Evaluation of Suspended Matter Content in the Coastal Zone of the Northeastern Part of the Black Sea by Relative Transparency

Abstract

Based on the materials of 20 expeditions of the IO RAS conducted in various areas of the coastal zone of the Russian sector of the Black Sea in the period from 1999 to 2021, empirical equations the relationship between the relative transparency (depth of visibility of the white disk Zd) and the mass concentrations of the total suspended matter-SM and its mineral – SMM and organic – POM fractions (Csm, Csmm and Csom, respectively) were obtained. The values of Zd were recorded in the range from 0.1 to 21 m, the concentrations of SMM – from 0.11 to 104 mg/L, POM – from 0.09 to 2.0 mg/l and chlorophyll a (Ca) – from 0.03 to 4.4 mcg/l. The relative abundance of the POM in the suspension ranged from 1.1 to 48.7%. The estimation of the error in the calculations according to these equations is carried out. The coefficients of determination r2 = 0.85 (for lgCsm and lgCsmm ) and 0.72 ( for lg Csom). The influence of the concentration of POM – on the accuracy of the calculation of Csmm and the concentration of chlorophyll a on the accuracy of the calculation of Csom was revealed. It is concluded that it is possible to use empirical formulas related to the entire array to calculate the concentrations of these fractions of suspension in the entire studied water area. It is proposed to consider the method of estimating the content of suspension fractions based on the obtained empirical equations as a regional variant of the method of passive sounding of the upper layer of the sea using a white disk.