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Definite increases in the components ratios of CO2/H2O, CO2/H2S, CO2/CH4and He/CH4were observed at the fumarolic gases from Owakudani geothermal area located at the center of Hakone volcanic caldera (Honshu Island, Japan), synchronized with the earthquake swarm in 2015. Such variations were due to the dominance of a magmatic component over a hydrothermal component, suggesting the earthquake swarm was produced by the injection of magmatic gases into the hydrothermal system. The CO2/H2O ratio of magmatic gas was estimated to be 0.0045 before the earthquake swarm, which increased up to 0.013 during the earthquake swarm, likely produced by the pressurization of magma as a result of magma sealing where the pressure increment in magma was estimated to be 3% to the lithostatic pressure. The H2O and CO2concentration in magma were estimated to be 6.3 wt% and 20 wt ppm, respectively, assuming a temperature 900 °C and a rhyolitic composition. In May 2015, a few months prior to the earthquake swarm in May 2015, a sharp increase in the Ar/CO2and N2/He ratios and a decrease in the isotopic ratio of H2O were observed at the fumarolic gas. The invasion of air into the hydrothermal system increased the Ar/CO2and N2/He ratios. The decrease in the isotopic ratio of H2O was induced by partial condensation of H2O vapor.

Remote sampling of water from Yugama crater lake at Kusatsu-Shirane volcano, Japan, was performed using a drone. Despite the high altitude of over 2000 m above sea level, our simple method was successful in retrieving a 250 mL sample of lake water. The procedure presented here is easy for any researcher to follow who operates a drone without additional special apparatus. We compare the lake water sampled by drone with that sampled by hand at a site where regular samplings have previously been carried out. Chemical concentrations and stable isotope ratios are largely consistent between the two techniques. As the drone can fly automatically with the aid of navigation by Global Navigation Satellite System (GNSS), it is possible to repeatedly sample lake water from the same location, even when entry to Yugama crater lake is restricted due to the risk of eruption.

The aim of this study is to assess the seasonal variation in major ion distribution patterns and identify the origin and geochemical behavior of some trace metals of streamwaters bathing the mineralized Lom Basin. Eighty-one water samples were collected during the dry and wet seasons and analyzed for major ions using AAS and 12 trace metals (Fe, Mn, V, Cr, Co, Ni, Cu, Zn, As, Cd, Pb, Hg) by ICP-MS. All physicochemical parameters besides pH and Cl–varied narrowly between both seasons. No seasonal variability was observed for Cl–given its conservative nature, while NO3–levels decreased in the wet period due to the dilution effect. Similarly, SO42–concentrations were low for both seasons reflecting the dissolution of low sulphide minerals associated with gold deposits. In contrast, the concentration of Ca2+, Mg2+, Na+, K+and HCO3–slightly increased during the wet season as they are flushed from the soil layers by rain. Water samples had very low concentrations (< 1 µg/l) of V, Cr, Co, Cu, Zn, Cd, Pb and significant concentrations of Fe and Mn. The seasonal regime of streamwater chemistry is controlled by groundwater supply of major cations and HCO3–from chemical weathering, leaching of ions from surface soil layers during precipitation and dilution of nitrate by surface runoff during the wet season. In this tropical basin, low acidity and trace metal loadings revealed lateritic weathering of sulphides, entrapment of trace metals in Fe and Mn oxides and leaching into deep groundwater. Although the streams have not been impacted, these findings may guide policymakers for water chemistry evaluation in Cameroon.

Hydrogen (D) and oxygen (18O) stable isotopes in precipitation are useful tools in groundwater recharge and climatological investigations. This study investigated the isotopes in rainfall during the 2013 and 2014 hydrological years in the Douala and Yaounde urban cities. The objectives were to generate local meteoric water lines (LMWLs), define the spatial–temporal variations of the isotopes in rainwater and their relationship to the regional precipitation cycle, and determine the factors controlling the isotopic variation. The LWMLs in Douala and Yaounde were δD = 7.92δ18O + 12.99 and δD = 8.35δ18O + 15.29, respectively. The slopes indicate isotopic equilibrium conditions during rain formation and negligible evaporation effect during rainfall. Precipitation showed similar wide ranges in δ18O values from −5.26 to −0.75 ‰ in Douala and −5.8 to +1.81 ‰ in Yaounde suggesting a common moisture source from the Atlantic Ocean. Enriched weighted mean δ18O (wδ18O) values during the low pre- and post-monsoon showers coincided with low convective activity across the entire region. Enriched isotopic signatures also marked the West African monsoon transition phase during each hydrological year. Abrupt wδ18O depletion after the transition coincided with the monsoon onset in the region. Peak periods of monsoonal rainfall, associated with high convective activities, were characterised by the most depleted wδ18O values. Controls on isotopic variations are the amount effect and moisture recycling. The stable isotope data provide a tool for groundwater recharge studies while the isotopic correlation with regional rainfall cycle demonstrate their use as markers of moisture circulation and detecting climatic changes in precipitation.

Knowledge of groundwater recharge and apparent age constitutes a valuable tool for its sustainable management. Accordingly, shallow groundwater (n= 72) in the Ndop plain has been investigated using the stable isotopes of oxygen (18O) and hydrogen (2H or D) and tritium (3H) to determine the recharge process, timing and rate of recharge, and residence time. The shallow groundwater showed low variability in δ18O values (−2.7 to −4.1 ‰) and 3H content (2.4–3.1 TU). The low variability suggests a similar origin, homogenous aquifer, good water mixing and storage capacity of the groundwater reservoir. Like surface water, a cluster of groundwater along the Ndop Meteoric Water Line (NMWL) and Global Meteoric Water Line indicates meteoric origin/recharge. The rainfall recharge occurs under low relative humidity conditions and negligible evaporation effect. About 80 % of the recharge is from direct heterogeneous/diffuse local precipitation at low altitude (<1,260 m) within the Ndop plain. Approximately 20 % is from high altitude precipitation (localised recharge) or is recharged by the numerous inflowing streams and rivers from high elevations. A homogenous cluster of δ-values in groundwater (and surface water) between May and June monsoon rains on the NMWL suggests dominant recharge during these months. The recharge represents at least 16 % (>251 mm) of the annual rainfall (1,540 mm) indicating high annual recharge; high enough for development of the groundwater resource for agriculture. The 3H content (>2.4 TU) in groundwater indicates post-1952 recharged water with an estimated residence time <30 years, suggesting short subsurface circulation, and subsequently a renewable aquifer.

A new method to measure the CO2concentration in lakes Nyos and Monoun using sound speed (SS) and electrical conductivity (EC) of the lake water was developed. Limnic eruptions at lakes Monoun and Nyos in Cameroon, characterized by a risk related to possible sudden release of magmatic CO2gas dissolved in the lake water, occurred in 1984 and 1986 respectively, killing about 1800 residents. CO2monitoring of the lake waters was initiated to prevent further disasters. Classical methods of CO2measurement, which require chemical analysis of water samples, are not suitable for frequent and multi-point monitoring. Inspired by the method of measuring salt concentration using SS, we obtained data for dissolved CO2(CO2(aq)) assuming the following formula [Formula], where Δvis additional SS due to dissolved ions and k1and k2are coefficients determined through experiments. The coefficient k1was determined with temperature T(°C) dependence as 0.0323–0.000523T[l m s−1mmol−1]. k2was estimated to be 0.132 at Lake Nyos and 0.0930 at Lake Monoun. Once k1and k2values are obtained, [CO2(aq)] and [Formula] are calculated using the SS, Tand EC.

A large amount of CO2is stored in the deep waters of Lake Nyos, a volcanic crater lake in Cameroon. The lake is meromictic and thus anoxic in the deeper areas, where dissolved iron exists as Fe2+. Since 2001, a controlled degassing of the lake has been underway. The degassing brings deep water containing Fe2+to the lake surface as a fountain. This resulted in the formation of Fe(OH)3precipitates and turned the lake surface red-brown. This coloration was accelerated after the addition of two further degassing pipes in 2011. The Fe(OH)3precipitates sink to deeper parts of the lake, re-dissolve and are reduced back to Fe2+, which is thought to be precipitating as siderite.The rates of dissolution and precipitation of siderite in Lake Nyos were examined. Fragments of siderite crystals were covered with gel (Epikote) and placed in lake water for 54 h at several depths characterized by chemical features. The change in the thickness of the crystal surface before and after the reaction was analysed by an interferometer in the laboratory. The siderite dissolves at a rate of −0.09 µm a−1for samples placed at a depth of 50 m, whereas precipitation took place in deeper waters. The precipitation rate of siderite increased by 0.29 µm a−1with an increase in depth from 100 to 200 m, and decreased to 0.25 and 0.09 µm a−1at depths of 208 and 210 m, respectively. However, the calculated saturation indices of siderite in the lake waters increased with depth. The objective of this study is to examine the observed rates of dissolution and precipitation of siderite and to compare them with the saturation index of siderite calculated from the chemistry of the lake water. We also discuss the change in Fe species from the oxidation of Fe2+to Fe3+at the surface and reduction to Fe2+and consequent precipitation as siderite in deeper parts of the lake by degassing of CO2from bottom water in Lake Nyos.

We assessed the potential for limnic eruptions at lakes Nyos and Monoun, Cameroon on the basis of numerical modelling and CO2profiles obtained by regular monitoring of the lakes. The change through time of the profiles suggests one particular scenario for producing an eruption: a supply of CO2-undersaturated fluid from the lake bottom that induces upwards growth of the CO2-rich bottom layer, leading eventually to CO2saturation at mid-depths of the lake. By using a numerical model for the ascent of a plume of CO2bubbles, we found that under realistic conditions (e.g. a profile of CO2as deduced from the regular monitoring data), a bubble plume generated from the middle depths of the lake can reach the lake surface with a high flux of CO2, which corresponds to a limnic eruption. In addition, we developed a numerical model to investigate how changes in the CO2concentration at the lake bottom affect the dynamics of a two-phase flow in the controlled degassing pipe, using the recently observed CO2profiles. This model enables us to estimate the CO2concentrations at the lake bottom from the heights of fountains that are observable at the lake surface.

The degassing systems installed in the early 2000s at lakes Nyos and Monoun, Cameroon, have been working well, resulting in significant removal of dissolved gas. However, the systems of both lakes started losing their capability due to a reduced CO2partial pressure in the bottom waters, especially after installation of additional pipes in 2011. After initiation of a degassing operation, changes in CO2profiles in the bottom layer of Lake Nyos over time showed that gas-poor shallow water has descended to the bottom, leaving little CO2in the bottom water. The degassing system at Lake Monoun has completely lost its gas self-lift capability as the reduced CO2partial pressure in the bottom water is too low to sustain the gas-lift system, and all the degassing pipes stopped working in 2010. This situation led to the accumulation of CO2due to continued natural recharge of magmatic CO2. To compensate this recharge of gas, we installed a new deep water removal system that is driven by solar power at Lake Monoun in December 2013. This system does not need power lines, fuel or complicated maintenance, thus it is convenient for remote lakes such as lakes Monoun and Nyos.

Vertical profiles of sound speed (SS) in lake water were measured at lakes Nyos and Monoun (Cameroon) in 2012 and 2014. A significant linear correlation with Pearson's rof 0.987 to 0.995 between total CO2concentration ([CO2]=[CO2(aq)]+[HCO[Formula]]) and SS excess (Δv) in water was found. Based on this correlation, we propose the SS method as a new simple tool to monitor CO2concentration in lakes Nyos and Monoun. We applied this method to multipoint measurements of CO2in lakes Nyos and Monoun, and found horizontal differences between CO2distributions in the two lakes. The results indicated that Lake Nyos water was stably stratified, and the total CO2decreased from 2012 to 2014. At Lake Monoun, which consists of three basins (the western basin, the central basin, and the main basin), waters in the western and central basins exhibited a higher dissolved CO2content than those in the main basin at the same depth. An increase in CO2was also detected in the main basin from 2012 to 2014.

Shallow groundwater of unknown quality, mineralisation and recharge processes is a major source of water supply to most households in the informal settlements in the Bonaberi (Douala IV) district, Cameroon. Accordingly, this study (December 2018) investigated the quality, hydrogeochemical controls, and recharge mechanism of 18 shallow groundwater (< 10 m deep) and 6 surface water sources in Bonaberi. Apart from Na+, Cl−, SO42−, Fe, Mn, and Al in some water sources, all other analysed chemical parameters were within the WHO (2011) guidelines for drinking water. The order of major ions abundance (meq/l) in the studied water was Na2+> Cl−> Ca2+> HCO3−> SO42> K+> NO3−> Mg2+while the trace element abundance (ppb) was Ti > Fe > Mn > Sr > Ba > Al > Rb > Zn > As > Se > Cr. Two main water types identified in Bonaberi are Na-Cl and mixed Ca-Na-HCO3. Mineral weathering and leaching from pit toilets and waste dumps are major factors influencing groundwater composition. Stable isotopes show overlaps in surface water and groundwater, indicating hydraulic connectivity. The narrow ranges in δ18O values of the shallow groundwater suggest good water mixing and a homogenous aquifer. The major source of groundwater recharge is rainfall occurring by direct diffused rapid recharge through the permeable alluviums. This recharge favours the leaching of pollutants from residential pit toilets into the shallow aquifer. However, the groundwater mixing and its dilution by heavy rains results in relatively low NO3−and Cl−concentrations in the water though relatively higher in densely populated areas. The shallow aquifer in Bonaberi is vulnerable to pollutants generated within the city. Thus, drilling deep boreholes (after detailed hydrogeochemical studies) is recommended for a good quality groundwater supply. This will prevent water-borne infections given the increasing urbanisation.

The hydrogeology of arid regions is becoming increasingly important due to diminishing projections of water resource availability in response to global environmental change. This paper aims to investigate the karst aquifer in the study area and clarifies the different factors which affect the occurrence and quality of its groundwater. The fractures systems are the main factor which controls the groundwater occurrence in the studied aquifer. The isotope analyses reveal that the groundwater has nearly similar isotopic compositions, suggesting similar recharge conditions; they also indicate that the groundwater of karst aquifer is meteoric water and the recharging source is the rainfall. The high values of total dissolved salts (TDS) of the groundwater are attributed to the rock-water interactions which lead to dissolution processes of marine salts into the aquifer matrix. Although most of the water levels in the drilled wells are under the sea level, the isotope analyses indicate that no contribution of seawater intrusion affects the groundwater. The present study reveals that some specific regions have more priorities than others in future groundwater explorations.

his study presents the first and detail field investigations of exposed deposits at proximal sections of the Barombi Mbo Maar (BMM), NE Mt Cameroon, with the aim of documenting its past activity, providing insight on the stratigraphic distribution, depositional process, and evolution of the eruptive sequences during its formation. Field evidence reveals that the BMM deposit is about 126m thick, of which about 20m is buried lowermost under the lake level and covered by vegetation. Based on variation in pyroclastic facies within the deposit, it can be divided into three main stratigraphic units: U1, U2and U3. Interpretation of these features indicates that U1consists of alternating lapilli-ash-lapilli beds series, in which fallout derived individual lapilli-rich beds are demarcated by surges deposits made up of thin, fine-grained and consolidated ash-beds that are well-defined, well-sorted and laterally continuous in outcrop scale. U2, a pyroclastic fall-derived unit, shows crudely lenticular stratified scoriaceous layers, in which many fluidal and spindle bombs-rich lapilli-beds are separated by very thin, coarse-vesiculatedash-beds, overlain by a mantle xenolith- and accidental lithic-rich explosive breccia, and massive lapilli tuff and lapillistone. U3 displays a series of surges and pyroclastic fall layers. Emplacement processes were largely controlled by fallout deposition and turbulent diluted pyroclastic density currents under “dry” and “wet” conditions. The eruptive activity evolved in a series of initial phreatic eruptions, which gradually became phreatomagmatic, followed by a phreato-Strombolian and a violent phreatomagmatic fragmentation. A relatively long-time break, demonstrated by a paleosol between U2and U3, would have permitted the feeding of the root zone or the prominent crater by the water that sustained the next eruptive episode, dominated by subsequent phreatomagmatic eruptions. These preliminary results require complementary studies, such as geochemistry, for a better understanding of the changes in the eruptive styles, and to develop more constraints on the maar’s polygenetic origin.

Direct sampling and analysis of fumarolic gas was conducted at Ebinokogen Ioyama volcano, Japan, between December 2015 and July 2020. Notable changes in the chemical composition of gases related to volcanic activity included a sharp increase in SO2and H2concentrations in May 2017 and March 2018. The analyses in March 2018 immediately preceded the April 2018 eruption at Ioyama volcano. The isotopic ratios of H2O in fumarolic gas revealed the process of formation. Up to 49% high-enthalpy magmatic vapor mixed with 51% of cold local meteoric water to generate coexisting vapor and liquid phases at 100–160 °C. Portions of the vapor and liquid phases were discharged as fumarolic gases and hot spring water, respectively. The CO2/SO2ratio of the fumarolic gas was higher than that estimated for magmatic vapor due to SO2hydrolysis during the formation of the vapor phase. When the flux of the magmatic vapor was high, effects of hydrolysis were small resulting in low CO2/SO2ratios in fumarolic gases. The high apparent equilibrium temperature defined for reactions involving SO2, H2S, H2and H2O, together with low CO2/SO2and H2S /SO2ratios were regarded to be precursor signals to the phreatic eruption at Ioyama volcano. The apparent equilibrium temperature increased rapidly in May 2017 and March 2018 suggesting an increased flux of magmatic vapor. Between September 2017 and January 2018, the apparent equilibrium temperature was low suggesting the suppression of magmatic vapor flux. During this period, magmatic eruptions took place at Shinmoedake volcano 5 km away from Ioyama volcano. We conclude that magma sealing and transport to Shinmoedake volcano occurred simultaneously in the magma chamber beneath Ioyama volcano.

We have investigated the chemical and isotopic composition of recently formed gases emitted by three fumaroles on the Mt. Mihara summit peak of the Izu-Oshima volcano in order to assess the formation process of these gases. The CO2/H2O ratio of these gases varied greatly, with the sD and s18O of the H2O being as low as a vapor phase equilibrated with the local meteoric water. These features are explained by a mixing of the vapor equilibrated with local meteoric groundwater and primary steam, which is a vapor phase generated by the mixing of magmatic gas and a cold meteoric groundwater. We concluded that there was no direct mixing between the magmatic vapor and a vapor phase of meteoric origin in the processes involved in fumarolic gas formation.

In this study, we sampled natural fumarolic gases, the gas from a steam well drilled to 800 m depth and natural hot spring waters from the Owakudani geothermal area, Hakone Volcano, Japan. We then measured the chemical composition and the D/H and 18O/16O ratios of H2O within the samples. On the basis of the analytical results, we investigated the differentiation processes of the magmatic fluid during ascent to the surface. Volcanic gas discharged from the No. 52 steam well has a CO2/H2O ratio that is much higher than those from fumarolic gases. The isotopic ratio of H2O in the gas are also much higher than those in the fumarolic gases, and the gas also contains high concentrations of SO2and HCl. The above observations indicate a magmatic origin for the gas from the No. 52 steam well. The hydrothermal system is principally explained by the mixing of a magmatic vapor, represented by the gas from the No. 52 steam well, and cold local meteoric water. Following mixing of the fluids, a separation of primary vapor and liquid occurs. The primary liquid is discharged as a component of hot spring water, and has high isotopic ratios. The primary vapor is mixed with vapor derived from the boiling of local meteoric water. The mixed vapor is then discharged to the surface, interacting with shallow meteoric water and undergoing partial condensation of H2O vapor. Hot spring water with isotopic ratios lower than those of the primary liquid is derived from the boiling of local meteoric water.

A major function of Rho-family GTPases is to regulate the organization of the actin cytoskeleton; filopodia, lamellipodia, and stress fiber are regarded as typical phenotypes of the activated Cdc42, Rac, and Rho, respectively. Using probes based on fluorescent resonance energy transfer, we report on the spatiotemporal regulation of Rac1 and Cdc42 at lamellipodia and membrane ruffles. In epidermal growth factor (EGF)-stimulated Cos1 and A431 cells, both Rac1 and Cdc42 were activated diffusely at the plasma membrane, followed by lamellipodial protrusion and membrane ruffling. Although Rac1 activity subsided rapidly, Cdc42 activity was sustained at lamellipodia. A critical role of Cdc42 in these EGF-induced morphological changes was demonstrated as follows. First, phorbol 12-myristate 13-acetate, which activated Rac1 but not Cdc42, could not induce full-grown lamellipodia in Cos1 cells. Second, a GTPase-activating protein for Cdc42, KIAA1204/CdGAP, inhibited lamellipodial protrusion and membrane ruffling without interfering with Rac1 activation. Third, expression of the Cdc42-binding domain of N-WASP inhibited the EGF-induced morphological changes. Therefore, Rac1 and Cdc42 seem to synergistically induce lamellipodia and membrane ruffles in EGF-stimulated Cos1 cells and A431 cells.

Fumarolic gases from the Kusatsu Shirane volcano, Japan were analyzed for the content and isotopic compositions of H2O, the abundances and isotopic compositions of noble gas. The observed δ18O and 36Ar/H2O ratios could not be explained by an existing hydrothermal model in which a mixing between magmatic vapor (MAV) and meteoric water (ASW), a single-step separation to vapor and liquid phases and a subsequent partial H2O vapor removal from the vapor phase have been considered. We constructed a revised model in which two-step mixing-separation and a subsequent partial H2O vapor removal by condensation were considered. In the model, the first step was the mixing between MAV and ASW, and a subsequent separation to a primary vapor and liquid phases. In the secondary step, the primary vapor mixed with another fluid which has a δ18O lower than the primary vapor phase and a low 36Ar/H2O ratio relative to ASW. The mixture separates to secondary vapor and liquid phases. The fluid with low 36Ar/H2O ratio could be ASW partially vaporized in the geothermal area. The secondary vapor ascended and discharged as fumarolic gas. In the ascending process, the secondary vapor suffers a partial H2O vapor removal by condensation in various degrees.

A change in the chemical compositions of volcanic gases is one of the noticeable phenomena that frequently occurs prior to an eruption. Analysis of the water-soluble components adhering to volcanic ash is available for remote monitoring of volcanic gases from inaccessible volcanoes. It is a secure method for monitoring volcanic activity without using particular devices. Prolonged volcanic eruption at the Unzen Fugendake volcano from 1990 to 1995 started with a phreatic eruption after 198 years of dormancy. Volcanic activity changed from a phreatic and phreatomagmatic eruption to a magmatic eruption with pyroclastic flows in May 1991. The relationship between the chemical composition of volcanic ash and the contents of the water-soluble components adhering to it are discussed in relation to the early stage of the long-term eruption. Volcanic ash ejected by phreatic and phreatomagmatic eruption before dome formation was the product of the alteration in the volcanoclastic materials beneath the surface. The ash had a high content of water-soluble components, which was caused by the absorption of hydrogen chloride and sulfur dioxide gases from magma into wet debris before dome formation. Volcanic ashes which were generated by pyroclastic flows after dome formation were fresh lava fragments. While the contents of water-soluble sulfate adhering to the ash noticeably decreased, those of water-soluble chloride adhering to the ash hardly decreased. The considerable decrease in the contents of water-soluble sulfate was caused by the reaction of volcanic gases with dry lava fragments. Contrary to this, the concentration of hydrogen chloride gas in ash clouds was extremely high, which obstructed the decrease in the water-soluble chloride content in the ash. Volatility of chlorine and sulfur from volcanic rock suggests that the inner temperature of pyroclastic flows was higher than 600∼700°C at least.

A small-scale steam explosion occurred on Karanuma crater on the summit of Akita-Yakeyama volcano on August 16, 1997 after a dormancy of 46 years. Chemical compositions of the fumarolic gases at the summit and hot spring waters around the volcano were monitored before the eruption.

The link between rainfall and groundwater recharge in the Rio del Rey Basin, which is of socio-economic importance to Cameroon, is poorly understood. Accordingly, the stable isotopes in monthly rainfall from January to December 2012 (in Lobe and Mundemba) and 52 surface water and groundwater samples were investigated. High values of δ18O and δD were recorded in the dry period (February to March), and the least values of δ18O and δD were observed in the wet period (September). This indicates that different condensation processes primarily influenced stable isotopes in rainfall as a function of the difference in moisture sources. The relationship between δD and δ18O defined the Lobe meteoric water line as δD = 7.97 δ18O + 12.48 and Mundemba water line as δD = 7.75 δ18O + 10.79. The similarity of their slopes to the global meteoric line suggests that the isotopic composition of investigated rains was not significantly affected by evaporation during precipitation. The ranges in deuterium-excess of precipitation from 5.8 to 16.56‰ suggest the source of vapour is from the Atlantic Ocean. The groundwater isotope values (ranging from −3.81 to −2.52‰ for δ18O) plotted close to and along the GMWL, showing that its isotopic composition is of meteoric origin under rapid recharge conditions. The isotopic similarity between groundwater and June–August rains suggests a significant recharge during this period.

Abstract:: In a previous study, we demonstrated that the protein phosphatase inhibitors, okadaic acid and calyculin A, induced apoptosis in human osteosarcoma cell lines, Saos-2 and MG63 cells. In the present study, to determine if new gene transcription and protein synthesis are required for okadaic acid-induced apoptosis in Saos-2 and MG63 cells, the cells were treated for 48 h with varying concentrations of the inhibitors of protein or RNA synthesis, i.e., cycloheximide, actinomycin D, and puromycin, in the presence of a fixed dose of okadaic acid. All these reagents in different concentrations prevented the okadaic acid-induced apoptosis in MG63 cells in a dose-dependent fashion. The same concentrations of cycloheximide, actinomycin D, or puromycin alone did not induce any apoptotic features in MG63 cells. However, not all the aforementioned reagents affected okadaic acid-induced apoptosis in Saos-2 cells. Okadaic acid-induced and cycloheximide-prevented apoptosis was shown by phase-contrast microscopy, WST-1 assay, direct visualization of nuclear condensation and fragmentation of chromatin, and the characteristic DNA ladder formation on agarose gel electrophoresis. The present results indicate that the induction of new cell death genes and ongoing protein synthesis may have a role in okadaic acid-induced apoptosis in MG63 cells and that such proteins are not required in Saos-2 cells.

The CT manifestations of renal metastases from nonurinary tract carcinomas were evaluated in five autopsy-proven cases. Three cases resembled renal inflammatory disease or renal cysts. The wide variety of CT manifestations of renal metastases underscores the need to bear renal metastases in mind when renal abnormalities are observed in any case of advanced malignancy.

The discharge rate of SO2from Unzen volcano, which started erupting in November 1990, has been measured with a correlation spectrometer (COSPEC) at a fixed ground‐based station about 2.3 km SSW from the summit lava dome. The discharge rate of SO2increased greatly after the explosive eruptions on June 8th and 11th, 1991. High discharge rates of SO2(an average of 180 ton/day) were observed from July 1991 to January 1992, followed by a general decrease to an average of 110 ton/day during March 1992 and May 1994. The discharge rate of SO2correlates with the extrusion rate of magma. Judging from the sulfur inventory, i.e., 130–450 g of discharged SO2per ton of erupted magma, and the sulfur content of the extruded lava, the proportion of sulfur degassed from the magma is estimated to be ca. 80%, suggesting an efficient volatile degassing. The discharge rate of the total volatiles is calculated to be 7,700 ton/day by combining the SO2discharge rate with the chemical composition of volcanic gases.

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To determine whether protein phosphorylation and dephosphorylation can affect apoptosis in osteoblastic cells, we examined the effects of okadaic acid (OA) and calyculin A (CA) on cultured human osteoblastic cells Saos-2 and MG63, and mouse osteoblastic MC3T3-E1 cells. After reaching confluence, these cells were exposed to varying concentrations of OA or CA. OA and CA induced cell death in all three cell lines in a dose- and time-dependent manner. Marked nuclear condensation and fragmentation of chromatin were also observed in these cells by using the Hoechst 33342 stain. DNA ladder formation, a hallmark of apoptosis, was detected in Saos-2 and MG63 cells, but not in MC3T3-E1 cells by treatment of OA or CA. In the Saos-2 cells, OA- and CA-induced DNA ladder formation was dose-dependent with maximal effect at concentrations of 10 and 2 nM,respectively, and was time-dependent from 14 to 48 h. DNA ladder formation in response to OA and CA was revealed by using conventional ethidium bromide staining of electrophoresed DNA without using autoradiography. Beyond the maximal effects at the respective concentrations, however, cell death did not indicate DNA laddering, suggesting that phosphatase activity may be required for ladder formation. Our results indicate that apoptosis in the cultured osteoblastic cells is induced by moderate inhibition of PP-1 or PP-2A based on the known selectivity of okadaic acid and of calyculin A.

The Bamenda Highlands contains numerous dilute and soda springs of unknown hydrological provenance. These dilute springs are a vital source of drinking water to the inhabitants. As a contribution to water management, this study investigated the spring water recharge, residence time and sub-surface circulation using δ18O, δD, 3H, CFCs, SF6and TDS. A plot of both water types along the local meteoric water line indicated the meteoric origin and rapid recharge following precipitation. Dilute springs with a δ18O altitude effect of 0.27/100 m suggested recharge at different elevations. The CFC-12, CFC-11 and CFC-113 dating (complemented by 3H) showed reasonable young apparent ages of dilute springs ranging from 21 to > 52 (mean/median of 25) years and old soda springs (> 52 years). SF6concentrations in dilute springs revealed exceptionally young ages relative to CFCs modelled ages suggesting a terrigenous enrichment of the former. Thus, groundwater dating with SF6is unreliable in the area. Besides the old apparent ages of soda springs, their highly depleted δ18O and high TDS (mean of 1396 mg/l) indicated palaeo-recharge and high water–rock interaction, respectively. In contrast, the low TDS of dilute springs (< 140 mg/l) indicated low-water interaction. Most dilute springs showed exponential mixing models indicating heterogeneous recharge under unconfined aquifer conditions. Conversely, the old soda springs displayed piston flow and binary mixing models. The meteoric recharge and similar residence time of the shallow dilute springs suggested natural resilience to short-term changes in climatic conditions. Thus, low shallow groundwater abstraction is sustainable at the Bamenda Highlands.

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