Neupane Bhanu B, Sharma Amita, Giri Basant, Joshi Mahesh K
Central Department of Chemistry, Tribhuvan University, Kirtipur, Kathmandu, Nepal.
Center for Analytical Sciences, Kathmandu Institute of Applied Sciences, Kathmandu, Nepal.
Heliyon. 2020 Apr 24;6(4):e03791. doi: 10.1016/j.heliyon.2020.e03791. eCollection 2020 Apr.
Kathmandu Valley is reported to be one of the highly polluted and populated cities in the world. Particulate matter is one of the major contributors of unhealthy air in Kathmandu. Although there are several reports on spatial and temporal variation of air quality of Kathmandu Valley, the morphological and mineralogical characteristics of particulate matter are very limited or none. In this study, we report on the mineralogical and morphological analysis of airborne particulate matter collected from densely populated core areas of Kathmandu Valley using spectroscopic and microscopic techniques. The Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) data showed the presence of clay minerals, crystalline silicate mineral, carbonate minerals, and asbestiform mineral in the dust samples. The field emission scanning electron microscopic analysis confirmed the existence of particles having diverse morphology with some of the particles having aspect ratio as high as twenty; indicating the existence of asbestiform type minerals. Based on SEM-EDX data, we found that the relative distribution of elements to be different in different samples and C, O, Mg, Ca, and Si were the major elements in the dust samples. Interestingly, the XRD data analysis showed that in all the samples quartz mineral having high degree of crystallinity was present. The XRD measurement was also carried out in three different brands of cement samples. Few minerals present in dust samples were also identified in the cement samples. This observation could indicate that cement is one of the sources of minerals in the airborne particulate matter in the Kathmandu Valley.
据报道，加德满都谷地是世界上污染严重且人口密集的城市之一。颗粒物是加德满都不健康空气的主要成因之一。尽管有若干关于加德满都谷地空气质量时空变化的报告，但颗粒物的形态和矿物学特征却非常有限，甚至没有相关研究。在本研究中，我们报告了利用光谱和显微镜技术，对从加德满都谷地人口密集核心区域采集的空气中颗粒物进行的矿物学和形态分析。傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）数据表明，粉尘样品中存在粘土矿物、结晶硅酸盐矿物、碳酸盐矿物和石棉状矿物。场发射扫描电子显微镜分析证实存在形态各异的颗粒，其中一些颗粒的长宽比高达20；这表明存在石棉状矿物类型。基于扫描电子显微镜-能谱仪（SEM-EDX）数据，我们发现不同样品中元素的相对分布不同，碳、氧、镁、钙和硅是粉尘样品中的主要元素。有趣的是，XRD数据分析表明，所有样品中都存在结晶度高的石英矿物。还对三个不同品牌的水泥样品进行了XRD测量。在水泥样品中也鉴定出了粉尘样品中存在的少量矿物。这一观察结果可能表明，水泥是加德满都谷地空气中颗粒物中矿物的来源之一。
