The method of calculating heavy metal release from the layer of water body bottom deposits

Summary

The basics of the method of predicting heavy metal distribution between water and solid phases of bottom deposits in water bodies is outlined. Compared to other models of calculating heavy metal distribution between bottom deposits and void water the developed methodology takes into account the ongoing geochemical processes at the improved level with the use of advanced methods of geochemical modeling. An example of calculating heavy metal distribution under the conditions of the chemical composition of the solution changing with the use of advanced calculation methods in PhreeqC 2.18 program code is presented. The method can be used for the following tasks: geological mapping of the pollution of bottom deposits with heavy metals in water reservoirs and lakes; evaluation of the impact of bottom deposits on the chemical composition of water in water reservoirs and lakes; evaluation of the possible elimination of bottom deposits pollution or their immobilization and other measures of mitigating their impact on the water quality; evaluation of bottom deposits removal during dredging and also for solving the problem of their further utilization; evaluation of the possible instantaneous release of heavy metals from polluted bottom deposits and other emergency situations.

Key words

suspended substances , ion exchange , heavy metals , bottom deposits , geochemical thermodynamic sorption model , cation sorption

Specificities of predicting metal distribution between aqueous phase and bottom sediments (by the example of strontium and cesium radionuclides)

Summary

The basic provisions of the developed methodological approach to predicting the coefficient of K_d radionuclide distribution on the material of bottom sediments and suspended substances in water bodies are presented. As a tool for predicting K_d coefficient of metals under the conditions of the changing chemical composition of water the use of geochemical modelling was suggested. The basic approaches, models and results of predicting the values of K_d coefficient of metals in a reference water body (a surface water reservoir – radioactive waste storage) characterized by high pollution with ⁹⁰Sr strontium and ¹³⁷Cs radionuclides as well as by the intensive decrease of water mineralization are laid out. During the research the specific features of hydrochemical and hydrodynamic behavior of metals in the water body system as well as the methods of geochemical modeling were studied in detail. The geochemical thermodynamic model of metal sorption (by the example of ⁹⁰Sr and ¹³⁷Сs) by the suspended matter and bottom sediment layer in the model water reservoir was developed that could be considered as a basis for modeling different scenarios of the evolution of real polluted water reservoirs. The values of K_d coefficient for ⁹⁰Sr and ¹³⁷Сs at decreasing water mineralization were calculated. It was determined that K_d value is increasing while water mineralization is decreasing. The model can be used for predicting the rate of metal elimination from polluted water bodies in the process of self-purification.

Key words

geochemical modeling , bottom deposits , surface water reservoir , sorption of heavy metals , radionuclide distribution coefficient , self-purification of a water reservoir

Estimation of the anthropogenic load on small rivers by the level of pollution of bottom sediments with organic matter, phosphates and iron

Summary

The results of studies on estimating the anthropogenic load on small rivers of the Vladimir region in terms of the level of pollution of bottom sediments with organic matter, phosphates and iron (III) compounds are presented. The Ilevna, Kamenka and Sodyshka rivers are characterized by different surface areas and population level of their watersheds, and by the identity of non-point sources of pollution. It has been established that water and bottom sediments of the studied watercourses are heavily polluted with organic matter, phosphates and iron (III) compounds; and, consequently they are eutrophicated. In terms of the pollution of hydroecosystems with organic matter and phosphates, the watercourses form a series: Sodyshka > Kamenka > Ilevna, and in terms of the concentration of iron (III): Kamenka > Sodyshka > Ilevna. Judging from the COD index that characterizes pollution with organic compounds, the water of the Ilevna river is dirty, and the Sodyshka and Kamenka rivers are very dirty. The ecosystems of the Sodyshka and Kamenka rivers are heavily polluted. In order to prevent hypereutrophication and degradation, cleaning their riverbeds to remove bottom sediments is proposed. A method is suggested for calculating the anthropogenic load of certain pollutants with account of their concentration in the bottom sediments and watershed area.

Key words

phosphates , anthropogenous impact , bottom deposits , small rivers , organic matter , iron (III)