Assessment of risk factors in pollution of coastal zone and river basins by numerical modelling

Full text: Significant radiation and Thechnogenic catastrophes and frequent natural disasters unequivocally point at necessity for organization of ecological control system for preparedness for possible catastrophic situations in both global and local ranges, and for envisaging their far etched outcomes. Important stage of such investigations implies provision of reliable system of verification information on possible sources of pollution of a territory, and a level of radioactivity concentration and chemical pollutants, with maximal accessibility of the data for the users of various range and level of qualification. The Kura River with its tributaries covers almost the whole territory of the Southern Caucasus and represents its major life-sustaining artery. The waters of this basin flow into the Caspian Sea, the shores of which are bordered by three additional countries - Turkmenistan, Iran, and Azerbaijan. Various non-controllable production activities in this region, as well as specific geological and geochemical structure, determine significant chemical and radiological pollution of the Caspian basin, in a whole. Epidemiological and ecological situation in the basin deteriorated especially after crushing of the former USSR and establishment of new independent states (NIS), because of the lack of respective monitoring over pollution of environment within the states, as such, and especially at the borders between the states. These processes created a prerequisite for further worsening of political tension and economical instability in above-mentioned countries. The strong anthropogenic impact on the territory of South Caucasus results in intense pollution of the waters and soil. Existing purification plants provide efficient purification of 5-10% only of the polluted water. In the meantime, ecological state of the Caspian Sea basin is one of the gravest in the world, while Kura River and its tributaries summarily long ago exceeded the third class of moderate pollution. For this aim the special deterministic models on the basis of passive admixture's turbulence diffusion equation is used. For numerical calculations Mc Kormack's predictor-corrector two steps scheme is used. The scheme is disintegrated, second order in space and time. Such scheme is established because the turbulent velocities very differ in horizontal and vertical directions and model allows implementing singular independent steps in different directions. Grid step for the model is 26.88 km in horizontal direction and 20 m m in vertical until 200 m. Time step is equal to 4 hours and computational time period - 4 months. Number of grid points is equal to 4983 for all calculation areas. Computations are carried out separately for big rivers basins as well as for Black and Caspian Seas water areas. The model calculations are made for cases with various locations of pollutant sources including accidental throws. For different realistic scenarios are calculated the concentrations of admixtures. The directions of their propagation are also determined. The risks are calculated in comparison with the Maximum Permissible Concentrations (MPC) of the pollutants according to achieved results. That gives possibility to define the most vulnerable areas in coastal zones. Realized methodology is verified by means of various scenarios for mentioned rivers and sea basins. The maps with indication of risk zones in river basins as well as of Black and Caspian Seas water areas are created