Vehicular particulate emissions and roadside air pollution

The composition of locally generated particulate emissions from vehicles has been assessed by comparison of two sampling sites, one adjacent to a main road and another on the same building but at an elevated level. The differences of the concentrations in the simultaneous samples were taken to represent the vehicle emissions. Total particle mass, black smoke, sulphur dioxide, lead and particulate sulphate were measured. Roadside enhancements of nitrate, chloride, iron and zinc have also been demonstrated. Using multiple regression analysis the use of black smoke and sulphur as tracers for diesel emissions and lead as a tracer for spark ignition emissions was investigated in an attempt to apportion the contributions to the total vehicular emissions to the two engine types. Although the results confirm the general expectation that smoke and sulphur originate mainly from diesel engines the spark ignition contributions to the concentrations of these species at the roadside are not negligible. This is because there are many more spark ignition vehicles (92%) at our site than diesels (8%).