Tracing CO2 sources in urban and rural areas characterized by different land-use patterns using carbon isotopes

Air samples were collected from urban and rural areas of Korea with different land-use patterns between October 2022 and April 2023 to identify the sources of atmospheric CO2. We analyzed representative end-members from natural and anthropogenic sources (soil, vehicle exhaust gases, and coal) to determine the CO2 concentrations and carbon isotope compositions of CO2 (δ13C-CO2). Urban samples exhibited lower δ13C values and higher CO2 concentrations than rural samples. Both urban and tunnel samples showing similar slopes and intercepts on the plot of 1000/CO2 vs. δ13C-CO2 likely shifted toward the vehicle exhaust end-member. Among the rural samples, those collected from coastal areas showed trends similar to the urban and tunnel samples, which differed from those collected from inland areas. This suggests that samples from coastal areas were affected by CO2 emissions from coal-fired power plants in the region. In contrast, inland samples showed the highest slope and lowest intercept (i.e., estimated δ13C-CO2 value of -27.0‰), suggesting that natural sources such as soil CO2 dominate the contribution to atmospheric CO2 in inland areas. This study demonstrates that the primary CO2 sources in regions with different land-use patterns can be distinguished using the relationship between atmospheric CO2 concentrations and δ13C-CO2 values.