Estimate of anthropogenic halocarbon emission based on measured ratio relative to CO in the Pearl River Delta region, China

摘要

Using a GC/FID/MS system, we analyzed the mixing ratio of 16 halocarbonspecies in more than 100 air samples collected in 2004 from the Pearl RiverDelta (PRD) region of southern China. The results revealed that there areelevated mixing ratios for most of halocarbons, especially forHClC = CCl (trichloroethylene, TCE), CHCl (dichloromethane,DCM), CH Br (bromomethane), HCFC-22, CHCl (trichloromethane),CCl (tetrachloromethane), ClC = CCl (perchloroethylene,PCE), CHCCl (methyl chloroform, MCF), and CFC-12. Comparisonswere done with the data from TRACE-P and ALE/GAGE/AGAGE experiments, wefound that the large variability in mixing ratios (relative standarddeviation ranged from 9.31 % to 96.55 %) of the halocarbons suggestedsubstantial local emissions from the PRD region in 2004. Correlationsbetween the mixing ratio of each species and carbon monoxide (CO) wasexamined, and then the emission of each halocarbon was quantified based onscaling the optimized CO emission inventory with the slope of the regressionline fitted to each species relative to CO. The calculated results revealedthat mass of CHCl (7.0 Gg), CHCCl (6.7 Gg), andClC = CCl (2.3 Gg) accounted for about 62.9 % of totalhalocarbon emissions, it suggested a significant contribution from solventuse in the PRD region. Emissions of HCFC-22 (3.5 Gg), an alternativerefrigerant to chlorofluorocarbons (CFCs), were about 2.3 times greater thanthose of CFC-12 (1.6 Gg). CFC-12 and HCFC-22 accounted for 21.5 % of totalemissions of halocarbons, so that the refrigerant would be the secondlargest source of halocarbons. However, the ratio approach found only minoremissions of CFCs, such as CFC-11, and the emission of CFC-114 and CFC-113were close to zero. Emissions of other anthropogenic halocarbons, such asCCl, CHCl, CHBr, and CHCl, were also estimated.Where possible, the emissions estimated from the measured ratios werecompared with results from source inventory techniques, we found that bothapproaches gave emissions at similar magnitude for most of the halocarbons,except CFC-11. The comparison suggested that the ratio method may be auseful tool for assessing regional halocarbon emissions, and emissionuncertainty could be further reduced by incorporating both longer-term andhigher-frequency observations, as well as improving the accuracy of the COinventory.