Elsevier

Atmospheric Environment

Volume 89, June 2014, Pages 816-826
Atmospheric Environment

Estimating halocarbon emissions using measured ratio relative to tracers in China

https://doi.org/10.1016/j.atmosenv.2014.03.025Get rights and content

Highlights

  • Ambient halocarbons are measured in 47 cities and by aircraft in China.

  • CO, HCFC-22 and benzene as multi tracers are used to estimate emissions.

  • Short-lived solvent halocarbons account for 79% in estimated halocarbon emissions.

  • The trends of halocarbon emissions are evaluated and compared with inventories.

Abstract

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.

Introduction

Halocarbons are of vital concern due to their toxicity and key role in ozone layer depletion and global warming (Mcconnell and Schiff, 1978, Molina and Rowland, 1974). Deadline for phase-out ozone depleting substances (ODS) in developed countries such as Japan and the U.S. was 1 January 1996 for CFCs, CH3CCl3 and CCl4. The Montreal Protocol allows their production in developing countries until 2010 (2015 for CH3CCl3). China has accelerated the phase-out of CFCs and CCl4 in July 2007, and CH3CCl3 were banned by 2010, 2.5 years ahead of schedule (SEPA, 2004). Therefore, the national emission inventory need to be revised after the accelerated ODS phase-out process.

The emissions of ODS species have kept on dropping while species mainly from chlorinated solvents such as CH3Cl, CHCl3, CH2Cl2, C2HCl3 and C2Cl4 are widely consumed in China, leading to large emissions into the atmosphere (Chan and Chu, 2007, Guo et al., 2009, Shao et al., 2011). Recent emission estimates showed that the emission of CH3Cl and CH2Cl2 were 239 Gg/year and 169 Gg/year respectively in China (Li et al., 2011). The average ratios for C2HCl3, C2Cl4 and CHCl3 between ambient concentrations in PRD and the background levels over the western Pacific and East Asian coast were 96, 6 and 3 times respectively (Chan et al., 2006). High levels of these short-lived solvent halocarbons suggest significant emissions in China.

Halocarbons emission inventories are derived from records of production/sales and other activity data. However, uncertainties arise if the production figures do not include all manufactures, or errors in end use sectors. Systematic investigation on the emission inventory of halocarbons in China only has been reported by Wan (Wan et al., 2009) and Streets, D.G (http://www.bio.cgrer.uiowa.edu/EMISSION_DATA), but their results differ largely from each other (69.94 Gg and 226.97 Gg for 2000), mainly due to the fact that the halocarbon species used to establish these two inventories were different. The inventory given by Wan et al. (2009) were actually the emission of ODS only, while David presented the emissions of ODS and short - lived halocarbon species. In fact, the emissions of the same species in the two inventories did not agree well either, the annual emission of CFC-12 for China in 2006 was 16.9 Gg according to Zhang (http://www.meicmodel.org/), almost three times as 5.4 Gg by Wan et al. (2009).

Since the measured concentration of halocarbon is actually the result of emissions with physical and chemical transformations, field measurements can be employed to evaluate emission inventory. It has been proposed to use concentration variability or incremental from the baseline as a measure to detect potential source areas (Hurst et al., 2006). Monitoring the long-term variability of CFC-113 and CCl4 was close to the precision of the analytical system, implying little emissions of these two species in Taiwan (Wang et al., 2000). Compared to the long-time observation, Fang et al. (2012a) has reported the ambient concentration of CFCs, HCFCs and HFCs in 46 Chinese cities in 2010, and found that levels of CFC-11 in 9 cities and levels of CFC-12 in 2 cities were 20% more higher than the background values, hinting evident local emissions of these compounds (Fang et al., 2012b).

A method using ratios of measured halocarbons to tracers with known emissions has been developed to estimate the emissions of halocarbons in China in the last decade (Guo et al., 2009, Palmer et al., 2003a, Shao et al., 2011, Xue et al., 2011). The first attempt to estimate emission with Halo/CO enhancement based on aircraft measurement was in TRACE-P campaign in 2001 for China (Palmer et al., 2003a, Palmer et al., 2003b). It revealed that both carbon tetrachloride (CCl4) and CFC-11 estimates were 25–50% higher than emission inventory data. Most studies in East Asia used in situ high-frequent measurement in remote background site to calculate emissions. Kim et al. (2010) estimated halocarbons emission using HCFC-22 tracer ratio to be lower than emissions from inverse modeling by Vollmer et al. (2009) for China. Except for ODS, short-lived solvent halocarbons emission were estimated based on CO tracer ratio in the Pearl River Delta (Shao et al., 2011), and the result showed that emissions of CH3CCl3, CH2Cl2 and C2Cl4 used for solvents account for 62.9% of total halocarbons emission. So far, the emission estimates were mainly performed for ODS in China, the short-lived halocarbon species based on other solvent tracers ratio were very rarely addressed.

In this work, 15 halocarbons in 47 main cities were measured, including aircraft measurement over east area in China. Halocarbon species with levels of 20% enhancement than background are selected to estimate their emissions. CO, HCFC-22 and benzene were used as tracers to derive halocarbon emissions in China. The estimated emissions from field measurements were used to compare with national emission inventories. The results also provided insights into ODS emission trends during 2000–2010 and allow us to evaluate the effects of ODS phase-out program.

Section snippets

Sampling and laboratory analysis

The sampling of the whole air samples were done by using evacuated electro-polished stainless steel canisters (3.2L Silonite Summa® Style Canisters, Entech Instruments Inc.) Total amount of 200 samples were collected typical urban sites in 47 cities (Fig. 1.), which cover 30 of 34 province-level divisions in China. 4 samples in each city and additional 12 samples in Beijing were collected at ground sites. For the representative of ambient air in each city, the following measures were taken:

Halocarbon concentrations

C1–C3 halocarbons were identified and quantified in this study. Table 1 lists the mixing ratios of 15 halocarbon compounds with the global background and data from previous studies in China. Comparing to the concentration obtained from TRACE-P and ALE/GAGE/AGAGE background, the levels of first generation ODS (CFCs, CH3CCl3 and CCl4) in 47 Chinese cities were close to the baseline levels with low relative standard deviations (RSD 6%–10%), indicating there were low emissions of these species in

Conclusions

15 halocarbon species were analyzed using both ground-based and aircraft measurements during 2010–2011. Ambient halocarbon concentrations in 47 cities were compared with global background levels. CFC-113 and CFC-114 levels were within 20% enhancement from background, indicating minor emissions in China. The emissions of other 13 halocarbons were estimated by tracer ratio method. Most of the measured halocarbon species exhibited significant correlations with tracers. The slope in aircraft data

Acknowledgments

This study was funded by the Natural Science Foundation for Outstanding Young Scholars (Grant No. 41125018).

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