Organic

Sulphate

Nitrate

Ammonium

Chloride

C3 filtre du 07/07/2012

C3 filtre du 10/07/2012

Organic

Sulphate

Nitrate

Ammonium

Chloride

C3 non filtre du 04/07/2012

Organic

Sulphate

Nitrate

Ammonium

Chloride

C3 non filtre du 07/07/2012

Organic

Sulphate

Nitrate

Ammonium

Chloride

P6 non filtre du 07/07/2012

Organic

Sulphate

Nitrate

Ammonium

Chloride

Organic

Sulphate

Nitrate

Ammonium

Chloride

P6 filtre du 07/07/2012

Peaks that appear in P3 and are not detected in C3:

m/z 116, 118 140 211 230

• Labo v ambient• Pie chart/Spectum de mass des sel• Mixing atmosphere real v ambient

• Operation

• As a result of several technical problems, the VHTDMA was only operational from the 5th to the 12th of August.

• For the experiment, only particles with mobility diameters of 40 nm and 80 nm were chosen. Each scan (V-VH-H) took approximately 1 hr 30 minutes. Scanning over the two sizes results in a time resolution of 3 hrs.

The oven temperature was chosen at 120oC, this temperature was high enough to remove the most volatile organic vapours but low enough to maintain the less volatile organics (Michoud et al., 2009?).

• From a V-scan we obtain a shrink factor (SF), indicating how much volatile mass the aerosol has lost after being exposed to 120oC.

• A H-scan provides us with a growth factor (GF), indicating how much an aerosol particle has increased in size after being exposed to 90% humidity.

• A VH-can provides us with a growth factor (GF), indicating how much an aerosol, that has passed through the oven and the humidifer, has increased in size. This GF is corrected (GF-corr) using the measured SF.

• Observations

• Fig.1 shows the GF (blue), the SF (red), and the GF-corr (orange). We observe two periods circled in red where the GF-corr is either significantly lower than the GF (6th of July 2012) or the GF-corr is higher than the GF (11th of July 2012). This suggests that the volatile coating on the aerosol was more hygroscopic, than during other periods. The SF is never less than 0.9 which shows that there was not a significant quantity of mass removed after the oven.

• A third type of observation is made on the 9th of July 2012, where we observe additional aerosol modes appearing after the aerosol is exposed to high temperatures in the oven. This might be evidence of an internally mixed aerosol (e.g seasalt and ammonium sulphate) coated with an organic material that inhibits the GF of the aerosol. After the coating is removed we can measure the growth factors of the separate aerosols