Diesel-powered equipment is known to emit significant quantities of fine particulate matter to the atmosphere. Numerous organic compounds can be adsorbed onto the surfaces of these inhalable particles, among which polycyclic aromatic hydrocarbons (PAHs) are considered potential occupational carcinogens. Guidelines have been established by various agencies regarding diesel emissions and various control technologies are under development. The purpose of this study is to identify, quantify and compare the organic compounds in diesel particulate matter (DPM) with the diesel fuel and engine oil used in a non-road diesel generator. Approximately 90 organic compounds were quantified (with molecular weight ranging from 120 to 350), which include alkanes, PAHs, alkylated PAHs, alkylbenzenes and alkanoic acids. The low sulfur diesel fuel contains 61% alkanes and 7.1% of PAHs. The identifiable portion of the engine oil contains mainly the alkanoic and benzoic acids. The composition of DPM suggests that they may be originated from unburned diesel fuel, engine oil evaporation and combustion generated products. Compared with diesel fuel, DPM contains fewer fractions of alkanes and more PAH compounds, with the shift toward higher molecular weight ones. The enrichment of compounds with higher molecular weight in DPM may be combustion related (pyrogenic).

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The emissions of diesel particulate matter (DPM) from diesel engines are causing increasing health concerns due to their suspected carcinogenicity, especially the carbonaceous fractions. The total DPM emissions and the organic and elemental carbon (OC and EC) distributions of the DPM depend on many operating factors, such as load, engine design parameters, fuel sulfur content, fuel usage rate, and sampling conditions. Results of previous studies on the OC/EC variations with load for heavy-duty vehicles have been reported, but information is scarce for nonroad diesel generators. There is a clear need to better characterize nonroad DPM emissions, as studies have indicated that DPM emissions from nonroad diesel engines are significantly higher than those from on-road sources. The objective of the study is to provide a detailed account of the OC/EC distributions for a nonroad diesel generator operated with high and low sulfur fuels under different load conditions. DPM emissions were collected using an EPA Method 5 (Determination of Particulate Matter Emissions from Stationary Sources) sampling train. The OC and EC concentrations were quantified by NIOSH Method 5040. DPM concentrations and the relative contributions of OC, EC, and noncarbonaceous materials vary significantly with engine load, fuel sulfur content, and sample collection temperature. The fractions of EC over DPM increase with increasing load from 21% at OkW to 84% at 75 kW for the low sulfur fuel, while those of OC decrease from 62% to 9%. This is consistent with other studies, and the same trends exist regardless of the sulfur content and DPM collection temperature. The fractions of organic compounds range from 77% to 19% for the high sulfur fuel. Noncarbonaceous materials are from 27% to 18% in fraction from high sulfur DPM as opposed to the 17% to 7% in the low sulfur diesel emissions. At lower collection temperatures, more OC and noncarbonaceous materials are observed.