Twin-cuvette measurement technique for investigation of dry deposition of O<sub>3</sub> and PAN to plant leaves under controlled humidity conditions
We present a dynamic twin-cuvette system for quantifying the trace-gas exchange fluxes between plants and the atmosphere under controlled temperature, light, and humidity conditions. Compared with a single-cuvette system, the twin-cuvette system is insensitive to disturbing background effects such a...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-02-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/9/599/2016/amt-9-599-2016.pdf |
| Summary: | We present a dynamic twin-cuvette system for quantifying the trace-gas
exchange fluxes between plants and the atmosphere under controlled
temperature, light, and humidity conditions. Compared with a single-cuvette
system, the twin-cuvette system is insensitive to disturbing background
effects such as wall deposition. In combination with a climate chamber, we
can perform flux measurements under constant and controllable environmental
conditions. With an Automatic Temperature Regulated Air Humidification
System (ATRAHS), we are able to regulate the relative humidity inside both
cuvettes between 40 and 90 % with a high precision of 0.3 %. Thus,
we could demonstrate that for a cuvette system operated with a high flow
rate (> 20 L min<sup>−1</sup>), a temperature-regulated
humidification system such as ATRAHS is an accurate method for air humidification of the flushing air. Furthermore, the fully automatic progressive fill-up of ATRAHS based on a floating valve improved the performance of the entire measurement system and prevented data gaps. Two reactive gas species, ozone (O<sub>3</sub>) and peroxyacetyl nitrate (PAN), were used to demonstrate the quality and performance of the twin-cuvette system. O<sub>3</sub> and PAN exchange
with <i>Quercus ilex</i> was investigated over a 14 day measurement period under controlled climate chamber conditions. By using O<sub>3</sub> mixing ratios between 32 and 105 ppb and PAN mixing ratios between 100 and 350 ppt, a linear dependency of the O<sub>3</sub> flux as well as the PAN flux in relation to its ambient mixing ratio could be observed. At relative humidity (RH) of 40 %, the deposition velocity ratio of O<sub>3</sub> and PAN was determined to be 0.45. At that humidity, the deposition of O<sub>3</sub> to the plant leaves was found to be only controlled by the leaf stomata. For PAN, an additional resistance inhibited the uptake of PAN by the leaves. Furthermore, the formation of water films on the leaf surface of plants inside the chamber could be continuously tracked with our custom built leaf wetness sensors. Using this modified leaf wetness sensor measuring the electrical surface conductance on the leaves, an exponential relationship between the ambient humidity and the electrical surface conductance could be determined. |
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| ISSN: | 1867-1381 1867-8548 |