Isotopic and chemical characterization of groundwater in the northern Tucson Basin, Arizona

The chemical and isotopic characteristics of the groundwater in the Canada del Oro Valley were investigated, and existing hydrologic information compiled to determine processes affecting groundwater chemistry in this area. Evidence suggests that dissolution of calcite and cation exchange on clays are the dominant reactions occurring in the aquifer. Values of 8D and 8 180 lie within the range for winter precipitation in the Tucson Basin. Tritium data indicate that most recharge to the valley occurs along the edges of the Santa Catalina Mountains, in particular along the Canada del Oro Wash. Recharge along Big Wash appears to be minimal. Relatively high concentrations of sulfate and lower 834S values in groundwater along the Cariada del Oro Wash may be a result of historical smelting operations to the northeast of the study area.hydrology collectio

Effect of citric acid on uranyl(VI) solution speciation, gas-phase chemistry and surface interactions with alumina

Activities related to nuclear weapons production have left a legacy of uranium contamination in the United States. Understanding the chemical interactions that uranium undergoes in the environment is important for prediction of uranium mobility and development of remediation strategies. A detailed spectroscopic examination of the pH-dependent behavior of the UO₂²⁺-citrate system in aqueous solution was completed using Raman, ATR-FTIR, and NMR spectroscopies, combined with ESI-MS. Three structurally-distinct UO₂²⁺-citrate complexes, {(UO₂)₂Cit2}²⁻, {(UO₂)₃Cit₃}³⁻, and (UO₂)₃Cit₂ exist in dynamic equilibrium over a pH range from 2 to 9. ¹⁷O and ¹³C NMR data confirm the previously published structure of {(UO₂)₂Cit₂}²⁻ and indicate that {(UO₂)₃Cit₃}³⁻ is a symmetric, fluxional molecule. The (UO₂)₃Cit₂ complex was found to have a rigid structure and two structural isomers. Chemical interactions of U(VI), citric acid and Al₂O₃ were investigated using ATR-FTIR spectroscopy to examine how complexation of U(VI) by citrate affects adsorption of U(VI) to Al₂O₃. Participation in UO₂²⁺-citrate complexes does not significantly affect the ability of citrate to chemisorb to Al₂O₃. The UO₂²⁺-citrate complexes dissociate upon adsorption, with hydrolysis of UO₂²⁺. Adsorption isotherms developed from ATR-FTIR data indicate enhanced citrate adsorption to Al₂O₃ in the presence of UO₂²⁺ , suggesting that UO₂²⁺ acts as a central link between two citrate ligands, one of which is complexed to Al₂O₃. UO₂²⁺-citrate complexes can physisorb to citrate-saturated Al₂O₃. This study demonstrates how an in-depth infrared spectroscopic analysis of UO₂²⁺-ligand complexes both in solution and adsorbed to oxide surfaces can be used to understand the adsorption mechanisms of these complexes. ESI-MS was investigated for the characterization of U(VI) species in groundwater. Both ion trap and FTICR instruments were used. UO₂²⁺ forms complexes with ligands such as acetate, trifluoroacetate, and nitrate, which readily react with CH₃CN, CH₃OH, and H₂O to form solvated gas-phase species of the form [(UO₂L)Sn]⁺, where L represents the ligand, S represents solvent, and 1 ≤ n ≤ 4. n is directly related to the number of available coordination sites on UO₂²⁺, providing insight into the coordination environment of UO₂²⁺. Solvent exchange and addition reactions readily occur. UO₂²⁺ also forms coordinately saturated negatively-charged complexes with nitrate. UO₂²⁺-carbonate complexes were also investigated

Garcinia buchananii bark extract is an effective anti-diarrheal remedy for lactose-induced diarrhea

Ethnopharmacological relevanceThe extract from the stem bark of Garcinia buchananii trees is used as an anti-diarrhea remedy in sub-Saharan Africa. We tested the hypothesis that G. buchananii bark extract and its anti-motility fractions are effective treatments against lactose-induced diarrhea.Materials and methodsA high-lactose (35%) diet was used to induce diarrhea in Wistar rats, which were then treated with either G. buchananii bark extract (0.1, 0.5, 1.0 and 5.0 g bark powder), and its anti-motility fractions isolated using preparative thin layer chromatography; termed PTLC1 (15 mg) and PTLC5 (3.8 mg) or loperamide (8.4 mg). Drug preparations were dissolved in 1L except PTCL1 and PTLC5 that were dissolved in 100mL tap water. Numerous parameters were measured in each condition including consistency, fluid and mucus content of feces, body weight, water and food consumption, urine production and bloating.ResultsDiarrheic rats produced watery or loose, mucuoid, sticky, feces. Fluids constituted 86% of stool mass compared with only 42% for control rats fed standard chow. Compared with controls, diarrheic rats produced more urine, lost weight and had bloated ceca and colons. All doses of the extract, its anti-motility fractions and loperamide individually stopped diarrhea within 6-24 h of administration, whilst significantly reducing mucus and fecal fluid content, urine production and intestinal bloating. Rats treated with 0.1g extract, PTLC1 and PTLC5 gained weight, whilst PTLC5 also increased water intake.ConclusionsGarcinia buchananii extract and its anti-motility fractions are effective remedies against lactose-induced diarrhea. The extract contains compounds that reverse weight loss, promote food and water intake, supporting the notion that characterization of the compounds could lead to new therapies against diarrheal diseases.Paul A. Boakye, Stuart M. Brierley, Sofie P. Pasilis, Onesmo B. Balemb