UV/Near-IR Aerosol Absorption Monitor

Light-absorbing aerosols can influence the global radiation budget and thermodynamic balance of the planet by reducing the amount of sunlight reaching the surface and heating their surroundings- At present, most aerosol absorption measurement techniques collect the airborne samples on a filter substrate and then measure light attenuation due to the collected samples- The filter-based methods usually need various corrections to account for changes in the filter properties due to particle deposit, which could significantly influence the accuracy of the aerosol absorption measurement- In addition to carbonaceous substances such as black carbons, many ambient aerosols also contains a class of light-absorbing organic carbon species, which have a brownish or yellowish appearance and are usually called brown carbons- Absorption by brown carbons is normally weak at visible wavelengths but increases significantly towardsUV- We propose to develop a highly sensitive and real-time optical measurement system to monitor aerosol light absorption at 360nm and 1064nm simultaneously- This approach will use our newly patented differential photoacoustic technique (DPAS) [U-S- Patent No- 9696283], which takes advantages of the rapid developments on MEMS microphone, diode-pumped solid state laser, and conductive thin-film coating techniques- It eliminates the interferences from gaseous absorbing species such as NO2 and O3- In the visible region, the DPAS instrument has achieved a detection limit of 0-35 Mm-1 in 10s and 0-12 Mm-1 in 100s data acquisition-