AGH Akademia Górniczo-Hutnicza
Chemical analyses usually present the overall concentration of the test element or ion in its most common form. Geochemical modeling allows the calculation of the distribution and concentrations of aqueous species, based on the results of chemical analysis and physical – chemical measurements. The initial characterization of inorganic forms of bromine in groundwater was based on the undertaken geochemical modeling. The studies considered waters of varying mineralization, including varyingious contents of bromine. Fresh water contains small quantities of bromine. The average content of bromine in surface water and active exchange zone groundwater generally does not exceed 0,2 mg/L. The mineralized waters and also some specific therapeutic waters, thermal waters and brines, may contain bromides in amounts greater than in ordinary groundwater. During water treatment processes, the oxidation of bromide can cause the formation of carcinogenic bromate and organic bromine compounds, also mutagenic. The distribution of bromine species in waters of different chemical type and of varied salinity, has been calculated using the program PHREEQC (Parkhurst, Apello 1999). The author used her own research of infiltration of saline water flowing into the Wieliczka salt deposits and also the results of sample analyses of waters with different contents of bromide, both in Poland and the U.S. The study also includes analyses of leachate from three different landfills in the south of Poland. Chemical characteristics were collected from author's own research as well as published data. There were 33 analyses of waters of different chemical characteristic, most of them saline (with chloride ion content larger than 20% milieqvalent). Bromine species were analyzed in terms of salinity and chemical type of water. The calculations also take into consideration the species of bromine which are potentially conducive to the formation of carcinogenic compounds. The quantitative relationship between speciation content and ionic strength, chlorides, bromides and pH was analyzed statistically and presented in the figures. Based on the results of calculations of bromine speciation resulting from geochemical modeling, it can be stated that the main form of bromine occurrence is bromide ion, which accounts for more than 93% of all speculations. In the waters of low ionic strength, it is typically up to 100%. The maximum content of NaBr in the studied waters exceedes 7%. It should be noted that bromide ion is not always present in aqueous solutions. The content of NaBr increases with the ionic strength of the aqueous solution. Other bromine speciations account for only a fraction of a percent. There was no occurrence of bromate BrO3 - and the percentage of undissociated forms (HBrO) did not exceed the value of 1E-19, which is about 5.4 E-21 mg/L. Geochemical modeling carried out confirmed the prevalence of bromine in aqueous solution in ionic form (bromide).
specjacja bromu, modelowanie geochemiczne
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