Will Aerosol Hygroscopicity Change with Biodiesel, Renewable Diesel Fuels and Emission Control Technologies?

Abstract

The use of biodiesel and renewable diesel fuels in compression ignition engines and aftertreatment technologies may affect vehicle exhaust emissions. In this study two 2012 light-duty vehicles equipped with direct injection diesel engines, diesel oxidation catalyst (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR) were tested on a chassis dynamometer. One vehicle was tested over the Federal Test Procedure (FTP) cycle on seven biodiesel and renewable diesel fuel blends. Both vehicles were exercised over double Environmental Protection Agency (EPA) Highway fuel economy test (HWFET) cycles on ultralow sulfur diesel (ULSD) and a soy-based biodiesel blend to investigate the aerosol hygroscopicity during the regeneration of the DPF. Overall, the apparent hygroscopicity of emissions during nonregeneration events is consistently low (κ < 0.1) for all fuels over the FTP cycle. Aerosol emitted during filter regeneration is significantly more CCN active and hygroscopic; average κ values range from 0.242 to 0.439 and are as high as 0.843. Regardless of fuel, the current classification of "fresh" tailpipe emissions as nonhygroscopic remains true during nonregeneration operation. However, aftertreatment technologies such as DPF, will produce significantly more hygroscopic particles during regeneration. To our knowledge, this is the first study to show a significant enhancement of hygroscopic materials emitted during DPF regeneration of on-road diesel vehicles. As such, the contribution of regeneration emissions from a growing fleet of diesel vehicles will be important.

High Summertime Aerosol Organic Functional Group Concentrations from Marine and Seabird Sources at Ross Island, Antarctica, during AWARE

“…In addition, absorption correlated 30 moderately to the non-activated CN particles (1-CCN/CN) (R=0.34 for 1% supersaturation, Figure 2 (b)). The correlation of more absorbing particles to those that did not take up water is consistent with the SLCE particles being freshly-emitted from fuel combustion, as such particles have high BC (Peng et al, 2017;Vu et al, 2017) .…”

High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE

“…2b). Since BC-containing particles, such as those freshly emitted from combustion sources, have been shown to have low hygroscopicity (Peng et al, 2017;Vu et al, 2017), these correlations are consistent with the particles that did not take up water being those that were emitted by local combustion activities.…”

Uncertainty in Predicting CCN Activity of Aged and Primary Aerosols

“…At BJ, even at 150 nm dry D p a significant fraction of the particles did not activate at S = 0.8%. The mean к HTDMA probability distribution functions (PDFs) shown in Figure show high‐amplitude peaks at к HTDMA < 0.05 at BJ for particles with D p ranging from 40 to 200 nm, reflecting the significant impact of local primary emissions (e.g., vehicle emissions and cooking sources) (Sun et al, ; Vu et al, ). The PDFs at each site have tails that extend to κ < 0, though the impact is <0.02% and deemed negligible.…”