METHOD FOR ASSESSING ALLOWABLE CONCENTRATIONS OF POLLUTING SUBSTANCES WITH CONDITIONS OF RIVER SEDIMENTS

The relevance of the research is determined by the need to take into account the interactions of river waters with bottom sediments when normalizing anthropogenic impacts on water bodies. The aim of the research is to develop the model of transformation of polluting substances in water objects with the account of waste dilution and interaction of river waters and sediments and development of sewage normalization technique. Methods: mathematical modelling of hydrochemical processes. Results and conclusions. The mathematical model of transformation of polluting substances in water objects with the account of sewage dilution interaction of river waters and river sediments is developed. Its approbation by the example of the small rivers in northern part of Vietnam (the Ban Thi and Dai rivers in the Hong river basin) has shown that the chemical composition of waters of researched rivers is determined more than on 60 % by interactions of river waters with sediments as a result of sedimentation of poorly soluble substances and sorbtion of some trace elements. It results in appreciable decrease of concentration of many substances on sites up to 4,5–5,0 kms. Influence of water flow is shown first of all, in changes of a bed-material discharge, to a lesser degree it is a regulation of intrawater processes for which more long time of balance establishment in a solution is required. On the basis of the offered model its simplified version and a technique of normalization of sewage for variants of presence and absence of observation data is developed. Thus, the influence of interactions with river sediments is taken into account indirectly through structure of model and value of its parameters. Approbation of the simplified model is executed on the example of the Jinjiang river in the Poyang lake basin (China)