Naslov
Metal deposition during the Holocene in Lake Vrana on the Island of Cres (Croatia)

Autori
Mesić, Saša ; Miko, Slobodan ; Prohić, Esad ; Šparica, Martina

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
22nd IAS Meeting of Sedimentology - Opatija 2003: Abstracts Book / Igor Vlahović - Zagreb : Institute of Geology, Zagreb, 2003, 125-124

Skup
22nd IAS Meeting of Sedimentology

Mjesto i datum
Opatija, Hrvatska, 17.09.2003. - 19.09.2003

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
heavy metals; lead isotopes; lake sediments; holocene; Lake Vrana; Cres

Sažetak
Sediment records of lakes are often used to estimate long-term changes in anthropogenic metal emissions. Lake sediment profiles from the karstic Lake Vrana, located on the island of Cres, in the northern Adriatic were analysed to validate historic records of trace metal deposition. A total of 13 cores 85 to 90 cm long were obtained by scuba diving from the flat bottom (50m +/- 2m) of the lake. All of the cores have a surface calcite poor (<10% CaCO3) dark layer to the depth of 40 cm (+/- 5cm) and a gray laminated calcite sequence with more than 60 % CaCO3 which extends to the base of the cores (85-90 cm). Schmidt et al., (2000) obtained a calibrated 14C date at the 80 cm core depth in the range of 1900 to 1700 BC. Multi-element analysis of sampled cores was used for the determination of both potential metal pollutants such as Pb, Zn and Cu, and lithophile elements such as Sc and REE (which are derived from catchment rock and soil surfaces) and which allow for the calculation of enrichment factors and the recognition of increases in pollution. Geochemistry indicates that the dark layer is a consequence of soil erosion caused by forest clearing in the lake catchment, that started before the Roman times (Schmidt et al., 2000, pollen data). Shotyk et al., (1998) found that due to Pb pollution from mining and smelting the Pb/Sc ratios have increased and 206Pb/207Pb ratios decreased since 3000 14C yr BP. The Pb/Sc ratios of 2.4 in section in the core interval from 90 cm up to 65 cm lie within crustal value range (1.8 - 2.4) and have high radiogenic values (206Pb/207Pb ratio of 1.24). These values are considered to be indicative of Pb concentrations of soil derived from rock weathering (Shotyk et al., 1998). The Pb/Sc ratios increase to over 3.5 from 65 to 50 cm, with a peak value of &#61627 ; ; 6 from 56 to 58. Then the ratios slightly drop (to &#61627 ; ; 3) and in the interval from 40 up to 18 cm the ratios range from 4 to 6. The highest Pb/Sc ratios are found above 18 cm and range from 7 to 8. The Lake Vrana sediment cores contain a continuous history both background anthropogenic inputs as reflected by Pb/Sc and 206Pb/207Pb ratios, which correspond to hemispheric Pb contamination observed in the past three millennia (Shotyk et al., 1998).

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA