What is depositional dust?
Dust is a term used to describe fine particles that are suspended in the atmosphere and formed by the action of wind, by physical disturbance of fine materials, or through the release of particulate-rich emissions. Gaseous emissions can also react over time in the atmosphere to form particles. Dust comes from a wide variety of sources, including soil, vegetation (pollens and fungi), sea salt, fossil fuel combustion, burning of biomass, and industrial activities.
Dust is typically classified according to its particle size, as follows:
deposited matter refers to any dust that falls out of suspension in the atmosphere
total suspended particles (TSP) typically refers to particles 50μm (micrometres) (0.05mm diameter) in size or less
PM10 refers to particles 10μm (0.01mm) in size or less
PM2.5 refers to particles 2.5μm (0.0025mm) in size or less
fine particles are of size PM10 or less
dust particle size is an important factor influencing dispersion and transport in the atmosphere and potential effects on human health.
How is it monitored?
Deposition Dust Gauges (DDGs) are used to measure the rate of dust deposition via a passive funnel and bottle arrangement as shown below. There is an Australian Standard (AS/NZS 3580) which identifies the equipment required for collecting a dust sample and how to use it, Gladstone Ports Corporation (GPC) and its contractors comply with this standard. Data is collected over approximately a month (usually 28-32 days) and results are expressed in g/m2/month (i.e. the mass of dust deposited per m2 per month). Although this method provides overall dust accumulation results to compare between locations it does not provide data on concentrations, particular events, sources or any potential health effects.