Procedia Earth and Planetary Science最新文献

Groundwater is a very important source for drinking and irrigation in the karst area, and therefore understanding the hydrogeochemistry of karst water is extremely significant. Groundwater were collected, and major chemical compositions were measured to analyse the geochemical processes in Guiyang-Anshun, southwest China. The chemical compositions of the groundwater of the study area are dominated by Ca²⁺, Mg²⁺, HCO₃^-, SO₄^2-, which have been derived largely from dissolution of carbonate rocks (limestone and dolomite). Compared to the rural areas, TDS value is higher in the city centre. Chloride as a conservative tracer can be used to discuss the source of main ions in the groundwater. In this case, we support that high concentrations of Ca²⁺, Mg²⁺, Na⁺ are observed with low Chloride concentration in the regional groundwater.

Almost 20 years’ multi-disciplinary study on geogenic high arsenic (As) groundwater systems in China has greatly improved our understanding of the major processes controlling hydrogeochemical behavior of As in the subsurface environment. Among them, sorption by Fe(III) oxide/hydroxides was found to be one of the dominant processes retaining As in the aquifer matrix. Managed Aquifer Rehabilitation (MAR) by enhancing Fe(II) oxidation to promote As sorption was proposed and tested in a pilot-scale field experiment. Periodical injection of Fe(II) and ClO⁻ into a high As sandy aquifer triggered formation of new Fe(III) (hydr)oxides coating on sediment particles via advanced heterogeneous oxidation of Fe(II) and concurrent oxidative adsorption of As(III) via co-precipitation and surface complexation with Fe(III) (hydr)oxides. Monitoring results indicate that aqueous As concentration decreased from the initial average value of 78.0 μg/L to 9.8 μg/L over the 25-day amendment period and leveled off below 10 μg/L for the following 30 days. MAR is thus proved to be a cost-effective approach for remediating high As aquifers.

The Monterrey Metropolitan Area (MMA) is the third greatest urban area of Mexico. Owing to the rapid industrialization and urbanization of this city, more water resources are necessary in this semi-arid region. Thus, the objectives of this work were to characterize the chemical properties of groundwater supplied to MMA and to assess inter-annual variations in the water chemistry. Three groups of water were identified: recharge waters from mountain belts dominated by marine sedimentary rocks (Ca-HCO₃ type), transition zone waters from alluvial sediments (Ca-HCO₃-SO₄ type) and waters flowing through conglomerates and alluvial sediments of the northeastern MMA (Ca-SO₄ type). The ionic composition and the salinity gradient of each water group were in agreement with the topographic flow paths of the study area. The non-parametric Mann-Whitney U-test indicated that there have been no significant changes on the groundwater quality supplied to the MMA between the years 2006 and 2012.

A deep geological repository of spent nuclear fuel has to be safe for at least 100 thousand years. During this time, water–rock interaction on surface as well as in the rock around the repository will progress. All exogenous processes will depend on future evolution of climate. Based on the research of Quaternary sediments, three limiting scenarios of future climate evolution are considered: Maximum cooling and drying in glacial periods; maximum warming and moistening in interglacial periods and climate evolution affected by elevated concentrations of CO₂ in the atmosphere. Formation of permafrost, infiltration of melted water and oxidation will influence chemical composition of ground water. Two analogues of the changes are presented. They are ground waters in two mines in the Bohemian massive: (1) Mine “Svornost” in an abandoned historical uranium deposit Jáchymov (Joachimstahl), (2) underground research facility of “Bukov” near the uranium deposit of Rožná. Ground water was sampled from surface to a depth of 1200 m. The water–rock interaction during the infiltration and flow of ground water is the cause of the observed stratification of the chemical composition. The chemical composition of the collected samples indicate a probable future composition of ground water within the repository.