Back from SALTENA measurement campaign in Chacaltaya, Bolivia

10.9.2018
Our group has been involved in the Southern hemisphere high ALTitude Experiment on particle NucleAtion and growth (SALTENA) campaign at the Chacaltaya station, 5240 meters above sea level, in Bolivia.

The campaign started in December 2017 and completed in June 2018. The station is located approximately 30km away from city area of La Paz and is influenced by Amazon airmasses in wet season (December-March) and airmasses from North-West in dry season (April-November). In collaboration with multiple institutes all over the world, we have operated state-of-the-art instruments for systematic description of New Particle Formation (NPF) and Secondary Organic Aerosol (SOA) in the area.

Some of the main research questions are outlined below.

What vapours are driving the formation of new aerosol particles at Chacaltaya?

To answer that question, Atmospheric Pressure interface Time-Of-Flight (APi-TOF) was used. APi-TOF can detect the composition of small molecular cluster ions, which have been naturally charged in the atmosphere. In addition, nitrate- based Chemical Ionization APi-TOF (CI-APi-TOF) was used to measure the concentration sulfuric acid (SA) and low-volatility organic vapours (HOM, Highly Oxygenated Molecules).

George and Diego are installing CI-APi-TOF

                                      Photo credit: Qiaozhi Zha

How many aerosol particles there are at Chacaltaya and what they consist of?

To charaterise aerosol particles in more detail, we measured particle concentration and distribution from 1.5 nanometers to about 1 micron in diameter. In addition, permanent measurements at Chacaltaya could detect the naturally-charged aerosols up to 40nm in diameter.

Federico Bianchi is tuning CI-APi-TOF

Photo credit: Qiaozhi Zha

We also wanted to understand what compounds are present in small aerosol particles, are they consist of sulphates, nitrates, ammonia or organics? To do so, we used Aerosol Chemical Speciation Monitor (ACSM, provided by CNR-ISAC, Italy and University of São Paulo, Brazil), which could provide us with the information about submicron aerosol particle constituents on a time scales of few minutes.

Liine is checking the ACSM

                      Photo credit: Qiaozhi Zha

The station long-term monitoring, beside aerosol particle measurements, also included the measurements of trace gases, such as ozone, solar radiation, and meteorological parameters.

The whole measurement laboratory is seen below:

Photo credit: Diego Aliaga

Photo credit: Diego Aliaga

The campaign came to an end in June and both instruments and our researchers are back in Helsinki.

More information:

Atmospheric Physical Chemistry group website

Polar and high Altitude Nucleation Dynamics in the Atmosphere (PANDA) group website