Optical soundings of cars exhaust and urban atmosphere with laser-plasma light and open-path spectrophotometry

Optical soundings of cars’ exhaust and urban atmosphere with laser-plasma light and open-path spectrophotometry based on a Laser-Produced Plasma as the light source. The measured optical depths are numerically inverted in terms of known species, by means of the Non-negative Least-Squares (NLS) algorithm. Concentrations of major UVabsorbing species are evaluated at the tailpipe of in-use vehicles (NO, NO2, EC) and in urban atmosphere over a 200m-long optical path (O2, O3. NO2, EC, nitrates). Also, we report on the detection in both environments of an additional compound, the nanometric organic carbon (NOC), known to form in fuel-rich flames, which is not considered yet in ordinary emissions inventories. Also, the problem of dilution/dispersion of primary species is addressed, by tracking the combustion-formed CO2 at the tailpipe and in urban atmosphere.