An Approach for Analysis and Assessment of the Pollution Indices of the Struma River in the Bulgarian Section

In this work, 13 pollution indices in 10 stations of the Struma river in the Bulgarian section are investigated: temperature (T°C), pH, dissolved oxygen (DO), oxygen saturation (SO₂), electrical conductivity (EC), biological oxygen demand (BOD), permanganate oxidation (KMn₃O₄), ammonia nitrogen (NH₃-N), nitrite nitrogen (NO₂-N), nitrate nitrogen (NO₃-N), orthophosphates (PO₄), dissolved substances (DS), and unsolved substances (US). The analysis and assessment of the studied indices of pollution of the Struma river in the Bulgarian section is carried out by means of a recently proposed multi-criteria decision-making method called intercriteria decision analysis (ICDA). Application of ICDA showed that we have a degree of agreement for T°C for all stations with very few exceptions. This also applies to DO, KMn₃O₄, SO₂ and EC. We had a degree of disagreement for all other indices. From the conducted research, it can be concluded that for all indicators, it is necessary to develop mathematical models in the studied stations according to the studied indicators of the Struma river in Bulgaria. The application of ICDA allows us to examine the correlations between individual indicators and eliminate those that are highly dependent on each other.