 30 70
silty
clay
loam medium 2-5 mm - 70%,
5-20 mm - 30% granular mild
1-2 mm - 50%
2-5 mm - 50% 7.45 3.59
Tab. 3. The content (mg/kg) of some metals (including heavy metals) in studied soils
Sample
number V Cr Fe Mn Co Ni Cu Zn As Mo Pb Cd
1 12.5 1.4 2841.5 54.3 2.1 1.3 53.3 4.9 0.6 5.2 1.1 0.03
2 16.3 0.6 3672.0 61.5 1.6 2.3 145.5 10.4 1.5 13.2 2.3 0.06
3 11.9 0.7 3242.0 32.3 1.3 0.7 123.5 7.1 1.0 8.5 3.9 0.04
4 14.1 3.8 3747.8 99.9 2.1 4.1 23.4 11.7 0.8 1.2 1.5 0.05
5 7.5 2.7 2299.7 70.0 1.3 2.2 25.3 7.7 0.4 1.5 1.7 0.03
6 11.2 2.0 3043.4 184.5 1.6 1.7 56.2 19.2 1.6 4.2 6.4 0.22
7 8.9 1.3 2974.3 113.0 1.4 1.0 81.2 10.8 1.0 6.2 3.5 0.04
8 9.5 6.8 2576.2 50.9 1.6 4.1 35.4 6.6 0.8 1.2 1.2 0.04
9 9.2 6.0 2592.9 49.0 1.4 3.7 39.7 6.5 0.9 0.9 1.4 0.05
10 8.2 2.8 2256.7 39.2 1.2 1.7 17.4 4.4 0.7 0.6 0.6 0.01
Control 7.5 2.6 2250.4 56.4 1.3 2.0 9.5 8.0 0.6 0.5 0.8 0.02
Taking into consideration all above-mentioned it is necessary to implement
recultivation activities in the areas around Agarak town as the source of eroded, heavy metal
polluted soils. The recultivation works are advisable to implement by the method of
hydroseeding which is considered as a subtype of biological recultivation. The main goal of
biological recultivation is the recovery of soil formation natural process, the sti-

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THE ECOLOGICAL ASSESSMENT OF SOILS AROUND AGARAK TOWN
mulation of soil self-purification properties and biocenosis self-recovery process. A biological
recultivation results in formation of a landscape with satisfactory biodiversity on disturbed and
polluted areas.
It is also desirable to add some plant hormones and microorganisms to specific mixture
used during the implementation of hydroseeding method for the increasing of germination
ability of seeds, as well as for the shortening of disease incidence and the acceleration of the
growth of plants. In 2-3 hours after the sowing of hydroseeding mixture the mulch material
forms a specific cover on the soil which provides satisfactory humidity for the soil as well as
prevents the erosion of the soil and the movement of seeds by wind and water. After the
growing of plants, the mulch material fibers are decomposed enriching the soil by organic
matters.
As the area of our studies was polluted especially with heavy metals it is also desirable
to add to seed mixture used in hydroseeding method the seeds of plants which have ability to
remove selectively from the soil some heavy metals making the process of recultivation more
effective.
It is also suggested to use meliorants especially the mixture of organic fertilizers
(manure, biohumus) and natural meliorants for utilization of heavy metals or at least for
reducing of their toxic impact on the environment. It is proved scientifically that it is possible
to improve the condition of soils polluted with heavy metals and to decrease the content of
mobile forms of these elements by joint use of natural meliorants and organic fertilizers.
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Received 16.10.2012