Short-term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions

The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara- dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha?1 Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al con- centrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine-root bio- mass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5?4.8). The added CaCl2 did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine-root biomass had decreased significantly. Decreasing fine-root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca2+ : Al3+ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had benefi- cial effects on some plants.

In-season calcium-spray formulations improve calcium balance and fruit quality traits of peach.

Experiments to evaluate the effect of in-season calcium (Ca) sprays on late-season peach (Prunus persica L. Batsch cv. Calrico) were carried out for a 2-year period. Calcium formulations (0.5% and 1.0% in 2008 and only 0.5% tested in 2009) supplied either as CaCl2 or Ca propionate in combination with two or three adjuvants (0.05% of the nonionic surfactants Tween 20 and Break Thru, and 0.5% carboxymethylcellulose, CMC) were sprayed four to five times over the growing season. Peach mesocarp and endocarp Ca concentrations were determined on a 15-day basis from the beginning of May until the end of June. Further tissue analyses were performed at harvest. A decreasing trend in fruit Ca concentrations over the growing season was always observed regardless of the Ca treatments. Both in 2008 and 2009, significant tissue Ca increments associated with the application of Ca-containing sprays in combination with adjuvants were only observed in June, which may be coincident with the period of pit hardening. In 2008, both at harvest and after cold storage, the total soluble-solids concentration (° Brix) of fruits supplied with Ca propionate (0.5% and 1.0% Ca) was always lower as compared to the rest of treatments. The application of multiple Ca-containing sprays increased firmness at harvest and after cold storage, especially when CaCl2 was the active ingredient used. Supplying the adjuvants Tween 20 and CMC increased fruit acidity both at harvest and after cold storage. Evaluation of the development of physiological disorders after cold storage (2 weeks at 0°C) indicated a lower susceptibility of Ca-treated fruits to internal browning. Fruits treated with multiple CaCl2-, CMC-, and Break Thru®-containing sprays during the growing season were significantly less prone to the development of chilling injuries as compared to untreated peaches.

Daños mecánicos en frutos de manzanas del cv. "Golden Delicious" tratadas con calcio.

Se han realizado tres ensayos con manzanas del cv. "Golden Delicious" procedentes de Lérida que diferían en sus tratamientos de calcio, siempre manteniendo un testigo sin tratar. En un primer ensayo se comparan manzanas tratadas con no tratadas; en el segundo se comparan manzanas tratadas en pre y post cosecha y en un tercero se comparan tratamientos en precosecha con CaCl2 y quelatos. Todos los frutos han sido sometidos a ensayos de impacto, corte y penetración. Se discute la posibilidad de que estos tratamientos mejoren la resistencia a los daños y la calidad.

Corrosión inducida por contaminantes hidrosolubles en la intercara metal/pintura

El objetivo principal de este trabajo es profundizar en el conocimiento del fenómeno de la corrosión subpelicular inducida por contaminantes hidrosolubles en la intercara metal/pintura. La contaminación salina del substrato es una situación común en la práctica: la superficie metálica suele estar expuesta a atmósferas contaminadas antes de ser recubierta, limpieza previa del metal con abrasivos contaminados, etc. La eliminación total de estos contaminantes resulta muy difícil de conseguir incluso con las técnicas más sofisticadas de limpieza. Esta investigación se centra en la determinación del efecto de la naturaleza del contaminante y la naturaleza y espesor del recubrimiento en el proceso de corrosión subpelicular del acero. En la investigación se utilizaron dos barnices de naturaleza diferente: poliuretano y vinílico; y se aplicaron a tres espesores diferentes. Los contaminantes empleados en este trabajo fueron: NaCl, NH4C1, CaCl2, Na2S04, (NH4)2S04, NaN03, NH4N03, Ca(N03)2. Los ensayos se realizaron en una cámara de condensación de humedad permanente. Los tiempos de exposición fueron 100, 300 y 600 horas. La velocidad de corrosión se evaluó gravimétricamente, mediante la técnica de pérdida de peso. Se realizaron estudios de permeabilidad al oxígeno y al agua de películas libres de substrato, evaluación de la velocidad de corrosión de probetas sin pintar inmersas en soluciones salinas de los contaminantes seleccionados, conductividad de dichas soluciones salinas, solubilidad del oxígeno en las soluciones salinas, adherencia en seco y en húmedo a diferentes tiempos de exposición. Se aporta evidencia respecto al control ejercido en el proceso corrosivo por el oxígeno que permea a través de la película, mientras que la permeación de agua controla la pérdida de adherencia del recubrimiento. Ambas permeabilidades dependen de la naturaleza del recubrimiento y de su espesor. Se ha investigado la influencia de la naturaleza del contaminante en la intercara metal/pintura. La naturaleza del catión parece quedar enmascarada por el efecto definitivo del anión. La concentración salina ejerce asimismo un efecto importante en la corrosión subpelicular. ABSTRACT The main aim of this work is to study in depth the knowledge of underfilm corrosión induced by hydrosoluble contaminants at the metal/paint Ínterface. The saline contamination of the substrate is a common situation in practice: metallic surfaces use to be exposed to polluted atmospheres, previous cleaning of the metal with contaminated abrasives, etc. Total elimination of these contaminants is hard to obtain even with modern cleaning techniques. This research is focused in determining the effect of contaminant nature, coating nature and its thickness on the steel underfilm corrosión process. In this work we used two varnishes with different nature: polyurethane and vinyl; they were applied in three different thicknesses. The saline contaminants employed were: NaCl, NH4C1, CaCl2, Na2S04, (NH4)2S04, NaN03, NH4N03/ Ca(N03)2. The tests were carried out in a condensation humidity chamber. The period of exposure were 100, 300 and 600 hours. Corrosión rate was assessed by weight loss. Simultaneously, studies on oxygen and water permeability of free films, assessing on corrosión rate of uncoated samples immersed in saline solutions of the selected contaminants, conductivity of these solutions, oxygen solubility in saline solutions, wet and dry adhesión of the polyurethane varnish at different periods of exposure, were carried out. There is clear evidence about control on corrosión process of oxygen that passes through the coating, while the passing of water controls the loss of adhesión of the coating. Both, water and oxygen permeation, depend on the nature and thickness of the coating. It has been researched the inf luence of the nature of contaminant at the metal/paint interface. The nature of the catión seems to be "masked" by the definitive effect of the nature of anión. The saline concentration also exerts an important effect on underfilm corrosión.