跡津川断層系の石灰質断層ガウジを用いたESR法による活断層の最新活動年代測定

富山大学・富理工博甲第103号・EMILIA Bi Epse FANTONG Shu Awambeng・2016/03/23・★論文非公開★富山大学201

Major ions, δ18O, δ13C and 87Sr/86Sr compositions of water and precipitates from springs along the Cameroon Volcanic Line (Cameroon, West Africa): Implications for provenance and volcanic hazards

A combined study of major ions, δ18O, δD, 13C, 87Sr/86Sr isotopes, X-ray diffraction, scanning electron microscopy, and electron probe microanalyses on springs and spring mineral precipitates along the Cameroon Volcanic Line (CVL) was undertaken to understand water chemistry, and infer the type and origin of the precipitates. The waters are of evaporated Na + KCl and non-evaporated Ca + MgHCO3 types, with the more mineralized (electrical conductivity-EC of 13130 μS/cm) Lobe spring inferred to result from interaction of circulating 49 °C waters with magmatic volatiles of the active Mt. Cameroon. Water mineralization in the other springs follows the order: Sabga A > Sabga B > Bambui B > Bambui A > Nyos Cave. But for the Nyos Cave spring, all other springs contain fluoride (up to 0.5–35.6 mg/l above WHO potable water upper limit). The Sabga spring contains arsenic (up to 1.3 mg/l above the WHO limits). The springs show low fractionation temperatures in the range of 19–43 ᵒC. The Lobe and Sabga A springs are precipitating dolomite (CaMg(CO3)2), while the Nyos Cave, Bambui A, Bambui B and Sabga B springs precipitate trona ((Na3H(CO3)2.H2O). Our data suggest a marine provenance for the carbonates, and point to a volcanic input for the Lobe, Nyos, Sabga A, and Bambui A springs. The latter springs are therefore proposed as proxies for monitoring volcanic activity for hazard mitigation along the CVL

Increased risk of fluorosis and methemoglobinemia diseases from climate change: evidence from groundwater quality in Mayo Tsanaga River Basin, Cameroon

Current assessments of the impacts of climate variability and change on water resources commonly exclude groundwater. Thus, the identification of actual and potential health threatening elements in the groundwater, and linking up to climate variation and change at hydrologic catchment scale is an important ingredient for identifying feasible local-scaled adaptation strategies. Against these backdrops the focus of this paper was to assess the implications of climate change on groundwater-derived methemoglobinemia, and fluorosis which have been identified in Mayo Tsanaga River Basin (MTRB), North Cameroon. The basic approach of the study involved collection and analyses of previously published reports and articles that are related to the impact of climate change on water resources in Cameroon. Moreover in addition to groundwater samples that were collected from hand dug wells and boreholes in the dry season, streams, rivers, springs, and dams were sampled in the rainy season. In-situ measurements, and determination of electrical conductivity, pH, water temperature, atmospheric temperature, and alkalinity, respectively, were done. Laboratory analysis of potassium, sodium, calcium, magnesium, chloride, sulfate, nitrate, and fluoride was done by ion chromatography. The succinct results showed that atmospheric averaged annual temperature has increased from 28ºC to 29ºC over the past 40 years. Projected temperature for the year 2030 is 30ºC. Twenty seven percent of the sampled drinking water sources were contaminated by fluoride, which is causing fluorosis. The variation in nitrate suggests that during the dry season water in rivers, springs, dams, boreholes, and shallow wells contained nitrate below the WHO upper limit of 45 mg/l, while in the rainy season some shallow wells were polluted by nitrate. In contrast to the relationship of fluoride with groundwater age and depth, nitrate concentrations increased with decreasing age and depth of the groundwater. Based on the premises that a complex nexus exists between climate change, groundwater quality and health in the study area, adaptation and mitigation strategies were identified, and summarized with the accronym “ADAPT” for: Avoid untreated groundwater from deeper aquifers, Drink water from rain, rivers, and springs, Adopt local drinking water norms, Prohibit shallow well water in the rainy season and Treat young groundwater for nitrate and old groundwater for fluoride before drinking.Keywords: Climate change, Groundwater quality, Fluorosis, Methemoglobinemia, Adaptation strategies, Mayo Tsanaga River BasinJOURNAL OF THE CAMEROON ACADEMY OF SCIENCES Vol. 11 No. 1 (2013