Solidpartikler

Solidpartikler, or solid particles, are small, discrete solids suspended in another medium, typically air or water. They vary widely in size, composition, and shape, and can be of natural origin such as dust, pollen, or sea salt, or anthropogenic origin such as soot, metal fragments, or industrial powders. In the atmosphere they are often referred to as aerosol particles when suspended in gas.

Size is a key characteristic. Solid particles span from nanometers to several tens of micrometers in diameter. In environmental science, size classifications like PM10 and PM2.5 are used to denote particles with diameters up to 10 or 2.5 micrometers, respectively, due to their differing health and transport impacts. Morphology ranges from roughly spherical to highly irregular or fractal-like, and composition can be mineral, organic carbon, metals, salts, or mixtures.

Formation and behavior are governed by both origin and physics. Particles can form by condensation from vapor, fragmentation or grinding, combustion, or mechanical processes. In fluids they experience Brownian motion, drag, and inertia, which influence transport, diffusion, and settling. They interact with light through scattering and absorption, affecting visibility and climate. In air, particles may act as condensation nuclei for cloud formation and can deposit on surfaces or be removed by filtration, coagulation, or sedimentation.

Measurement and use are diverse. Particle size distributions are characterized using optical counters, electron microscopy, dynamic light scattering, and gravimetric methods. Solid particles have wide applications, including pigments, catalysts, reinforcing agents in composites, drug delivery systems, and environmental remediation. They also pose health and environmental concerns when inhaled or deposited, guiding regulations on air quality and emissions.