Detailed Characterization and Hazard Level Analysis of the Ambient Fine and Ultrafine Particulate Mixture at a Construction Site
Open Access
- Author:
- Ilci, Firdevs
- Graduate Program:
- Energy and Mineral Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 04, 2015
- Committee Members:
- Jeremy Michael Gernand, Thesis Advisor/Co-Advisor
- Keywords:
- particulate matter
ultrafine particles
fine particles
exposure to particulate mixture
characterization of particles - Abstract:
- Exposure to airborne particulates is an important health concern for workers. Since the biological activity of nanoparticles has been shown to depend on physicochemical properties, it is important to characterize particle size and size distribution, particle number concentration, mass concentration, shape, chemical composition, and surface area to clarify the toxic potential. These parameters that are necessary to comprehend the particles effects on human body need to be analyzed and measured anytime exposure is assessed. As studies on the toxicity of engineered nanomaterials have shown, both size distributions and chemical characteristics are important predictors of the hazard level posed by particulate exposures. Typically these parameters are not all measured simultaneously in the assessment of ambient particulate exposures. Knowing the size, number and mass distributions can better aid to identify cation of the sources of the particles. This study aims to characterize the complex mixture of fine and ultrafine particles present in the workplace by measuring the aerodynamic and physical diameters of particles, characterizing their chemical makeup, and evaluating the concentrations of the ambient aerosol mixture at the construction site. Particles were collected by using a cascade impactor, and transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were utilized to analyze the particles and establish size distributions separated by particle type (e.g. silica vs. soot). The diameters of particles found in the construction site atmosphere ranged from 0.99 nm to 10500 nm. 89.3% of the particles collected were ultrafine particles (<100nm) or aggregates of ultrafine particles that disaggregated during the collection process. Number and mass particle concentrations detected during sampling ranged from 2.1× 103 to 1.6× 104 particles/cm3, and 33.4 to 270 µg/m3, respectively, which is generally in agreement with previous studies of PM2.5 and PM0.1. Significantly higher numbers of ultrafine particles were observed through direct imaging than were expected. This occurred due to these particles being distributed throughout all stages of the impactor rather than being preferentially collected at the expected location. Particles are consisted of Carbon (41 %), Oxygen (26 %), Silicon (7.66 %), Sulfur (5.1 %), Calcium (4.7 %), along with other trace elements. Also some oxide and carbonate compounds derived from these elements such as calcium carbonate, silicon dioxide (silica), sulfates were identified, and size distributions for each of these particulate chemical species have been resolved. Additionally, shape analysis shows that 72.2 % nanoparticles have almost circular shape with circularity between 0.9 and 1.0. 50.34 % of particles have between 1:1 and 3:1 aspect ratio. These results enable for the first time a comparison of the exposure environment to the hazard level determined through single-particle-type exposure studies. Finally, these results suggest more comprehensive exposure studies should be performed to better understand the hazards of aerosol emissions from a wider array of workplaces.