# Urban CO2 Budget: Spatial and Seasonal Variability of CO2 Emissions in Krakow, Poland
## 2 Methods
### Study Site
Sites characteristics are presented in Table 1.  
Three sites have been selected along the Vistula to measure CO\({}_{2}\) flux from the water column: (i) site R1, upon the entrance of the river to the city; (ii) site R2, close to the city center; and (iii) site R3, at the outflow from the city, downstream of the discharge points of municipal wastewater treatment plants (Figure 2). Regular CO\({}_{2}\) flux measurements have been performed at those three sites in the course of one year (2011-2012), in approximately monthly time intervals. Apart of CO\({}_{2}\) flux, selected physico-chemical parameters of water have been determined (temperature, pH, conductivity, alkalinity) for the calculation of CO\({}_{2}\) content in the river. Site characteristics are presented in Table 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Site**} & \multicolumn{2}{c}{**Urban Local**} & \multirow{2}{*}{**Soil Type 2**} & \multicolumn{2}{c}{**Vegetation**} & \multirow{2}{*}{**pH 3**} & \multicolumn{2}{c}{**Volumetric**} & \multirow{2}{*}{**Carbon Content**} \\  & **Climate Zone 1** & & & **Maintenance** & & & **Porosity 4** & **4 [wt.\%]** \\ \hline S1 & LCZ 2 & Urbisols & Regularly cut during vegetation period & 7.6 & 0.50 & 3.4 \\ S2 & LCZ D & Cambic & Cut upon reaching 20–30 cm in height & 7.0 & 0.51 & 3.7 \\ S3 & LCZ B & Technosols & Regularly cut during vegetation period & 7.7 & 0.50 & 2.3 \\ S4 & LCZ 6 & Hortisols & Regularly cut during vegetation period & 7.9 & 0.37 & 0.5 \\ \hline \hline \end{tabular} \({}^{1}\) According to [19]. 2 According to [20]. 3 Averaged over 0–15 cm depth. 4 Averaged over 0–5 cm depth.  
\end{table} 
Table 1: Characteristics of soil CO\({}_{2}\) flux measurement sites. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Site**} & \multicolumn{2}{c}{**Channel**} & \multirow{2}{*}{**Temperature**} & \multirow{2}{*}{**pH**} & \multicolumn{2}{c}{**Conductivity**} & \multirow{2}{*}{**Alkalinity**} & \multirow{2}{*}{**pCO\({}_{2}\) 1**} \\  & & & [\({}^{\circ}\)C] & & & [mS cm\({}^{-1}\)] & & [meg/L] \\ \hline R1 & 90 & 1.9–29.1 & 7.5–7.9 & 1.34–5.69 & 1.54–3.46 & 1267–5052 \\ R2 & 110 & 1.9–26.4 & 7.5–7.9 & 1.28–4.39 & 1.64–3.85 & 1132–5446 \\ R3 & 70 & 3.3–26.0 & 7.5–7.9 & 1.38–4.20 & 1.76–3.81 & 1271–5072 \\ \hline \hline \end{tabular} \({}^{1}\) CO\({}_{2}\) partial pressure in the surface layer of the water derived from alkalinity, temperature, and pH.  
\end{table} 
Table 2: Characteristics of riverine CO\({}_{2}\) flux measurement sites. Figure 2: CO\({}_{2}\) flux measurement locations in Krakow: soil chamber sites S1–S4 marked in green, riverine sites R1–R3 marked in blue, and relaxed eddy accumulation(REA-AGH) site marked in red. Arrow indicates river flow direction; black triangles indicate inflows of treated municipal wastewater effluents to the river (map source: Google Maps; modified). The REA-AGH net CO\({}_{2}\) flux measurement site was located within university campus near the city center (Figure 2). Various elements of the urban environment can be identified within 500 m of the site, including traffic routes, built-up areas, and the park, where one of the chamber measurement sites was located. The university campus is located west and east of the site. The area south of the site is mainly green, with the public park and a city stadium, but also with minor traffic routes. North of the site, numerous four- to six-stories household blocks are located. Approximately 115 m north, a busy and often jammed traffic intersection is located. In total, within 500 m of the measurement site, built-up, or otherwise transformed areas comprised 41% of the total area, low-rise green (i.e., lawns) 18%, high-rise green (i.e., trees and bushes) 34%, and roads 6%.