Launching

Microbes and Atmosphere
Part-1
Relationship between Microbes and Atmosphere
Atmosphere as a Habitat
Transport of Spores
Sampling of Air
Launching
Transport of Microorgannisms in Air
Deposition and Adhesion
Types of Deposition
Gravitational Settling
Surface Impaction
Rain and Electrostatic Deposition
Methods of Air Sampling
Impingement
Impaction
Centrifugation
Filtration and Deposition
Sampling Methods and their characteristics

Launching

Launching
Launching is the process whereby particles become suspended within earth' s atmosphere. The launching of bio-aerosols is mainly from terrestrial and aquatic sources, with greater airborne concentrations or atmospheric loading being associated with terrestrial sources than with aquatic sources. Launching into the surface boundary layers can include diverse mechanisms such as:

air turbulence created by the movement of humans
animals and machines
the generation, storage, treatment and disposal of waste material
natural mechanical processes such as the action of water and wind on contaminated solid or liquid surfaces
the release of fungal spores as a result of natural fungal life cycles

Transport or dispersion is the process by which the movement of air is transferred to airborne particles thus resulting in dissemination of airborne microbes over long distances. Most common type of transport phenomenon ranges from 10 minutes (submicroscale transport) for 100 m which is common within buildings. Microscale transport ranges from 10 minutes to 1 hour and from 100 m to 1 km and is the most common type of transport phenomenon.

Microorganisms have limited ability to survive when suspended in atmosphere. However, viruses, spores (fungal) and spore forming bacteria can survive transportation up to 100 km in the atmosphere. For example, coliforms aerosolised from sewage treatment plants have been transported over 1.2 km. Bio-aerosols travel with the force of diffusion or dispersion. Diffusion is scattering of bio-aerosols in response to gravity and is aided by airflows and atmospheric turbulence.

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