Characterization of airborne dust samples collected from core areas of Kathmandu Valley

Our plain-English summary of Characterization of airborne dust samples collected from core areas of Kathmandu Valley, by B.B. Neupane, A. Sharma, B. Giri, et al (Heliyon, 2020).

The study

• Authors: B.B. Neupane, A. Sharma, B. Giri, M.K. Joshi
• Journal: Heliyon
• Published: 2020;6(4):e03791
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

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.

© 2020 The Author(s).

In plain English

This study analyzed the minerals in airborne dust collected in March 2018 from eleven densely populated core locations in Kathmandu Valley, Nepal. Falling dust was caught over 24 hours at each site in petri dishes placed 10 m above the ground. It was examined by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and electron microscopy. Infrared signals the authors attributed to chrysotile were found in all samples, and signals attributed to crocidolite in samples S6 to S11. By XRD, chrysotile peaks were reported in all samples except S5 and S9, and crocidolite was not detected in any sample. Most particles were symmetrical, with length one to three times their width. A few were elongated, including ribbon-shaped particles in one sample with length up to twenty times their width, which the authors classed as asbestiform. All samples contained highly crystalline quartz. Three cement brands also showed quartz, carbonate minerals and chrysotile, and the authors concluded cement could be one source of these minerals. The authors stated that without data on mineral concentrations, exposure dose and epidemiology, they could not comment on cardiovascular-related health issues.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental sampling study: laboratory mineralogical and morphological analysis of airborne dust samples (FTIR, XRD, field emission SEM with EDX), plus XRD of cement samples
• Who was studied: Passively collected free-falling dust from 11 densely populated core locations of Kathmandu Valley, Nepal (samples S1 to S11). It was collected on dry sunny days in March 2018, over 24 hours per site, in petri dishes 10 m above ground. Three cement samples from three major suppliers were also analyzed.
• Exposure: Mineral content of urban airborne dust, including asbestiform minerals (chrysotile, crocidolite), crystalline silica (quartz), clay minerals, carbonate minerals and hematite. No concentrations or doses were measured.
• Main results:
  • FTIR signals characteristic of chrysotile were present in all eleven dust samples
  • FTIR signals characteristic of crocidolite were present in samples S6 to S11
  • By XRD, chrysotile peaks were found in all samples except S5 and S9
  • By XRD, no sample showed peaks characteristic of crocidolite
  • In the FE-SEM images, most dust particles were symmetrical, with aspect ratios (length divided by width) of 1 to 3
  • A few particles had diverse shapes. These included ribbon-shaped particles in sample S9 with aspect ratio as high as twenty, which the authors classified as asbestiform.
  • Quartz of high crystallinity was present in all dust samples, with crystallinity index values from 7 to 9.7 on a 0 to 10 scale
  • XRD of three cement brands showed peaks of quartz, of the carbonate minerals vaterite, calcite and dolomite, and of chrysotile
• The authors' conclusion: The authors concluded that cement could be one of the sources of quartz, vaterite, calcite, dolomite and chrysotile in the dust samples studied
• Limitations the authors state:
  • Without data on mineral concentrations, exposure dose and epidemiological studies, the authors could not comment on cardiovascular-related health issues
  • Because of differences in crystallinity, minerals detected by FTIR may not be detected by XRD

Topics

Medical terms in this study, explained in our Lexicon: X-Ray Diffraction (XRD), Crystalline, Silicate, Carbonate Mineral, Asbestiform, Aspect Ratio (Length-to-diameter ratio).

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