Fluid Chemistry of Mid-Ocean Ridge Hydrothermal Vents: A Comparison between Numerical Modeling and Vent Geochemical Data

Seawater-basalt interaction taking place at mid-ocean ridges was studied using numerical modeling to determine the compositional evolution of hydrothermal fluids and associated alteration mineralogy forming within newly emplaced crustal material. Geochemical modeling was carried out in a closed seawater-basalt system at discrete temperature intervals between 2 and 400°C at 500 bars, varying fluid/rock ratios, and secondary mineral assemblages representative of basalt alteration in natural systems. In addition to temperature, the fluid/rock ratio has a fundamental control on the resulting system chemistry. At rock-buffered conditions (low fluid/rock ratios), the mineral-solution equilibrium was characterized by high cation to proton activity ratios foraCa2+/(aH+)2andaNa+/aH+and very low dissolved Mg concentrations due to the precipitation of smectites and chlorite. A complex secondary mineral alteration assemblage dominated by Ca- and Na-bearing minerals including zeolites, calcite, epidote, prehnite, clinozoisite, and albite was predicted to form. The resulting fluid composition was alkaline and reduced relative to ambient seawater, with Eh values ranging between −0.2 and −0.6 V. In contrast, seawater-buffered conditions (high fluid/rock ratios) resulted in lower cation to proton activity ratios foraCa2+/(aH+)2andaNa+/aH+and higher dissolved Mg concentrations comparable to the value of this element in ambient seawater. A more simple mineral assemblage was predicted to form at these conditions with the predominance of Al-Si- and Mg-bearing minerals including kaolinite, quartz, and talc in addition to large amounts of anhydrite. The resulting fluid composition was mildly acidic and oxidized relative to seawater with Eh values ranging between −0.2 and 0 V. These modeling results were compared to a compilation of submarine hydrothermal vent fluid compositions from mid-ocean ridge settings and analogous basalt-dominated environments. The agreement obtained between the simulations and the compiled fluid data indicates that mid-ocean ridge hydrothermal processes can be closely reproduced by mineral-solution equilibria for a broad range of temperatures and fluid/rock ratios.

Optimization of Penicillium Lagena Medium Cultivication on Antifungal Pathogen of Phellinus Lamaoensis Using Surface Methode

Phellinus lamaoensis (Murr.) Hein is fungal pathogen that can cause brown root rot disease in cocoa, tea, rubber, and coffee plants. Endophytic fungi, Penicillium lagena, isolated from bandotan (Ageratum conyzoides Linn.), medicinal plant, is able to inhibit the growth of pathogenic, P. lamaoensis. The effect of carbon source, nitrogen source, and mineral solution was studied. Lactose, yeast extract, and mineral solution were media components which showed significant effect toward production of P. lagena active compound. Composition optimization of these three medium components was done by response surface methodology (RSM). The Optimal response region of the significant factor was predicted by using a second order polynomial model with statistical design, central composite design (CCD). Higest production of P. lagena active compound by quadratic model was predicted to be 69.233% with medium composition 44.77 g L-1 lactose, 13.02 g L-1 yeast extract, and 15.95 mL L-1 mineral solution. Verification value in laboratory is 58.365%, lower 15.7% than its prediction. Optimization increase P. lagena active compound 9 fold compared to unoptimize media.

Growth of hydroponic lettuce with optimized mineral and organomineral nutrient solutions

ABSTRACT The objective of this study was to evaluate the growth of crisp lettuce in hydroponic cultivation, following the nutrient film technique (NFT), using optimized mineral and organomineral nutrient solutions. The experiment was set in 8 x 3 factorial scheme, with treatments distributed in randomized blocks and split plots, with three replicates. The plots corresponded to eight nutrient solutions, of which four were mineral solutions with chemical composition suggested by Bernardes, Furlani, Castellane & Araújo and Ueda, and four were organomineral solutions, suggested by this research with chemical composition similar to those of the previously mentioned mineral solutions. The subplots corresponded to three varieties of crisp lettuce: Thaís, Vanda and Verônica. At 25 days after transplanting, the following parameters were evaluated: stem and crown diameter, root length, leaf area and number of leaves. For stem and crown diameters and number of leaves, the mineral solutions promoted the highest means. The mineral solution of Furlani and the organomineral solutions, except the modified solution of Castellane & Araújo, promoted the greatest root lengths. The smallest leaf area was obtained in the organomineral solution of Ueda. The cultivar Verônica had the highest root length and stem diameter.

Molecular fractionation of a soil fulvic acid (FA) and competitive sorption of trace metals (Cu, Zn, Cd, Pb) in hematite–solution systems: effect of the FA-to-mineral ratio

Understanding of the interactions occurring between fulvic acids (FAs) and trace metals in mineral–solution systems is a major issue for cycles of organic matter and micro-pollutants in surface media.