Chemical and Toxicological Characterization of Residential Oil Burner Emissions: I. Yields and Chemical Characterization of Extractables from Combustion of No. 2 Fuel Oil at Different Bacharach Smoke Numbers and Firing Cycles

Abstract

Particulates and complex organic mixtures were sampled from the exhaust of a flame retention head residential oil burner combusting No. 2 fuel oil at three firing conditions: continuous at Bacharach Smoke No. 1, and cyclic (5 min on, 10 min off) at Smoke Nos. 1 and 5. The complex mixtures were recovered by successive Soxhlet extraction of filtered particulates and XAD-2 sorbent resin with methylene chloride (DCM) and then methanol (MeOH). Bacterial mutagenicity [see Paper II (8)] was found in the DCM extractables. Samples of DCM extracts from the two cyclic firing conditions and of the raw fuel were separated by gravity column chromatography on alumina. The resulting fractions were further characterized by a range of instrumental methods. Average yields of both unextracted particulates and of DCM extractables, normalized to a basis of per unit weight of fuel fired, were lower for continuous firing than for cyclic firing. For cyclic firing, decreasing the smoke number lowered the particulates emissions but only slightly reduced the average yield of DCM extractables. These and similar observations, here reported for two other oil burners, show that adjusting the burner to a lower smoke number has little effect on, or may actually increase, emissions of organic extractables of potential public health interest. Modifications of the burner firing cycle aimed at approaching continuous operation offer promise for reducing the amount of complex organic emissions. Unburned fuel accounted for roughly half of the DCM extractables from cyclic firing of the flame retention head burner at high and low smoke number. Large (i.e., greater than 3 ring) polycyclic aromatic hydrocarbons (PAH) were not observed in the DCM extractables from cyclic firing. However, nitroaromatics, typified by alkylated nitronaphthalenes, alkyl-nitrobiphenyls, and alkyl-nitrophenanthrenes were found in a minor subfraction containing a significant portion of the total mutagenic activity of the cyclic low smoke samples (8). Oxygen-containing PAH, typified by phenalene-1-one and its alkyl derivatives, are important mutagens from cyclic firing at high smoke conditions. Thus, oil burner effluents differ markedly from those of several other combustors, including the automotive diesel engine, where multiring PAH, typified by fluoranthene and alkylated phenanthrenes, account for a significant portion of the effluent mutagenicity. Implications for combustion and emissions source identification are discussed.