RV Investigator Ultrafine Aerosol Volatility and Hygroscopicity (VH-TDMA) - Selected Voyages (2016 onwards)

The VHTDMA was constructed at QUT for measurement of ultrafine aerosol volatility and hygroscopicity. It uses electrostatic classifiers to select particles of a particular electrical mobility diameter, conditions them (using a thermodenuder and humidifier) and re-measures the particle diameter. The VH-TDMA is made up of three purpose built electrostatic classifiers and two condensation particle counters (CPCs). One TSI 3010 CPC and one TSI 3787 CPC.

The pre-classifier (used to select particles of a particular dry diameter) most commonly cycled between measuring 40, 100 and 150 nm diameter particles during IN2016_v02. For short periods other particle diameters were selected (20, 30, 60,80 nm), to examine features in the ambient size distribution. The thermodenuder was set to 250 °C for the majority of IN2016_v02, with short periods at other temperatures (150°C, 200°C). The relative humidity of the H-SMPS was set to 90% RH for most of the voyage, however it was periodically lowered for size calibration scans and to measure the deliquescence RH for ambient particles. The sample was passed through a nafion drier and inlet RH logged to ensure that dry particle diameter was selected i.e. RH < 30%, the efflouresence RH for common marine salts.