Spatial distribution and controlling mechanisms of high fluoride groundwater in the coastal plain of Bohai Rim, North China

•Deep groundwater in the coastal plain of Bohai Rim witnessed an extensive F- excess.•Mineral dissolution and precipitation contributed 61% to groundwater F- contents.•Seawater intrusion had little effect on F- enrichment in groundwater.•More than 85% of deep groundwaters posed potential health hazards to humans.