Size-segregated urban particulate matter characterization by electron microscopy and dynamic light scattering during the sample preparation
Abstrakt
Size-segregated particulate matter (PM) is frequently used in chemical and toxicological studies. In vitro studies working with the whole particles often lack the evaluation of PM real size distribution and characterization of agglomeration under the experimental conditions.
In this study, changes in particle size distributions during PM sample manipulation and also semiquantitative elemental composition of particles were determined. Coarse (1-10 μm), upper accumulation (0.5-1 μm), lower accumulation (0.17-0.5 μm), and ultrafine (<0.17 μm) PM fractions were collected by high volume cascade impactor in Prague city center.
Particles were examined using electron microscopy and their elemental composition was determined by energy dispersive X-ray spectroscopy. Dynamic light scattering was used to measure particle size distribution in water and in cell culture media.
Mineral and high-temperature produced particles occurred together with nanosphere-soot predominantly in the coarse fraction. In the accumulation fractions, nanosphere-soot and other carbonaceous particles were prevalent, but iron-rich metallic nanospheres were frequently identified as well.
The ultrafine fraction consisted of nanosphere-soot and other carbonaceous particles. Inorganic particles as e.g. natrium, potassium or calcium sulphates were found in all fractions.
PM suspension of lower accumulation fraction in water was agglomerated after freezing/thawing the sample, and the agglomerates were disrupted by subsequent sonication, while ultrafine fraction was not agglomerated. Fetal bovine serum in cell culture media prevented the particle agglomeration, therefore providing the sample stability during cell culture experiments. [Supported by the Czech Science Foundation, project No.
P503-12-G147].