This study presents a geochemical framework and geographic information system (GIS) method for assessing the intrinsic potential of surface water and groundwater to mobilize arsenic, molybdenum, selenium, uranium, and vanadium. The method was created using published groundwater and surface water geochemical data from the National Uranium Resource Evaluation database for 2302 groundwater and 915 surface water samples. The method was evaluated using published groundwater geochemical data from the Texas Water Development Board. Geochemical data were analyzed in GIS. Samples were categorized by environmental condition, which was determined by using reduction–oxidation—as indicated by pe—and pH ranges for each sample based on geochemical mobility frameworks developed by Smith (2007) and Perel’man (1986). Reduction–oxidation and pH influence the occurrence, persistence, and mobility of arsenic, molybdenum, selenium, uranium, and vanadium in groundwater and surface water. Reduction–oxidation categories were assigned to water samples using concentrations of redox-active constituents, including dissolved oxygen, iron, manganese, and sulfur. The presence of iron substrates and hydrogen sulfides were considered in relation to mobility mechanisms. Twelve-digit hydrologic unit code (HUC) boundaries were used in GIS as analysis areas to determine the most commonly occurring environmental condition in each HUC. The resulting maps identify the environmental conditions in different areas that can be used to identify where the elements are mobile. This methodology provides a systematic approach to identify areas where elements in groundwater and surface water may occur and persist and may be transferable to other locations.
This report summarizes the primary sources of potash in the United States. Potash is an essential nutrient that, along with phosphorus and nitrogen, is used as fertilizer for growing crops. Plants require sufficient potash to activate enzymes, which in turn catalyze chemical reactions important for water uptake and photosynthesis. When potassium is available in quantities necessary for healthy plant growth, disease resistance and physical quality are improved and crop yield and shelf life are increased. Potash is a water-soluble compound of potassium formed by geologic and hydrologic processes. The principal potash sources discussed are the large, stratiform deposits that formed during retreat and evaporation of intracontinental seas. The Paradox, Delaware, Holbrook, Michigan, and Williston sedimentary basins in the United States are examples where extensive potash beds were deposited. Ancient marine-type potash deposits that are close to the surface can be mined using conventional underground mining methods. In situ solution mining can be used where beds are too deep, making underground mining cost-prohibitive, or where underground mines are converted to in situ solution mines. Quaternary brine is another source of potash that is recovered by solar evaporation in manmade ponds. Groundwater from Pleistocene Lake Bonneville (Wendover, Utah) and the present-day Great Salt Lake in Utah are sources of potashbearing brine. Brine from these sources pumped to solar ponds is evaporated and potash concentrated for harvesting, processing, and refinement. Although there is sufficient potash to meet near-term demand, the large marine-type deposits are either geographically restricted to a few areas or are too deep to easily mine. Other regions lack sources of potash brine from groundwater or surface water. Thus, some areas of the world rely heavily on potash imports. Political, economic, and global population pressures may limit the ability of some countries from securing potash resources in the future. In this context, a historical perspective on U.S. potash production in a global framework is discussed.
This report presents results from laboratory studies involving the net acid production (NAP), acid neutralizing capacity (ANC), and magnetic mineralogy of thirtyfour samples collected in the Upper Animas River watershed near Silverton, Colo., during the summer of 2003. Sampling focused mainly on the volumetrically important, Tertiary-age volcanic and plutonic rocks that are host to base and precious metal mineralization in the study area. Rocks in the study have all been subjected to a regional propylitic alteration event that modified the primary mineralogy of the host rock, while introducing minerals with an acid neutralizing capacity (ANC) including calcite, chlorite and epidote. Locally, hydrothermal alteration has consumed any ANC and introduced minerals, mainly pyrite, that has a high net acid production (NAP). Laboratory studies included hydrogen pyroxide (H 2 O 2) acid digestion and subsequent sodium hydroxide (NaOH) titration to determine NAP, and sulfuric acid H 2 SO 4 acid titration experiments to determine ANC on selected samples that generally had low NAP. In addition to these environmental rock property determinations, mineralogical, chemical, and petrographic characteristics of each sample were determined through multiple methods including semi-quantitative Xray diffractometry (Rietveld method), optical mineralogy, wavelength dispersive X-ray fluorescence, total carbon-carbonate, and 40-element inductively coupled plasma analyses. Magnetic susceptibilities, converted to estimates of volume-percent magnetite were also calculated. Although magnetite is a minor mineral constituent, it is easily measured, and can be positively correlated to measurable percentages of important acidneutralizing minerals, such as chlorite and calcite and inversely correlated to NAP indicator minerals including pyrite and clay minerals. Ranks were assigned to the samples based on ANC quantity in kilograms/ton (kg/ton) calcium carbonate equivalent, and ratios of ANC to NAP. Results show the Pyroxene Andesite Member of the Silverton Volcanics has highest ANC with little to no NAP in either the propylitic or weakly sericitically-altered samples. Samples of the propylitically altered Pyroxene Andesite Member also contains the highest mean magnetite abundance (over 8 volume percent) and therefore, may permit its regional mapping using the airborne magnetic and electromagnetic survey data. Samples from the Burns Member of the Silverton Volcanics, in general have a low ANC, high to moderate NAP, and in general, contain little to no magnetite. Samples containing pyrite (≤ 1 weight percent) have NAP that ranges from non-detectable to 39 kg/ton CaCO 3. Samples with no detectable calcite often contain abundant chlorite species (clinochlore and chamosite). Acid titration was performed on a chlorite mineral separate comprised mainly of the minerals clinochlore and chamosite, collected from a Burns Member lava with a high ANC (second highest ANC of all samples studied) and that lacks calcite. Acid titration results indicate that chlorit...
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