Nutrients adsorption from seawater by new porous carrier made from zeolitized fly ash and slag

This study investigated the adsorption and precipitation of phosphate by blast furnace slag (BFS) separately.

In order to evaluate the adsorption capacity of BFS, BFS was treated before its use by acid. The authors aim to develop a new porous carrier to adsorb simultaneously ammonium and phosphate from seawater under eutrophic conditions. The current paper deals with a promising new approach to improve the utilization of some industrial solid wastes such as BFS and zeolite synthesized from fly ash [ZFA(Fe)] by their solidification to cylindrical porous carriers using a hydrothermal hot-pressing (HHP) method.

Attempts to produce porous carriers using an arranged HHP method with different porosities (24%, 40% and 52% (v/v)) were carried out. Physical properties of carriers such as porosity, compressive strength and height have been investigated. Laboratory studies showed strong evidence that the porous carrier was very selective towards phosphate and ammonium. The results demonstrated the role of porosity in enhancing phosphate and ammonium adsorption by the increase of the surface area per weight. The estimates of the parameters and the correlation coefficients according to the Freundlich equations revealed that adsorption was related to the porosity of carriers and phosphate and ammonium were adsorbed well on the carriers having large porosity.

The results suggested that developing carrier with high porosity was a promising way to enhance nutrients adsorption.     

Spectroscopic analysis (FTIR, Raman) of water in mafic and intermediate glasses and glass inclusions

Micro-Raman spectroscopy, even though a very promising technique, is not still routinely applied to analyse H₂O in silicate glasses. The accuracy of Raman water determinations critically depends on the capability to predict and take into account both the matrix effects (bulk glass composition) and the analytical conditions on band intensities. On the other hand, micro-Fourier transform infrared spectroscopy is commonly used to measure the hydrous absorbing species (e.g., hydroxyl OH⁻ and molecular H₂O) in natural glasses, but requires critical assumptions for the study of crystal-hosted glasses. Here, we quantify for the first time the matrix effect of Raman external calibration procedures for the quantification of the total H₂O content (H₂O_T = OH⁻ + H₂O_m) in natural silicate glasses. The procedures are based on the calibration of either the absolute (external calibration) or scaled (parameterisation) intensity of the 3550 cm⁻¹ band. A total of 67 mafic (basanite, basalt) and intermediate (andesite) glasses hosted in olivines, having between 0.2 and 4.8 wt% of H₂O, was analysed. Our new dataset demonstrates, for given water content, the height (intensity) of Raman H₂O_T band depends on glass density, reflectance and water environment. Hence this matrix effect must be considered in the quantification of H₂O by Raman spectroscopy irrespective of the procedure, whereas the parameterisation mainly helps to predict and verify the self-consistency of the Raman results. In addition, to validate the capability of the micro-Raman to accurately determine the H₂O content of multicomponent aluminosilicate glasses, a subset of 23 glasses was analysed by both micro-Raman and micro-FTIR spectroscopy using the band at 3550 cm⁻¹. We provide new FTIR absorptivity coefficients (ε₃₅₅₀) for basalt (62.80 ± 0.8 L mol⁻¹ cm⁻¹) and basanite (43.96 ± 0.6 L mol⁻¹ cm⁻¹). These values, together with an exhaustive review of literature data, confirm the non-linear decline of the FTIR absorptivity coefficient (ε₃₅₅₀) as the glass depolymerisation increases. We demonstrate the good agreement between micro-FTIR and micro-Raman determination of H₂O in silicate glasses when the matrix effects are properly considered.     

Biochemical adaptation of phytoplankton to salinity and nutrient gradients in a coastal solar saltern,Tunisia

The distribution of protein and carbohydrate concentrations of the particulate matter (size fraction: 0.45–160 μm) was studied, from 22 January 2003 to 02 December 2003, in three ponds of increasing salinity in the Sfax solar saltern (Tunisia). The coupling of N/P: DIN (DIN = NO₂⁻ + NO₃⁻ + NH₄⁺) to DIP (DIP = PO₄³⁻) with P/C: protein/carbohydrates ratios along salinity gradient allowed the discrimination of three types of ecosystems. Pond A1 (mean salinity: 45.0 ± 5.4) having marine characteristics showed enhanced P/C ratios during a diatom bloom. N/P and P/C ratios were closely coupled throughout the sampling period, suggesting that the nutritional status is important in determining the seasonal change in the phytoplankton community in pond A1. In pond A16 (mean salinity: 78.7 ± 8.8), despite the high nitrate load, P/C ratios were overall lower than in pond A1. This may be explained by the fact that dinoflagellates, which were the most abundant phytoplankton in pond A16 might be strict heterotrophs and/or mixotrophs, and so they may have not contributed strongly to anabolic processes. Also, N/P and P/C ratios were uncoupled, suggesting that cells in pond A16 were stressed due to the increased salinity caused by water evaporation, and so cells synthesized reserve products such as carbohydrates. In pond M2 (mean salinity: 189.0 ± 13.8), P/C levels were higher than those recorded in either pond A1 or A16. N/P and P/C were more coupled than in pond A16. Species in the hypersaline pond seemed paradoxally less stressed than in pond A16, suggesting that salt-tolerant extremophile species overcome hypersaline constraints and react metabolically by synthesizing carbohydrates and proteins.     

Automated Coronal-Loop Detection based on Contour Extraction and Contour Classification from the SOHO/EIT Images

Arch-shaped coronal loops that are isolated from the background are typically acquired manually from massive online image databases to be used in solar coronal research. The manual search for special coronal loops is not only subject to human mistakes but is also time consuming and tedious. In this study, we propose a completely automated image-retrieval system that identifies coronal-loop regions located outside of the solar disk from 17.1 nm EIT images. To achieve this aim, we first apply image-preprocessing techniques to bring out loop structures from their background and to reduce the effect of undesired patterns. Then we extract principal contours from the solar image regions. The geometrical attributes of the extracted principal contours reveal the existence of loops in a given region. Our completely automated decision-making procedure gives promising results in separating the regions with loops from the regions without loops. Based on our loop-detection procedure, we have developed an automated image-retrieval tool that is capable of retrieving images containing loops from a collection of solar images.     

Water use efficiency of olive tree under two water treatments in Tunisian semi-arid conditions

Olive trees are grown under high evaporative demand and less precipitations that are variable in time and space especially in semi-arid conditions. The objective of this work is to determine the most efficient water treatment applied in an olive field (Olea europaea L. cv Chemlali) from the 98th to the 294th Julian day, in Tunisian semi-arid conditions. The choice of this time frame was done to control the effect of irrigation on the trees behavior in the irrigation period of the year (from April to October) and determine the most sensitive phenological stages to irrigation. For this reasons, two water treatments were applied: T100% (irrigation at 100% of Available Water Content (AWC)) and T50% (irrigation at 50% AWC). The results show that, according to leaf water potential, carbon isotope discrimination, and olive production parameters, the T50% AWC water treatment is the most efficient. The leaf water potential of the two water treatments applied has not exceeded ?2.5 MPa during the whole experiment which indicates that the trees of the two water treatments were not stressed. The T50% AWC shows a water use efficiency of 5.18 g/l compared to 2.93 g/l for T100% water treatment. This result demonstrate that Chemlali cultivar valorizes better low quantities of water rather than high quantities, so saving 50% of water resources applied will ensure the sustainability of water resources and stability of olive production.     

Determination of the aquifers geometry in arid zones by using geoelectrical method

Water resources in the Algerian South are rare and difficult to reach because they are often too deep. This is the case of Guerrara which is characterized by an annual precipitation average of less than 60 mm. The water supply is warranted from groundwater, frequently too deep and badly known. The main purpose of the present study is to determine the geometry of aquifer from geophysical data. Fourteen vertical electrical soundings covering the total surface area were carried out by using an arrangement of electrodes called “Schlumberger array.” The length of the selected transmission line (AB) was 1,000 m, which allowed a vertical investigation reaching up to 160 m of depth. The analysis of the results shows that the prospected zone is characterized by the succession of layers with different electrical resistivities. A sandstone aquifer characterized by resistivities near 100 Ω m overcoming a limestone aquifer stronger with values that exceed 1,000 Ω m, separated by a conductive layer of clay with average resistivity of 15 Ω m. Distribution map of sandstones thickness shows the structural variations of this horizon allowing an estimation of its hydraulic potential.