The assessment of particulate matter emitted from stone-crushing industry by correlating rock textures with particles generated after comminution and dispersed in air environment

Our plain-English summary of The assessment of particulate matter emitted from stone-crushing industry by correlating rock textures with particles generated after comminution and dispersed in air environment, by G. Belardi, G. Vignaroli, P. Plescia, et al (Environmental Science and Pollution Research International, 2013).

The study

• Authors: G. Belardi, G. Vignaroli, P. Plescia, L. Passeri
• Journal: Environmental Science and Pollution Research International
• Published: 2013;20(7):4711-28
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The generation and emission of particulate matter from abrasion industry are subjects of the pollution monitoring by multidisciplinary study involving earth sciences and engineering disciplines. This work investigates the correlation between textural properties of in situ rock with class size distribution and morphology of particles generated after rock comminution and particles emitted in the air. A special comminution-dust sampling architecture was realised. The combined use of scanning electron microscopy and particle size analyser was considered in performing digital image analysis on both crushed products and airborne particles collected onto membrane filters. The results show that the size and morphology of crushed particles are linked to the petrographic rock properties. In particular, particles with fibrous morphology are prominent in rocks showing foliated textures where elongated minerals occurred, with implication for asbestos-bearing rocks. For what concerns the airborne particles, the results show that their aerodynamic diameters are independent of the crusher operating conditions. External parameters probably intervene in the distribution of the airborne particles emission, including the dynamic air fluxes, or environmental conditions. By applying mathematical models, the morphology and size range of airborne particles following the comminution processes can be predicted, and results has implication for pollutants contamination due to particulate matters emitted by crush stone industry.

In plain English

This was a laboratory experiment on rocks; no people were studied. The authors crushed six rock types from an ophiolite suite (serpentinite, basalt, lherzolite, gabbro, marble and metagabbro) in a jaw crusher at four closed-side settings (5 to 20 mm) and collected airborne dust on filters near the crusher. They examined the rocks under the microscope and measured the size and shape of crushed particles finer than 0.125 mm and of airborne particles. For all materials, about 85% of the fine crushed particles had a length-to-width (aspect) ratio of 2 or less; particles with ratios of 3 or more, described as acicular-to-fibrous, formed the tails of the distributions. The crusher setting changed the amount of fine material but hardly its size or shape. The airborne particle distributions had means between 5 and 7 μm in aerodynamic diameter. The authors called their link between rock texture and particle shape preliminary. They concluded that foliated structures seem to enhance the generation of fibrous particles, with implications for evaluating asbestos in such rocks.

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: Laboratory experiment: microscope study of rock textures, crushing tests in a jaw crusher with dust sampling, and mathematical modelling of crushing
• Who was studied: Rock samples, not people: six rock types from an ophiolite suite, coded AN (serpentinite), AQ (basalt), LH (lherzolite), ME (gabbro), MF (marble) and TA (metagabbro). Where and when the samples were collected is not stated.
• Exposure: Crushing of the rock samples in a laboratory jaw crusher at four closed-side settings (5, 10, 15 and 20 mm). Airborne dust was collected on filters near the crusher at aspiration rates of 1.0, 1.5, 2.5 and 8.5 litres per minute.
• Main results:
  • For all materials, about 85% of crushed particles finer than 0.125 mm had an aspect ratio of 2 or less (prismatic). Particles with an aspect ratio of 3 or more (acicular-to-fibrous) formed the tails of the frequency distribution.
  • Only the amount of fine material (finer than 0.125 mm) depended on the crusher operating conditions. Mean particle diameter and particle shape were roughly independent of the crusher jaw opening.
  • The model parameter K, which is related to the quantity of fine product, decreased as the crusher setting increased, except in the metagabbro (TA) sample, where it stayed constant at 0.04.
  • For the airborne particles of each sample, the maximum aerodynamic diameter was about 70 to 80 μm. The mode of the distributions was between 3 and 5 μm and the mean between 5 and 7 μm, independent of crusher operating conditions.
  • In tests on the metagabbro (TA) sample at a 5 mm setting, the aspiration rate affected the amount of particles collected but not their shape distribution.
  • Where fibre-shaped particles occurred, the shape distribution of the airborne particles was shifted toward lower aspect ratios than that of the crushed particles, for all materials and settings tested. The authors suggested this was probably because fibre-like particles are hardly held in suspension.
  • Under the microscope, the serpentinite (AN) and marble (MF) samples were dominated by pervasive foliation and had the highest mean aspect ratios of the traced objects (2.30 and 2.29). The marble's foliation included green amphibole identified as tremolite.
  • In the metagabbro (TA), the amphibole (actinolite) showed a fibrous morphology often detected in micro-veins.
• The authors' conclusion: The authors concluded that the size and morphology of crushed particles are linked to the rock's petrographic texture. In their view, foliation seems to enhance the generation of particulate matter with fibrous morphology, with possible implications for evaluating asbestos when ophiolitic rocks are processed.
• Limitations the authors state:
  • The authors described the correlation between rock texture and particle size and shape as preliminary.
  • The authors stated that their simulation approach applies only to materials whose textures fall within those studied; other materials require experimental crushing tests.

Topics

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM).

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