DBPapers
DOI: 10.5593/sgem2017/31/S12.097

USE OF HEAVY METAL SPECIATION DATA FOR EFFECTIVE THERMODYNAMIC PARAMETERS DETERMINATION OF ABSORBED HEAVY METALS IN BOTTOM SEDIMENTS

O.A. Lipatnikova, D.V. Grichuk
Monday 11 September 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-04-1 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 31, 769-776 pp, DOI: 10.5593/sgem2017/31/S12.097

ABSTRACT

It is rather difficult to apply thermodynamic simulation in the forecast of heavy metals migration in aquatic ecosystems due to the fact that the composition of bottom sediments in reservoirs is very changeable and uncertain. An alternative approach is proposed for solving similar problems based on the use of empirical information on heavy metal speciation in bottom sediments. This type of information can be obtained using sequential extraction scheme (for example Tessier scheme). Based on these data, effective thermodynamic parameters for a specific object are calculated.
The “interstitial water – solid phase” system in bottom sediments is considered as a multicomponent system in thermodynamic model. It includes the aqueous phase, individual solid phases and basic sorbing phases (clay minerals, iron and manganese hydroxides and organic matter), which are considered as ideal solid solutions.
The selectivity coefficients of heavy metals with respect to calcium for the main sorbed forms were calculated on the basis of the results of the analysis of extracts from the solid phase of bottom sediments and pressed interstitial waters. Using these coefficients, the apparent increments of the Gibbs free energy Δg°(T) for the sorbed forms were calculated. The value Δg°*(T)CaX=0 was taken as a reference point of the apparent Δg°*.
We calculated the distribution of metals between sorbents and pore solution using estimated values of Δg°*. The results of calculations reproduce the empirically obtained distribution of trace metals in bottom sediments accurately

Keywords: heavy metal speciation, bottom sediments, sequential extraction scheme, thermodynamic simulation