Isotopic characterisation of anthropogenic CO2 emissions using isotopic and radiocarbon analysis

At the station Kollumerwaard (Netherlands), for monitoring tracers in the troposphere, air is sampled in sixteen containers for off-line 13C, 18O and 14C isotopic analysis of CO2. The timing of the sampling is chosen such that CO2 variations correlating with pollutants like CO and CH4 are optimally covered. The 14C measurements enable us to discriminate between biospheric and fossil fuel contributions to background atmosphere CO2. Results during the first year of operation show that the δ13C values for the anthropogenic CO2 are significantly more negative than generally assumed (values ranging from -30 to -58 ‰ VPDB), which clearly indicates the importance of natural gas consumption in the Netherlands. We compare these experimental values with results from a detailed study of CO2 emission estimates from combustion of fossil fuels and the corresponding δ13C values. As an important side result, the method produces reliable values for the regionally averaged ratio CO : fossil CO2 (results ranging from 0.5 to 1%), a direct measure for combustion quality.