Twin-cuvette measurement technique for investigation of dry deposition of O<sub>3</sub> and PAN to plant leaves under controlled humidity conditions

Abstract

Abstract. 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 −1 ), 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 3 ) and peroxyacetyl nitrate (PAN), were used to demonstrate the quality and performance of the twin-cuvette system. O 3 and PAN exchange with Quercus ilex was investigated over a 14 day measurement period under controlled climate chamber conditions. By using O 3 mixing ratios between 32 and 105 ppb and PAN mixing ratios between 100 and 350 ppt, a linear dependency of the O 3 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 3 and PAN was determined to be 0.45. At that humidity, the deposition of O 3 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.

Monoterpene chemical speciation in a tropical rainforest:variation with season, height, and time of dayat the Amazon Tall Tower Observatory (ATTO)

“…The latter also involves a potentially important role in the deposition to wet leaf surfaces (the inferred wet surface uptake resistances for the monoterpenes are ∼ 300 s m −1 , similar to values reported by Zhou et al (2017)); the MLC-CHEM uses relative humidity as a proxy for the fraction of the leaf surface being wet (Lammel, 1999;Sun et al, 2016). This results in substantially smaller estimates of canopy wetness on 17 October compared to the following days, which partly explains the simulated high α-pinene mixing ratios.…”

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

“…A widely used assumption is that reactions inside the leaf do not limit stomatal ozone uptake (i.e., negligible r meso ). While some laboratory studies (Laisk et al, 1989;Omasa et al, 2000;S. Sun, Moravek, von der Heyden, et al, 2016;Wang et al, 1995) and the modeling study of Plöchl et al (2000) suggest this assumption holds, the findings of other laboratory studies and the modeling study of Tuzet et al (2011) suggest otherwise.…”

“…Capturing unexpected variability with ozone flux records allows the community to build hypotheses about controlling processes, target laboratory and field measurements (Altimir et al, 2006;Fumagalli et al, 2016;Pleijel et al, 1995;Potier et al, 2017;S. Sun, Moravek, Trebs, et al, 2016;S. Sun, Moravek, von der Heyden, et al, 2016) and build mechanistic models (e.g., Potier et al, 2015).…”

“…Cuticular ozone fluxes are shown as a function of relative humidity (RH). Error bars represent the random error calculated according to S Sun, Moravek, von der Heyden, et al (2016)…”

Investigation of the influence of liquid surface films on O3 and PAN deposition to plant leaves coated with organic/inorganic solution

“…; Teklemariam and Sparks ; Sun et al . ]. However, nonstomatal deposition of PAN to the leaf cuticles is still a strong matter of discussion [ Turnipseed et al ., ; Wolfe et al ., ; Moravek et al ., ], which demonstrates the needs to investigate PAN exchange with vegetation as it is still poorly understood.…”