Ouargla Region Research Articles

Qualitative and Quantitative Evaluation of Quartz in Different Granular Types of Ouargla Region Sand Dunes – Algeria

In this paper, it is shown that Ouargla region (Algeria) sand dunes are very rich in quartz. This study aims to assess the quartz in the different granular sand types, using XRD spectroscopy. Granulometric classification and the size distribution curve were carried out. The X’Pert HighScore program based on the Rietveld refinement was used in analyzing the XRD data. Qualitative and quantitative quartz evaluations were carried out. It was deduced that the quartz was of the α phase. The concentrations of quartz have been calculated as: the very fine sand (0.063-0.100 mm) possessing the highest value of 82.05 %, followed by the coarse sand (0.500-1.000 mm) with 78 %, while in both the medium (0.250-0.500 mm) and the fine (0.100-0.250 mm) the concentration was about 67 %, whereas, the lowest one was 18.2 % in the very coarse sand (1-2 mm). These results were confirmed by FTIR spectroscopy. Crystallite sizes of quartz have been estimated, and their distribution curve versus grain sizes has been illustrated. It was found that the crystallite sizes in the fine sand are less than 100 nm, and thus may be considered as nanometric particles.

The determination of some crystallographic parameters of quartz, in the sand dunes of Ouargla, Algeria

In this work, the crystallographic phase, degree of crystallinity, crystal system, space group and unit cell parameters of quartz in the Ouargla region (Algeria) sand dunes have been determined using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The mid-infrared absorption spectrum showed the characteristic doublet for α-quartz at 796 and 779cm−1. The observed principle diffractions at the d-spacings of 3.7937, 3.3539 and 1.8204Å confirm the presence of α-quartz in Ouargla sand. The calculated absorption ratio (degree of crystallinity) of A796/A779≅1.756 indicated that our quartz exhibits a highly crystalline nature. The crystallographic parameters of quartz in Ouargla sand have been determined through analysis of X-ray diffraction data, carried out using the simulation code DICVOL06. These parameters were found as: hexagonal crystal system, space group P3221 (154), unit cell parameters: a=b=4.9294Å, c=5.4093Å and V=113.832Å3.

Modeling the effects of climate on date palm scale (Parlatoria blanchardi) population dynamics during different phenological stages of life history under hot arid conditions.

The date palm scale (DPS) Parlatoria blanchardi is a serious pest due to the damage it inflicts on its host tree (Phoenix dactylifera). To develop an effective control against DPS in arid regions, it is essential to know its bio-ecology including population dynamics and climatic factors influencing the duration and timing of life history and also the densities of different phenological stages (crawlers, first and second instars nymphs, adult males, and adult females). Monitoring of biological cycle and population dynamics of the pest were achieved through weekly counts of DPS densities on leaflets sampled at different position of date palm trees in an oasis of Ouargla region (Algerian Sahara Desert). Within this hyper-arid region, DPS established four generations per year, the most important was the spring generation. Two overlapping generations occurred in spring-early summer and two in autumn-early winter; these two pairs of generations were interspersed by two phases of high-mortality rates, the first corresponds to winter cold and the second refers to the extreme heat of summer. Statistical analysis of the effects of the studied climatic conditions (minimum, maximum and mean temperatures, precipitation, humidity, wind, rain days, and climatic indices) on the DPS densities at different phenological stages showed great variability from one stage to another. Among these, adult females were the most affected by climate factors. For the total DPS population, high values of minimum temperatures negatively affected population density, while high maximum temperatures, hygrometry, and De Martonne aridity index showed a positive influence.

Ouargla Region, Algeria, North Africa: ABSTRACT

Ouargla Region, Algeria, North Africa: ABSTRACT