25 Years of Tropospheric ¹⁴C Observations in Central Europe

Abstract

A long-term mountain station series of tropospheric 14C data for the period 1959 to 1984 is presented. This series is considered representative of the higher altitude14C level over central Europe. Even tree-ring 14C levels from a rural ground level site in southern Germany are consistently lower (by Δ14Cdepression = −15‰ if compared with the mountain station summer average in atmospheric CO2). The rural tree-ring series is considered to represent the additional continental Suess effect at ground level without local contamination. This Suess effect decreases gradually with the distance from the ground (ie, source) level. We therefore estimate the additional continental Suess effect in the vegetation period to be Δ14Cdepression = −5‰ for the mountain station and −20‰) for a rural ground level site, respectively. Based on this assumption, yearly mean tropospheric 14C levels corrected for fossil fuel contamination and representative of the Northern Hemisphere are provided for use in global carbon cycle models.

Advection of surface-derived organic carbon fuels microbial reduction in Bangladesh groundwater

“…2) for DOC at 11 m confirms that young DOC has been transported to this depth. This elevated radiocarbon in DOC is consistent with DOC formation from ∼1963 to 1977 when atmospheric radiocarbon was above 350‰ (28). In contrast, there is no indication of a significant bomb-carbon input in the DOC at 19 m (Δ 14 C −205 ± 4‰; Fig.…”

Downward Movement of Soil Organic Matter and Its Influence on Trace-Element Transport (210Pb, 137Cs) in the Soil

“…Total carbon input to the soil is subdivided into a fast component, j1, with a residence time of i1 = 1 yr and a slowly decomposable component, j2, with a residence time of t2 = 100 yr. The model is run with a time step of 1 yr for a total of 100 yr (M1 & M2) and of 300 yr (M3 & M4), respectively, according to the age of the forest ecosystem under investigation (see Sites), to reach a steadystate Corg profile and for a total of 3ITyr (starting in 1957) to calculate the 14C profile using the known contemporary 14C cdntnt of the atmosphere (Levin et al, 1985 Table 1). The higher downward velocity at M1 and M2 than at M3 and M4 can be explained by greater input of organic matter to the soil at M1 and M2, and by the fact that the slowly decomposable soil carbon reservoir (i2 = 100 yr) has not yet reached a steady state due to the comparatively young age of this forest ecosystem.…”

Regional Δ14C patterns and fossil fuel derived CO2 distribution in the Beijing area using annual plants

“…The amount of atmospheric 14 CO 2 is disturbed by human activities via the ongoing emissions of fossil fuel CO 2 [18] and nuclear weapon tests that occurred in the late 1950s and early 1960s [19]. After the nuclear tests, the level of 14 C in plants surged up to twice the normal level [20,21].…”