The influence of water column density shifts on vertical transport of dissolved chemicals: applications to problems of monitoring and predicting water resource quality

摘要

A steep gradient density layer (density shift) in a water column often forms due to intense summer heating of the surface and wind mixing the upper layer. It influences the vertical transport of chemicals and pollutants, due to the significant power generated, overcoming Archimedes forces. The mechanism of Vertical transport of dissolved chemicals through the density shift is connected with the stochastic formation of local turbulent structures - "turbulence flares", which arise because of shifts of current speed in internal waves and eddy-wave formation of the "billows" type. Analyses of data from the Black Sea and Lake Kinneret indicate the universal character for conditions of the dimensionless dependence of logRi = f(Z/Zm) and logRi = f(2logN/Nm), where Ri = the Richardson number, Z = depth, Zm = the depth of the Brunt-Vaisala frequency N(Z) maximum (Nm). A high positive correlation (R = 0.75) between logRi and 2 logN/Nm values allows the use of vertical density profile data (water temperature) for estimating the vertical fluxes of chemical elements and pollutants. The simplicity of measurement and availability of data on density structure of water basins provide means for effective monitoring of vertical transport of chemical elements and pollutants under various conditions. [References: 8]