Taseiko O.   Spitsina T.   Pitt A.  

Mathematical modeling of self-purification processes in small river of the Central Siberia

Reporter: Taseiko O.

The hydrochemical processes in small rivers are characterized by the accumulation of organic compounds from natural or anthropogenic sources. The high concentrations of biogenic matter lead to high levels of plankton. The high level of plankton reduces the concentrations of dissolved oxygen in the water which increases/encourages the development of algal blooms. Natural eutrophication occurs over thousands of years, but anthropogenic eutrophication can occur very fast (ten years), especially in water basins filled by a slow stream, such as a lake, pond, or reservoir.
All unpolluted natural bodies of water in central Siberia have a common characteristic: the lowest concentration of phosphorus limits the process of eutrophication and the highest concentration of nitrogen allows this process.
In the small Siberian rivers examined here, eutrophication is inhibited by low temperatures, rapid currents and poor development of planktonic cenosis.
The consequences of these processes for the vital activity of river can be predicted by applying computing experiments based on mathematical modeling and numerical methods. To mathematically describe how a river cleans itself is a difficult and mostly ignored problem, as most researchers study the cleansing processes of lakes and ponds. 
This paper offers a new approach to modeling how small Central Siberian rivers cleanse themselves under different climate conditions. This model includes principle factors such as chemical oxygen demand, biochemical oxygen demand, concentrations of biogene element (nitrogen, phosphorus, etc.).
The results of this numerical modeling are verified by data from the environmental monitoring of three rivers in the basin of the Central Siberia.