Assessment of Physical-Chemical Characteristics of Surface Water from Key Sites of the Mesta River: State and Environmental Implications

The anthropogenic source pollution of the Mesta River was assessed during the period 2011 and 2016 in terms of pH, conductivity, chemical oxygen demand (COD), anions and heavy metals in key sites of the Mesta river pointed as: S1 (the Mesta river before the Iztok river); S2 (the Iztok river before the Mesta river); S3 – the river Mesta after the Iztok river); S4 - the river Mesta at Momina Klisura, near Bukovo) and S5 – the river Mesta before the Greece border, after the Matnitsa river. The application of multivariate clustur analysis (CA) for the interpretation of a large and complex data matrix obtained during a monitoring program of surface water in Mesta river is presented in this study. The dataset consists of analytical results from a 6-yrs survey conducted in selected points of the river system. The physical-chemical characterization in the water samples were made in accordance with the Directive 2000/60/EU–Water Framework Directive (WFD) and its equivalent criteria transposed into the Water Law (WL) in Bulgaria. In water, concentrations (mg L⁻¹) during 2016 of NO₂ ^- (0.006 to 0.052), NO₃ ^-(0.01 to 1.33) and total contents in µg L⁻¹ of Cu (<0.002), Pb (<0.003), Co(<0.002), Ni(<0.003), S(<0.050) and Zn(<0.02), pH (5.60 to 8.00), and electrical conductivity (0.12 to 48.60 mS.cm⁻¹) were agreed with environmental standards except cadmium Cd (>0.15 µg L⁻¹) and PO₄ ^3-(0.15 mg L^-1). During analyzed period the cadmium concentration was much higher than recommended limit only. In this sense, it was possible to demonstrate relatively good quality of river water even with numbers of industrial and touristic activities in the analyzed area but also to consider a future concept on cadmium sources and their eliminated. (paper)