A study on carbon dioxide concentrations and carbon isotopes measured in East Asia during 1991–2011

Abstract

Carbon dioxide (CO2) concentrations and the isotope composition (δ13C) were analyzed in Mt. Waliguan (WLG), China; Ulaan Uul (UUM), Mongolia; Tae-ahn Peninsula (TAP), Korea; Ryori (RYO), Japan; and Mauna Loa (MLO), Hawaii during 1991–2011. The average CO2 growth rate at MLO was 1.7 ppm year−1 during 1993–2004 and accelerated to 2.0 ppm year−1 during 2005–2011. The average difference from MLO during 1993–2004 was 0.27, 0.98, 4.18, and 2.83 ppm for WLG, UUM, TAP, and RYO, respectively. During 2005–2011, the average differences for WLG, UUM, TAP, and RYO increased to 0.33, 1.40, 5.81, and 2.99 ppm. Also, the annual range of CO2 at TAP has become large compared with MLO. CO2 concentrations at TAP, located on the downwind site of China, are increasing slightly faster than in the rest of the Northern Hemisphere, especially since about 2005. The long-term increase is caused by the burning of fossil fuels, although with some year-to-year variation caused by terrestrial ecosystems. CO2 concentration increases were due to the consumption of fossil fuels for heating in winter and agricultural activities in spring. The variations of δ13C reflect the large seasonal variation and increasing trend of CO2. The integrated value of δ13Cs of the sources in the East Asian region ranges from −28.0 to −27.1 ‰, with CO2, which was emitted by fossil fuels, being added. Airflow that arrived at TAP was divided into continental background (CBG) route, regionally polluted continental (RPC) route, and oceanic background (OBG) route. CO2 concentration was higher in CBG and RPC routes, and δ13C stayed at a low value. The isotopic fractionation factor of sources and sinks in the three sectors CBG, RPC, and OBG was −27.5 ± 0.3 ‰ (one sigma), −29.0 ± 0.6, and −23.0 ± 1.5 ‰, respectively. In the RPC route, traversing the industrial regions in eastern China where fossil fuels are consumed in large quantities, the lightest δ13C value was registered. Lower CO2 concentrations and heavier δ13C values were dominant in summer in OBG signatures.