CONTAMINATION IN WATER AND ECOLOGICAL RISK OF HEAVY METALS NEAR A COAL MINE AND A THERMAL POWER PLANT (REPUBLIC OF SRPSKA, BOSNIA AND HERZEGOVINA)
. Water samples were collected near the thermal power plant and coal mine (Gacko, Republic of Srpska, Bosnia and Herzegovina) and analyzed to measure the concentration of 33 parameters (pH, temperature, electrical conductivity, alkalinity as CaCO 3 , total hardness as CaCO 3 , total solids, total suspended matter, dissolved oxygen, oxygen saturation, biological oxygen demand, chemical oxygen demand with permanganate, ammonia, nitrite, nitrate, P, PAH, PCBs, phenolic index, mineral oils, detergents, content of As, Cd, Cr, Fe, Mn and Pb, sulfates, chlorides, fluorides, aerobic organotrophs, total coliforms, fecal coliforms and fecal streptococci). Determined average mean pH values and EC are within the reference values for class I surface water quality. The surface water in the study area is alkaline, with a mean pH value of 8.01. Depending on the location, other analyzed parameters correspond from I to V water quality classes. The ERI for As, Cd, Cr and Pb is low and for Mn is appreciable. The RI of the surface water in location 1 and 2 were moderate. In other locations, risk coefficients are low.