title: Radium geochemistry in Na-Cl type groundwater in Niigata Prefecture, Japan.
abstract: Radium isotopes in 23 Na-Cl type groundwater sampled mainly from deep wells in Niigata Prefecture, which is the site of the largest oil- and gas-fields in Japan, were measured along with U isotopes, chemical components and hydrogen and oxygen isotope ratios to elucidate the distribution and behavior of Ra in a brackish environment underground. Also analyzed were U and Th isotopes in 38 rock samples collected from outcrops at 17 locations. Ra-226 concentrations (8.86-1637 mBq kg(-1)) of groundwater samples roughly correlated with total dissolved solid (TDS) concentrations and other alkaline earth contents. Their (228)Ra/(226)Ra activity ratios (0.32-5.2) were similar to or higher than the (232)Th/(238)U activity ratios (0.6-1.7) in the rocks. The most likely transport mechanism of Ra isotopes into groundwater was due to their alpha-recoil from the solid phase, probably from the water-rock interface where Th isotopes had accumulated, and adsorption/desorption reaction based on the increase in (226)Ra contents with TDS.
authors.affiliation: Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Wake, Nomi, Ishikawa 923-1224, Japan. jun.16@llrl.ku-unet.ocn.ne.jp
authors.forename: Junpei
authors.initials: J
authors.lastname: Tomita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Satake
authors.forename: Taijiro
authors.initials: T
authors.lastname: Fukuyama
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sasaki
authors.forename: Aya
authors.initials: A
authors.lastname: Sakaguchi
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D001966:Bromine / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000737:chemistry; D007564:Japan; D011834:Radiation Monitoring / Q000379:methods; D011883:Radium / Q000032:analysis*; D012494:Sampling Studies; D012965:Sodium Chloride / Q000032:analysis; D012990:Soil Pollutants, Radioactive / Q000032:analysis; D013431:Sulfates / Q000032:analysis; D014867:Water / Q000032:analysis / Q000592:standards; D014873:Water Pollutants / Q000032:analysis; D014875:Water Pollutants, Radioactive / Q000032:analysis
chemical_list: D012990:Soil Pollutants, Radioactive; D013431:Sulfates; D014873:Water Pollutants; D014875:Water Pollutants, Radioactive; D014867:Water; D012965:Sodium Chloride; D002713:Chlorine; D001966:Bromine; D011883:Radium