AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Dieselgate - The Aerosol Analyst´s View
REINHARD NIESSNER, Analytical Chemistry, Institute of Hydrochemistry, TU Munich
Abstract Number: 43 Working Group: Control and Mitigation Technology
Abstract Volkswagen dieselgate has created much public attendance. The reason for this is the possible violation of emission threshold limits for diesel exhaust, especially by particulate matter and nitrogen oxides.
From the viewpoint of an analyst there is a tremendous need for discussion, whether the determination techniques applied to determine particulate matter (PM), and NOx as well, are accurate. In Europe, the non-gravimetric monitoring of diesel exhaust (PMP particle counting) seems especially vulnerable.
This lecture likes to illuminate the possible artifacts of NO2 determination with and without soot particle filters at the entrance of a NOx box. Interaction of nitrogen dioxide with soot creates heavy deviations. Secondly, the determination of PM is still unclear. Depending on chemistry of filter material (PTFE-coated glass fiber), total mass or soot determination result in non-comparable results among the various techniques. Any combination with a thermo-separation step opens the way to tremendous particle losses by early oxidation, or phoretic effects.
PMP - adequate particle counting exhibits strong dependencies on particle surface and its inner particle composition. The freely selectable pretreatment of the probed exhaust sample (catalytic stripping, volatilization and dilution) also creates ambiguities. New particle formation may happen. Calibration of these devices is still unsolved.
Currently, only on-line and in situ techniques (e.g. photoacoustics, incandescence) seem less affected by artifact formation. Filtration as sampling technique should be avoided. Thermophoretic particle sampling is proposed. Calibration remains discussable.