“In situ CO2” refers to the direct measurement of carbon dioxide in its natural location. The Latin phrase “in situ” means “in place,” signifying that analysis occurs where the gas is found, rather than by collecting a sample for later lab evaluation. This approach provides a continuous stream of data, capturing real-time fluctuations within an environment. Measuring CO2 directly allows scientists to observe immediate changes without the delays or potential alterations from sample transport.
Methods for In Situ CO2 Measurement
A prevalent technology for on-site CO2 measurement is the Non-Dispersive Infrared (NDIR) sensor. It works by passing infrared light through an air sample. A specific wavelength of this light is absorbed by CO2 molecules, so the more CO2 present, the less light reaches the detector. This reduction in light intensity is correlated to the CO2 concentration.
For higher precision, Tunable Diode Laser Absorption Spectroscopy (TDLAS) is used. This method uses a laser tuned to a wavelength uniquely absorbed by carbon dioxide. By measuring the amount of absorbed laser light, TDLAS provides highly accurate and sensitive CO2 readings, distinguishing it from other gases.
Other methods involve direct chemical interactions. Some sensors are coated with materials that change their optical or electrical properties upon contact with CO2. These changes, like a shift in color or electrical resistance, are measured and converted into a concentration reading. The sensors can be integrated into probes for deployment in various environments, such as soil or water.
Environmental and Ecological Applications
In situ CO2 measurements help in understanding terrestrial ecosystems. Scientists use probes to measure CO2 concentrations directly in the soil, which reveals the rate of soil respiration from microorganisms and plant roots. Tracking this activity provides insights into soil health, nutrient cycling, and an ecosystem’s carbon balance.
Oceanography uses in situ CO2 data to monitor climate change impacts. Probes on buoys, gliders, or vessels measure CO2 dissolved in seawater. These measurements are for tracking ocean acidification, as more atmospheric CO2 dissolves and lowers the water’s pH. This monitoring helps assess stress on marine organisms like corals and plankton.
Atmospheric monitoring stations in locations like forests or near volcanoes use in situ sensors to track CO2 fluxes. A forest station can determine if the ecosystem is a carbon sink or source. Near a volcano, sensors provide data on geological emissions. This information helps refine global carbon models and understand the contributions of natural systems to atmospheric CO2.
Geological Carbon Sequestration Monitoring
In situ CO2 measurement is applied in geological carbon sequestration, a part of Carbon Capture and Storage (CCS) strategies. This process involves capturing industrial CO2 emissions and injecting them into deep underground formations like saline aquifers for long-term storage.
To ensure safety, arrays of in situ CO2 sensors are deployed in injection wells and the surrounding area, including groundwater aquifers and the soil surface. These sensors continuously measure CO2 concentrations to track the underground plume of the injected gas.
This real-time data provides an early warning system for safety. An unexpected increase in CO2 levels far from the injection site could indicate a leak, allowing for rapid response. The measurements also help validate models of the CO2 plume’s behavior, confirming the gas is securely trapped.
Planetary and Industrial Process Monitoring
The application of in situ CO2 measurement extends to planetary exploration. NASA’s Mars rovers, like Curiosity and Perseverance, have instruments to measure carbon dioxide directly in the Martian atmosphere. These measurements help in understanding Mars’s climate, atmospheric pressure cycles, and surface-shaping processes.
In situ CO2 sensors also have industrial uses. In greenhouses, they monitor and control CO2 levels to optimize plant growth and enhance crop yields. They are also used in bioreactors to maintain precise CO2 concentrations for cultivating algae or yeast. The food packaging industry uses this technology to monitor gases inside packaging to extend shelf life.