Dust Deposition Gauges

 Dust depositional gauges are designed to determine the mass of particles which settle from ambient air during a reporting period.  Particles are collected on a glass funnel and enter a vessel below following rainfall during the sampling period.  

Static Dust Deposition gauges should be sampled according to the following standards: 

• AS3580.10.1 Determination of particulates- Deposited Matter-Gravimetric method 
• AS3580.1.1 Methods for sampling and analysis of ambient air Part 1.1 Guide to siting air monitoring equipment 

Dust gauges are installed 10m from any tall trees and 5m from any buildings, allowing a clear sky angle of 120°.  The top of the funnel stands vertically 2.0±0.2m from the ground.   

The funnel and bottle is removed from the gauge and any residue remaining in the funnel should be rinsed into the bottle to ensure residue is contained in the correct sampling period.  The bottle is then sealed and the following are recorded: sampler, date and time sampled, gauge name, the date the gauge was first installed will also need to be recorded to determine the sampling period.  Following collection of the vessel, the contents (rainwater and particles) are filtered to retrieve insoluble solids, ash and combustible matter.  As some organic matter is expected to be collected during the sampling period, the filtered residue is fired in a kiln to retrieve the insoluble contents collected.  Results are expressed as insoluble solids, ash, and combustible matter. 

What do the results mean? 

The results show the amount of insoluble solids that have fallen on the funnel during the sampling period, possibly originating from industrial operations.  Deposited dust becomes a nuisance when certain concentration levels are exceeded, the national recommended limit is 4 g/m2/month as recommended by the National Energy Research Development and Demonstration Council (NERDDC).

What are high vols? 

High Volume Air Samplers (HVAS) are automatic devices which draw air through different size selective inlets at a known flow rate and capture particles from the air onto glass fiber filters for a programmed amount of time.  Two sizes of particulate matter (PM) are commonly measured: PM10, which refers to particles smaller than 10µm and PM2.5, referring to particles smaller than 2.5µm.  Total Suspended Particles (TSP) refers to larger particles and is often monitored alongside particulate matter. 

Sampling Method 

HVAS should be installed and sampled to the following standards:  

• AS 3580.1.1 Methods for sampling and analysis of ambient air.  Part 1.1: Guide to siting air monitoring equipment. 
• AS 3580.9.3 Methods for sampling and analysis of ambient air.  Part 9.3 Determination of suspended particulate matter – Total suspended particulate matter (TSP) – High volume sampler gravimetric method 
• AS 3580.9.6 Methods for sampling and analysis of ambient air.  Part 9.6 Determination of suspended particulate matter – PM10 high volume sampler with size selective inlet – Gravimetric method  
• AS 3580.9.14 Methods for sampling and analysis of ambient air.  Part 9.14 Determination of suspended particulate matter – PM2.5 high volume sampler with size selective inlet – Gravimetric method 

HVAS are installed onto level concrete, away from trees or any infrastructure which may interfere with particulates entering the machinery. Glass fibre filter papers are placed onto a tray within the PM and TSP machine and automatic programs are set to control the air flow.  Filter papers are collected, weighed and compared to the mass prior to entering the HVAS machines.

What do the results mean? 

Though PM10 and PM2.5 particles can be caused by natural sources such as bushfires and pollens as well as the construction industry, particles of these sizes are able to be inhaled and reach the lungs, causing detrimental health effects over time.  Larger particles are more likely to settle in the nose, mouth or throat.  Results are stated as a mass concentration of TSP, µg/filter and show the deposited mass onto a filter dependent on duration of flow time, inlet size and atmospheric pressure.