The sustainability of high-level radioactive waste repositories situated in fractured crystalline rocks depends on the stability of bentonite liners, and this can pose a problem in certain groundwater conditions that favor the formation of colloids from backfill materials that are prone to erosion. The influence of different environments on the structure of Gaomiaozi bentonite (GMZ) and GMZ colloids (GMZC) is presented here. Different hydrated interlayer structures of bulk and colloidal forms of this bentonite from small-angle X-ray scattering (SAXS) data are demonstrated. Analysis of the scattering data showed that GMZ had three interlayer water structures: dehydrated (0W), monohydrated (1W), and bi-hydrated (2W). The colloids readily agglomerated at acidic pH (pH <5) but showed resistance to agglomeration in an alkaline condition (pH >7). The effect of Na+, K+, Mg2+, and Ca2+ on the lamellar structure and agglomerate morphology of GMZC particles was investigated. In general, the tendency of colloids to agglomerate was greater in the presence of divalent metal cations compared with monovalent metal cations. High concentrations (10–5 to 10–3 mol L–1) of divalent ions imparted order into the stacked lamellar structure after the saturation of the interlayer. In contrast, monovalent ions reduced the tendency of the particles to aggregate, leading to an abundance of colloidal nanoparticles prone to erosion. This work helps to better understand the structural characteristics of GMZC in the groundwater environment, and provides a valuable reference for the evaluation of nuclide migration in the deep geological disposal of high-level radioactive wastes.

A sample of ferripyrophyllite, a mineral with ideal composition Fe2SiO10(OH)2, was analyzed by Mössbauer spectroscopy, magnetization and magnetic susceptibility measurements. The iron is entirely ferric, and the main feature of the Mössbauer spectrum at room temperature is a single absorption line with isomer shift δ = 0.36(1) mm/sec due to iron in M2 sites. The line is broadened by a slight quadrupole splitting Δ = 0.18(1) mm/sec, the smallest yet reported for a sheet silicate. Weaker features corresponding to quadrupole doublets with relative intensities of 7% and 8% having δ = 0.43(1) mm/sec; Δ = 1.22(2) mm/sec and δ = 0.14(1) mm/sec; Δ = 0.59(2) mm/sec are assigned to ferric iron in nonequivalent octahedral and tetrahedral sites, respectively, giving the following formula, based on published chemical analysis: Ca0.05(Fe3+1.87Mg0.11Al0.09)VI(Si3.80Fe3+0.16Al0.04)IVO10(OH)2, where Ca is in interlayer sites. Ferripyrophyllite orders antiferromagnetically at 18(2)°K. The Mössbauer spectrum at 4.2°K consists of a single, resolved magnetic pattern with hyperfine field Bhf = 51.8 T. The relatively high Néel temperature compared with other dioctahedral ferric phyllosilicates provides further evidence that Fe3+ cations tend to be ordered on M2 sites within the octahedral sheet.

Schäferite, NaCa2Mg2(V5+O4)3; palenzonaite, NaCa2Mn22+(V5+O4)3; berzeliite, NaCa2Mg2(As5+O4)3; and manganberzeliite, NaCa2Mn2+2(As5+O4)3, are cubic minerals with garnet structures (space group Iad) in which tetrahedrally coordinated V5+ and/or As5+ at the Z site are charge balanced by disordered Na+ and Ca2+ at the X site, and divalent Mg2+ and Mn2+ cations at the octahedrally coordinated Y site. The crystal chemistry of palenzonaite (from the Molinello and Gambatesa mines, Italy, and the Fianel mine, Switzerland), berzeliite (from Långban, Sweden, and Montaldo, Italy), and manganberzeliite (from Varenche, Italy, and the Gozaisho mine, Japan) were studied by electron microprobe analysis and single-crystal X-ray diffraction methods. Structure refinements converged to R1 values of 1.36–2.42%. The tetrahedral site in these garnet structures is mainly occupied by pentavalent As5+ or V5+ (only up to about 20% randomly distributed Si4+ is present). Charge balance is maintained by variations in the Ca/Na ratio at the X site. Heterovalent substitution (Na+ ↔ Ca2+) at the distorted square antiprism X site in vanadate- and arsenate-bearing garnets allows full occupancy of the octahedral Y site by divalent cations (primarily Mg2+ and Mn2+). There is a positive correlation between the <Z–O> and <Y–O> bond lengths and the mean ionic radii of the substituent elements, but there is no correlation between the <X–O> bond length and the variable Na/Ca site occupancy. The ionic radii of octahedrally coordinated Mg2+ and Mn2+ are such that the shared octahedral–dodecahedral edges are similar in length to the unshared octahedral edges, which is a measure of lattice distortion in garnet structures.

Effects of several inorganic ions on short-term glyphosate absorption by cultured plant cells were determined by measuring the glyphosate content of cells exposed to inorganic salts in a 0.01-mM glyphosate solution buffered at pH 5.7. Within 10 min, glyphosate absorption by potato and velvetleaf cells was stimulated about equally by 1.5 mM CaCl2 or 1.5 mM MgCl2 but was not affected by 1.5 mM KCl. Glyphosate absorption by both species increased linearly with log10 CaCl2 concentration; for velvetleaf cells, the response was greatest for CaCl2 concentrations greater than 0.2 mM. Over time of absorption, glyphosate concentration within velvetleaf cells approached an asymptote. Addition of 0.1 mM KH2PO4 inhibited glyphosate absorption by potato cells in the presence or absence of Ca2+ and Mg2+ salts; all other K+ salts tested had no effect. Glyphosate absorption by potato, velvetleaf, soybean, corn, and rice cells was stimulated by 5.0 mM CaCl2 but was inhibited by 0.1 mM KH2PO4 in the presence of 0.05 or 5.0 mM CaCl2.

Dicamba or 2,4-D will be used POST for the control of weeds in soybean when dicamba- or 2,4-D-resistant soybean are commercialized. The active ingredients of both herbicides are weak acids in solution and may bind to cations present from hard water used as herbicide carrier or from foliar fertilizers added to spray solutions. The objectives of this research were (1) to determine if the efficacy of dicamba or 2,4-D are influenced by divalent cations, namely calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn), in the spray solution, and (2) to determine if adding ammonium sulfate (AMS) to the spray solution can overcome antagonism. The factorial study included five cation solutions (deionized water [dH2O], Ca at 590 mg L−1, Mg at 630 mg L−1, Mn at 4.97 L ha−1, and Zn at 2.33 L ha−1), two herbicide treatments (dicamba or 2,4-D), and two water conditioner treatments (without or with AMS at 20.37 g L−1). Treatments were applied to common lambsquarters, horseweed, and redroot pigweed. Control of horseweed and redroot pigweed increased when AMS was added to the 2,4-D treatments, irrespective of cation solution. Control of common lambsquarters was increased when AMS was added to 2,4-D for only the Ca and Mn cation solution. In contrast to the results obtained with 2,4-D, control of horseweed with dicamba was not influenced by cation solution. Tank-mixing AMS with dicamba increased control of both redroot pigweed and common lambsquarters in the dH2O, Mg, and Mn solutions.

The role of monovalent (Na+, K+) and divalent (Ca2+, Mg2+) cations in Bufo arenarum fertilization was analysed. Our results showed that the highest fertilization percentages were obtained when strings of uterine oocytes (UO) were inseminated. Under these conditions, full jelly (FJ), which represents the jelly coats surrounding the oocytes at the time of deposition, contained 68.5 ± 7.0 mM Na+, 27.4 ± 2.4 mM K+, 6.3 ± 0.9 mM Ca2+ and 6.9 ± 0.9 mM Mg2+. When the strings of oocytes were washed in deionized water, these cations diffused into the liquid medium surrounding them. There was a marked similarity between the loss of Ca2+ in the jelly and the decrease in the fertilizability of the UO. Furthermore, the use of chelating agents of divalent cations showed the importance of the Ca2+ contained in the jelly. When Ca2+ was sequestered from the jelly coats by the addition of the chelating agents to the insemination medium as well as by pretreatment of the UO strings, a decrease in fertilization percentages occurred, this effect being dose dependent and more marked with EGTA. These results demonstrate that the Ca2+ in the jelly plays a role in fertilization. Nevertheless, taking into account that during the washing of the jelly other jelly coat components were diffused and considering that the addition of Ca2+ to the insemination medium reverted significantly, but only partially, the loss of fertilizability of jellied UO (washed), the participation of other components in the fertilization mechanism is suggested.

The elemental composition of cells of Anabaena flos-aquae was investigated by energy-dispersive electron probe X-ray microanalysis (10 kV) of mixed phytoplankton samples obtained from different depths within a stratified eutrophic freshwater lake. Preliminary studies had indicated that at 10 kV, X-ray information was derived mainly from the peripheral region (up to 1–2 μm) of cells. Routinely detectable elements (present in at least 50% of cells) included Mg (overall mean 112 mmol kg−1 dry mass), Si (1850), P(313), S (113), Cl (92), K (300) and Ca (56). Peaks of Na and Al were also frequently present. Individual elements showed a wide range of intracellular concentrations at each depth within the lake. Si had a clear bimodal distribution at depths of 1–8 m, indicating both low-Si (mean concentrations 54–290 mmol Si kg−1) and high-Si (2770–3800 mmol Si kg−1) cell subpopulations. Low-Si cells had significantly higher concentrations of other detectable elements compared with high-Si cells, but could not be distinguished from the latter in terms of morphology or stage of cell cycle (comparison of dividing and non-dividing cells). High-Si cells were intermixed with low-Si cells in individual Anabaena colonies and decreased proportionally with depth, ranging from approximately 75% in the surface sample to 10% at 8 m. With the exception of Si, mean elemental concentrations of Anabaena populations were closely similar throughout the epilimnion. These differed from the metalimnion sample, which had significantly higher concentrations of Mg, P, S and K, and a lower concentration of Si. Mean ratios of certain elements (Mg, P, S and K) and ion groups (monovalent/divalent cations) were highly constant throughout the sampled water column. At each depth, most of the cell elements were significantly and positively inter-correlated (Pearson analysis), with Mg, P, S and K typically constituting the major group (factor analysis). Correlations with Si were invariably negative, suggesting a separate (possibly cell wall) location of this element in the cell.

Following a precultivation with pedospheric nitrogen nutrition, Ricinus plants were supplied with nitrogen solely by spraying nitrate or ammonium solution onto the leaves during the experimental period. The chemical composition of tissues, xylem and phloem exudates was determined and on the basis of the previously determined nitrogen flows (Peuke et al., New Phytologist (1998), 138, 657–687) the flows of potassium, sodium, magnesium, calcium, chloride and ABA were modelled. These data, which permit quantification of net-uptake, transport in xylem and phloem, and utilization in shoot and root, were compared with results obtained in plants with pedospherically-supplied nitrate or ammonium and data in the literature. Although the overall effects on the chemical composition of supplying ammonium to the leaves were not as pronounced as in pedospherically supplied plants, there were some typical responses of plants fed with ammonium (ammonium syndrome). In particular, in ammonium-sprayed plants uptake and transport of magnesium decreased and chloride uptake was increased compared with nitrate-sprayed plants. Furthermore, acropetal ABA transport in the xylem in ammonium-sprayed Ricinus was threefold higher than in nitrate-sprayed plants. Additionally, concentrations of anions were more or less increased in tissues, particularly in the roots, and transport fluids. The overall signal from ammonium-sprayed leaves without a direct effect of ammonium ions on uptake and transport systems in the root is discussed.

We tested the hypothesis that functional attributes of living leaves provide a basis for predicting the decomposition rate of leaf litter. The data were obtained from standardized screening tests on 38 British herbaceous species. Graminoid monocots had physically tougher leaves with higher silicon contents than did herbaceous dicots, and this corresponded with the lesser decomposibility of the former. Total base content of living leaves was a good predictor of litter decomposition rate, but the evolutionary and ecological basis for this relationship appeared to differ between graminoid monocots and herbaceous dicots. In the monocots, litter decomposition rate was strongly predicted by leaf potassium content, which appeared to reflect other growth-related plant attributes such as seedling maximum relative growth rate, foliar nitrogen and phosphorus content, specific leaf area and short leaf lifespan. In the dicots the relationship between total leaf base content and litter decomposition rate was not unambiguously explained by growth-related leaf attributes, possibly because of the considerable calcium uptake by dicots, which varies according to calcium availability in the soil.