Atmospheeric Aerosol Measurements by Cavity Ringdown Turbidimetry

摘要

We have investigated monitoring th e ambient air extinction co-efficient as a sensitive indicator of micrometer sized airborne particles through cavity ringdown spectroscopy(CRDS) at 2 wave-lengths.Scatter and absorption of light by the airborne particles induced a measureabledecrease in the ringdown decay time of our ringdown cell.When a copper vapor laser operating at 8-10 Khz was employed an d1,500 individual ringdowns were averaged on an oscilloscope,minimal detectale extinction coefficients of 10~-6 m~-1 could be could be achieved.We have used our ringdown instrument to detect a correlation between the observed ringdown extinction coefficient and particulate mass concentrations (mug/m~3 ofair).The correlation we have oserved allows estimation of suspended mass concentrations in a matter of minutes,rather than a sampling time of several Additionally,we hae constructed a variable cut diameter inertial diametr while making ringdown system.By varying the cut diameter while making ringdown measurements,it was possible to extract a size resolved extinction spectrum of ambient atmospheric aerosol in a matter of minutes.