The Bexley 4 monitoring site has consistently exceeded the EU Limit Value / AQS Objective for PM₁₀since 2000 by a wide margin.

The vast majority of the days with mean PM₁₀ concentration above 50 µg m-3 TEOM*1.3 were due to PM₁₀ from a local source which exceeded the local primary PM₁₀ by a factor of 16. If the local - other PM₁₀ source was not present during 2006, the site would have almost certainly achieved the AQS Objective / EU Limit Value for the year.

The local PM₁₀ source exhibited greatest concentrations during working hours on weekdays and on Saturday mornings. It is likely that the local - other PM₁₀ originated from sources that operated at these times and it was also found to be linked to local primary emissions.

The local PM₁₀ had the largest concentrations when the wind originated from a broadly northerly direction between (280o to 150o). These directions agreed with the orientation of Manor Road with respect to the monitoring site. The local source also exhibited a substantial seasonal variation with greatest concentrations being measured during summer.

Comparing the results from the source apportionment study to that obtained in previous studies; the concentration of PM₁₀ at Bexley 4 was consistent with the monitoring site being close to the entrance / exit from a waste facility.

The local PM₁₀ sources were linked to road traffic, but could not be accounted for by tailpipe emissions and expected mechanical tyre and brake wear. It was therefore likely that the local PM₁₀ originated from the resuspension of silt from the road surface or direct suspension of material from ‘dusty’ vehicles. There is some evidence to suggest that the local PM₁₀ may come from two separate activities, one linked to to transport and another which may be due to a fugitive source (though none was found in the analysis) or wind blown resuspension of locally deposited silt.

A copy of report may be found by following the ‘more information’ link below.

Future studies at Manor Road will look in more detail at the local PM₁₀ concentrations with respect to wind speed and direction and also the additional toxic burden from local sources in the area.

More Information

Item date 23/06/2008