Gas monitoring
With our gas monitoring systems, we enable continuous monitoring and measurement of the concentration of gaseous substances in soil, air or other environments. A prerequisite for the analysis of gases is the detection of these gases so that they can be fed into an analyzer. We focus on the detection of soil-borne gases and the gas exchange between soil, plants and the atmosphere.
Our products
Things to know about soil-borne gases
Soil-borne gases play a crucial role in the global climate system and include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). These gases are produced by numerous, complex and non-linear biological, chemical and ecological processes in the soil. The release of these gases can provide valuable information about soil processes, ecosystem health and the impact of human activities.
By precisely measuring and analyzing soil-borne gases, scientists can better understand the dynamics of the carbon and nitrogen cycles. For example, measuring the release of CO2 from the soil into the atmosphere provides information about soil respiration. This process is driven by the activity of microorganisms and plant roots in the soil that break down organic substances. Comparative studies between different soil substrates, plant populations and climates can help to develop measures to reduce greenhouse gas emissions.
Such gas flows can be recorded both in the field and experimentally in the laboratory. Our products for gas monitoring enable precise measurements of soil-borne gases and provide valuable data for ecological and climatic studies.
Detection of gas flows outdoors with gas measuring chambers
Types of gas measuring chambers
Gas flows can be recorded in various ways. Gas measuring chambers have proven to be a good reference method, which either generate a controlled gradient (open systems) or which prevent the exchange with the free atmosphere over a short or longer period of time (closed systems).
On our website you will find various types of gas measuring chambers that form a closed system. We are happy to manufacture gas measuring chambers as open systems on request.
Open dynamic gas measuring chambers allow the exchange of gases across the upper edge. They are also referred to as "steady-state, through flow systems". In the steady-state, the properties in the system remain constant during the measurement period, although processes continue to take place. This means that fluxes, concentrations and exchange processes of gases between soil and atmosphere do not change during the measurement period. As the gas measuring chambers are open at the top, a gradient is created from the soil to the atmosphere, which provides a measuring path. The differences in concentration along this path can be used to determine the flow rates (gradient measurement). The top opening also ensures that the plants are affected as little as possible and that the temperature and gas composition hardly differ from the surroundings. Please note that open gas measuring chambers should only be used in windless measuring locations.
Closed gas measuring chambers make it possible to observe the enrichment or depletion of gas components over a period of time because they temporarily prevent the air in the sample chamber from exchanging with the atmosphere. The term "non-steady-state" is used. The properties in the system change over time, which leads to temporally variable fluxes, concentrations and exchange processes of gases between soil and atmosphere. Through the accumulation of soil-borne gases in the closed measuring chamber, the concentration of gas components with low concentrations can be increased to such an extent that these can also be measured.
Closed "non-steady-state" gas measuring chambers can be differentiated into:
- "closed static chambers" or "non-steady-state, non-through-flow systems"
- "closed dynamic chambers" or "non-steady-state, through-flow systems"
Livingston, G. P. and Hutchinson, G. L.: Enclosure-based measurement of trace gas exchange: applications and sources of error, in: Methods in Ecology. Biogenic Trace Gases: Measuring Emissions from Soil and Water, edited by: Matson, P. A. and Harris, R. C., Blackwell Science, Oxford, UK, 14–51, 1995.
Closed "non-steady-state" gas measuring chambers can be differentiated into:
- "closed static chambers" or "non-steady-state, non-through-flow systems"
- "closed dynamic chambers" or "non-steady-state, through-flow systems"
Non-though flow systems are non-recirculating systems (open path) in which gas is extracted by a gas analyzer and a pump connected behind it and the exhaust air is released into the environment. This creates a negative pressure in the chamber, which rises as the extraction volume increases. This increases the risk of unwanted soil gases being sucked into the chamber from the soil. This means that the larger the chamber, the more gas volume can be extracted without measurement errors due to the negative pressure becoming relevant.
Through-flow systems are a recirculating system (closed path, loop system) in which the resulting pressure differences during gas extraction are compensated for by recirculating the exhaust air behind the gas analyzer back into the chamber. The advantage of this method is that there is no negative pressure in the chamber, but these systems must be very tight, especially for longer measurements. To compensate for (thermal) pressure differences in the chamber during measurements, it is possible to use a diffusion tube.
The compensation of (thermal) pressure differences during the measurement in the "through-flow system" must be distinguished from the compensation of pressure differences during the lowering of closed chamber onto the soil by means of a pressure compensation hose or valve.
Livingston, G. P. and Hutchinson, G. L.: Enclosure-based measurement of trace gas exchange: applications and sources of error, in: Methods in Ecology. Biogenic Trace Gases: Measuring Emissions from Soil and Water, edited by: Matson, P. A. and Harris, R. C., Blackwell Science, Oxford, UK, 14–51, 1995.
Depending on the size and application, our closed gas measuring chambers are available as small portable versions or larger stationary / fixed or mobile gas measuring chambers. We offer our mobile systems with manual or automatic movement.
Gas measuring chambers can be made of transparent or opaque material. When transparent material is used, the net ecosystem exchange (NEE) is measured. Net Ecosystem Exchange (NEE) is a measure of the total flux of carbon dioxide (CO2) between an ecosystem and the atmosphere. It is calculated as the difference between CO2 uptake (primarily through photosynthesis, gross primary production GPP) and CO2 release (through respiration by plants, animals and microorganisms as well as through decomposition processes, ecosystem and soil respiration). If only the proportion of soil or dark respiration (ecosystem and soil respiration) is the focus of the investigations, then opaque gas measuring chambers should be used.
Tips for successful gas monitoring with gas measuring chambers
General requirements
Before deciding on a gas measuring chambers, you should precisely define the intended use and your requirements. Take the following points into account:
- Use a standardized measurement procedure.
- Carry out correct and reproducible sampling. This also includes the use of suitable measuring devices and sampling points.
- Ensure that external influences are minimized as much as possible during the measurement. Stable ambient conditions, in particular temperature, humidity or air currents, should prevail during a measurement in the gas measuring chambers.
- Closed gas measuring chambers can cause pressure anomalies when the gas measuring chambers are placed on the soil. Use pressure equalization hoses or valves. Due to the enrichment of gases in closed gas measuring chambers, you should carry out a detailed interpretation of the measurement data in relation to "Brownian motion".
- Ensure complete air exchange under the gas measuring chambers after each measurement, otherwise there is a risk of carry-over of subsequent measurements and distortion of the measurement results.
Requirements for the gas measuring chambers
- Robust construction, including durable material
- Appropriate size and shape depending on the application: efficient detection of gases while ensuring sufficient air circulation (ventilation of the gas measuring chambers)
- Easy installation and handling
- Easy ventilation after each measurement
- Compatibility with various types of gas analyzers, flow meters or other sensor technology
- Integrated seals (gas-tight gas measuring chambers for accurate measurements)
- Easy to clean
We ensure that our gas measuring chambers meet these specific requirements, taking your individual needs and wishes into account.
Sampling of soil-borne gases at different depths
Soil air lances and substrate lances
Sampling of soil-borne gases at different depths is possible using special soil air lances or substrate lances. The lances are inserted into the soil and allow soil gases to be sampled from the desired depths.
The soil air lances can be used to carry out continuous sampling in the field as well as to take discrete samples for analysis in the laboratory.
The substrate lances were developed for depth-graded field measurement of air permeability and pore gas composition in loose substrates.
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