INTRODUCTIONDetermining peak metamorphic temperature of low grade rocks has always been a challenge. X-ray diffraction (XRD) is an established technique for the determination of constituent phases in solid-solution series. Differences in ionic sizes between substitute and host cations lead to systematic variations in unit-cell parameters and inter-planar spacings that can be measured using XRD. This approach has been widely used in analyzing rhombohedral Ca-Mg carbonates, for example, the composition of biogenic and inorganic (Ca, Mg)CO 3 crystals are often calculated by comparing the difference in d 104 value with the published determinative curves (Zhang et al., 2010;Raz et al., 2000; Falini et al., 1996; Bischoff et al., 1983;Milliman et al., 1971). At least five empirical curves are currently known in the literature (Bischoff et al., 1983;Milliman et al., 1971;Goldsmith et al., 1961Goldsmith et al., , 1955Goldsmith and Graf, 1958; Chave, 1952). Determinative curves based on synthetic magnesian calcite crystals are probably the most widely used (Milliman et al., 1971;Goldsmith et al., 1961;Goldsmith and Graf, 1958).Owing to the abundance of calcite and dolomite in the Earth's crust, knowledge of their limits of stability can be used to assess the conditions of temperature prevailing during their formation and subsequent metamorphism. The calcite-dolomite solvus in the system CaCO 3 -MgCO 3 was first investigated by Graf and Goldsmith (1955) and Harker and Tuttle (1955). They recognized that the temperature dependence of the amount of MgCO 3 in calcite in equilibrium with dolomite is potentially a precise method of estimating metamorphic temperatures. Goldsmith (1958, 1955) and Goldsmith et al., (1955) used XRD to determine the MgCO 3 content in natural and synthetic samples to establish phase relationships in the CaO-MgO-CO 2 system from the concentration of 0 to 15 mol.% of MgCO 3 . Later on, calcite-dolomite thermometry has been widely used (e.g., Wada and Suzuki, 1983; Bowman and Essene, 1982;Iii et al., 1982;Nesbitt and Essene, 1982;Ralph and Diane, 1980;Rice, 1977;Suzuki, 1977;Puhan, 1976;Hatcher et al., 1973; Hutcheon and Moore, 1973;Sobol, 1973). Talantsev (1978Talantsev ( , 1976, Bickle and Powell (1977), and Barron (1974) evaluated the effect of FeCO 3 on calcitedolomite thermometry and reported that its effect is negligible at concentrations <1 mol.%. Bickle and Powell (1977) reported that the metamorphic temperature of coexisting calcitedolomite samples from the Glockner area of the Tauern Window, Austria ranged from 410 to 490 o C. The solvus temperature determined from XRD data for Grenville calcite ranged from 415 to 485 o C (Sheppard, 1966). Höy (1970) estimated a temperature of 600 o C by using the calcite from brucite marble.
This study reports on a water quality assessment of the Water, Sanitation and Hygiene program implemented by the Swiss Agency for Development and Cooperation in the districts of Charsadda and Nowshera in Khyber Pakhtunkhwa, Pakistan, in the aftermath of the severe flood of 2010. During emergency operations, over 4,500 shallow wells were cleaned using the standard protocol suggested by the World Health Organization. Bacteriological analysis and chemical-physical parameters such as temperature, conductivity, turbidity and pH were tested before and after cleaning. Four to five years after the emergency operation, in 2014–15, a set of 105 representative wells was analyzed again, considering the same parameters and looking for additional contaminants (pesticides, arsenic and fluoride). The post-flood well-cleaning campaign was effective in the immediate reduction of fecal contamination of water (from 85% to 20% as measured 7–30 days after cleaning); however in the following months/years the rate of fecal contamination rose again (up to 62% of all measured domestic wells, n = 105). Along with laboratory analysis data, this study investigated the source of contamination of shallow wells and identified human practices in several cases. This information was useful for the design of future SDC interventions in the WASH sector.
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