• Changes of the CO2 Sources and Sinks in a Polluted Urban Area (Southern Poland) Over the Last Decade, Derived from the Carbon Isotope Composition

      Kuc, Tadeusz; Zimnoch, Mirosław (Department of Geosciences, The University of Arizona, 1998-01-01)
      Time series of Delta-14C, delta-13C, and concentration of atmospheric CO2 covering the last 12 years are available at the Krakow sampling site (southern Poland) representing an urban area exposed to anthropogenic pollution of both local and regional origin. The samples represent continuous monitoring in biweekly intervals. Observations covering the time period 1983-1994 show a linear decrease of the 13C/12C ratio (delta-13C = -9.6 per mil in Jan. 1983) with a slope of -0.02 per mil a-1. The decreasing tendency in the case of 14C (Delta-14C = 227 per mil in January 1983) is weaker with a broad minimum in 1991 (Delta-14C = 124 per mil) and subsequent gradual increase by ca. 10 per mil, coinciding with a substantial reduction of coal consumption in Poland (26% reduction in 1991-1994 for heat and electricity production), partly compensated in agglomerations by increased gas consumption. The 12-year record of the CO2 concentration in Krakow points to a constant value fluctuating at a high level (average: 373 ppmv) reaching a maximum yearly average of 376 ppmv. These carbon isotope signatures were used for the separation of fossils from biogenic and "background" components, reflecting the strength of relevant sources. The monthly mean of the fossil component varies from ca. 10 ppmv in June to 27.5 ppmv in March while the yearly mean decreased ca. 16 ppmv since 1991.