LAUSR

The aim of this study is to monitor the fluoride ion (F−), as well as chloride ion (Cl−), variation in the Eastern Black Sea Basin streams, and to evaluate drinking water quality of these streams, with reference to national and international directives and guidelines. The water samples (240) were semimonthly collected from three surface water resources, namely from the Değirmendere and Galyan streams in Trabzon Province, the biggest city on the Southeastern Black Sea Coast with a total population of 768 417, and the Harşit Stream in Gümüşhane and Giresun provinces. The monitoring results have revealed that the average F− concentration had varied between 0.154 and 0.200 mg/l in the Değirmendere Stream and between 0.156 and 0.163 mg/l in the Galyan Stream, respectively. However, the treated stream waters had lower F− concentrations, varying between 0.010 and 0.080 mg/l, than the untreated stream waters. In the Harşit Stream, the average F− concentrations were at relatively higher values, which ranged from 0.211 to 0.296 mg/l, in the uppermost stations, however showed a steadily decreasing trend throughout the lowermost stations and fell from 0.230 to 0.141 mg/l due to the hydropower dam reservoirs, namely Torul, Kürtün, and Akköy, operated in the watershed. The average Cl− concentrations have varied between 2.00 and 6.48 mg/l. On the one hand, the waters from the Değirmendere, Galyan, and Harşit streams are classified as high quality, considering the upper threshold values of 1.5 mg F−/l and 250 mg Cl−/l. On the other hand, these streams can be regarded as the fluoride-poor water resources.