Chemical characterization of PM2.5 emitted from China IV and China V light-duty vehicles in China

Abstract

This study reported the emission factors (EFs) and detailed chemical compositions of PM2.5 collected from China IV and China V light-duty vehicles (LDVs) through dynamometer test. The China IV LDVs containing 4 gasoline vehicles (GVs) and 4 natural gas vehicles (NGVs) had port fuel injection (PFI) engines, while the China V LDVs included 2 GVs with PFI engines and 2 GVs with gasoline direct injection (GDI) engines. The average EFs of PM2.5 were 1.90 ± 0.70 mg km−1, 1.44 ± 0.29 mg km−1, and 0.56 ± 0.05 mg km−1 for China IV GVs, China IV NGVs, and China V GVs, respectively. PM2.5 profiles of LDVs were characterized by abundant carbon species (60.59–68.58%) with low amounts of water soluble ions (WSIs, 6.96–16.37%) and elements (5.20–7.53%). In general, the EFs of PM2.5 constituents including organic carbon (OC), elemental carbon (EC), WSIs, and elements were reduced obviously by strengthening emission standards from China IV to China V. While the contributions of most WSIs and elements to PM2.5 increased as vehicle technology improved. Furthermore, the EFs of PM2.5 components from China IV LDVs also decreased when shifting fuels from gasoline to natural gas. While the fractions of OC, WSIs and most elements in PM2.5 increased due to the highest reduction rate of EC mass. For China V LDVs, GDI vehicles emitted less OC but more EC compared to PFI vehicles, and the EFs of most WSIs and elements also increased. Overall, GDI vehicles exhibited lower fractions OC and WSIs but higher contents of EC and elements in PM2.5. Besides, PM2.5 and its chemical species were heavily dependent on vehicle's driving patterns. The average EFs of PM2.5 components under aggressive driving pattern increased significantly compared to those under moderate driving pattern.