Dust deposition
What is dust deposition?
Dust deposition is the deposition of substances that fall as dry dust along with rainwater or as gaseous components from the air onto surfaces such as soil, plants, buildings, and bodies of water. Because dust deposition is either bound to raindrops or consists of coarse-grained material, only small amounts of it are inhaled and do not directly affect health.
How dangerous is dust deposition?
| component | Immission value |
|---|---|
| Dust deposition | 0.35 g/(m²d) |
| Lead | 100 µg/(m²d) |
| cadmium | 2 µg/(m²d) |
| arsenic | 4 µg/(m²d) |
| nickel | 15 µg/(m²d) |
| Thallium | 2 µg/(m²d) |
| mercury | 1 µg/(m²d) |
The persistent release of air pollutants leads to harmful soil changes. Furthermore, dust deposition and its constituents indirectly pose a health risk when contaminated vegetables, fruit, or feed are consumed, or when children put contaminated soil in their mouths.
Therefore, in section 4.5.1 of the Technical Instructions on Air Quality Control (TA Luft), emission values are specified for dust deposition (protection against significant nuisance or significant disadvantages) and for the components of dust deposition (protection against harmful environmental impacts due to deposition) (see table).
Exceeding these emission values does not automatically mean that harmful environmental impacts within the meaning of the Federal Immission Control Act (BImSchG) are present.
Rather, a harmful environmental impact can only be assumed if the immission values for the deposition are exceeded and a special case assessment according to section 4.8 of the TA Luft has shown that, due to the special circumstances of the individual case, harmful environmental impacts are caused (section 4.5.2 d of the TA Luft).
How is dust deposition measured?
Fig.: Collection vessel
for dust deposition
Dust deposition is collected using simple, open-topped plastic containers called Bergerhoff collection vessels (see figure). These vessels are placed in selected areas at a height of 1 to 1.5 meters above the ground. After a storage period of approximately one month, the vessels are replaced, and the contents are dried and weighed in the laboratory.
The monthly samples are usually combined into annual samples, from which constituents such as arsenic, lead, cadmium, and nickel are then determined. The amount of dust deposition in grams per m² per day (g/(m²*d)) is calculated from the sample mass.
This collection method primarily captures dust particles with a grain diameter of 50 to 200 µm. These dust particles sink relatively quickly to the ground, meaning they are only transported a few hundred meters in the air.
