25th International Meeting on Organic Geochemistry IMOG 2011

P-148
Seasonal Contamination in Lake Van (Turkey)
Carme Huguet 1 , Susanne Fietz 1 , Mona Stockhecke 2 , Núria Moraleda 1 , Antoni Rosell-
Melé 1,3
1 Institut de Ciència i Tecnlogia Ambientals, Universitat Autònoma de Barcelona, Cerdanyola, Spain, 2 Eawag,
Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Water Research and
Management, Dubendorf, Switzerland, 3 cInstitució Catalana de Recerca i Estudis Avançats (ICREA),
Barcelona, Spain (corresponding author:carme.huguet@uab.es)
Lake Van in Eastern Anatolia (Turkey) is the world‘s
largest soda lake (3570 Km 2 ) 1 . It is located in a
heavily populated area and receives over 1 million m 3
of domestic wastewater a year 2 . Moreover oil
contamination was detected in sediments but its origin
could not be determined 2 . This study aimed to assess
contamination seasonality and sources. This was
achieved by measuring biomarkers in monthly
sediment traps
Biomarkers such as hopanes, steranes and n-alkanes
provide information on anthropogenic contamination,
especially from petrogenic sources 3 , while branched
tetraethers abundance and the BIT index indicate
natural terrestrial input 4 . Natural terrestrial input was
found to be mainly related to increased precipitation
and snowmelt in autumn and spring (Fig. 1). While
almost all n-alkanes in summer 2006 and at least half
in summer 2007 are derived from natural sources, in
winter we observe a marked increase in
anthropogenic contamination related n-alkanes (Fig.
1). This winter peak has a carbon preference index
(CPI) below 1 (Fig. 1) indication of a kerogen rich
source and petrogenic contamination. This is
supported by higher hopane and sterane maturity
indices during the winter months. Contrastingly the
summer peaks show a relatively high CPI and lower
maturity values indicating a different source of
contamination.
We postulate that the winter peak is due to the winter
fossil fuel contribution from domestic heating, while
the summer increase is caused by touristic activity.
References
[1] Kempe, S. et al. 1991 Nature 349, 605-608.
[2] Öğün E. et al. 2005. Fres.Envir. Bull. 14, 1031-
1035.
[3]Hostettler, F. D. et al. 1999. Mar. Chem. 64, 115-
127.
[4] Hopmans, E.C. et al., 2004. Earth and Planet, Sci.
Let. 224, 107-116.
Figure 1. Terrestrial input (August 2007 to July
2007; 38º38‘N 42º46‘E). a) branched GDGT
abundance (orange) and BIT index (grey line), b) nalkane
abundance divided into algal (green),
terrestrial plants (brown) and anthropogenic
contamination (yellow), carbon preference index CPI
(black line), c) Temperature (solid line), wind speed
(dashed line) and precipitation (histogram).
289