Estimating halocarbon emissions using measured ratio relative to tracers in China

China is one of the most important halocarbons emitters in the world. However, differences exist in the compiled national emissions inventories (bottom-up) with those derived from ambient measurements (top-down). In this study, CO and 15 halocarbon species including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), CCl4, CH3CCl3 and other halogenated solvents were measured in 47 cities and using aircraft over Shandong Peninsula during 2010–2011 for China. Halocarbon species with concentrations 20% higher than that of global background levels were considered to have their local emissions; these species were chosen for developing emissions estimates using tracer ratios method. Three tracers namely CO, HCFC-22 and benzene were used to examine correlations with halocarbons in this work; HCFC-22 combined with benzene as multi-tracers showed better correlations than CO did. Halocarbon emissions were estimated using tracer emission multiplied by Halo/Tracer obtained from measured data. The calculated results revealed that HCFC-22 emission based on CO tracer was the largest ozone depletion substance (ODS) at 129.3 Gg/year; Solvent halocarbon species such as CH3Cl, CHCl3, CH2Cl2, C2HCl3, C2Cl4, etc., mainly used as solvents but not under control accounted for 79% in total halocarbon emissions. Comparisons of the tracer ratio emission estimates have been made with other emissions inventories. Results from this study showed our emission estimates for CFC-11 and CFC-12 were 80%∼85% and 120%∼430% of emission inventories respectively. Also the recently phased-out species of CCl4 and CH3CCl3 were 586%–1173% and 330%–660% of the emission inventories respectively. The estimated emissions from the different studies for China during 2000–2010 were summarized. It was shown that HCFC-22 increased by 49.1% accompanied with CFC-12 decreasing by 48.9% during 2007–2010 and a significant decrease trend in CH3CCl3 emission which dropped from 6.5 Gg/year in 2001 to 2.1 Gg/year in 2010.