Runoff Formation Factors and Ecosystem State of the Lena River in the 21st Century. Part 2: The Lena River Water Quality in the 21st Century

The results of the hydrochemical analysis of the samples at the Roshydromet monitoring network in the Lena River during the years with different water content and their generalization are presented. The methodology for selecting gaging sections and years with different river runoff levels was given in the first part of the paper. Both the primary data of the hydrochemical analysis (mg/L) and the calculated data (with respect to fisheries maximum permissible concentrations and the mass of a specific substance per day) are analyzed. Mineralization, suspended solids, total iron, and petroleum products are considered as priority indicators of the ecological state. Most of them, with the exception of petroleum products, are of natural origin. An ambiguous influence of the water content of the year on the concentration of various ingredients is revealed. Economic activity has a relatively small impact on the water quality. The state of the Lena River ecosystem is also assessed using the entropy index developed at the Hydrochemical Institute. It is concluded that the Lena River ecosystem is generally safe, although water pollution occurs in some areas.