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The effect of humic acid addition on the capacity of inorganic sorbents to sorb radioactive cesium and strontium was studied on montmorillonites in a calcium and potassium form. The Sips isotherm for humic acid sorption and multisite distribution model of ion sorption was found to suit well for the description of mobility of ions as a function of equilibrium humic acid concentration as a single variable at given pH and type of silicate. Complexation of the ions was of minor importance at the conditions investigated. Influence of humic acid on the specific radiocesium interception potential (SRIP) was also evaluated.

The effect of Aldrich humic acid (HA) on the mobility of ~37Cs, 85Sr, ~SZEu and 239pu radionuclides was studied in Ca-montmorillonite suspensions. Verified 2-sites-2-species (2s2s) models correspond to an intensive interaction of all elements with humificated surface, what is in a remarkable contrast with the weak complexation of cesium and even strontium in solutions -the neutral ligand interaction constants 13 (1/mol) are log 13<-9.9 and 7.56+0.21 for Cs and Sr, respectively. The result for europium complexation in solution, log 13= 12.49-2-_0.18 is in a good agreement with literature data. For plutonium(IV) not only a high proton competitive constant in solution was obtained, log 13=(-0.67+ 0.32)+3pH, but also a strong chemisorption, which at high concentrations ofhumic acid (above 0.05 g/I) indicates the formation of bridge humate complexes of plutonium on the humificated surface. Logarithms of heterogeneous interaction constants (~10, I/g) of the elements with surface humic acid are 4.47+0.23, 4.39+0.08, and 6.40+0.33 for Cs, Sr, and Eu(III), respectively, and the logarithm of the proton competitive constant (~24, I/g) for Pu(IV) -3.80+0.72. Distribution coefficients of humic acid and metal humates between 0.01 g HA/1 solution and montmorillonite were derived as log Ka(AH ) =-1.04_+0.11, log Ka(EuA ) = 1.56_+0.11 and log Ka(PUA ) = 2.25+0.04, while the values for Cs and Sr were obtained with very high uncertainty. Speciation of the elements on montmorillonite surface is illustrated as a function of equilibrium concentration of humic acid in solution and ofpH.*

The high-performance size-exclusion chromatography (HPSEC) and radiochromatography (HPSERC) was used for the identification of radiocesium and radiostrontium interaction with humic acid. It was found that the behavior of humic acid on size-exclusion chromatography is sensitive to the salt concentration and pH of the mobile phase. At lower ionic strength and in acidic region ofpH, the Aldrich humic acid exhibited three main fraction within the ranges >760 kDa, 25-100 kDa and <5 kDa. Radiocesium was found in the low-molecular fractions (<1 kDa) of humic acids but radiostrontium interacts preferably with the fractions of humic acid of molecular weight within the range 2-5 kDa.

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Monitoring the concentrations of heavy metals in natural and waste water at and below the level of their maximum permissible concentrations is an urgent environmental problem. Hence, new procedures for the preconcentration of heavy metals with their subsequent determination by different methods are required. Along with other sorbents, significant attention is attracted to polymer chelating sorbents, which provide individual or group extraction of trace elements, eliminate matrix effects, and provide high concentration factors. The effect of the various parameters such as electrochemically and chemically synthesis methods, physical oxidation state of the polymer, polymer thickness, solution pH and metal ion concentration on the adsorption, kinetics and efficiency were investigated. The results showed a vary broad concentration range of the heavy metals from (0.05 to 10 mg/L) can be adsorbed on different kinds of polymers at different pH values and different efficiently. The adsorption capacity of the polymer to different concentrations of heavy metals was evaluated as the milligram of metal ions by one gram of various forms of the polymer. The DC conductivity measurements were also employed on the solid polymer before and after adsorption of metal ions. The experimental adsorption date was fitted to different mathematical isotherms to estimate the binding constant of heavy metals with the polymer in both single and mixed ion solutions. The method provides the extraction of analytes from natural water of complex composition containing high concentrations of alkali, alkaline-earth and other elements and is characterized by rapidly, selectivity, low detection limits, and a high reproducibility of the results. The relative standard deviation is 2-4%. The technique was test with real waste water samples.

A standard analytical technique for determination of the partial ion exchange capacity of mineral or soil for selective uptake of cesium, the specific radiocesium interception potential (SRIP) is formulated and theoretically discussed. The method is based on the determination of a retained, leached or sorbed fraction of cartier-free cesium-137 in soil contacted with 0.01M KNO 3 0.01M Ag thiourea complex solution at the phase ratio solution:sorbent 10 m1:0.1 g. Reliability of the method is discussed in connection of radiocesium cartier and humic substances presence.

The development of electrochemical nano sensor was described for the detection of total arsenic in groundwater, soil, food and honey samples based on the formation of gold nanoparticles. Screen printed carbon electrodes were modified with gold nanoparticles and linked with 1,6-hexanedithiol self-assembled monolayers. The electrodeposition of Au nanoparticles was applied in 10 mL of the solution that totally cover the screen-printed carbon electrode while applying a constant potential of -0.4 V (vs Ag within SPCE) for 600 sec. Cyclic voltammetry was used to characterize the gold nanoparticles before and after modified with 1,6-hexanedithiol self-assembled monolayers on screen printed carbon electrode (Figure 1). Square wave anodic stripping voltammetry with multi point standard addition method was examined for the detection of As(III) and As(V) on Au NPs-1,6-hexanedithiol modified screen printed carbon electrode under optimized conditions. As(III) and As(V) was firstly, deposited for 60 seconds by the reduction of arsenic in buffer solution: (citric acid, sodium chloride and ascorbic acid pH 2.0), followed by As stripping between -0.20 and 0.35 V at the following parameters: scan rate: 100 mV s-1, frequency: 60 Hz, amplitude: 0.025 V and increment: 5.0 mV. it was found that Au- NPs with 1,6-hexanedithiol modified screen-printed carbon electrode had a highest anodic stripping peak current at 0.201V. The limit of detection value for arsenic was identified to be 1.7 ng ml-1. Also, the electrochemical nanosensor showed excellent reproducibility and high stability. The developed method was successfully applied to detect total arsenic in ground water, soil and wastewater samples. Figure 1