Bulgarian Academy of Sciences, Sofia, Bulgaria Thermodynamic Modeling of Inorganic Chemical Speciation in River Waters Affected by Mine Water Discharges D. Rabadjieva, S. Tepavitcharova, T. Todorov, M. Dassenakis, V. Paraskevopoulou, M. Petrov D. Rabadjieva Bulgarian Academy of Sciences, Sofia, Bulgaria didiarab@svr.igic.bas.bg PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

CONTENT Introduction Purpose Experiments Field Studies Chemical Analyses Results Thermodynamic Modeling of Inorganic Species Theoretical Base Computer Programs Review of Databases Conclusions PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

INTRODUCTION PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

INTRODUCTION Natural surface waters - MULTICOMPONENT SYSTEMS Major components of natural genesis Na+, K+, Mg+2, Ca+2, HCO3-, Cl-, SO4-2 Major pollutants nutrients trace metals PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

INTRODUCTION MONITORING The actual collection of information at set locations and at regular intervals in order to provide the data which may be used to define current conditions, establish trends,etc. PROBLEM It usually shows the total content of the pollutants, without defining their chemical species, which determine element toxicity and bioavailability in the ecosystem. PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

specific form of an element defined as isotopic composition INTRODUCTION Chemical species specific form of an element defined as isotopic composition oxidation state complex or molecular units PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

INTRODUCTION ANALYTICAL METHODS Hyphenated instrumental analytical methods HPLC-ICP-MS ; PROBLEMS Time consuming Expensive Applicable to a limited number of species. SOLUTION Thermodynamic modeling PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

PURPOSE Determination of the inorganic chemical species in mining polluted surface waters by: ♦ chemical analyses; and ♦ thermodynamic modeling of the systems. CASE STUDIES: Maresh and Luda Yana rivers Asarel-Medet copper mine in Bulgaria. PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

EXPERIMENTS - Field Studies Asarel-Medet, an open pit copper mine, is a major producer of pyrite and copper concentrates in Bulgaria and is one of the largest in Europe PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

EXPERIMENTS - Field Studies Sampling stations in the Asarel mine region PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

EXPERIMENTS - Chemical Analysis Major ions and Nutrients Spectrophotometry Dissolved Al, Fe, Mn, Pb, Cd, Cu and Zn Atomic Absorption Spectrometry (GFAAS) PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

EXPERIMENTS - Analytical Results Physicochemical characteristics and chemical parameters in Maresh and Luda Yana rivers waters pH 3.1 – 8.8 O2, mg/l 7.2 - 8.4 Cl, mg/l 3.5 – 11.9 SO42-, mg/l 45 – 5500 K, mg/l 1.5 – 6.5 Na, mg/l 2 – 8 Ca, mg/l 9 – 100 Mg, mg/l 1.8 – 234 PO4, μmol/l 0.32 – 1.05 NO2, μmol/l 0.22 – 11.3 NO3, μmol/l 14.4 – 466 NH4, μmol/l 0.56 – 23.9 SiO2, μmol/l 235 – 1179 Al, mg/l 0.1 – 431 Fe, mg/l 0.2 – 21.9 Mn, mg/l 0.01 – 36.9 Cu, mg/l 0.03 – 274 Zn, mg/l 0.01 – 6.66 Pb, μg/l 1 – 1.4 Cd, μg/l 0.1 – 85 PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

EXPERIMENTS - Analytical Results Suspended materials in Maresh and Luda Yana rivers waters Measured values SPM, mg/l 0.8 – 32.7 Al, mg/l 0.02 – 4.58 Fe, mg/l 0.03 – 1.77 Mn, mg/l 0.01 – 0.04 Cu, mg/l 0.002 – 1.93 Zn, mg/l 0.001 – 0.016 Pb, μg/l 0.18 – 2.29 Cd, μg/l 0.01 – 0.21 PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Centre of Competence MISSION Sixth Framework Programmе Specific Support Action EC-INCO-CT-2005-016414 Centre of Competence MISSION Thermodynamic Modeling of Inorganic Species Theoretical Base k Mm + j Xin = Mk(Xi)jkm-jn PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Theoretical Base PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Computer programs PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

PHREEQCI computer program Thermodynamic Modeling of Inorganic Species Computer Programs PHREEQCI computer program Thermodynamic Ion-Association Model extensions of the Debye-Huckel theory The formation of each aqueous specie is defined by a mass-action expression with the appropriate thermodynamic constant. The program claims calculation of the activity coefficients of the species that are valid up to an ionic strength approximately 0.7 mol.kg-1H2O. PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

a,  and m Thermodynamic Modeling of Inorganic Species Computer Programs INPUT pH, toC, total concentrations DAVIES equations, DATABASE for K, H CALCULATION a,  and m OUTPUT species concentrations major elements minor elements trace elements PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Review of Databases PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Review of Databases PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Results Major metals speciation distribution in the waters of Maresh and Luda Yana rivers sampling stations PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thermodynamic Modeling of Inorganic Species Results Trace metals speciation distribution in the waters of Maresh and Luda Yana rivers waters PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

CONCLUSSIONS The experimental results of this study combined with thermodynamic modelling of the inorganic chemical speciation based on the new database sst2008.dat revealed that the small lake, (location of station Ba1), acted as the main point pollution source. The acidic conditions that are generally found in this lake and in the downstream affected stations favor the dominance of dissolved metal forms. High levels of SO42-, Cu, Mg, Al, Mn and Fe were determined in the affected stations. PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

CONCLUSSIONS The increased concentration of SO42- ions led to their competitiveness in the processes of complex formation. Thus, differently from non impacted river waters, complex sulphate species of major and trace metals appeared in the whole polluted and affected water system at the expense of free Men+ species. The percentage of free metal species, which are more toxic, increased downstream of station Ba1. The trace elements decreased downstream mainly due to dillusion, sorption processes, and precipitation. PROMITHEAS-2, 8,9 October 2008, Athens (Greece)

Thank You for the Attention PROMITHEAS-2, 8,9 October 2008, Athens (Greece)