Abstract:
Polynuclear aromatic compounds (PAC) were characterized in diesel fuel, kerosene fuel and unmodified sunflower oil as well as in their respective engine exhaust particulates. Diesel fuel was found to contain high amounts of different PAC, up to a total concentration of 14,740 ppm, including carbazole and dibenzothiophene, which are known carcinogens. Kerosene fuel was also found to contain high amounts of different PAC, up to a total concentration of 10,930 ppm, consisting mainly of lower molecular weight (MW) naphthalene and its alkyl derivatives, but no PAC component peaks were detected in the unmodified sunflower oil. Engine exhaust particulates sampled from a modified one-cylinder diesel engine running on diesel, kerosene and unmodified sunflower oil, respectively, were found to contain significantly high concentrations of different PAC, including many of the carcinogenic ones, in the soluble organic fraction (SOF). PAC concentrations detected at the exhaust outlet indicated that most of the PAC that were present in diesel and kerosene fuels before the test runs got completely burnt out during combustion in the engine whereas some new ones were also formed. The difference between the character and composition of PAC present in the fuels and those emitted in the exhaust particulates indicated that exhaust PAC were predominantly combustion generated. High amounts of PAC, up to totals of 52,900 and 4830 µg m−3 of burnt fuel, in diesel and kerosene exhaust particulates, respectively, were detected in the dilution tunnel when the exhaust emissions were mixed with atmospheric air. Significant amounts of PAC were also emitted when the engine was run on unmodified sunflower oil with a total concentration of 17,070 µg m−3 of burnt fuel detected in the dilution tunnel. High proportions of the combustion-generated PAC determined when the engine was run on diesel, kerosene and unmodified sunflower, respectively, consisted of nitrogen-containing PAC (PANH) and sulphur-containing PAC (PASH).