Experimental study of phase equilibria in the systems Fe-Zn-O and Fe-Zn-Si-O at metallic iron saturation

The reported experimental work on the systems Fe-Zn-O and Fe-Zn-Si-O in equilibrium with metallic iron is part of a wider research program that combines experimental and thermodynamic computer modeling techniques to characterize zinc/lead industrial slags and sinters in the system PbO-ZnO-SiO2-CaO-FeO-Fe2O3. Extensive experimental,investigations using high-temperature equilibration and quenching techniques followed by electron probe X-ray microanalysis (EPMA) were carried out. Special experimental; procedures were developed to enable accurate measurements in these ZnO-containing systems to be performed in equilibrium with metallic iron; The systems Fe-Zn-O and FeZn-Si-O were experimentally investigated in equilibrium with metallic iron in the temperature ranges 900 degreesC to 1200 degreesC (1173 to 1473 K) and from 1000 degreesC to 1350 degreesC (1273 to 1623 K), respectively. The liquidus surface in the system Fe-Zn-Si-O in equilibrium with metallic iron was characterized in the composition ranges 0 to 33 wt pet ZnO and 0 to 40 wt pet SiO2. The wustite (Fe,Zn)O, zincite (Zn,Fe)O, willemite (Zn,Fe)(2)SiO4, arid fayalite: (Fe,Zn)(2)SiO4 solid solutions in equilibrium with metallic iron were measured.

Predicting sheetwash and rill erosion over the Australian continent

Soil erosion is a major environmental issue in Australia. It reduces land productivity and has off-site effects of decreased water quality. Broad-scale spatially distributed soil erosion estimation is essential for prioritising erosion control programs and as a component of broader assessments of natural resource condition. This paper describes spatial modelling methods and results that predict sheetwash and rill erosion over the Australian continent using the revised universal soil loss equation (RUSLE) and spatial data layers for each of the contributing environmental factors. The RUSLE has been used before in this way but here we advance the quality of estimation. We use time series of remote sensing imagery and daily rainfall to incorporate the effects of seasonally varying cover and rainfall intensity, and use new digital maps of soil and terrain properties. The results are compared with a compilation of Australian erosion plot data, revealing an acceptable consistency between predictions and observations. The modelling results show that: (1) the northern part of Australia has greater erosion potential than the south; (2) erosion potential differs significantly between summer and winter; (3) the average erosion rate is 4.1 t/ha. year over the continent and about 2.9 x 10(9) tonnes of soil is moved annually which represents 3.9% of global soil erosion from 5% of world land area; and (4) the erosion rate has increased from 4 to 33 times on average for agricultural lands compared with most natural vegetated lands.

Salinity tolerance in Schinopsis quebracho colorado: Seed germination, growth, ion relations and metabolic responses

Soil salinity is a major abiotic stress influencing plant productivity worldwide. Schinopsis quebracho colorado is one of the most important woody species in the Gran Chaco, an and and salt-prone subtropical biome of South America. To gain a better understanding of the physiological mechanisms that allow plant establishment under salt conditions, germination and seedling growth of S. quebracho colorado were examined under treatment with a range of NaCl solutions (germination: 0-300 mmol l(-1) NaCl; seedling growth: 0-200 mmol l(-1) NaCl). The aim was to test the hypothesis that S. quebracho colorado is a glycophite that shows different salt tolerance responses with development stage. Proline content, total soluble carbohydrates and Na+, K+ and Cl- concentrations in leaves and roots of seedlings, and the chlorophyll concentration and relative water content of leaves were measured. Germination was not affected by 100 mmol l(-1) NaCl, but decreased at a concentration of 200 mmol l(-1). At 300 mmol l(-1) NaCl, germination did not occur. Seedling growth decreased drastically with increasing salinity. An increase in NaCl from 0 to 100 mmol l(-1) also significantly reduced the leaf relative water content by 22% and increased the proline concentration by 60% in roots. In contrast, total soluble carbohydrates were not significantly affected by salinity. Seedlings showed a sodium exclusion capacity, and there was an inverse correlation between Cl- concentration and the total chlorophyll concentration. S. quebracho colorado was more tolerant to salinity during germination than in the seedling phase. The results suggest that this increased tolerance during germination might, in part, be the result of lower sensitivity to high tissue Na+ concentrations. The significant increment of proline in the roots suggests the positive role of this amino acid as a compatible solute in balancing the accumulation of Na+ and Cl- as a result of salinity. These results help clarify the physiological mechanisms that allow establishment of S. quebracho colorado on salt-affected soils in arid and semi-arid Gran Chaco. (c) 2008 Elsevier Ltd. All rights reserved.

Effect of specific leaf nitrogen on radiation use efficiency and growth of sunflower

Specific leaf nitrogen (SLN, g/m(2)) is known to affect radiation use efficiency (RUE, g/MJ) in different crops, However, this association and importance have not been well established over a range of different nitrogen regimes for held-grown sunflower (Helianthus annuus L.). An experiment was conducted to investigate different combinations and rates of applied nitrogen on SLN, RUE, and growth of sunflower, A fully irrigated crop was sown on an alluvial-prairie soil (Fluventic Haplustoll) and treated with five combinations of applied nitrogen, Greater nitrogen increased biomass, grain number, and yield, but did not affect harvest index energy-corrected for oil (0.4) or canopy extinction coefficient (0.88), Decreases in biomass accumulation under low nitrogen treatments were associated,vith reductions in leaf area index (LAI) and light interception, When SLN and RUE were examined together, both were less in the anthesis to physiological maturity period, but relatively stable between bud visible and anthesis, However, the effects of canopy SLN on RUE were confounded by high SLN in the top of the canopy and the crop maintaining SLN by reducing LAI, Measurements of leaf CO2 assimilation and theoretical analyses of RUE supported that RUE was related to SLN, The major effect of nitrogen on early growth of sunflower was mediated by leaf area and the distribution of SLN in the canopy rather than direct effects of canopy SLN on RUE alone. Greater responses of RUE to SLN are more evident later in growth, and may be related to the demand of nitrogen by the grain.