Arsenic pollution caused by Eocene volcanism in the Sivas basin: The old drinking water source of the Yalıncak village (Hafik, Sivas)

The aim of this study is to investigate the origin of the highconcentration (1512 μg/L) of arsenic (As) in the olddrinking water source of Yalıncak village (Hafik, Sivas).For this purpose, 48 samples were collected from the rocksoutcropping in the recharge area of the drinking watersource. The major oxide contents of the rock samples weredetermined by XRF method, mineralogical compositionsby polarizing microscope and XRD methods and Asconcentrations of minerals were determined by using SEM- EDS method. As revealed by these analyses, the source ofarsenic in the waters of the region was found out to betuffite unit, containing pyroxene and plagioclase minerals,as well as volcanic glass fragments of different origins andsizes. It has been detected that arsenic oxide (As2O3)concentrations in rock samples vary between 0.01% and0.14% and some minerals contain As up to 14%. It wasdetermined that arsenic pollution in surface andgroundwater in the region was caused by the dissolution (bywater-rock interaction) of FeAsS (arsenopyrite) and BAsO4(boron arsenate) minerals found in the tuffites of theEocene age Bozbel formation in the Sivas Basin.