The strontium to calcium ratio of coral aragonite is mainly controlled by three factors: (1) the strontium distribution coefficient between aragonite and seawater, (2) the Sr²⁺/Ca²⁺ ratio of the surface oceanic water, and (3) biological effects. The mean oceanic residence time of strontium and calcium are calculated to be 4.9×10⁶ years and 1.0×10⁶ years, respectively. Therefore, the Sr/Ca ratio in seawater is considered to be quite uniform throughout the world's surface seawater. If biological effects are considered to be negligible, Sr/Ca ratio of coral aragonite can vary as a simple function of temperature in which corals have grown. Steve Smith has clearly demonstrated, from a series of careful macrocosm experiments on Pocillopora damicornis, that a relationship exists between Sr/Ca in coral aragonite and ambient seawater temperature. The Sr/Ca ratio in coral aragonite is shown as a simple linear equation of ambient seawater temperature, classified of the "Sr/Ca thermometry". Recent high precision data of Sr/Ca analysed by mass-spectrometer, further calibrated the Sr/Ca thermometer using Porites corals. But recent studies also pointed out spatial variations (〜1%) of surface seawater Sr/Ca. In addition, biological effects such as taxonomy and growth rate are discussed in this paper. Re-evaluation of above three factors will provide a more reliable coral Sr/Ca thermometer.

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Activities of cosmogenic nuclides have been numerously reported for extraterrestrial material, meteorites (especially chondrites). In addition to noble gases, cosmogenic radionuclides (e.g., ²²Na, ²⁶Al, ⁴⁶Sc, ⁵³Mn, ⁵⁴Mn and ⁶⁰Co) have also kept important records of their history during last ten million years. For example, low ⁶⁰Co activity observed in most chondrites (<30 dpm/kg) suggests that their preatmospheric radii are less than 〜30 cm, and activities of ²²Na and ²⁶Al reflect various irradiation conditions by cosmic-ray such as shielding effect, exposure age and cosmic-ray flux with time and space. Terrestrial age (Antarctic meteorites; H group, <0.4×10⁶y; L, LL,<10⁶y estimated from ²⁶Al, ³⁶Cl and ¹⁴C activities) as well as exposure age (H, 3 -40×10⁶y; L, LL, 3 -50×10⁶y) shows different distributions between H- and L-, LL-group chondrites, which have possibly preserved the information about breakage of parent body and so on. The combined data of exposure age and activities of cosmogenic nuclides also give constraints on the complex history of chondrites (e.g., multi-stage irradiation as a result of fragmentation) until the collision with the Earth. Recently, with the progress of nondestructive γ-ray techniques, activities of relatively short-lived nuclides such as ⁴⁶Sc, ²²Na implied the irradiation conditions just before fall to the Earth. In this paper, "the evolution history of chondrites after separation from the parent body" is represented from activities of cosmogenic radionuclides in meteorites including recently fallen ones.

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Spring waters from limestone terrains of the southern area of Okinawa Island have been analysed for chemical and isotopic compositions. The isotopic compositions of river waters from the central and northern areas of the island have also been measured. Spring and river water samples were collected during the following periods: spring waters from April 26th to June 28th, river waters June 1 st and 2nd, and July 20, 21 and 22, 1996, respectively. P_CO2 of spring waters is 10^-2.3 to 10^1.1 atm. These high P_CO2 are probably caused by a large supply and fast decomposition of litter, owing to the climatic characteristics of the island. High concentrations of Ca²⁺ and HCO₃^- in spring waters may be caused by the reaction of limestone with CO₂. High concentrations of SO₄^2-, HCO₃^- and excess Na⁺ (Na⁺ of non sea water origin) are found in spring waters from the southern area. These Ca-SO₄・HCO₃ type spring waters are possibly formed by oxidation of pyrite occurring in the bedrock (Shimajiri Group). Equilibrium relationships among the spring water, feldspar, and clay mineral suggest that spring waters may be equilibrated with kaolinite. The NO₃^--N content of spring waters has been increased by contamination with chemical fertilizers and waste waters from domestic areas. The increment is striking in the central areas, comparing with data of 1987. Values of δD and δ¹⁸O for spring and river waters are -36 to -18‰ and -5.6 to -3.3‰, respectively. These values are almost the same with those of groundwaters in Hateruma and Yonaguni Islands, located about 2° south of Okinawa Island. This is probably due to that the water vapor in these areas are mainly recharged from the sea around the islands. The d-parameter (d=δD-8δ¹⁸O) of spring and river waters ranges from 2.8 to 13.4 with an average of 8.6. This indicates that these waters are mainly recharged with precipitations from the Pacific Ocean airmass in summer.

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This paper describes a study on environmental and igneous geochemistry using volatile elemental isotopes such as ³He/⁴He and ⁴⁰Ar/³⁶Ar rations, and δ¹³C and δ¹⁵N values. Helium escapes from the Earth's atmosphere to inter-planetary space because of its low atomic mass. In contrast it is degassed from the solid Earth into the air. Degassing rate of helium, hereafter called helium flux, may provide useful information on the average concentration of uranium and thorium in the crust and generation of heat through radioactive decay. We have estimated helium flux from a continental land area based on the gradient of the ³He/⁴He ratios down a natural gass well. The observed flux of 2-3×10⁶atoms/cm²s agrees well with a theoretical flux calculated by a correlation between terrestrial heat flow and production of helium via a-decay of uranium and thorium. Extensive mining of fossil fuels such as natural gas and petroleum may release radiogenic helium with a low ³He/⁴He ratio accumulated in the crust. In order to check the anthropogenic release of radiogenic helium, we have measured the secular variation of atmospheric ³He/⁴He ratio. The ratio decreases with time and the rate of change suggests that anthropogenic helium flux yields 5×10¹⁵ cm³ STP/year, which is significantly larger than the natural flux of 1×10¹³cm³ STP/year. The estimated flux is consistent with annual production of natural gas and petroleum and their helium/carbon ratios. In addition to anthropogenic release, CO₂ may also be degassing from the solid Earth through volcanic and hydrothermal activity. We have measured δ¹³C values and CO₂/³He ratios of high temperature fumaroles in cir-cum Pacific volcanic regions. Based on the simple mixing equation of three components, the upper mantle, organic sediment and limestone, the orgin of the carbon in the sample is assessed. Contribution of mantle-derived carbon is about 20% and a major part is attributable to recycled limestone carbon in the subduction zones. Global volcanic flux of carbon, 1.8×10¹² mol/year, is estimated by using CO₂/³He ratios and ³He flux from literature. It is significantly smaller than the anthropogenic flux of 5×10¹⁴ mol/year, but is not negligible. The flux, if accumulated over 4.5 billion years of geological time, amounts to 8.3×10²¹ mol which agrees well with the 9×10²¹ mol of the present inventory of carbon on the Earth's surface. We have investigated the origin of nitrogen in volcanic gases in island arc and back-arc basin basalt glasses based on the δ¹⁵N values and N₂/³⁶Ar ratios. Contribution of mantle-derived nitrogen is about 15% in subduction zones and the major fraction is derived from recycled sedimentary nitrogen. Global volcanic flux of nitrogen, 2.4×10⁹mol/year, is estimated by corrected N₂/³He ratios for elemental fractionation and the ³He flux from literature. The flux, if accumulated again over 4.5 billion years, yields 1.3×10¹⁹ mol, which is one order of magnitude smaller than the present inventory of nitrogen on the Earth's surface, consistent with a catastrophic degassing of the atmopshere.

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