Watering of equipment, flooding of
oil products, dismantling of facilities,
etc.As can be seen from Table 1,
during the 20th century, the level of
the Caspian Sea increased and
diminished respectively over the
years. In the southern and central
areas, the Caspian Sea is exposed to
more hydrodynamic hazards. In
addition, the bottom of the Caspian
Sea is susceptible to mud volcanoes.
Areas with sulfur content are more
dangerous. If there is a strong
earthquake, it can take up to 1 million
tons of sulfur-containing
hydrocarbons at 1000 atmospheres,
which is a global disaster.
Table 1.
The change of the Caspian Sea level during XX century
References
Galib Huseynli, The Global problems of the world, Inam Pluralizm center? Baku 1997
Shirinov N.SH, Valiyev X.A, Aliyev Y.Q - The nature and ecology of the Caspian Sea, Baku 1998
Problems of the Caspian are being investigated (text), Baku 1993, 22nd June
İsmailov Ch, Ecology of the Caspian Sea and coastal areas, Baku : Ayna, 2005
Q.T.Mustafaev, Ecology of water in Azerbaijan and biodiversity of the Caspian Sea, Baku, 2007
www.sia.az
www.trend.az
Years
Level
(compared
Baltic sea)
Area
(1000
km²)
1910
-26,30
405,5
1920
-27,80
389,0
1930
-27,10
398,5
1940
-28,09
379,0
1950
-27,93
376,5
1960
-27,81
374,1
1970
-27,73
374,0
1980
-27,57
371,6
1990
-27,44
386,0
336
Historical profile of selected metals in the core sediments of southeastern part
of Caspian Sea (Gorgan Bay)
Bagheri
1
, H., Mahmoudi Gharaei
2
, M. H., Darvish Bastami, K
1
1-
Iranian National Institute for Oceanography and Atmospheric Science (INIOAS), Tehran, 1411813389, Iran
2-
Department of Geology, Faculty of Sciences, Ferdowsi University Of Mashhad .
Keywords
:
Gorgan Bay, sediment, selected metals,Cores
Introduction
Core sediments are very useful instrument for reconstruction and detecting different process
as paleoclimate, effects of anthropogenic activities and natural events on sedimentary
environments (Harikumar and Nasir, 2010), also investigation on Geochemical and geo-
statistical assessment of aquatic ecosystems (Karbassi et al., 2005; Mohamed et al., 2005; Sun
et al., 2012; Vallius, 2014; Veerasingam et al., 2015). coastal zones with their variable physical
and chemical properties are suitable environment for accumulation of pollutants (such as
heavy metals), and may activity cases sinks or sources of heavy metals in bottom sediments
(Harbison,1986; Szefer et al., 1995). Trace metals concentrations from natural and
anthropogenic sources in coastal area can be increase due to high input and urbanization
(Harikumar and Nasir, 2010). In fact, increase of metal contamination in aquatic environments
because of industrial or human activities have directly influence on coastal ecosystems
(Alessandro et al., 2006). Thus, core sediments obtained from these coastal areas provide a
good chronological record of contamination (Morelli et al., 2012). Understanding trace metal
emissions in coastal environments is an important task for researchers and policy makers, and
regulatory actions can be implemented to reduce potential health risks.
Materials and methods
In this research for Historical profile of selected metals in the core sediments of southeastern
part of Caspian Sea (Gorgan Bay), 5 sedimentary cores (K1, K3, K5,K7,N1) and 15 superficial
samples were collected from different parts of Gorgan Bay using a Gravity Corer and Van Veen
grab. The grain size analysis was carried out with a laser particle size analyzer major and trace
elements were measured by the ICP-OES method.
Fig.1. sampling map
Result and Discussion
336
Grain size analysis showed most of the surface samples from eastern part of the Grogan Bay
are generally in the range of sandy silt or sandy mud and in the central and western parts are in
the range of muddy sand and silty sand, while in the core sediments, grain size was very
variable from sand to clay due to sea level fluctuations in different periods. In the geochemical
study, it was determined that the concentration of the major elements (including aluminum,
iron, calcium, magnesium, potassium, sodium and sulfur), and trace elements (including
arsenic, copper, chromium, cobalt, lead, zinc, molybdenum and nickel) are comparable to the
natural grade in the earth crust (less than or equal) expect the chrome because of specific
gravity in coastal area and arsenic due to the high solubility in seawater and the desire for
enrichment in evaporative minerals showed a higher concentration than the mean earth crust.
Geochemical maps showed that concentrations of major elements in most samples were more
concentrated in the eastern parts, and the concentration of all trace elements (Co, Zn Cr, Ni,
As, Pb), except molybdenum decreased, from east to west of the Bay. These changes are
probably related to the finer content of bed sediments in these sectors, as well as higher
sediment inputs and more traffic on fishing boats. Also, the results of heavy metal
concentration changes in cores indicate that the highest concentration of heavy metals is
generally in the depths of 0-50 cm and the lowest concentrations of these elements are at a
depth of 70 cm and more. (Figure.2)The high correlation between trace elements shows the
same geochemical properties and the potential source of contamination. Also, the positive
correlation of these elements with aluminum and iron is probably due to the absorption of
these elements by clay minerals and iron hydroxides, while the negative correlation of calcium
with these metals is probably owing to the non propensity of trace elements to presence in
calcium carbonate ( Generally, biological origin).
337
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