Detailed studies of the factors controlling atmospheric PCDD/F concentrations
Thirty-seven 2--3 day air samples were collected between September and December 1997 to investigate the factors controlling PCDD/F concentrations at a semirural site near Lancaster on the west coast of the U.K. {Sigma}CL{sub 2--8}DD/F ({Sigma}TEQ) concentrations varied by a factor of {approximately}40, from 4.1 to 182 pg/m{sup 3}(5.5--220fg{Sigma}TEQ/m{sup 3}) with a mean concentration of 37.2 pg/m{sup 3} (38 fg {Sigma}TEQ/m{sup 3}). Atmospheric PCDD/F concentrations depended strongly on air mass origin, with lowest {Sigma}Cl{sub 3--8}DD/F concentrations coming from the west and higher ones arriving over land, suggestive of ongoing land-based sources. In marked contrast, Cl{sub 2}DD/F levels were highest with westerly winds, suggestive of specific sources west of Lancaster. Most homologue groups and 2,3,7,8-substituted congeners showed a significant inverse relationship with ambient temperature, consistent with domestic burning of coal/wood as an important source during colder periods. In contrast, the Cl{sub 2}DD/Fs were positively correlated with temperature, rain, and wind direction. Principal components analysis, based on the relative homologue pattern of Cl{sub 3--8}DD/Fs, discriminated few sample groups. Samples originating from the cleaner ocean sector were weathered and relatively depleted in PCDDs. An individual sample, taken around Bonfire night was dominated by Cl{sub 7/8}DDs. However, the majority of samples was clustered together, regardless of air mass origin. It is hypothesized that diffuse land-based sources principally supply CL{sub 3--8}DD/Fs to the atmosphere and that their long atmospheric residence times mean that the PCDD/F mixture is only slowly altered during air mass movement.
- Research Organization:
- Lancaster Univ. (GB)
- OSTI ID:
- 20006575
- Journal Information:
- Environmental Science and Technology, Vol. 33, Issue 24; Other Information: PBD: 15 Dec 1999; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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