Selma Ünlü

An assessment of trace element contamination in the freshwater sediments of Lake Iznik (NW Turkey)

Iznik Lake, a freshwater lake surrounded by a fertile basin of land in NW Turkey, is deteriorating gradually depending upon the increment in loadings which is ascribed to the inputs from streams, agriculture, excessive irrigation, urbanization and industrial activities along the shore, and atmospheric deposition. The main scope of this study is to assess the content, distribution and ecological risk of the elements (Al, Fe, Mn, V, Cd, Co, Cr, Cu, Ni, Pb, As and Zn) in the surficial sediments collected from 25 sites in the Lake Iznik. Quantitative indices and sediment quality guidelines were used to evaluate the pollution status of metals. The resulting estimates reflected a natural environment of low to moderate degree of impaction, and an approximate contribution of geogenic and anthropogenic inputs, with some variations among the stations. The enriched concentrations of As and Mn could be depending on the thermogenic activity along the active faults bounding the lake. Multivariate analysis demonstrated that the sources of Al, Fe, Co, Cr, Zn and V, concentrated at near-shore stations, could be attributed to mixed (lithogenic/anthropogenic) sources via streams. The enriched concentrations of Cd, Cu, Ni and Pb observed at the deep stations, and their sources were attributed to the transported/deposited sediments and partly atmospheric deposition. Except Ni, the metal concentrations in the majority of sediment samples were believed to be safe for living organisms. Local governments must prepare rational environmental strategies and suitable drainage programs to decrease the level of contaminants that pollute the environment and to prevent the dramatic drop of the lake’s water.

A study on phytoplankton following ‘Volgoneft-248’ oil spill on the north-eastern coast of the Sea of Marmara

Following the ‘Volgoneft-248’ oil spill, phytoplankton distribution within the affected area was investigated for two years. Simultaneously measured physical variables such as salinity, temperature, Secchi disc, current speed and direction, and total petroleum hydrocarbons (TPH) were evaluated together with phytoplankton data. At the time of the accident, the TPH concentration in surface water was measured as 2.17 mg l and decreased to 88.5 mg l after five days. In the first sampling period, no diatoms were detected in surface water, while dinoflagellates were dominant in the phytoplankton community. The species composition of phytoplankton changed rapidly in two months and the diatoms increased in terms of abundance and diversity. This indicated that the diatoms might be more sensitive to oil pollution than the dinoflagellates. In comparison with the historical datasets, the low phytoplankton abundance following the oil spill should be considered as the small effect of oil on the phytoplankton rather than natural variability of the ecosystem. High oil concentration in the water column caused stress on the phytoplankton and influenced the species composition negatively depending on the sensitivity of groups and the natural variability of the ecosystem.

New approaches in assessment of tsunami deposits in Dalaman (SW Turkey)

Some earthquakes in the Eastern Mediterranean are tsunamigenic, and some of their tsunamis affected the coastal area of the Gulf of Fethiye, SW Turkey. Recent trenching surveys on the low-lying coastal areas of Dalaman delta beach across the Rhodes Pass revealed three probable tsunami impacts as a result of the historical earthquakes of 1303, 1481, and 1741. Yet there have been relatively few studies of the processes associated with tsunami sediment transport, their deposition, and nature in geological record. In addition to the interpretation of sedimentary features, accurate palaeo-environmental assessments might be possible by distinctive biogeochemical researches on marine-sourced organic matters, geochemical properties, quantitative amounts of marine biomarkers, and deterministic ratios. The identification of major lipid biomarkers (fatty acids and sterols) in the samples recovered from the sidewalls of the studied trench, for example, indicated biogenic contributions due to the presence of phytoplankton, zooplankton, bacteria, and dinoflagellates. Quantitative estimation of biomarkers and deterministic ratios also indicated some evidences for marine-sourced organic matters, implying that biomarkers can be used to answer the open questions in tsunami and palaeo-tsunami researches.

Petroleum Residue following Volgoneft-248 Oil Spill at the Coasts of the Suburb of Florya, Marmara Sea (Turkey): A Critique

Abstract The chemical fingerprinting approach to environmental assessment is illustrated in the evaluation of marine oil pollution on the coasts of the suburb of Florya (Marmara Sea). The samples of unknown origin collected during three leg expeditions on April 2003, December 2003, and February 2004 were analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Hydrocarbon distribution patterns of samples indicated different known and unknown origins. The group hydrocarbon compositions of the samples from leg one are the same as those from the cargo oil spill of tanker Volgoneft-248, which ran aground after structural failure. When it broke apart at the end of the year 1999, tons of oil were spilled into the Marmara Sea. The results show that the remainder of the buried oil in the seabed may come ashore during strong onshore winds even after comprehensive clean-up operations and after 4 years. On the other hand, the samples collected during legs 2 and 3 appear to be from unknown sources.

Evaluation of sediment contamination by monoaromatic hydrocarbons in the coastal lagoons of Gulf of Saros, NE Aegean Sea

The concentrations and distribution of monoaromatic hydrocarbons (benzene, toluene, ethyl benzene and the sum of m-, p- and o-, xylenes) were determined in the sediments of coastal lagoons of the Gulf of Saros, using a static headspace GC-MS. The total concentrations of BTEX compounds ranged from 368.5 to below detection limit 0.6μgkg-1 dw, with a mean value of 61.5μgkg-1 dw. The light aromatic fraction of m-, p-xylene was the most abundant compound (57.1% in average), and followed by toluene (38.1%)>ethylbenzene (4.1%)>o-xylene (2.5%)>benzene (1.1%). The factor analysis indicated that the levels and distribution of BTEX compounds depend on the type of contaminant source (mobile/point), absorbance of compounds in sediment, and mobility of benzene compound and degradation processes. Point sources are mainly related to agricultural facilities and port activities while the dispersion of compounds are related with their solubility, volatility and effect of sea/saline waters on lagoons.