Characterization of Condensable Particulate Matter Emissions in Agricultural Diesel Engines Using a Dilution-Based Sampling Train

Particulate matter, especially fine particulate matter (PM2.5) originating from the combustion of fossil fuels, has become the main cause of air pollution [Feng, Y.; Fuel 2018, 224, 801-813]. There is currently growing interest worldwide in maintaining the emissions of these particles within levels, which allows preventing their negative effects on the environment and human health. The PM2.5 fraction of the particles emitted by stationary and mobile sources is comprised of both filterable particulate matter (FPM) and condensable particulate matter (CPM). Environmental regulations do not envisage readings of the CPM fraction, even though it has been shown that in some characterized sources, this type of particle represents higher emissions than FPM [Li, J.; Energy Fuels 2017, 31, 1778-1785; Cano, M.; Energy Fuels 2017, 31, 7831-7838; Goodman, N.; Stationary Source Test Methods for Condensible Particulate Matter and PM2.5; Electric Power Research Institute, 2006; Vol. 3, pp 1-34; Yang, H.; Aerosol Air Qual. Res. 2015, 15, 1672-1680]. Given above, it is vitally important to quantify the CPM fraction of the different types of sources and to establish the best measurement method by ensuring its reproducibility and accuracy. This work presents an estimate of the contribution of CPM to total PM2.5 emissions deriving from Non-Road Mobile Machinery (NRMM). Specifically, it presents the results of CPM and FPM concentrations emitted by an agricultural diesel engine, obtained using a dilution sampling train developed by the Department of Chemical and Environmental Engineering (DIQA, according to its Spanish acronym) in accordance with the method EPA CTM-039, as well as chemical analysis of the samples, obtained using the combined ion chromatography-mass spectrometry technique. The conclusions reached in this study confirm that the ratio of CPM/FPM concentrations oscillates between 0.29 and 0.36, depending on the conditions under which the engine is working, that the CPM emissions increase as the engine torque rises and that quantifying CPM as particulate matter emitted by the NRMM would raise the percentage of total annual PM2.5 emissions by up to 1.65%.