Monitoring surface and groundwater quality parameters of Foldere (Tonya, Vakfikebi̇r, Trabzon) Basin

In this study, the surface and groundwater quality of the Fol Dere Basin (Tonya-Vakfıkebir) was aimed to be determined. For this purpose, sampling was carried out for 3 periods from 10 surface water and 2 groundwater points in the basin. The examined surface waters are generally of the Ca-Mg-HCO3 and Ca-Na-HCO3 types, while the groundwater is of the Ca-Na-HCO3 and Ca-HCO3 type. The pH of surface waters varies between 7.72-8.28 on average, electrical conductivity (EC) ranges from 140.6 to 266.3µS/cm on average, and dissolved oxygen (DO) ranges from 7.85 to 8.96 mg/L. The pH of groundwater averages 8.3-8.25, EC averages 43.5-45.6 µS/cm, and DO averages 8.75-8.88 mg/L. According to the Surface Water Quality Regulation (YSKY), all examined waters fall into the I. class "very good" and II. Class "good" in terms of pH, DO, EC, NH4_N, NO3_N, TP, F-, and Mn. According to the regulations of the World Health Organization (WHO) and the Turkish Standards Institute (TSE 266), the waters do not pose any threat in terms of Ca+2, Mg+2, Na+, K+, Cl-, SO4-2 contents. Waters are classified as "excellent water" in terms of Sodium Adsorption Ratio (SAR), and "excellent-good" class in terms of % Na, while suitable for irrigation purposes in terms of Kelly Index (KI), Residual Sodium Carbonate (RSC), and Magnesium Hazard (MH). The waters belong to the category of soft waters in terms of total hardness parameters. Heavy metal concentrations are generally low, with Al (except FD-1, FD-2, FD-3, FD-4) and Ni exceeding the standard limit values. According to the Water Quality Index (WQI) values, the Foldere Basin is classified as "Excellent water", with pH, DO, and TP being the most effective water quality parameters on the WQI. According to the Heavy Metal Index (HPI) quality class, FD-4 is "excellent", while all other water points are "good" class