Fractal Dimension of Combustion Particles by in-situ Atomic Force Microscopy
Abstract
The environmental fate of road run-off particles is still poorly understood. While many studies have analysed and characterised airborne particles, none of them has focussed on their behaviour once in runoff-waters. In this context, we have analysed airborne particles originating from combustion, by means of Atomic Force Microscopy. This technique allows us to determine the morphological characteristics of the particles and of their aggregates at the nanometer scale. In addition, particles can be analysed either in air or in water, under their native, undisturbed state. In the case of our combustion particles, these two different environments were investigated. It is possible to characterise the reactions which individual particles undergo during aggregation, by means of the fractal dimension f of the aggregates. This parameter is a very sensitive indication on the surface roughness and the compacity of the aggregates. The analysed airborne particles (n = 20) showed a very smooth surface (f = 1.15 +/- 0.05), either in air samples or in water samples. For the latter, pure water (pH = 7) was used to perform the measurements. On the other hand, aggregates of individual particles showed a high compacity (f = 2.5 +/- 0.2), and they did not exhibit morphological changes under the experimental conditions of analysis. The fractal dimension of these aggregates suggests that they are formed under conditions of reaction-limited colloid aggregation (RLCA), which are mainly controlled by repulsive electrostatic forces. Further studies will be performed on in-situ samples in the near future. Physico-chemical conditions such as pH and ionic strength will be varied, to determine their influence on the behaviour and fate of these entities.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.A41B0051M
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801);
- 0345 Pollution: urban and regional (0305);
- 0394 Instruments and techniques