This paper presents emission factors (EFs) derived for a range of persistent organic pollutants (POPs) when coal and wood were subject to controlled burning experiments, designed to simulate domestic burning for space heating. A wide range of POPs were emitted, with emissions from coal being higher than those from wood. Highest EFs were obtained for particulate matter, PM10, (approximately 10 g/kg fuel) and polycyclic aromatic hydrocarbons (approximately 100 mg/ kg fuel for sigmaPAHs). For chlorinated compounds, EFs were highest for polychlorinated biphenyls (PCBs), with polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) being less abundant. EFs were on the order of 1000 ng/kg fuel for sigmaPCBs, 100s ng/ kg fuel for sigmaPCNs and 100 ng/kg fuel for sigmaPCDD/Fs. The study confirmed that mono- to trichlorinated dibenzofurans, Cl1,2,3DFs, were strong indicators of low temperature combustion processes, such as the domestic burning of coal and wood. It is concluded that numerous PCB and PCN congeners are routinely formed during the combustion of solid fuels. However, their combined emissions from the domestic burning of coal and wood would contribute only a few percent to annual U.K. emission estimates. Emissions of PAHs and PM10 were major contributors to U.K. national emission inventories. Major emissions were found from the domestic burning for Cl1,2,3DFs, while the contribution of PCDD/F-sigmaTEQ to total U.K. emissions was minor.

PCBs and PAHs were quantified in air samples taken every 6 h over a 7 day period in August 1995 at a rural site in northwest England. For the first 5 days, a stable high-pressure system moved slowly across northern England from the east. During this time, PCB air concentrations responded very closely to the changes in ambient temperature, following a clear diurnal cycle. All PCB congeners correlated well with temperature, but the correlation was strongest for lower chlorinated species. Daily PCB concentration maxima exceeded minima by a factor of 2.1-3.7 for different congeners; in contrast, daily maxima:minima ratios for different PAHs were in the range 0.47-1.44. These data are interpreted as providing evidence that rapid, temperature-controlled air-terrestrial surface exchange of PCBs influencing air concentrations and, hence, regional/global scale cycling of these compounds occurs. Toward the end of the study period, the stable air conditions were replaced by a turbulent (windy), unstable low-pressure system, when day/night temperature differences were small and the diurnal PCB congener pattern was not discernible. Diurnal PAH concentration changes were not correlated with temperature, but groups of compounds were strongly correlated with each other (e.g., phenanthrene, fluoranthene, and pyrene; benzo(k)fluoranthene, benzo(a)pyrene, benzo-(ghi)perylene). It is therefore hypothesized that short-term PAH air concentrations are controlled by ongoing recent local/regional source inputs (rather than air-surface recycling), atmospheric reactions, and deposition processes. The air-surface exchange of PCBs is satisfactorily modeled by a sine curve describing ambient temperatures and controlled by a temperature-dependent air-terrestrial surface (K TA ) partition coefficient.

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