Hi Anne
High lead is also often found on allotments. The source is ash from burned wood that had previously been painted. A lot of wood was primed with lead based paint.
I did the analysis (using XRF) of several school playing fields in the London area. An initial SI showed very high lead. The lead was in a distinct layer of ash and rubble. This was from the remains of bomb damaged buildings during WW2 and had been used to fill in the dip in the field many years ago. It was easy to see the ash layer. The soil just above and below was lead free. The source was again lead based paint used to preserve and prime wood and metal.
Another source, if close to a road was from traffic, when lead was in petrol. I measure over 600 mg/kg lead on numerous roadsides and allotments where they were right next to a main road. The lead slowly settles to about 50 cm below the surface (worm action? and rainfall)
Having seen the amount of plastic being burned on allotments, I do wonder about the dioxin concentrations. Better not go there though........
Have a good weekend everyone. It looks like another sunny one
Regards
Colin
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