Anthropogenic activity in surface sediments in Izmit Bay (Sea of Marmara), Turkey

Ünlü S., ALPAR Ş. B.

General Assambly of European Geosciences Union, France, 1 - 04 April 2004

  • Publication Type: Conference Paper / Full Text
  • Country: France
  • Istanbul University Affiliated: Yes


Izmit Bay is an important industrial settlement in the Sea of Marmara region (Turkey)
with rapidly increasing transportation activities between its seaports, oil terminals,
plants and seashore urban centres. About 10% of crude oil in the oceans comes from
natural oil seeps, whereas about 27% comes from oil production, transportation, and
refining. The remaining 63% comes from atmospheric emissions, municipal and
industrial sources, and urban and river runoff (Kvenvolden. and Cooper, 2003).Within
the three morphologic basins of Izmit Bay, the Black Sea inflow, heavy marine traffic,
oil spill, inputs from coasts, rivers and atmosphere contribute intensive anthropogenic
pressure. Common anthropogenic source of PAHs is spillage of fossil fuels including
crude and refined products. As the total crude oil imported exceeds 27.6 million
tons per year, the refineries in the bay has received very variable compositions of
hydrocarbons with different crude oil origins.
Using UVF and GC/MS, we obtained significant levels of hydrocarbons in the
sediments of the basins of Izmit Bay. The distribution of petroleum hydrocarbons in
the sediments is not only governed by sediment types, but it may also be controlled
by the prevailing currents in the area, bottom morphology and sediment disturbance.
The inflow of two different water masses, the upper Black Sea water and the lower
Mediterranean Sea water, has a profound effect on the sediment transportation and
deposition in the bay. No or very little sediment transportation there are from the
central to the eastern basin.
Higher PAH concentrations in the central basin originates mainly from municipal
effluents, discharges from the local refinery, oil spillage from vessels, port operations
and presumably atmospheric transport as well. In contrast, the low PAH concentrations
observed at the stations located to the SE corner of the central basin may be
attributed to possible co-seismic slumps during the 1999 earthquake. During this
event an accident occurred in a refinery causing an environmental damage in the
bay. The spilled oil became diffused as a thick film for miles on sea surface and
deposited on seabed. Abundant monomethylated derivatives (0.4-2.5) in the central
basin implies higher petrogenic (Garrigues et al., 1988) but lower pyrolytic activities.
Accidental spilling of fuel into the sea during the loading operations (during the 1999
earthquake as well) might be the cause of petrogenic contamination. Likewise, this
result is similar for the eastern basin (0.6-2.0).
On the other hand, in the western basin, the phenanthrene predominates if compared
with methylated and dimethylated derivatives. This implies pyrolytic PAHs resulting
from atmospheric combustion residues (forest fires and fossil fuels) and confirms the
lower petroleum influence.