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

Abstract

ABSTRACT. Time series of 6140, 613C, 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 13(/12( ratio (613C = -9.6%o in Jan. 1983) with a slope of -0.02% a'1. The decreasing tendency in the case of 14C (614C = 227% in January 1983) is weaker with a broad minimum in 1991(614C =124%o) and subsequent gradual increase by ca. 10%o, 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.

Reconstructing Tritium Exposure Using Tree Rings at Lawrence Berkeley National Laboratory, California

“…The 14 C in these rings closely matches the clean-air atmospheric 14 C between 1970 and 2000 ( Figure 3). The 14 C in the earliest rings (i.e., [1964][1965][1966][1967][1968][1969]) is lower than clean-air atmospheric levels of 14 C during those years.…”

“…Eucalyptus A had a peak 14 C activity in 1977 that was 700‰ above cleanair 14 CO 2 levels that year. Eucalyptus B and C had large spikes in 14 C activity in 1976 that was 200-400‰ above clean-air values.…”

“…The 14 C levels were expected to closely match clean-air 14 C measurements, but instead a few 14 C spikes were measured. Because the intent of measuring 14 C was to estimate a growth rate, there were sections in the tree core where no 14 C was measured.…”

“…Samples were collected for 14 C and 3 H analysis on two occasions, September 25 and December 18,2001. Tree cores 244-400-mm-long were collected using a 500-mm-long increment borer that was 5.15 mm diameter.…”

“…The 14 C levels in the upwind pine tree were used to determine the background 14 C levels for this location because the annual tree rings of the pine tree are not in doubt.…”