Development and application of nuclear-physical methods in studying of physical and chemical forms of heavy metals in natural and sewage waters

The Fifth Conference “ Nuclear Science and Its Application”, 14-17 October 2008

DEVELOPMENT

AND

APPLICATION

OF

NUCLEAR-PHYSICAL

METHODS IN STUDYING OF PHYSICAL AND CHEMICAL FORMS OF

HEAVY METALS IN NATURAL AND SEWAGE WATERS

R. KULMATOV- A. AZIZOV (National University of Uzbekistan.)

For getting quantitative data about forms o f being heavy metals (HM) in natural and sewage Section

in.

The Fifth Conference “ Nuclear Science and Its Application”, 14-17 October 2008

waters we have developed a neutron-activation method, which uses ultra filtration and electrodialyze fractionating and concentrating of separate forms of HM. By using of radionuclides 60C o ,51 Cr and 124Sb in cationic and anionic forms were established optimal conditions of division form of HM. Limits of determination of HM are 10-6- 10'10 g/1. Relative error o f detection of 20 HM, including Hg, Zn, Cd, Sb, Co, U, Br, Cr and rare earth elements in water make 10-20%.

During2002-2007 we have studied space-temporal variations of content and phase distribution of Hg, Zn, Cd, Sb, Co, Br, Cr, Th, Au, La, and Eu in water of the main rivers o f Amudarya and Syrdarya. Average concentration of HM fluctuates from 2.1 mg/1 for Fe to 1.9 ng/1 for Au.

The basic amount (more than 50 %) of the toxic elements, such as mercury, chromium, antimony, zinc and cadmium in the rivers of region migrate in the dissolved form that is necessary to take into account on estimating o f pollution and migration of HM in the investigated rivers.

On the other hand, less toxic elements - scandium, iron, europium, lanthanum and cobalt, basically migrate, as a suspension, i.e. in not dissolved form. Primary factor o f formation suspended solids making of river waters of arid zone is, apparently the lixiviation of mountain breeds and ground in upper reaches o f the investigated rivers.

At comparison of the total contents of elements with their MPC (Maximum Permissible Concentration) excess o f value of MPC for mercury, cadmium and iron in some ranges of the investigated rivers ware marked.

The basic sources o f HM in the dissolved phase o f river waters, apparently, is the atmospheric precipitation (glacial waters), in suspended - displacement of breed and ground.

Our data on element composition of atmospheric precipitation selected in “background areas”, it is visible, that the basic amount of toxic elements - Co, Cz, Zn, Hg, Sb, Br and As are migrated in the dissolved form, on the identical contents with river waters. We have investigated the forms of migration of HM in river waters.

Heavy metals in the river waters of arid zone migrate as complex set suspended, colloid, cationic, anionic and neutral forms, the ratio between which varies depending on a type of water and physical-chemical properties of an element.

On the long-term data, the contents of colloid forms of HM changed within the limits of 5-20 % for various elements.

On the basis of natural researches and results of experimental modeling with application appropriate radionuclides, and also thermodynamic calculated date, we have established, that as against river waters of humid zones, in migration o f HM in river waters of arid zone the main role played inorganic ligands (OH*, S 0 42*, CL ).

. The experimental data on the forms of migration of HM and radionuclides in river waters of region are used for clearing drinking waters from Hg, Cd, Zn, Cs, Sb, Cl, Fe, U and other elements.

In the work for the first time are established the spatio-temporal variations o f the contents and forms of migration o f some HM in river waters o f Aral Sea basin.

Section III. Radiation Ecology