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The history of the sedimentation processes and heavy metal pollution in the Central Danube Delta (Romania)

Begy R. C., Kelemen S., Simon H., Tănăselia C.

Geochronometria

2018

Vol. 45, no. 1

97--106

The aim of this study was to investigate the effects of the Iron Gates (IG) hydroelectric power station on the Danube Delta sediment dynamics, and to assess the heavy metal concentrations and pollution in a typical Central Danube Deltaic lake. Eight sediment cores were analysed. The total 210Pb content was measured with 210Po using alpha spectrometry, and the supported 210Pb (226Ra) and 137Cs were measured by gamma spectrometry. The age depth model was derived by applying the 210Pb dating method, and for the calculation of the ages and the sedimentation rates the CRS model was used. The sedimentation rates can be divided into four periods:1940–1972, 1972–1980, 1972–1989 and 1989–2013. In the case of Lake Iacob in the first period, the average sedimentation rate was 0.418 g/cm2y, while in the second it slowly decreased to 0.376 g/cm2y. In the third period, the sedimentation fell to 0.209 g/cm2y, which means the retention of 27.3% of the sediment by the IG dam. In the case of Lake Isac the changes were more visible: in the first period the average sedimentation rate was 0.446 g/cm2y, while in the second it decreased to 0.197 g/cm2y, which means a 42.35% retention of sediment. In the last period, in both cases, a high increase in the sedimentation rate is shown: 0.677 g/cm2y for Lake Iacob and 0.715 g/cm2y for Lake Isac. The heavy-metal concentrations for As, Co, Cr and Ni show decreasing and Hg increasing tendencies, while Cd and Pb show constant values of 310 ± 12 ppb and 9 ± 1 ppm respectively.

Numerical and experimental study of a two-phase flow with condensation in a microchannel

Simon H., Coulon N., Nahas G.

Turbulence : international journal

2004

Vol. 10

139-146

A two-phase homogeneous model for the one-dimensionnal flow of an air-steam mixture in a microchannel with condensation and thermal coupling with the channel wails has been developped in the Finite Element code CAST3M. Experiments on a microchannel 50 cm long, with 50, 100 and 140 urn have been performed, for mass fraction of steam between 0.7 to 0.96. Comparison between experimental and numerical results has shown a good agreement for the total mass flow rate for channel openings of 100 fim and 140 um. An overheating of the internal surfaces of the channel was observed. For the 50 um opening, the calculation gives a 50% estimate of the experimental total mass flow rate. We point out the hypothesis contained in this simple model in order to explain the results.