Influence of arsenic and boron on the water quality index in mining stressed catchments of Emet and Orhaneli streams (Turkey)

Emet and Orhaneli stream basins are characterized by intense mining of colemanite, the main borate mineral in the area. Unlike other global borate deposits, the colemanite of this region contains arsenic minerals (realgar and orpiment). Undoubtedly, improper management of mine wastes causes pollution of water resources, affecting human life and biota. In the present study, spatial and temporal variation in water quality of Emet and Orhaneli streams was assessed. The water quality index (WQI) model was used to rate the overall status of the water, and geographical information systems (GIS) was used to aid the visualization of results. No significant differences in WQIs for the three-monitoring periods (March, July and October 2017) were noted. The WQI in the region is highly influenced by arsenic (As) and boron (B), with a strong positive correlation (p < 0.05, r2 = 0.971). The As and B concentrations in Emet stream were 1.88–1907 μg/L and 0.01–1900 mg/L, respectively. Whereas for Orhaneli stream, respective As and B levels ranged from 5.17 to 116 μg/L and 0.01 to 5.45 mg/L. Globally, the As level in Emet stream basin is comparable to some of the words major contaminated regions such as Rapti River Basin (India) and Xieshui River (China). However, the uniqueness of this basin is seen in B and As trends, and input routes like active geothermal waters and weathering of the realgar (AsS) and orpiment (As2S3) from colemanite nodules. This paper demonstrates the influence of pollutants associated with basin geochemistry and exploration of mineral resources on WQI.