1,721,054 research outputs found
Geochemistry of groundwater in an intensely urbanised karst area (Lusaka, Zambia)
No full textThe capital of Zambia Lusaka (about 2 million inhabitants) is built on a plateau where dolomitic marbles widely crop out. The carbonate formation hosts a very intensively exploited karstic groundwater resource. Considering the fast urban expansion and the lack of environmental control, this resource is in serious danger of pollution that could compromise the social and economical development of the capital. In this paper the geochemistry of the ground water is for the first time being analysed on the basis of a small number of samples taken in July 2001 in order to get a preliminary idea of the water quality. In some samples the concentrations of reduced nitrogen species and mercury exceed the guidelines proposed by the WHO for drinking water. Lusaka is a good example of the potential human impact on a vulnerable karst environment, and if no measures will be taken in the very near future, the quality of life in the city will be at serious risk
From acid-rock drainage to acid-mine drainage: extreme contamination in waters at the Furtei Au-mine (Sardinia, Italy)
Full text linkThe weathering of sulfide-bearing mineral deposits, exposed either by natural erosion or by mining to
oxygen and water, can produce natural acid-rock drainage (ARD) and mining-related acid-rock drainage (acid
mine drainage, AMD), respectively. The composition and extent of acid drainage is highly variable, depending
on many factors, such as the composition of ore bodies and related host rocks, climate, mining operations and
processing (Nordstrom and Alpers, 1999). Due to the low pH and high concentrations of contaminants, acid
drainages can severely degradate surface and groundwater systems, as well as soils.
At Furtei (Sardinia, Italy), a high-sulfidation epithermal gold deposit consists of pyrite and enargite with
minor amounts of luzonite, tennantite, and chalcocite. The oxidized cap mainly consists of iron oxy-hydroxides,
gypsum, jarosite, halotrichite and scorodite. The gold deposit was exploited by open pit from 1997 to 2003.
The Au and Ag were recovered from oxidized ores by cyanidation. Sulfide ores were processed by flotation to
recover Cu concentrates. Total production was about 4 t of Au, 6 t of Ag, and 1500 t of Cu (Cidu et al., 2013).
Pre-mining conditions showed waters (flow <0.1 L/s) with pH down to 2.3, a typical example of ARD
characterized by high salinity (26 g/L) with predominant sulfate (20 g/L) and very high amounts of dissolved
contaminants (in mg/L): Al 2000, Fe 1700, Mn 35, Cu 29, Zn 11, Ni 4, Co 3, Cr 1, As 0.4, and Cd 0.1 (Cidu
et al., 1997).
During exploitation and after the mine closure, the number of sites with contaminated water increased.
Contaminated waters showed pH and chemical compositions similar to those observed under pre-mining
conditions, but much higher concentrations of Cu, Zn, As and Cd, respectively up to 180, 97, 5, and 1.7 mg/L
(Da Pelo et al., 2009; Cidu et al., 2013). The seepage from the tailings impoundment is collected in a well
and back pumped into impoundment. The highly contaminated water in the open pits and drainages from the
pyrite-rich waste dumps may flow downstream from the mine under heavy rain periods and pose a hazard to
agricultural areas
Origin and evolution of pore-water solutes in the very low premeability Opalinus Clay, Switzerland
No full text
CI-Isotopes as indicator for a complex paleohydrogeology in jurassic argillaceous rocks, Switzerland.
No full textCore infiltration experiment investigating high-pH alteration of low-permeability argillaceous rock at 30˚C.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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