The gas analyzer that is not “Amazon proof”

Hello everyone, I’m Eliane Gomes-Alves. I have been working at ATTO since 2015 with measurements of plant emissions of Volatile Organic Compounds (VOC), which we can all call “the forest scent”. We measure these compounds because they play an important role in the forest-atmosphere interactions, effecting biogeochemical cycles and climate.

To sample VOC emissions, we use equipment that was originally developed to measure gas exchanges between the air and plant leaves.

It is called IRGA – infrared gas analyzer. The IRGA measures gas exchanges to calculate photosynthesis and transpiration of plants. This portable equipment has a chamber, where we can enclose the leaf. Inside, we can control the conditions, such as temperature, light, CO2 and water vapor concentrations. Then the IRGA can compare the concentration of CO2 and water vapor going in and coming out of the leaf chamber. From that the gas analyzer calculates photosynthesis and transpiration rates.

As I said, the gas analyzer was originally developed to measure CO2 and water vapor. This means that we had to make some adjustments to sample VOCs. For that, we collect a sub-sample of air that is going out of the chamber with tubes, and then take the tubes to the lab for the final chemical analysis. Here we can then identify and quantify VOCs.

Eliane measures VOC emissions of leafs with the IRGA, a gas analyzer.
Eliane measures VOC emissions of leafs with the IRGA, a gas analyzer.

Using this kind of equipment in tropical rainforests is a bit challenging. Even though the gas analyzer was designed to be portable and is field equipment, I often say that these types of equipment were developed in temperate regions. They are not “Amazon-proof”. This means that they often break or sometimes temporally stop working due to the high humidity and temperature. In these situations, we sometimes get a bit disappointed and upset.

When this happens, we have to be very creative and investigate the problem. And, in most cases, we are still in the field. There, we do not the resources of a laboratory to fix the equipment. But with a group of many brains thinking together, we have so far always managed to do our fieldwork successfully and measure many trees.