Extracted from the CAI-Asia Listserv archives
11 February to 20 February 2004

Question: Do you have any research study related to the road resuspension from vehicles? It would be helpful, if I can get information like: method to find out the share of road dust on ambient air with the available data on ambient PM10, PM2.5 or other gaseous pollutants; rate of resuspension from the road with respect to the flatness of the vehicle tyre; speed of the vehicle; and other related issues.

- Anil K. Raut, Nepal

Response #1

I have been following the various contributions on resuspension, but what is clear to me is that this area remains very uncertain. The following issues/questions need to be considered:

• What materials are being resuspended - size distribution and chemical composition?
• What is the source of the resuspended particulate?
• What is the contribution of natural particles - soil etc, which will vary by climatic region and season?
• What is the effect of street cleaning/cleansing?
• What proportion of the particulate matter is derived from brake wear, tyre wear or the wear of the road surface?

In the UK we assume that the resuspended component is the mass fraction between PM2.5 and PM10. Again in the UK the National Atmospheric Emission Inventory uses a resuspension value of 0.04 g/km.


- Ian McCrae, UK

Response #2

The five questions you list have been studied extensively here in the US because of the importance of dust emissions to PM10 air quality. There has been much research done on all of these topics, both by USEPA and US state air pollution agencies. Major windblown dust studies have been conducted in Eastern Washington State (agricultural lands) and desert environments (California Air Resources Board and local Districts). Complex soil wind erosion models and related research has been done by the Natural Resource Conservation Commission under the US Department of Agriculture. Studies of street dust cleaning techniques, including numerous sweeper designs, have also been completed here in the US. So there is much information available if you can find it.

From my general knowledge of the subject:

1. Material being resuspended

Coarse fraction PM2.5-PM10 and larger crustal (soil) particles principally composed of Si, Ca, Fe, Al and other trace elements. May include Pb if leaded petrol has been used or near lead sources (such as a smelter).

2. Sources

Ground pavement and asphalt; soil dust tracked onto the roadway from the shoulders; construction materials in the roadway, soil deposited on roadways by wind transport/erosion action; soil deposited on the roadway from the under-carrage or trucks/cars. The specific sources are dependent on local conditions and can vary by season of the year.

3. Street cleaning

Once the heavy deposits of soil/dust are removed from the roadway, street sweepers can create more dust than they collect as sweepers are designed to collect beer cans, not PM-10. Even specially built vacuum sweepers tested in California specifically for PM10 emission reduction have generally not performed well (and are very costly). Best option is to keep the dust off of the streets in the first place.

4. Brake, tyre wear and road surface wear

Brake and tyre wear emissions are insignificant in comparison to road surface wear and soil dust resuspension emissions. Dust emissions from agricultural sources can be very large, overwhelming all other sources in the emissions inventory.

If there is sufficient interest in this topic, it might be good for the CAI to put together a list of references or compile a synopsis of the knowledge on this topic.

- John Core, USA