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 for 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 to 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) such a temperature regulated humidification system 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 (O3) and peroxyacetyl nitrate (PAN), were used to demonstrate the quality and performance of the twin-cuvette system. O3 and PAN exchange with Quercus ilex was investigated over a 14 day measurement period under controlled climate chamber conditions. By using O3 mixing ratios between 32–105 ppb and PAN mixing ratios between 100–350 ppt a linear dependency of the O3 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 O3 and PAN was determined to be 0.45. At that humidity, the deposition of O3 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.

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, ; Omasa et al, ; S. Sun, Moravek, von der Heyden, et al, ; Wang et al, ) and the modeling study of Plöchl et al () suggest this assumption holds, the findings of other laboratory studies and the modeling study of Tuzet et al () suggest otherwise. In particular, laboratory findings of nonlinear relationships between stomatal uptake of water vapor and stomatal uptake of ozone (Eller & Sparks, ; Fares et al, ; Fares, Park, et al, ; Loreto & Fares, ; Tuzet et al, ) may imply nonnegligible resistance to ozone reaction inside the leaf.…”

“…Unconstrained variations in ozone dry deposition challenge the ability to attribute changes in tropospheric ozone to other processes (e.g., sources) accurately. Capturing unexpected variability with ozone flux records allows the community to build hypotheses about controlling processes, target laboratory and field measurements (Altimir et al, ; Fuentes & Gillespie, ; Fumagalli et al, ; Pleijel et al, ; Potier et al, ; S. Sun, Moravek, Trebs, et al, ; S. Sun, Moravek, von der Heyden, et al, ) and build mechanistic models (e.g., Potier et al, ).…”

“…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 (). Figure is adapted from Figure 6 of S. Sun, Moravek, Trebs, et al () with permission.…”

Spatiotemporal Controls on Observed Daytime Ozone Deposition Velocity Over Northeastern U.S. Forests During Summer

“…Laboratory and field measurements that isolate nonstomatal pathways advance fundamental process‐level understanding (Cape et al, ; Fares et al, ; Fuentes & Gillespie, ; Fumagalli et al, ; Potier et al, ; von der Heyden, et al, ; Sun, Moravek, Trebs, et al, ) but are limited in constraining the relative importance of a specific deposition pathway at the ecosystem scale (i.e., what is measured through eddy covariance [EC] above the canopy). Interpreting ozone EC measurements relies on observation‐driven modeling for resistances to turbulence, molecular diffusion, and individual deposition pathways (Altimir et al, ; Clifton et al, ; Lamaud et al, ; Launiainen et al, ; Rannik et al, ).…”

Environmental Evaluation of Soil Salinity with Various Watering Technologies Assessment

“…The harmful properties of salts are less developed in clay soils than in sandy soils, since the water capacity of clay soils is greater than that of sandy soils, which is why the salt concentration is lower. Another impact factor is air humidity: with a decrease in the humidity level, the transpiration of plants reduces and, consequently, the plants' water supply reduces as well (Sun et al, 2016). Soil salinization can occur in different ways.…”