Chemical speciation of PM emissions from heavy-duty diesel vehicles equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) retrofits

Four heavy-duty diesel vehicles (HDDVs) in six retrofitted configurations (CRT(sic), V-SCRT(sic), Z-SCRT(sic), Horizon, DPX and CCRT(sic)) and a baseline vehicle operating without after-treatment were tested tinder cruise (50 mph), transient UDDS and idle driving modes. As a continuation of the work by Biswas et al. [Biswas, S., Hu, S., Verma, V., Herner, J., Robertson, W.J., Ayala, A., Sioutas, C., 2008. Physical properties of particulate matter (PM) from late model heavy-duty diesel vehicles operating with advanced emission control technologies. Atmospheric Environment 42, 5622-5634.] oil particle physical parameters, this paper focuses Oil PM chemical characteristics (Total carbon [TC], Elemental carbon [EC], Organic Carbon [OC], ions and water-soluble organic carbon [WSOC]) for cruise and UDDS cycles only. Size. resolved PM collected by MOUDI-Nano-MOUDI was analyzed for TC, EC and OC and ions (such as sulfate, nitrate, ammonium, potassium, sodium and phosphate), while Teflon coated glass fiber filters from a high Volume sampler were extracted to determine WSOC. The introduction of retrofits reduced PM mass emissions over 90% in cruise and 95% in UDDS. Similarly, significant reductions in the emission of major chemical constituents (TC, OC and EC) were achieved. Sulfate dominated PM composition in vehicle configurations (V-SCRT(sic)-UDDS, Z-SCRT(sic)-Cruise, CRT and DPX) with considerable nucleation mode and TC was predominant for configurations with less (Z-SCRT(sic)-UDDS) or insignificant (CCRT(sic), Horizon) nucleation. The transient operation increases EC emissions, consistent with its higher accumulation PM mode content. In general, solubility of organic carbon is higher (average similar to 5 times) for retrofitted vehicles than the baseline vehicle. The retrofitted vehicles with catalyzed filters (DPX, CCRT(sic)) had decreased OC Solubility (WSOC/OC: 8-25%) unlike those with uncatalyzed filters (SCRT's, Horizon; WSOC/OC similar to 60-100%). Ammonium was present predominantly in the nucleation mode, indicating that ternary nucleation may be the responsible mechanism for formation of these particles. (C) 2008 Elsevier Ltd. All rights reserved.