Abstracts of Annual Meeting of the Geochemical Society of Japan

Mass-independent sulfur isotopic anomalies have been found in ice core sulfate associated with volcanic events. It has been suggest that this isotope anomaly is a reliable metric for events with a Volcanic Explosivity Index of 3 or above, with obvious utility in reconstructing the history of volcanic events able to impact climate. However a physicochemical model is necessary to extract information from the record and the details of the chemical mechanism have been lacking. Using UV absorption cross sections of 32SO2, 33SO2, 34SO2 and 36SO2 from 250 to 320 nm , calculated isotopic fractionation factors for SO2 photoexcitation at altitudes of 10 to 60 km predict mass-independent distributions that are consistent with those found in stratospheric sulfate preserved in Antarctic snow and ice cores.

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Carbon dioxide underground sequestration is able to reduce enormous quantities of CO2 emission. It has been attracted and researched.But, there are several unclear mechanism of CO2 behavior in underground. Therefore, it is difficult to estimate exact time for CO2 storage.For estimating time of CO2 sequestration, we consider water-rock-CO2 reaction.Water-rock-CO2 reaction attract attention in many parts of science. It consists of three following reactions:CO2 + H2O = H2CO3 = H+ + HCO3- (1)MSiO3 + 2CO2 + H2O = M2+ + H4SiO4 + 2HCO3- (2)M2+ + 2HCO3- = MCO3 + CO2 + H2O (3)where M is bivalent metal ion.There are two steps. First, CO2 dissolves in the water by (1) or mineral and water react CO2 by (2). Next, bivalent metal ion and hydrogen carbonate ion generate and carbonate minerals (MCO3) precipitate by (3).If CO2 is fixed as MCO3 by (3), it is very safety. But, this reaction mechanism is very complex. And calculation method of dissolution rate constant is not clear. Furthermore, water-rock-CO2 reaction is useful for estimating ancient CO2 concentration and considering carbon flux in the global circulation, too.In this study, the purposes are 1)To consider dissolution mechanism in water-rock-CO2 reaction. 2)To compare many calculation method of dissolution rate constant.3)To estimate time of CO2 storage by precipitation of carbonate minerals.We used basalt samples for the dissolution experiment. Because,1) It contains metals which can become divalent cation.2) It is widely distributed in the world.3) Oceanic ridge is almost composed of basalt.The basalt samples ware obtained nearby Mt. Fuji.

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In the middle of 1980s, the explosive discharges of CO2 gas (= limnic eruption) at Lake Nyos and Monoun killed about 1800 of resident around the lakes. The cause of the limnic eruption was the CO2 gas dissolved in lake water. The CO2 gas is originated in a degassing magma. A thermal water containing CO2 gas is expected to be discharged on the floor of lake bottom. The accumulation of the dissolved CO2 gas is brought by the strongly stratified lake water. The investigation on the water chemistry and the elucidation on the formation of stratification is important for the prediction of next limnic eruption.

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In recently years, large amounts of low-calorie sweeteners have been used in a wide variety of soft drinks and foodstuffs in the world. These compounds are less degradable during wastewater treatment process, and are detected in the aquatic environment in European countries. Our previous studies reported the occurrence and concentrations of artificial sweeteners in wastewater treatment plants (WWTPs) in Japan. In addition, these compounds were detected in a spring water sample, which imply the occurrence of artificial sweeteners in groundwater. Since groundwater has been used as drinking water in Kumamoto, conservation of groundwater and safety management of its flow systems are of great concerns in this city. In this study, we analyzed artificial sweeteners in 135 groundwater samples collected from both observation wells and water supply wells. As a result of analysis, three artificial sweeteners, acesulfame, sucralose and saccharin were detected in groundwater samples, at geometric mean concentrations of 0.73 ng/L, 20 ng/L and 0.40 ng/L, respectively. Acesulfame showed high detection frequency among three sweeteners analyzed, suggesting its extensive distribution in groundwater in Kumamoto region. High concentration of acesulfame was detected in groundwater samples collected from wells located nearby recharges area of river water into groundwater. The concentrations of acesulfame decreased with the increasing of distance along to the general groundwater flow, which was reported previously. These results imply the possibility of artificial sweeteners as chemical tracer for understanding the groundwater flow systems. The high concentrations of acesulfame and sucralose were detected in several wells around urbanized area of Kumamoto. This may suggest the potential effect of leaking wastewater into groundwater by a break of sewer pipeline networks.

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