Two Decades of Regular Observations of ¹⁴CO₂ and ¹³CO₂ Content in Atmospheric Carbon Dioxide in Central Europe: Long-Term Changes of Regional Anthropogenic Fossil CO₂ Emissions

Abstract

Time series are presented of radiocarbon and 13C contents in atmospheric carbon dioxide over eastern Europe (southern Poland), covering the periods 1983–1994 and 2000–2004. The carbon isotope composition was measured in biweekly composite samples of atmospheric CO2, collected about 20 m above the local ground level. The data for 2 observational sites are presented: i) city of Kraków (50°04′N, 19°55′E; 220 m asl; for 1983–1994 and 2000–2004); and ii) Kasprowy Wierch, Tatra Mountains (49°14′N, 19°56′E; 1989 m asl; for 2000–2004). The latter site is considered a regional reference station, relatively free of anthropogenic influences. During the period 1983–1994, observations in the Kraków area revealed a gradual decrease of 14C content with a broad minimum around 1991 and a small increase by about 10% in the subsequent years. δ13C also changes with time, showing a decreasing trend from approximately −9.6% in 1983, with a slope of −0.02%/yr. The observed trends for both isotopes coincide well with a substantial reduction of coal consumption in Poland and partial replacement of coal by natural gas, especially in urban regions. After 2000, the δ13C slightly increases, reaching a mean value of −10% in 2004, while Δ14C is below the reference level by ∼3.5%. Observations at Kasprowy Wierch (regional reference station) also reflect a diminishing input of fossil carbon into the regional atmosphere. The fossil component in atmospheric CO2, calculated with the aid of 14C data available for the 2 study periods, shows a reduction of anthropogenic input by a factor of 2, which is confirmed by annual statistics of coal consumption.

Carbon Isotope Composition of Atmospheric Carbon Dioxide in Southern Poland: Imprint of Anthropogenic CO2 Emissions in Regional Biosphere

“…years 1900-2002. A distinct offset of  14 CO 2 values observed at Kraków station with respect to the European reference background curve is attributed to local emissions of CO 2 originating mostly from burning of fossil fuels within the Kraków agglomeration (Kuc et al 2007). During the 1980s, the average offset was equal to 55‰ for the annual averages and ~30‰ for the growing-season means.…”

Seasonal variability of soil CO2 flux and its carbon isotope composition in Krakow urban area, Southern Poland

“…Anthropogenic and biogenic contributions of CO 2 to an urban atmosphere were studied using several approaches, mostly involving carbon and oxygen isotopes in CO 2 [7][8][9][10][11][12]. Levin et al [8] used analyses of the 14 CO 2 content in atmospheric CO 2 samples collected weekly in a densely populated area of the Rhine valley in Germany to determine the contribution of fossil fuel-derived CO 2 to the local urban atmosphere.…”

“…Using isotope mass balance approaches, they were able to demonstrate that, apart from anthropogenic CO 2 , also a significant contribution originating from local biogenic sources is present in the investigated urban atmosphere. Kuc et al [9] used a similar approach using biweekly cumulative sampling of atmospheric CO 2 in the urban atmosphere of Krakow. They found that both concentration and isotopic composition ( 14 C/ 12 C and 13 C/ 12 C) of atmospheric CO 2 in the urban environment differ distinctly from atmospheric baseline conditions.…”

On the use of 14CO2 as a tracer for fossil fuel CO2: Quantifying uncertainties using an atmospheric transport model

“…This is strictly true in the limit that the time (and space) between background and observation goes to zero. Some authors [e.g., Riley et al, 2008;Kuc et al, 2007] have instead assumed that D 14 C of photosynthesis is equal to D obs , and in this case, equation (3) can be rewritten as…”