Open-path cell for online measurement of atmospheric H2O and CO2 fluxes

According to a study published in fast opticsA research team from the Hefei Institute of Physical Sciences of the Chinese Academy of Sciences has proposed a new design for online measurement of atmospheric H.₂O and CO₂ flux.

“We designed an open and pollution-resistant multipath cell, and applied it on a tunable diode laser absorption spectrophotometer sensor,” said Professor Gao Xiaoming, who led the research team. correction (TDLAS)”.

The new gas analyzer exhibits good consistency with commercial instruments and its accuracy is comparable.

One of the most important ways to reduce greenhouse gas concentration is to store carbon in soil and vegetation. Scientists propose to use turbulent vortices created by airflow to measure greenhouse gas emissions.

The instrument based on tunable laser absorption spectroscopy combined with vortex covariance technology has many advantages including high sensitivity, high precision and fast response. There are two airway methods for measuring air flow: open path and closed path. However, the traditional open multipath cell is not suitable because its optical path is exposed to the air, causing the coating of the lens to corrode in the atmosphere.

Different from the traditional multi-path cells, this new anti-pollution open multi-path cell mainly consists of two planar-convex mirrors coated on a convex surface.

“It’s covered on the back,” Gao said. “The design does not allow direct contact between the lens coating and the air, which is why it is anti-pollution.”

This design effectively avoids contamination and corrosion of the lens film by the external environment. When it is applied to atmospheric CO flux monitoring equipment₂ and THEY₂O, the long-term stability and durability of the open path system are improved.

The design was further demonstrated in a field comparative observation experiment on CO .₂ and THEY₂O flux of the cropland ecosystem according to the wheat season. The results are in good agreement with those obtained using commercial equipment based on non-dispersive infrared.

“We see strong application prospects for flush measurements in any ecosystem,” said Gao.