Volatile organic compound concentration in the air is small. Their proportional presence in the air volume is about milliard parts (ppb) when CO2 concentration is about million parts (ppm). It is very difficult to study VOCs since the instruments require high accuracy and VOCs are also reactive compounds in the air. In certain situations like in forest after rain and wood loggings, we can detect these compounds in air simply through smell. The accurate characterization and amount determination is not possible without high technical tools. We can take sample into canister or inside the sample tube (adsorbent tubes) and it can be analyzed in the laboratory with gas-chromatograph (GC) mass-spectrometry (MS). GC separates compounds and MS detects exact amount of these compounds based on mass to charge ratio.
The methodological range is large since the amount of different compounds released by soil or plants is large. Continues measurements can be executed with proton-transfer-reaction mass-spectrometry (PTR-MS) since this instrument has high accuracy and sensitivity. We can take sample from the chamber which is air tided and closed around a shoot. Air can be circulate from the chamber into the adsorbent tube and back to the chamber and this tube includes compounds which will absorb inside the tube. We have placed chamber also on the ground and they measure soil and ground vegetation emissions from the forest floor. We can measure the concentration difference with dynamic and automated measurement and manual sampling with certain measurement period.
We can also determined the VOC flux with soil gradient measurements. We can determined the soil flux by using diffusion based model, where we can observe how flux is proceeding the soil driven by concentration differences between different soil horizons. We can measure concentration in soil from gas collectors placed into soil.
At the larger scale we can analyze volatile organic compound emissions with micrometreological methods (including eddy covariance and gradient method). Depending on the used method, we can analyze the amount of volatile organic compound and separate the masses of individual compounds.