| چکیده انگلیسی مقاله |
The dust and the environmental pollutions caused by dust storms are a serious environmental hazard, particularly in arid and semi-arid civilian regions in the world. Controlling and decreasing the harmful or undesirable effects of dust can be achieved by accurately identifying and analyzing dust samples. For this goal, various elemental analysis methods are commonly used for identifying and characterizing dust materials. The City of Yazd (UNESCO Heritage Center) is located in Iran's central region. It is surrounded by many industrial, mineral sites, and deserts. The city's urban areas suffer air pollution due to seasonal wind, the lack of annual rainfall, and dust storms. Hence, the dust concentration reaches higher than of standard limits occasionally in this city. In this paper, a study to characterize and analyze the falling-dust in Yazd city is reported. Initially, the sampling procedure was conducted at five different locations for two months using marble dust collectors. The size distributions and morphology of dust samples were studied by Scanning Electron Microscopy (SEM), X-Ray Diffraction technique (XRD). Moreover, samples' elemental composition was analyzed using Energy Dispersive X-Ray Spectroscopy (EDX) and distinctly, Laser-Induced Breakdown Spectroscopy (LIB). The analysis of SEM images and XRD patterns of dust particles allows studying the dust's size and morphology of samples. The size of 1 to 30 microns was estimated for the dust particles with the maximum size distributions between 2 to 7 microns. Also, capsular, triangular, spherical, irregular, and polyhedral shapes are revealed by recorded particles' images. The XRD analyses show the existence of silicates, carbonates, phosphates mineral groups, calcites, quartz, gypsum, magnesium carbonate, and aluminum phosphates components in samples. Laser-induced breakdown spectroscopy (LIBS) is a non-contact, fast response, high sensitivity, real-time, and multi-elemental analytical detection technique based on emission spectroscopy to measure the elemental composition. The elemental characterization of powder samples was carried out by investigating the emission spectra of breakdown plasma in the sample region. A 1064-nm Nd:YAG laser operating at high energy (100 mJ, 1 to 20 Hz), was focused on the surface of the tiny amount of powder sample to form an emitting plasma. The emission of produced plasma from the sample was collected by eight optical fibers and was detected by the spectrometer. The applied experimental setup allowed to record spectra in the range of 200 to 1200 nm with a spectral resolution of 0.4 nm. In total, 74 atomic emission lines of generated plasma were analyzed. Spectral analysis of obtained spectra enables to identify several elements such as calcium, silicon, iron, magnesium, aluminum, carbon, and other elements with less abundance such as potassium, sodium, strontium, manganese, titanium, cobalt, vanadium, barium and lead in the elemental composition of dust samples. The results deduced using the LIBS technique agree unambiguously with results obtained by EDX analysis of dust samples in this work. It is found that Laser-Induced Breakdown spectroscopy is a rapid, reliable, and powerful analytical tool for the diagnostic and detection of multiple elements for solid dust samples. Also, this technique is comparable with standard methods such as atomic absorption spectroscopy (AAS) and X-Ray Fluorescence (XRF) for chemical and elemental analysis of urban, mineral, and industrial dust. |