Nanoparticle air pollution in major cities and its origin

Suspended particles with a diameter below 1 mu m act as vehicles transporti ng toxic chemicals into the human respiratory system. It is therefore of in terest to record the intensity of these particles and to determine the sour ce from which they were emitted. It is shown that this can be done by simul taneously measuring the light scattering (LS), the photoelectric charging ( PC), and the diffusion charging (DC). Particles carrying polycyclic aromati c hydrocarbons (PPAH) are detected by their large PC and are generated in c ombustion of organic materials whereas particles from other sources only ex hibit LS and DC. The fraction of particle mass due to PPAH is independent o f location and weather conditions. As an example of an application, we stud y the nanoscale particles found on motorways in or near various large citie s. The sources of the majority of these particles are Diesel motors or cars with defect catalysts. Promising strategies for improving the air quality emerge from these observations. (C) 1999 Elsevier Science Ltd. All rights r eserved.