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Cation Concentration (cation + concentration)
Selected AbstractsThe solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site, southern ChileHYDROLOGICAL PROCESSES, Issue 13 2002Geertrui Y. P. Uyttendaele Abstract Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44,S, 73°10,W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca2+ l,1, 0·13 mg K+ l,1, 0·11 mg Mg2+ l,1 and <0·08 mg NH4,N l,1), except for sodium (1·10 mg l,1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO3,N l,1, total flux 6·3 kg NO3,N ha,1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l,1) for all events. Stream-flow pH was 6·3 and conductivity was 28·3 ,s. Stream-water chemistry was also dominated by sodium (2·70 mg l,1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l,1). The solute budget indicated a net loss of 3·8 kg Na+ ha,1 year,1, 5·4 kg Mg2+ ha,1 year,1, 1·5 kg Ca2+ ha,1 year,1 and 0·9 kg K+ ha,1 year,1, while 4·9 kg NO3,N ha,1 year,1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO3,N ha,1 year,1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na+ ha,1 year,1, 21·5 kg K+ ha,1 year,1, 5·1 kg Mg2+ ha,1 year,1) compared with the secondary native forest site (24·7 kg Na+ ha,1 year,1, 18·9 kg K+ ha,1 year,1 and 4·4 kg Mg2+ ha,1 year,1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca2+ ha,1 year,1) compared with the pine stand (12·6 kg Ca2+ ha,1 year,1). Copyright © 2002 John Wiley & Sons, Ltd. [source] Elementary processes of soil,water interaction and thresholds in soil surface dynamics: a reviewEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2004Richard S. B. Greene Abstract Elementary processes of soil,water interaction and the thresholds to these processes are important to understand as they control a range of phenomena that occur at the soil surface. In particular processes involved with wetting by rainfall that lead to particle breakdown are critical. This breakdown causes soil detachment and crust formation, which are both key elements in erosion. This paper reviews the range of approaches that have been taken in describing the processes associated with the wetting of a soil surface by rainfall. It assembles the studies that emphasize soil physics, soil chemistry, and erosion mechanics in a framework to enable a balanced consideration of important processes and management strategies to control erosion for a particular situation. In particular it discusses the factors associated with the two basic processes of soil structural breakdown, i.e. slaking and dispersion, and how these processes are critical in particle detachment, transport and surface crust formation. Besides the balance between the exchangeable cation composition and electrolyte concentration (measured as the sodium adsorption ratio (SAR) and total cation concentration (TCC) respectively) of the soil, the importance of energy input and soil organic matter content in controlling clay dispersion is emphasized. Based on the balance between these factors, the soil can be in one of three different regions, i.e. a dispersed region, a ,occulated region and one where the resilience of the soil is variable. The implications of each of these regions to soil erosion management are brie,y outlined, as are the critical roles that soil cover levels and organic matter have in controlling erosion. Finally, the relationship between various laboratory measures of aggregate stability, and corresponding ,eld erosion characteristics, is discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cationELECTROPHORESIS, Issue 5 2009Sille Ehala Abstract This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb+. Capillary affinity electrophoresis was employed for the experimental evaluation of the strength of the Val,Rb+ complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb+ cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb+ cation concentration in the BGE (methanolic solution of 100,mM Tris, 50,mM acetic acid, 0,1,mM RbCl), the apparent binding (stability) constant (Kb) of the Val,Rb+ complex in methanol was evaluated as log,Kb=4.63±0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of Val,Rb+ complex, Val is stabilized by strong non-covalent bond interactions of Rb+ with six ester carbonyl oxygen atoms so that the position of the "central" Rb+ cation in the Val cage is symmetric. [source] Lead and cadmium uptake in the marine fungi Corollospora lacera and Monodictys pelagicaFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Michael A.S. Taboski Abstract This study provides observations on the effects of lead and cadmium ions on the growth of two species of marine fungi, Corollospora lacera and Monodictys pelagica. On solid media lead appeared to have no effect on the radial rate of growth of fungi. Exposure to increasing cadmium concentrations on solid media resulted in significant reduction (P < 0.05) in the radial mycelial growth rates of both fungi, especially in M. pelagica. These results reveal significant difference in species sensitivity toward cadmium and, essentially, insensitivity toward lead exposure. In liquid cultures, the metal content of mycelia (metal mass found in mycelium, in mg), and the concentration of metal in dry mycelium (metal mass in 1 g of mycelium, in mg g,1) were both found to increase (P < 0.05) with the increase in the metal cation concentration, while mycelium dry mass decreased. As it was observed on solid media, cadmium cation affected more severely (P < 0.05) the growth of M. pelagica in liquid cultures. Ergosterol content of mycelia of C. lacera exposed to increasing cadmium cation concentration decreased, similarly to the trend observed for dry mycelial mass. It was found that ca. 93% of all lead sequestered by C. lacera is located extracellularly. M. pelagica was found to bioaccumulate over 60 mg of cadmium and over 6 mg of lead per 1 g of mycelium, while C. lacera bioaccumulated over 7 mg of cadmium and up to 250 mg of lead per 1 g of mycelium. Overall, the results indicate that both metal ions affect the growth of marine fungi with lead being accumulated extracellularly in the mycelia. Both metals accumulated by fungi may then enter the marine ecosystem food web, of which marine fungi are integral members. [source] Preparation of Ba6,3xNd8+2xTi18O54 via Ethylenediaminetetraacetic Acid PrecursorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Yebin Xu Ba6,3xNd8+2xTi18O54 ceramic powders were synthesized by the modified Pechini method using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. A purplish red, molecular-level, homogeneously mixed gel was prepared, and transferred into a porous resin intermediate through charring. Single-phase and well-crystallized Ba6,3xNd8+2xTi18O54 powders were obtained from pulverized resin at a temperature of 900°C for 3 h, without formation of any intermediate phases. Meanwhile, the molar ratio of EDTA to total metal cation concentration had a significant influence on the crystallization behavior of Ba6,3xNd8+2xTi18O54. The Ba6,3xNd8+2xTi18O54 (x= 2/3) ceramics prepared via EDTA precursor have excellent microwave dielectric characteristics: ,= 87, Qf= 8710 GHz. [source] Mineralogical Characteristics and Cationic Exchange Properties of a Zeolite Mineral from Romana, NW Sardinia, ItalyRESOURCE GEOLOGY, Issue 1 2009Maria L. Fercia Abstract An investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy,energy-dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1-N NaCl solution yielded a 1.3,5-fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non-European countries. [source] The cation and silica chemistry of a Subandean river basin in western AmazoniaHYDROLOGICAL PROCESSES, Issue 7 2002J. A. Sobieraj Abstract We sampled river water at 13 locations in the Pichis basin, a 10 500 km2 large rainforest-covered drainage basin in Peru, to assess the influence of lithological variability and seasonality on water chemistry. The concentrations of major cations and silica show a strong seasonal dependence and a remarkable variability over short distances that is only weakly reduced in the wet season; cation concentrations in streams differ by up to 100% within a few kilometres. The lowest cation concentrations were associated with relatively cation-depleted upper Tertiary and lower Quaternary formations, whereas relatively cation-rich lower Tertiary and Jurassic formations left a clear calcium and sodium signal in the respective rivers. Cluster analysis, in conjunction with boxplots, suggests that the sampling locations can be segregated into three groups based on similarities of their geochemical signals. According to the previously defined criteria, one river is classified as a Group 2 river with 200 < TZ+ < 450 µeq/L, whereas all other rivers fall into Group 3 with 450 < TZ+ < 3000 µeq/L (where TZ+ refers to the total cation charge). Based on a comparison with other studies at different sections of the Amazon mainstem, the river chemistry of our study area is relatively enriched in K+, Mg2+ and Ca2+, and, consequently, has a higher TZ+ value, while being relatively depleted in silica. The influence of lithological variability on water chemistry must be considered in land-use change studies even at watershed areas of 26,3382 km2. Copyright © 2002 John Wiley & Sons, Ltd. [source] Mineralogical Characteristics and Cationic Exchange Properties of a Zeolite Mineral from Romana, NW Sardinia, ItalyRESOURCE GEOLOGY, Issue 1 2009Maria L. Fercia Abstract An investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy,energy-dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1-N NaCl solution yielded a 1.3,5-fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non-European countries. [source] P2X7 receptors in rat parotid acinar cells: formation of large poresAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2001Simon J. Gibbons 1 Permeabilization of cells mediated by P2X7 receptors occurs to varied degrees in native and heterologous expression systems. Previous studies on P2X7 receptors in parotid acinar cells suggested that ATP does not permeabilize these cells. 2 Modification of the assay conditions showed that ATP permeabilizes freshly dissociated rat parotid acinar cells to the fluorescent dye YOPRO-1. 3 The pharmacological and physiological properties of this effect indicate that permeabilization is mediated by the P2X7 receptor. Adenosine 5,-triphosphate (ATP) and 3,- O -(4-benzoyl)benzoyl adenosine 5,-triphosphate (BzBzATP) were effective agonists with EC50 values of 49.3 and 0.6 ,M, respectively. 4 Permeabilization was best observed in low divalent cation concentrations and at physiological temperatures. Previous studies failed to detect permeabilization because of the sensitivity of this effect to temperature and divalent cations. 5 An important consideration in understanding the effect of divalent cations is that the fluorescence of YOPRO-1/nucleic acid complexes is directly quenched by addition of divalent cations. This must be considered if quantitative study of the interaction of divalent cations with P2X7 receptors is carried out using fluorescent DNA-binding dyes. 6 In summary, our data show that P2X7 receptors in parotid acinar cells can form large pores in the plasma membrane. This property likely contributes to signalling and may be cytotoxic and have particular significance in damaged or inflamed salivary glands. [source] Survival, Growth, and Ecosystem Dynamics of Displaced Bromeliads in a Montane Tropical Forest1BIOTROPICA, Issue 2 2002Jennifer Pett-Ridge ABSTRACT Epiphytes generally occupy arboreal perches, which are inherently unstable environments due to periodic windstorms, branch falls, and treefalls. During high wind events, arboreal bromeliads are often knocked from the canopy and deposited on the forest floor. In this study, we used a common epiphytic tank bromeliad, Guzmania berteroniana (R. & S.) Mez, to determine if fallen bromeliads can survive, grow, and reproduce on the forest floor and evaluate the potential impact of adult dispersal on plant and soil nutrient pools. Bromeliads were transplanted to and from tree stems and the forest floor and monitored intensively for six months; survival, growth, and impacts on ecosystem nutrient pools were followed on a subset of plants for 16 months. Six months after transplanting, bromeliad mortality was low (3%), and 19 percent of study individuals had flowered and produced new juvenile shoots. Mortality on the subset of plants followed for 16 months was 14,30 percent. Although survival rates were relatively high in all habitats, bromeliads transplanted to trees grew significantly more root length (x,± SE: 189 ± 43 cm) than those moved to the forest floor (53 ±15 cm) and experienced lower rates of leaf area loss. All transplanted bromeliads rapidly altered the substrate they occupied. Individuals transplanted to and among trees rapidly decreased base cation concentrations but significantly increased P concentrations of their underlying substrate. On the ground, bromeliads increased C, N, and P concentrations within nine months of placement. Our results suggest that in this montane tropical forest, bromeliads respond rapidly to displacement, locally modify their substrates, and can access the resources needed for survival regardless of habitat. [source] | |||||||||||||