# Stomatal and Non-Stomatal Turbulent Deposition Flux of Ozone to a Managed Peatland
## 2 Materials and Methods
### Data Analysis
#### 2.3.2 Resistance Terms and Deposition Velocity  
\(F_{O_{3}}\) was measured with the eddy covariance method as described above on the basis of high-frequency measurement of \(c_{O_{3}}\) and the vertical wind component \(w\) (Equation (1) in [24]),  
\[F_{O_{3}}=\overline{c_{O_{3}}{}^{\prime}\cdot w^{\prime}} \tag{1}\]  
where the primes describe the deviations of individual data points from the half-hour means and the overbar indicates the half-hour averages. Further, \(F_{O_{3}}\) can be expressed in terms of concentration gradients and resistance terms (Equation (4) in [24]):  
\[F_{O_{3}}=\frac{c_{O_{3}}-c_{0}}{R_{tot}}=\frac{c_{O_{3}}-c_{0}}{R_{a}+R_{b}+ R_{c}} \tag{2}\]  
Here, \(c_{O_{3}}\) is the ambient O\({}_{3}\) concentration at measurement height and \(c_{0}\) is the concentration within the sub-stomatal cavities, which can be assumed to be zero [50]. The total resistance against the O\({}_{3}\) deposition \(R_{tot}\) is equal to the sum \(R_{a}+R_{b}+R_{c}\) (Equation (2)), where the aerodynamic resistance (\(R_{a}\)) and the bulk leaf boundary layer resistance for ozone (\(R_{b}\)) are computed from ultrasonic anemometer data as (Equations (8) and (9) in [50])  
\[R_{a}=\frac{\left(\frac{\varphi_{c}}{\mathrm{i}\mathrm{e}}\right)^{2}}{u\cdot \left(\frac{\varphi_{c}}{\mathrm{i}}\right)^{2}} \tag{3}\]  
and (Equation (6) in [50])\[R_{b}=\frac{2\cdot\left(\frac{Sc}{Pr}\right)^{\frac{2}{3}}}{k\cdot u^{*}} \tag{4}\]  
Here, \(\sigma_{\mathrm{v}}\) is the standard deviation of the lateral wind component, \(u^{*}\) is the friction velocity, \(u\) is the horizontal wind velocity, \(Sc=1.07\) is the Schmidt number for ozone and \(Pr=0.72\) is the Prandtl number [51]. The surface resistance \(R_{c}\) can now be calculated from Equation (2) with \(c_{0}=0\) and by using the measured ozone flux \(F_{\mathrm{O_{3}}}\) (Equation (1)) and the ambient ozone concentration \(c_{\mathrm{O_{3}}}\):  
\[R_{c}=\frac{c_{\mathrm{O_{3}}}}{F_{\mathrm{O_{3}}}}-(R_{a}+R_{b}) \tag{5}\]  
Following the reasoning of [PERSON] et al. [25] and [PERSON] et al. [17], \(F_{\mathrm{O_{3}}}\) can be divided into \(F_{sto}\) and \(F_{nsto}\) (Equation (9) in [24]),  
\[F_{\mathrm{O_{3}}}=F_{sto}+F_{nsto} \tag{6}\]  
\(F_{sto}\) happens together with the exchange flux of CO\({}_{2}\) and H\({}_{2}\)O vapor through the plant stomata. \(F_{nsto}\) includes all other O\({}_{3}\) sinks in the vegetation including plant, water, soil surfaces, and chemical reactions. It is further presumed that the flux-resistance concept can be applied for both terms on the right-hand side of Equation (6) separately while using an ozone concentration near the surfaces \(c_{\mathrm{O_{3}}surf}\) (Equation (9) in [24]):  
\[F_{\mathrm{O_{3}}}=\frac{c_{\mathrm{O_{3}}surf}}{R_{sto}}+\frac{c_{\mathrm{O_ {3}}surf}}{R_{nsto}} \tag{7}\]  
Note that \(c_{\mathrm{O_{3}}surf}\) is not measured but will be computed as a residual once \(R_{sto}\) and \(R_{nsto}\) are known (see below, Equations (8)-(12). The surface resistance \(R_{c}\), which is known from Equation (5), can be partitioned into two resistances acting in parallel, the stomatal (\(R_{sto}\)) and the non-stomatal (\(R_{nsto}\)) resistances (Equation (9) in [21]):  
\[R_{c}=\left(\frac{1}{R_{sto}}+\frac{1}{R_{nsto}}\right)^{-1} \tag{8}\]  
To calculate the stomatal resistance of ozone, \(R_{sto}\), we use the estimate of the stomatal conductance for water vapor from the Penman-Monteith approach (\(g_{sto,PM}\)) and the molecular diffusivities for water vapor \(D_{H_{2}O}\) and ozone \(D_{\mathrm{O_{3}}}\) (Equation (4) in [11]),  
\[g_{sto,PM}=\frac{D_{\mathrm{O_{3}}}}{D_{H_{2}O}}\cdot\frac{ET\cdot\left(es_{ T_{surf}}-e_{z_{m}}\right)^{-1}}{1+ET\cdot\left(es_{T_{surf}}-e_{z_{m}} \right)^{-1}\cdot\left(R_{a}+R_{b,H_{2}O}\right)\cdot\left((\beta\cdot s\cdot \gamma^{-1})-1\right)} \tag{9}\]  
where \(\beta\) is the Bowen ratio H / ET, \(s\) is the slope of the water vapor saturation curve (Pa K\({}^{-1}\)), and \(\gamma\) is the psychrometric constant (kPa K\({}^{-1}\)).