Exchange fluxes of NO₂ and O₃ at soil and leaf surfaces in an Amazonian rain forest

Abstract

[1] Trace gas exchange of NO 2 and O 3 at the soil surface of the primary rain forest in Reserva Biológica Jarú (Rondônia, Brazil) was investigated by chamber and gradient methods. The ground resistance to NO 2 and O 3 deposition to soil was quantified for dry and wet surface conditions using dynamic chambers and was found to be fairly constant at 340 ± 110 and 190 ± 70 s m À1 , respectively. For clear-sky conditions, the thermal stratification of the air in the first meter from the forest floor was stable during daytime and unstable during nighttime. The aerodynamic resistance to NO 2 and O 3 deposition to the ground in the first meter above the forest floor was determined by measurements of 220 Rn and CO 2 concentration gradients and CO 2 surface fluxes. The aerodynamic resistance of the 1-m layer above the ground was 1700 s m À1 during daytime and 600 s m À1 during nighttime. The deposition flux of O 3 and NO 2 was quantified for clear-sky conditions from the measured concentrations and the quantified resistances. For both trace gases, deposition to the soil was generally observed. The O 3 deposition flux to the soil was only significantly different from zero during daytime. The maximum of À1.2 nmol m À2 s À1 was observed at about 1800 and the mean daytime flux was À0.5 nmol m À2 s À1 . The mean NO 2 deposition flux during daytime was À1.6 ng N m À2 s À1 and during nighttime À2.2 ng N m À2 s À1 . The NO x budget at the soil surface yielded net emission day and night. The NO 2 deposition flux was 74% of the soil NO emission flux during nighttime and 34% during daytime. The plant uptake of NO 2 and O 3 by the leaves of Laetia corymbulosa and Pouteria glomerata, two typical plant species for the Amazon rain forest, was investigated in a greenhouse in Oldenburg (Germany) using branch cuvettes. The uptake of O 3 was found to be completely under stomatal control. The uptake of NO 2 was also controlled by the stomatal resistance but an additional mesophyll resistance of the same order of magnitude as the stomatal resistance was necessary to explain the observed uptake rate.

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

“…All tubing and tubing connections that were in contact with the air flow consisted of PFA-Teflon ® (Swagelok, USA). A fan (APC Propellers, USA), which had been coated with Teflon ® by the MPIC mechanical workshop, was installed inside both cuvettes to assure well-mixed conditions in order to reduce the aerodynamic resistance for the trace gas fluxes (Gut et al, 2002). The purified air stream supplied with a certain mixing ratio of O 3 and PAN reached the inner cuvette through the inlet PFA-tube (see Fig.…”

Seasonal variation of ozone deposition to a tropical rain forest in southwest Amazonia

“…In a greenhouse experiment by Gut et al (2002b) young tropical tree species showed substantial leaf damage (S. Rottenberger, personal communication) after a few days of O 3 fumigation (daytime maximum values of ∼60 ppb). On the other hand, it was recognized, e.g.…”

“…It was estimated on the basis of measurements by Gut et al (2002b), which were performed simultaneously with our flux measurements. D S (z) is the actual deposition to plant surfaces.…”

“…Possible pathways are (i) the deposition to the ground surface and (ii) to outer plant surfaces (leaves' cuticles, bark) as well as (iii) the chemical loss due to reaction with NO (Reaction R3). The first mechanism was quantified by Gut et al (2002b) and is included in Figs. 8c and d. Its effect is very small during both seasons and does not significantly contribute to the observed nighttime deposition.…”

Influence of meteorology and anthropogenic pollution on chemical flux divergence of the NO–NO<sub>2</sub>–O<sub>3</sub> triad above and within a natural grassland canopy

“…It is defined as the time at which the mixing ratio of one of the compounds significantly changes from its initial value when reacting with the other ones. It can also be seen as the time required for reaching a new photostationary state following a change in O 3 , NO or NO 2 mixing ratios, or the reaction rate constants j NO 2 and k 3 (see Ganzeveld et al, 2012 The data gaps in the measured time series of j NO 2 (in s −1 ) above the canopy were filled using the parameterization of j NO 2 as a function of G (in W m −2 ) by Trebs et al (2009). This approach was also used to parameterize in-canopy j NO 2 from a vertical in-canopy profile of G. The latter was calculated as a function of the LAI profile using the method of Monsi and Saeki (1953):…”