Right, I have done the double ratio plots, and the source is coal derived. I have attached the plot.



This must be a legacy of historic practices, as I don't know of any plot holders who bring ash from their fireplaces/coal burning stoves to their allotments. Just how persistent are PAHs in soil that is regularly worked for growing veg? 



Also, plant derived ash is definitely present, but if the PAHs detected in the lab analysis are coal derived, does this imply that the PAH concentrations of the wood ash are negligible in comparison, i.e. do  we have a mixture of the two ash types where a dominant more highly concentrated coal derived PAH is dominating the results?



This is all I have found on the composition of wood ash, from the following paper: http://www.forestry.gov.uk/pdf/use_of_ash_in_forestry.pdf/$FILE/use_of_ash_in_forestry.pdf (thanks to Jonathan Parry for the link)



Polyaromatic hydrocarbons (PAHs)

Data quoted by Someshwar from Diebel et al. (1992) indicate that the types of PAHs found in wood ash are

those of the two and three ring constituents, which are less toxic than the four and five ring compounds.

Naphthalene proved the most plentiful in his study (1.6 mg/kg), but many compounds were below detection

levels in the samples. In a recent study in Switzerland wood ash derived from a pure burn at 550 – 650 ºC was

added to mineral soils, and monitored for both PAH and PCB compounds (Bundt et al., 2001). The wood ash

was found to have high concentrations of PAHs (the sum of 20 types equated to 16.8 mg/kg). However, the

PCB addition to soils from the wood ash was low (totalling 14 types which equated to 3.4μg/kg) . The exact

nature of the wood burned was not recorded. 



I imagine that the temperature of the fire, type and age of plant material etc, all have a role to play in the PAH composition. Seems like a great MSc/PhD project to investigate the PAH composition of purely plant derived ash. 





Regards



Christopher Taylor

Enforcement Officer

Regulatory Services

Brent Council



Tel: 020 8937 5159



www.brent.gov.uk 







-----Original Message-----

From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Russell Corbyn

Sent: 23 April 2015 16:28

To: [log in to unmask]

Subject: Re: Wood ash / Allotment BaP



Now there is a sensible scientific approach, not just an idea!



Not that they (double ratio plots) are at exceptionally accurate but there are so many other sources of deposition for PAHs and their attachment to fugitive dusts from exhausts, fire depositions, weathered macadam dust, spilt oils and so on. They are ubiquitous and it would give an approximation and the grouping of data would become immediately apparent.



I now have several hundred macadam PAH analyses and there is good agreement with the vast majority of data. It also becomes apparent what level of PAH is noise. With the levels of most environmental soil PAH analysis being quite noisy due to the distribution being in reality quite close to the limit of detection of tests (and let us not forget the lab error bars that must be applied to that) I feel sure that there would be substantially more noise than in my macadam samples.



I don't like the "let's just look at BaP level" approach to PAH provenance assessment because it is a very narrow view and tells us not very much.



Cheers



Russell







-----Original Message-----

From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Mark Henderson

Sent: 23 April 2015 11:42

To: [log in to unmask]

Subject: Re: Wood ash / Allotment BaP



It would be interesting to see the whole BaP set with  fluoranthene, pyrene, BaA and chrysene. You could then plug them into a double ratio plot and see if they point to a single source.



Just an idea



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-----Original Message-----

From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Taylor, Christopher

Sent: 23 April 2015 07:57

To: [log in to unmask]

Subject: Re: Wood ash / Allotment BaP



Hi Chris



Sure. Here are the BaP results from 7 random allotments.



3.44	17.70	26.30	5.97	7.20	2.93	9.45	15.12	12.25	14.73																		

1.58	2.17	0.64	2.56	3.20	7.14	2.85	0.85	0.85	6.37																		

0.83	<0.05	<0.05	0.98	8.72	0.59	3.47	0.32	3.16	0.70																		

3.48	1.87	5.40	2.54	3.71	2.34	0.67	8.56	1.73	1.96	2.02	11.67	2.52	10.86														

2.69	1.95	8.11	12.43	7.73	0.58	8.99	8.69	14.17	5.65	3.56	5.86	3.32	3.62	7.46	6.13	7.63	6.54	9.59	3.52	3.20	3.78	0.83	7.42	4.74	3.55	9.95	4.19

3.60	3.13	5.33	5.13	3.96																							

1.02	0.99	1.38	2.32	1.02	2.44	2.44	3.16																				





Regards



Christopher Taylor

Enforcement Officer

Regulatory Services

Brent Council



Tel: 020 8937 5159



www.brent.gov.uk 





-----Original Message-----

From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Chris Dainton

Sent: 22 April 2015 23:33

To: [log in to unmask]

Subject: Re: Wood ash / Allotment BaP



Neil & Chris



Can you share the BaP results (just the numbers will do) from the allotment testing you've undertaken so the List can get a feel of the range of BaP numbers encountered, rather than just min - max etc.



Cheers



Chris Dainton



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