Impact of boron-enriched geothermal wastewater drainage on aqueous environment of the Yangbajing geothermal field, Tibet

The boron-enriched wastewaters generated by the Yangbajing geothermal power plant in Tibet were drained directly into the Zangbo River that flows across Yangbajing. The boron concentrations of all water samples collected from the study area were determined using Inductive Coupled Plasma Mass Spectrometer (ICP-MS), and the total boron and water-soluble boron in all riverbed sediment samples were extracted with sequential chemical extraction procedure and then their concentrations were measured as well. The boron concentration in the Zangbo River water was evidently affected by the geothermal wastewater drainage. The distribution of water-soluble boron in the riverbed sediments matches well with the locations of geothermal wastewater drainage sites, and therefore it was speculated that the riverbed sediment should be a sink of boron derived from geothermal wastewater. The boron concentration in the Zangbo River water and the water-soluble boron concentration in the riverbed sediment were impacted by the river runoff variation under the control of local precipitation. The riverbed sediment became a source of boron in the river as heavy precipitation occurred at Yangbajing.