Workshop on “Solving the Mystery of Carbon Tetrachloride” Zürich, Switzerland 5-6 October 2015 Review of Emissions of Carbon Tetrachloride from Industrial and Other Sources Tekn. Dr. Husamuddin Ahmadzai, Chartered Engineer (IMM), Chartered Professional (FAusIMM), Swedish Environmental Protection Agency and Nordic Environment Finance Corporation Abstract Carbon tetrachloride (CCl4, CTC) is a controlled ozone-depleting substance under the Montreal Protocol. According to the Protocol’s agreements most emissive uses of CTC have been phased-out. However, many specific uses of CTC are still exempted and are sources for continued release to the environment and the atmosphere. Exemptions have been granted on an understanding that controlled substances originating from inadvertent or coincidental production during a manufacturing process, from unreacted feedstock, or use as process agents, presence in products as trace impurity, or emissions during handling are insignificant quantities. Such quantities, for a worst case, have been reported (TEAP 1994) to be of the range 0.1 - 0.5 percent for CTC feedstock and process related emissions and about 0.006 percent are released as trace impurities in the finished product. Overall process and trace impurity related emissions of ODS was reported to be 7,145 ODP-tonnes (1992) projected to decrease to 5,841 ODP tonnes by 2000. Emissions of CTC were included in the above and estimated to be 1,440 ODP tonnes in 1992 and expected to reduce to 771 ODP tonnes by 2000. International studies, however, are indicating that the global concentration of CTC in the atmosphere is much greater than what is being expected from the known sources. Recent reporting suggests CTC sources to be contributing up to about 40,000 - 90,000 tonnes annually. The UNEP Scientific Assessment Panel has revised the atmospheric lifetime for CTC in their OEWG report (2012) resulting in a revision of emission rate to about 10,000-20,000 tonnes per annum, CTOC (2015) estimates emissions to be about 8,000 -12,000 tonnes per annum. While these figures reduce the discrepancy between the two types of estimates, an anomaly remains. This review will provide information that infers emissions discrepancy may partly be explained by under-rated emission levels also. In some cases, e.g. in the production of chlorinated rubber (CR) and chloro-sulphonated polyolefin, CTC emissions have been, historically, of the order of 650-1200 kg CTC/tonne product (65 - 120 percent) compared to reported 0.04 to 3 kg CTC/tonne product (0.005 - 0,3 percent emission rate) for well operated plants. For the case of CR, 2-10 percent of the CTC may remain in the product and eventually emitted with the use of the product. Estimation of CTC emission sources thus needs to address processes, monitoring and adequate reporting where CTC is a by- and/or co-product, where it is used as a feedstock or process agent/solvent, nature of continuous and/or batch processes, and handling of CTC. CTC is also used for laboratory and analytical uses and there are quantities are associated with stocks and banks. Inadvertently produced, unwanted or contaminated CTC is destroyed or converted to other substances and such waste processing may have inefficient destruction efficiency. Steps to minimize emissions of CTC include avoidance of the creation of such emissions, reduction of emissions using practicable control technologies or process changes, containment, recovery from equipment during servicing and recycle or destruction of the waste including that redundant at the end-of-life of the equipment/process.

Evaluation of CCl4 Atmospheric Loss Process, Lifetime, and Uncertainties James B. Burkholder – Poster to be presented by TBD Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA. James.B.Burkholder@noaa.gov Eric L. Fleming NASA Goddard Space Flight Center, Greenbelt, Maryland, USA and Science Systems and Applications, Inc., Lanham, Maryland, USA. fleming@kahuna.gsfc.nasa.gov In this work, a summary of the atmospheric (gas-phase) loss processes for CCl4 and 2-D model1 calculations used to evaluate the contributions of the loss process and local and global atmospheric lifetimes will be presented. This work was part of the SPARC2 (2013) Report on the Lifetimes of Stratospheric Ozone-Depleting Substances (Chapter 3), which built on results from recent laboratory studies and the recommendations from the NASA/JPL data evaluation.3 Short wavelength UV photolysis in the stratosphere was shown to be the predominant, >98%, atmospheric loss process for CCl4. Stratospheric loss due to reaction with O(1D) accounts for the majority of the rest of the loss, while reactive loss with the OH radical and Cl atom are calculated to be extremely small. The global annually averaged atmospheric lifetime of CCl4 was calculated to be 48.7 years. The 2σ range in the calculated lifetime based solely on the uncertainty in the model kinetic and photochemical input parameters was evaluated to be 45.2–52.3 years, ±7.3%. This range is significantly smaller than the total range due to all sources of uncertainty (~+/-20-30%) given in SPARC (2013). The atmospheric chemistry and associated lifetime of CCl4 are, therefore, defined very well by the accuracy of the available kinetic and photochemical data. References: (1) Fleming, E. L.; Jackman, C. H.; Stolarski, R. S.; Douglas, A. R. A Model Study of the

Impact of Source Gas Changes on the Stratosphere for 1850-2100. Atmos. Chem. Phys. 2011, 11, 8515-8541, doi:10.5194/acp-11-8515-2011.

(2) Ko, M. K. W.; Newman, P. A.; Reimann, S.; Strahan, S. E.; Plumb, R. A.; Stolarski, R. S.; Burkholder, J. B.; Mellouki, W.; Engel, A.; Atlas, E. L.; Chipperfield, M.; Liang, Q. Lifetimes of Stratospheric Ozone-Depleting Substances, Their Replacements, and Related Species, SPARC Report No. 6, WCRP-15/2013, 2013, http://www.sparc-climate.org/publications/sparc-reports/sparc-report-no6/.

(3) Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; Orkin, V. L.; Wine, P. H. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 17, JPL Publication 10-6, Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, 2011, http://jpldataeval.jpl.nasa.gov.

The ocean sink and other constraints on the budget of atmospheric CCl4 James H. Butler1, Shari A. Yvon-Lewis2,7, Jürgen M. Lobert3,7, Daniel B. King4,7, Stephen A. Montzka1 , John L. Bullister5, Valentin Koropalov6,James W. Elkins1, Bradley D. Hall1, Lei Hu1,2, Yina Liu2,8

, 1Global Monitoring Division, NOAA Earth System Research Laboratory, Boulder, CO, USA 80305; 2Department of Oceanography, Texas A&M University, College Station, TX, USA 77843; 3Entegris Inc., Franklin, MA, USA 02038; 4Chemistry Department, Drexel University, Philadelphia, PA, USA 19104; 5NOAA Pacific Marine and Environmental Laboratory, Seattle, WA, USA 98115; 6Roshydromet, Moscow, RU, 7Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA 80309; 8Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, MA, USA, 02543

Presenting Author: James H. Butler

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Abstract: Observations made on 17 research cruises from 1987-2010, ranging in latitude from 60o N to 77o S in Pacific, Atlantic, and Southern Ocean surface-waters indicate that atmospheric CCl4 is consumed in large amounts by the ocean. Observed undersaturations, corrected for physical effects, were -5% to -10%. The atmospheric flux required to sustain these undersaturations is 15-27 Gg y-1, a loss rate implying a partial atmospheric lifetime with respect to the oceanic loss of 108 (79-137) y and suggesting that 20-37% of atmospheric CCl4 is lost to the ocean. Large undersaturations in intermediate depth (400-800 m) waters associated with reduced oxygen levels, observed in this study and by numerous other investigators, indicate that CCl4 is consumed ubiquitously at mid-depth, presumably by microbiota. Although this subsurface sink creates a gradient that drives a downward flux of CCl4, the gradient flux alone is not sufficient to explain the observed surface undersaturations, suggesting a possible biological sink for CCl4 in surface waters of the ocean as well. If we consider the overall ocean sink, the less robustly-determined soil sink (195y), and the removal rate of CCl4 in the stratosphere (44-50 y), the mid-range estimate of the atmospheric lifetime of CCl4 would be 28 (+/-3) y, thus not significantly different from that used in the past four quadrennial assessments [ 26 (23-33) y ]. These results strongly suggest that a large source of atmospheric CCl4 has not been identified. To be consistent with firn air records and the observed interhemispheric gradient of atmospheric CCl4, most of the unidentified source would have to be anthropogenic.

Carbon Tetrachloride over Eastern Himalaya in India: A Well Deviation from

Global Trend

Abhijit Chatterjee*a, Chirantan Sarkara, Dipanjali Majumdarb, Anjali Srvastavac and Sibaji Rahaa

aBose Institute, Kolkata and Darjeeling, India

bNational Environmental Engineering Research Institute, Kolkata, India cNational Environmental Engineering Research Institute, Nagpur, India

An interesting observation was made on annual distribution of carbon tetrachloride (CTC) during a first ever ground-based study on volatile organic compounds (VOC) over eastern Himalaya in India during July, 2011-June, 2012. The study was carried out over a high altitude hill station Darjeeling (27.01 degree N, 88.15 degree E, 2200 m asl) where weekly samples were collected using glass sampling tube containing charcoal and chromosorb. The analysis was done by thermal desorption followed by detection by GC-MS in accordance with USEPA TO-17 compendium method. Interestingly, the annual CTC concentration was found to be 30 ppt which is much lower than the global mean values (~90 ppt) during the said period. However, CTC varied from the values below its detection limit (10 ppt) to 275 ppt during the entire study period. However, ~10 % of the sampling days showed very low (< 20 ppt) and very high (> 110 ppt) CTC concentrations. CTC concentration values mostly accumulated in the range of 25-35 ppt and occasionally in the range of 90-110 ppt. The most important and interesting observation is that all the higher values were associated to the air masses arriving from W/NW (Indo-Gangetic Plains) and S/SE directions (Bangladesh, Kolkata etc) i.e. the regions of high industrial population as no industries exist in and around Darjeeling. Although, CTC was fully banned from 2010, India started the regulation of its use probably from late 2012. Thus, CTC over eastern part of India was found to maintain a good source-receptor relationship at least in 2011-2012. This study thus strongly suggest that ground-based in-situ observations on CTC over India (at least over eastern part and Himalaya) need to be increased vis-à-vis the satellite-based observations, model-based simulation studies and other remote sensing observations. This will in turn help us to better understand and minimize the uncertainties used in the models. At very least, such ground-based observations have much importance over ecologically and geographically important regions like Himalaya to better understand the source-receptor relationship. *Presenting author (abhijit.boseinst@gmail.com)

Forward and Inverse Global Modelling of CCl4

Chris Wilson1,2, Wuhu Feng1,3, Qing Liang4,5, and Martyn Chipperfield1*

1. School of Earth and Environment, University of Leeds, Leeds, UK

2. National Centre for Earth Observation, University of Leeds, Leeds, UK

3. National Centre for Atmospheric Science, University of Leeds, Leeds, UK 4. NASA Goddard Space Flight Center, Greenbelt, MD, USA 5. Universities Space Research Association, Columbia, MD, USA * Presenting author

We have performed simulations with the TOMCAT off-line 3-D chemical transport model (CTM) aimed at further quantifying the imbalance in our understanding of the CCl4 budget over recent years. The model is forced by ECMWF ERA-Interim meteorology and parameterises the atmospheric loss of CCl4, principally through photolysis. Emissions in the forward model are the same as those used in Liang et al. (2014), allowing direct comparison with that study. We will present results from forward and inverse experiments. Results from the forward model run will be compared with surface observations and satellite profiles in the stratosphere. Inverse experiments will be performed by two methods (i) simple synthesis inversion and (ii) full 4D-variational assimilation (Wilson et al., 2014). Results of the study will show to what extent quantification of the known imbalance in the CCl4 budget may be sensitive to 3D model parameters (e.g. transport and mixing) and, through the inverse modelling, possible geographical region(s) for the apparent missing sources. Liang, Q., P.A. Newman, J.S. Daniel, S. Reimann, B.D. Hall, G. Dutton, and L.J.M. Kuijpers,

Constraining the carbon tetrachloride (CCl4) budget using its global trend and inter-hemispheric gradient, Geophys. Res. Lett., 41, 5307–5315, doi:10.1002/2014GL060754, 2014.

Wilson, C., M.P. Chipperfield, M. Gloor, and F. Chevallier, Development of a variational flux inversion system (INVICAT v1.0) within the TOMCAT chemical transport model, Geosci. Model Dev., 7, 2485-2500, doi:10.5194/gmd-7-2485-2014, 2014.

Atmospheric  Carbon  Tetrachloride  Enhancements  Measured  in  Texas    J.S.  Daniel,    E.  Atlas,  J.  Brioude,  J.B.  Gilman,  J.A.  de  Gouw,  W.C.  Kuster,  M.  Trainer    It  is  likely  that  missing  atmospheric  sources  is  at  least  part  of  the  explanation  for  the  current  global  CCl4  budget  imbalance.    We  will  present  CCl4  observations  from  whole  air  samples  taken  on  board  the  NOAA  WP-­‐3D  aircraft  as  well  as  on  the  NOAA  research  vessel,  the  Ronald  H.  Brown,  made  in  2006  during  the  Texas  Air  Quality  Study/Gulf  of  Mexico  Atmospheric  Composition  and  Climate  Study.  Some  of  these  data  show  significant  enhancements  relative  to  the  global  background.  In  addition  to  providing  information  about  the  location  of  point  sources,  we  will  also  show  correlations  with  other  compounds  to  gain  insight  into  possible  emissions  processes.  

To be presented at the Workshop on ‘Solving the Mystery of Carbon Tetrachloride’, 5-6 October 2015, Zurich, Switzerland

Australian carbon tetrachloride (CCl4) emissions: a paradigm for a ‘missing’ CCl4 source of possible global significance?

P. Fraser1, B. Dunse1, P. Krummel1, P. Steele1 and A. Manning2

1CSIRO Oceans and Atmosphere Flagship, Aspendale, Victoria, Australia 2UK Meteorological Office, Exeter, UK

In Chapter 1 of the Scientific Assessment of Ozone Depletion: 2014 (Carpenter and Reimann, 2014), ‘bottom-up’ estimates of global carbon tetrachloride (CCl4) emissions (~10 Gg/yr), based on fugitive emissions from the production, use and destruction of CCl4, as recorded by UNEP (with some adjustments and additions), fall well short (currently by about 50 Gg/yr) of ‘top-down’ estimates of global emissions (~60 Gg/yr) derived from AGAGE and NOAA global atmospheric observations.

Australian production of carbon tetrachloride (CCl4) ceased in the 1980s and Australian consumption of CCl4 effectively ceased in the early 1990s, when imports were severely restricted, following Australia’s ratification of the Vienna Convention (1987) and Montreal Protocol (1989). However the long-term AGAGE CCl4 record at Cape Grim (1978-2015; Xiao et al., 2010; Krummel et al., 2014) shows significant, but relatively small, CCl4 emissions from South East Australian urban and industrial centres (Dunse et al., 2005; Fraser et al., 2014; Figure 1).

Australia’s contribution to the global fugitive emissions described above is essentially zero, so where do the Australian emissions come from? This paper will report an update of current CCl4 emissions from the Melbourne/Port Phillip/Latrobe Valley region of South East Australia, based on Cape Grim in situ GC-ECD CCl4 data, using inter-species correlation and regional transport modeling (NAME/InTEM) (Dunse et al., 2005; Manning et al., 2011, Fraser et al., 2014). We attempt to identify the location and nature of these sources within the Melbourne/Port Phillip region, using in situ GC-MSD measurements of CCl4 at CSIRO, Aspendale. The possible global significance of these emissions will be discussed.

Figure 1. Australian CCl4 emissions (3 yr average) obtained from AGAGE GC-ECD CCl4 observations at Cape Grim, Tasmania (1994-2014), using interspecies correlation (ISC) and inverse modeling via the Lagrangian particle dispersion model NAME/InTEM (Dunse et al., 2005; Manning et al., 2011; Fraser et al., 2014; CSIRO unpublished data).

References

Dunse, B., P. Steele, S. Wilson, P. Fraser & P. Krummel, Trace gas emissions from Melbourne Australia, based on AGAGE observations at Cape Grim, Tasmania, 1995-2000, Atmospheric Environment, 39, 6334-6344, 2005.

Fraser, P., B. Dunse, A. Manning, R. Wang, P. Krummel, P. Steele, L. Porter, C. Allison. S. O’Doherty, P. Simmonds, J. Mühle & R. Prinn, Australian carbon tetrachloride (CCl4) emissions in a global context, Environ. Chem., 11, 77-88, 2014.

Krummel, P., P. Fraser, P. Steele, N. Derek, C. Rickard, J. Ward, N. Somerville, S. Cleland, B. Dunse, R. Langenfelds, S. Baly & M. Leist, The AGAGE in situ program for non-CO2 greenhouse gases at Cape Grim, 2009-2010, Baseline Atmospheric Program (Australia) 2009-2010, N. Derek P. Krummel & S. Cleland (eds.), Australian Bureau of Meteorology and CSIRO Marine and Atmospheric Research, Melbourne, Australia, 55-70, 2014.

Carpenter, L. & S. Reimann (Lead Authors), Update on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol, Chapter 1 in Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project – Report No. 55, 1.1-1.101, World Meteorological Organization, Geneva, Switzerland, 2014.

Manning, A., S. O’Doherty, A. Jones, P. Simmonds & R. Derwent, Estimating UK methane and nitrous oxide emissions from 1990 to 2007 using an inversion modelling approach, J. Geophysical Research, 116, d02305, doi:10.1029/2010JD014763, 2011.

Xiao, X., R. Prinn, P. Fraser, R. Weiss, P. Simmonds, S. O’Doherty, B. Miller, P. Salameh, C. Harth, P. Krummel, A. Golombek, L. Porter, J. Elkins, G. Dutton, B. Hall, P. Steele, R. Wang & D. Cunnold, Atmospheric three-dimensional inverse modelling of regional industrial emissions and global oceanic uptake of carbon tetrachloride, Atmos. Chem. Phys., 10, 10421-10434, 2010.

Current  Trend  in  Carbon  Tetrachloride  from  several  NDACC  FTIR  stations    James  Hannigana,  Mathias  Palmb,  Stephanie  Conwayc,  Emmanual  Mahieud,  Dan  Smalee,  Eric  Nussbaumera,  Kim  Strongc,  Justus  Notholtb    

a. National  Center  for  Atmospheric  Research,  Boulder,  CO,  USA  b. University  of  Bremen,  Bremen,  Germany  c. University  of  Toronto,  Toronto,  Canada  d. University  of  Leige,  Liege,  Belgium  e. National  Institute  of  Water  and  Atmospheric  Research,  Lauder,  New  Zealand  

   To  obtain  a  global  perspective  on  total  column  trends  of  Carbon  Tetrachloride  (CCl4)  we  use  measurements  from  several  stations  of  the  ground-­‐based  NDACC  (Network  for  the  Detection  for  Atmospheric  Composition  Change,  www.ndacc.org)  from  the  Arctic  to  mid-­‐latitudes.    Data  from  Eureka  (80ºN),  Ny  Alesund  (79ºN),  Thule  (76ºN),  Jungfraujoch  (47ºN),  Mauna  Loa  (20ºN)  and  Lauder  (45ºS)  are  included.    Retrievals  for  these  stations  were  performed  in  a  homogeneous  manner  in  the  12µ  spectral  region  of  the  solar  absorption  spectra  routinely  recorded  at  0.0035cm-­‐1  resolution.      The  retrieval  follows  the  methods  described  in  Rinsland  [Rinsland  et  al.,  2012]  with  some  updates  where  specific  accounting  for  CO2  linemixing  must  be  applied  in  the  forward  model  to  achieve  fitted  residuals  appropriate  to  the  SNR  &  quality  of  the  spectra.    The  observation  starting  dates  for  each  site  varies,  but  are  all  analyzed  through  2014.    The  data  used  in  the  trends  are  daily  averages  from  inhomogeneous  sampling  due  to  observing  limitations  of  a  required  clear  sky  and  which,  in  the  Arctic  is  further  limited  by  the  polar  night.    A  bootstrap  resampling  technique  is  used  to  statistically  mitigate  the  sampling  [Gardiner  et  al.,  2008].      We  will  discuss  the  altitude  sensitivity  of  the  retrievals,  the  annual  cycle  and  long-­‐term,  approximately  15  year  trend  in  the  data  by  latitude.        Rinsland,  C.  P.,  et  al.:  Decrease  of  the  carbon  tetrachloride  (CCl4)  loading  above  Jungfraujoch,  based  on  high  resolution  infrared  solar  spectra  recorded  between  1999  and  2011,  Journal  of  Quantitative  Spectroscopy  and  Radiative  Transfer,  2012,  113(11),  1322–1329,  doi:10.1016/j.jqsrt.2012.02.016    Gardiner,  T.,  et  al.:  Trend  analysis  of  greenhouse  gases  over  Europe  measured  by  a  network  of  ground-­‐based  remote  FTIR  instruments,  J.  Atmospheric  Chemistry  and  Physics,  2008,  8,  22,  6719-­‐6727,  doi:10.5194/acp-­‐8-­‐6719-­‐2008      

Soil uptake of CCl4: flux estimates and uptake mechanisms. Authors: James Happell, Yudania Mendoza, Kelly Goodwin Presented by J. Happell

Static flux chamber measurements of CCl4 uptake by soils in boreal,

subtropical and tropical forests have been made by our group. Previous partial lifetime (τsoil) estimates of soil uptake have ranged from 90 (Happell and Roche, 2003) to 195 years (Montzka et al, 2011). In the work here, the rate of CCl4 uptake was calculated from 453 flux chamber measurements using an exponential fit to the chamber CCl4 concentration change with time. This analysis indicated that the flux rate estimate in Happell and Roche (2003) was overestimated by 2.75, yielding a new estimate of τsoil for CCl4 of 245 years. Significant correlations of CCl4 uptake to temperature, soil moisture, or time of year were not observed. This work provides additional evidence that CCl4 uptake by soils is a common process and needs to be considered when developing an atmospheric budget for this compound.

We also conducted incubation experiments to investigate the soil removal mechanism. Atmospheric concentrations of CCl4 were removed by bulk aerobic soils from tropical, subtropical, and boreal environments. Removal of CCl4 and removal of CH4 were compared to explore whether the two processes were linked. Removal of both gases was halted in laboratory samples that were autoclaved, dry heated, or incubated in the presence of HgCl2. In marl soils, treatment with antibiotics such as tetracycline and streptomycin caused partial inhibition of CCl4 (50%) and CH4 (76%) removal, but removal was not affected in soils treated with nystatin or myxothiazol. These results indicated that bacteria contributed to the soil removal of CCl4 and that microeukaryotes may not have played a significant role. Amendments of methanol, acetate, and succinate to soil samples enhanced CCl4 removal by 59%, 293%, and 72%, respectively. Additions of a variety of inhibitors and substrates indicated that nitrification, methanogenesis, or biological reduction of nitrate, nitrous oxide, or sulfate (e.g., occurring in possible anoxic microzones) did not play a significant role in the removal of CCl4. Methyl fluoride inhibited removal of CH4 but not CCl4, indicating that CH4 and CCl4 removals were not directly linked. Furthermore, CCl4 removal was not affected in soils amended with MeF suggesting that the observed CCl4 removal was not significantly mediated by methanotrophs.

Towards improving the ACE-FTS retrieval of carbon tetrachloride Jeremy J. Harrison1,2, Chris D. Boone3, Peter F. Bernath4

(1) Department of Physics and Astronomy, University of Leicester, Leicester, United

Kingdom

(2) National Centre for Earth Observation (NCEO), University of Leicester, Leicester, United

Kingdom

(3) Department of Chemistry, University of Waterloo, Waterloo, Canada

(4) Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, United

States of America

The Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), on

board the SCISAT satellite, has been recording solar occultation spectra through the Earth’s

atmospheric since 2004 and continues to take measurements with only minor loss in

performance. The ACE-FTS measures a range of chlorine ‘source’ gases, including CCl3F

(CFC-11), CCl2F2 (CFC-12), CHF2Cl (HCFC-22), CH3Cl and CCl4. However, the current

ACE-FTS v3.5 CCl4 retrieval is biased high by ~ 20–30%, largely due to spectroscopic

errors in the CCl4 absorption cross-section dataset and inadequacies in the lineshapes of

interfering species, such as a Q-branch of CO2 for which line mixing parameters are not

known.

Preparation is underway for a new processing version of ACE-FTS data, v4.0, which will use

a better a priori CO2 VMR profile than v3.5 for the pressure-temperature retrievals, enabling

more accurate trends to be derived from ACE-FTS data. Additional improvements for the

CCl4 retrieval will include a more judicious microwindow selection, an improved accounting

for a number of water lines with bad fitting residuals overlapping the heart of the CCl4

spectral feature, and the use of new laboratory spectroscopic measurements of CCl4, which

improve upon the absorption cross-section dataset used for v3.5. This presentation will

focus on these improvements and provide a status update on the development of the ACE-

FTS v4.0 CCl4 retrieval scheme.

Carbon tetrachloride (CCl4) emission estimates for China: an inventory for 1992-2014 and a

projection to 2030

Pengju BIE1, Li LI1, Zhifang LI1, Jianxin HU*,1

1 Collaborative Innovation Center for Regional Environmental Quality, College of

Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.

* Corresponding author phone: 86 10 62756593; email: jianxin@pku.edu.cn (J.Hu).

Abstract

We estimated the emissions of carbon tetrachloride (CCl4 or CTC) in Mainland China from

1992 to 2030, using an emission factor approach based on surveyed and projected production and

consumption data. Historically, annual total CCl4 emissions have ascended since 1992, reaching a

tipping point of 11.05±0.80Gg/yr in 2004, and descended to ca. 1.74±0.09 Gg/yr in 2010 as a

result of the phase-out of CTC pursuant to the requirement of the Montreal Protocol.

Approximately 90% of the historical emissions came from chemical industrial processes where

CCl4 was used as a processing agent. In the future, annual emissions will remain at a lower level

of 0.49 Gg/yr ~ 0.82 Gg/yr. The bulk of future CCl4 emissions will originate from the use of CCl4

as feedstock in producing tetrachloroethylene and hydrofluorocarbons (HFCs); moreover, its

share is anticipated to increase at an average rate of 2.88%/yr. Given this, major future regulatory

and technical efforts are encouraged to restrict exhaust release fulfilling the China’s law of

prevention and control of atmospheric pollution, and to reduce the leakage in operation to

accomplish the Montreal Protocol. Our estimates are believed to be reliable since there is a

significant correlation (p<0.01) between the estimated annual emissions and the literature-

reported atmospheric CTC mixing ratios during same period 1992-2014. However, it should be

noted the mixing ratios maintained a stable level at about 100ppt while the emission showed a

significant decrease from 7.13±0.05Gg/yr of 2009 to 0.6Gg/yr or so. This disagreement could be

a consequence of the long lifetime of CTC or the existence of storage emission or other poorly

quantified sources.

Atmosphere-derived carbon tetrachloride emission from the US during 2008 - 2012 L. Hu1,2, S. A. Montzka2, B. R. Miller1,2, A. E. Andrews2, J. B. Miller1,2, S. Lehman3, C. Sweeney1,2, S. Miller4, K. Thoning2, C. Siso1,2, E. Atlas5, D. Blake6, J. A. de Gouw1,7, J. B. Gilman1,7, W. C. Kuster1,7, G. Dutton1,2, J. W. Elkins2, B. D. Hall2, D. Godwin8, H. Chen9, M. L. Fischer10, M. Mountain11, T. Nehrkorn11, S. C. Biraud12, M. S. Torn12, and P. Tans2 1. Cooperative Institute for Research in Environmental Sciences, University of Colorado-Boulder, Boulder, CO, USA; 2. NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, CO, USA; 3. Institute of Arctic and Alpine Research, University of Colorado-Boulder, Boulder, CO, USA; 4. Department of Global Ecology Carnegie Institution, Stanford University, CA, USA; 5. Rosenstiel School of Marine & Atmospheric Science, University of Miami, FL, USA; 6. School of Physical Sciences, University of California – Irvine, CA, USA; 7. NOAA Earth System Research Laboratory, Chemical Science Division, Boulder, CO, USA; 8. US Environmental Protection Agency, Washington DC, USA; 9. Centre for Isotope Research, University of Groningen, Groningen, The Netherlands; 10. Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA; 11Atmospheric and Environmental Research, Lexington, MA, USA; 12Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA Global atmospheric observations suggest substantial ongoing emissions of carbon  tetrachloride  (CCl4)  despite  a  100%  phase-­‐out  of  production  for  dispersive  uses  since  1996  in  developed  countries  and  2010  in  other  countries.    Little  progress  has  been  made  in  understanding  the  causes  of  these  ongoing  emissions  or  identifying  their  contributing  sources.  This  study  uses  the  expanded  national  CCl4  flask  air  sampling  network  from  the National Oceanic and Atmospheric Administration (NOAA) over the US to quantify national and regional emissions of CCl4. Average national total emissions of CCl4 between 2008 and 2012 determined from these observations and an ensemble of inversions range between 2.5 and 6.1 Gg yr-1. This emission is substantially larger than the mean of 0.06 Gg/yr reported to the US EPA Toxics Release Inventory over these years, suggesting that under-reported emissions or non-reporting sources make up the bulk of CCl4 emissions from the US. But while the inventory does not account for the magnitude of observationally-derived CCl4 emissions, the regional distribution of derived and inventory emissions is similar. Furthermore, when considered relative to the distribution of uncapped landfills or population, the variability in measured mole fractions was most consistent with the distribution of industrial sources (i.e., those from the Toxics Release Inventory). Our results suggest that emissions from the US only account for a small fraction of the global on-going emissions of CCl4 (30 - 80 Gg yr-1 over this period). Finally, to ascertain the importance of the US emissions relative to the unaccounted global emission rate we considered multiple approaches to extrapolate our results to other countries and the globe.  

1  

 

Workshop “Solving the mystery of CTC” Zurich (CH), 5-6 October 2015

Abstract CTC reported production and consumption data, which part of the mystery ? Lambert Kuijpers (TEAP-RTOC) Since CTC is a controlled substance under the Montreal Protocol, data on total production, feedstock production and consumption have to be reported annually by all Parties. For this presentation, the UNEP reported CTC data on total and feedstock production have been analysed for the period 1995-2013 in an aggregated form, globally as well as separately for the developed and developing country groups. For the year 2013, it can be calculated that reported CTC feedstock production is in the order of 100,000 tonnes for both groups of countries, stable for the developed, with a 10-15% annual growth trend for the developing countries. Analysis of the reporting of global data, as well as the aggregated developed and developing country data will show the limits originating from the reporting to UNEP. This will include a brief analysis on regional breakdowns. Emissions data are not reported to UNEP, but best estimates on emissions occurring from various uses will be presented for both the developed and developing county groups. The presentation will conclude with a brief discussion in how far these reported production and estimated emission data can shed more light on the CTC mystery.

CCl4 measurement by satellite with the infrared sounder MetOp/IASI

Authors :

Myriam PEYRE (corresponding author : myriam.peyre@noveltis.fr), Olivier LEZEAUX,

Claude CAMY-PEYRET, Bernard TOURNIER, Pascal PRUNET, NOVELTIS (FRANCE)

Presentation : Olivier LEZEAUX

IASI is an infrared sounder aboard MetOp satellites. It is designed to measure the thermal

infrared spectrum emitted by the Earth. Its very high spectral resolution allows to potentially

detect in the measurement the signal of many atmospheric trace gases, including CCl4. On a

polar orbit, the instrument provides global Earth coverage twice a day. The work presented here

addresses the capability of IASI to measure CCl4 atmospheric content at global/regional scales

and its space/time variability.

A first theoretical analysis has allowed to determine and analyse the CCl4 signature in the IASI

spectrum, as well as its expected sensitivity to typical atmospheric variability. The IASI

measurement clearly contains useful information, however the signal is also sensitive to other

elements that disturb CCl4 signal and make the retrieval process complex. These elements are

basically water vapor content, surface (emissivity, temperature), temperature profile and

CO2 concentrations. It has been shown that IASI is not enough sensitive for measuring CCl4 in

the lower layers of the atmosphere, its maximal sensitivity being in the upper troposphere.

Simulations indicated that the retrieved mean mixing ratios potentially allow to detect

latitudinal gradients. This information could be useful for modelers to derive emissions

estimate.

Work on real data has been initiated to develop appropriate methods to extract and quantify

CCl4 signal from the measurement. A first tested approach is to remove the signal due to

perturbing elements by simulating the atmosphere at the measurement time. To this end, IASI

level 2 products provided by EUMETSAT are used. The CCl4 content is tentatively estimated

by comparing observed and simulated signal. First results indicate that differences between

simulated and observed signal due to other sources than CCl4 (uncertainties on water vapor, on

surface parameters, model error, …) are still too important, and avoid a proper extraction of the

useful information with this method. Other approaches, based on the direct use of measured

spectra only are currently tested.

Global modeling of CCl4: How can we use airborne and ground-based measurements to constrain the emissions and atmospheric losses for CCl4?

Qing Liang1,2, Eric L. Fleming1,3, Paul A. Newman1, James Elkins4, Bradley D. Hall4, Geoff

Dutton4,5, Steve C. Wofsy6, Elliot Atlas7

1 NASA Goddard Space Flight Center, Greenbelt, MD USA 2 Universities Space Research Association, Columbia, MD, USA 3 Science Systems and Applications, Inc., Lanham, MD, USA 4 NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, CO, USA 5 Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, USA. 6 Harvard University, Cambridge, MA, USA 7 University of Miami, Miami, FL, USA Carbon tetrachloride (CCl4), like many other regulated ozone-depleting substances, has a

long lifetime ~35 years. While CCl4 is relatively well mixed in the troposphere, its atmospheric distribution still displays significant spatial and seasonal variations, which reflect the intricate balance between surface emissions and stratospheric photolysis (the predominant atmospheric sink), ocean and land degradation. Thus, the observed spatial and temporal variations of CCl4 concentration in the atmosphere can be used in global chemistry models to constrain the sources and sinks of CCl4. For example, the inter-hemispheric gradient and long-term trend can be used to derive global emissions and total lifetime for CCl4, as demonstrated in Liang et al. (2014). For this work, we will further our modeling effort and use the atmospheric vertical profile of CCl4 to constrain its atmospheric photolysis lifetime. Second, we will use the observed seasonal variation of CCl4 at surface monitoring stations to improve the regional emissions from Asia, Europe, North America, respectively.

The rate CCl4 falls off with altitude in the stratosphere with respect to a reference gas, e.g. CO2, provides quantitative information of its atmospheric loss via photolysis. We will use the NASA GEOS-5 Chemistry Climate Model and the observed vertical profiles of CCl4 and CCl4-CO2 tracer-tracer correlation from balloon and high-altitude aircraft measurements to constrain the atmospheric photolysis lifetime for CCl4. In addition, we will conduct model sensitivity simulations using the NASA GSFC-2D model with varying photolytic loss rates to estimate the most likely range of photolysis lifetime based on the current best-estimate uncertainty in photolysis cross-section rates.

The seasonal cycle of CCl4 at a particular surface monitoring site reflects the combined influence of surface emissions and sinks as well as the injection of CCl4-depleted stratospheric air, and can differ greatly from place to place due to differences in their proximity to different sources and sinks. Thus the seasonal cycle at an observational site contains unique information that can be used to infer emissions and sinks. GEOSCCM model simulated CCl4 seasonality, driven with the emissions distribution from Xiao et al (2010), shows large discrepancies with that observed at almost all NOAA GMD and AGAGE stations, implying inaccurate estimate of emissions from individual regions. We will use a suite of tagged CCl4 tracers in the GEOSCCM model to track emissions from different geographic regions, e.g. North America, Europe, South and East Asia. The seasonality of modeled CCl4 and its contribution from individual tagged source regions will be compared and analyzed with the observed seasonal cycle at GMD and AGAGE stations to derive an optimized CCl4 emissions estimate.

Decrease of carbon tetrachloride (CCl4) over 2004-2013 as inferred from global occultation measurement with ACE-FTS

Emmanuel Mahieu1, Peter F. Bernath2, Christopher D. Boone3 and Kaley A. Walker3,4

1. Institute of Astrophysics and Geophysics – University of Liège, Belgium 2. Old Dominion University – Norfolk, VA 3. Department of Chemistry – University of Waterloo – ON 4. Department of Physics – University of Toronto – ON

In this contribution, we use infrared solar occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) instrument onboard the SCISAT-1 Canadian satellite (Bernath et al., 2005). Since its launch in August 2003, this spectrometer has been in continuous operation with no significant degradation of its performance, and global measurements are available from late February 2004 onwards, spanning now more than a decade.

ACE-FTS achieves a spectral resolution of 0.02 cm-1 and covers the 750-4400 cm-1 range, encompassing the strong unresolved and broad CCl4 ν3 band around 796 cm-1, near a strong CO2 Q-branch affected by line-mixing (Rinsland et al., 2012). Systematic analysis of sunset and sunrise occultation measurements in the 787.5 – 805.5 cm-1 window (version 3.5; Boone et al., 2013) provides mixing ratio profiles of CCl4 in the 7 – 25 km altitude range, with mean vertical resolution of 2-3 km.

More than 24000 occultations have been included in the present study, covering the 85°N-85°S latitude range and updating the work of Allen et al. (2009). We determine a significant positive bias with respect to surface measurements by the AGAGE and NOAA networks, confirming the findings of Rinsland et al. (2012) when using ground-based column measurements at the Jungfraujoch station. However, when accounting for the systematic uncertainty affecting the CCl4 line parameters and the impact of the CO2 line-mixing, we show that it is possible to close the gap between the surface and remote-sensing measurements.

Focusing on the tropical observations near 9 and 17 km altitude, we characterize a significant yearly decrease for CCl4 (at the 2-sigma level) of -1.3 ppt (or -1.35%) over the last decade, in agreement with results from Jungfraujoch (updated from Rinsland et al., 2012) and the in situ networks (WMO 2014). Finally, we analyze ACE-FTS global data in order to check for possible contrasted evolutions of CCl4 in both hemispheres.

References

Allen, N. D. C., et al.: Global carbon tetrachloride distributions obtained from the Atmospheric Chemistry Experiment (ACE), Atmospheric Chemistry and Physics, 9(19), 7449–7459, doi:10.5194/acp-9-7449-2009, 2009.

Bernath, P. F., et al.: Atmospheric Chemistry Experiment (ACE): Mission overview, Geophysical Research Letters, 32(15), doi:10.1029/2005GL022386, 2005.

Boone, Chris D., et al., Version 3 Retrievals for the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), The Atmospheric Chemistry Experiment ACE at 10: A Solar Occultation Anthology (Peter F. Bernath, editor, A. Deepak Publishing, Hampton, Virginia, U.S.A., 2013), 103-127, 2013.

Rinsland, C. P., et al.: Decrease of the carbon tetrachloride (CCl4) loading above Jungfraujoch, based on high resolution infrared solar spectra recorded between 1999 and 2011, Journal of Quantitative Spectroscopy and Radiative Transfer, 113(11), 1322–1329, doi:10.1016/j.jqsrt.2012.02.016, 2012.

WMO 2014, Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol, Chapter 1 in Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project – Report No. 55, World Meteorological Organization, Geneva, Switzerland, 2014.

European  emissions  of  carbon  tetrachloride  based  on  high  frequency  atmospheric  measurements  and  a  Bayesian  inversion  method  

 Francesco  Graziosi,  Jgor  Arduini,  Francesco  Furlani,  Umberto  Giostra  and  Michela  Maione*  

 Dep.  of  Basic  Sciences  and  Foundations  (DiSBeF),  University  of  Urbino,  Urbino,  Italy  

   European   carbon   tetrachloride   emissions   are   estimated   from   high-­‐frequency   atmospheric  observations   at   four   European   stations   embedded   in   the   Advanced   Global   Atmospheric   Gases  Experiment  (AGAGE)  network  combined  with  a  Bayesian  inversion  method.    The   inversion   is   based  on  20-­‐day  backward   simulations  obtained  with   the   FLEXPART   Lagrangian  particle  dispersion  model.  An  a  priori  emission  field  has  been  created  based  on  emissions  given  in  Xiao  et  al.  (2010),  who  estimated  global  and  regional  emissions  from  1996  to  2004  using  AGAGE  atmospheric  data  and  3D  inverse  modelling,  applying  a  decreasing  rate  of  10%  per  year  (Fraser  et  al.,   2011).   The   a   posteriori   emission   fluxes   obtained   using   the   inversion   algorithm   described   in  Stohl  et  al.  (2009)  have  been  then  redistributed  over  the  European  geographic  domain  according  to  the  population  distribution    Emission  estimates  are  given  for  a  nine-­‐year  period,  from  January  2006  to  December  2013,  from  the   whole   European   geographic   domain   and   at   the   country   (or   groups   of   countries)   level.   A  decline  in  emissions  is  observed  over  the  study  period,  consistent  with  the  implementation  of  the  Montreal   Protocol.   In   addition,   the   method   allowed   us   to   identify   emission   hot   spots,   in  correspondence  with  industrial  facilities.        References    Fraser  P.,  Krummel  P.,  Dunse  B.,  Steele  P.,  Derek  N.  and  Allison  C.   (2011).  Global  and  Australian  emissions   of   ozone   depleting   substances,   Report   of   the   DSEWPaC   research   projects   2010–11.  Australian   Government   Department   of   Sustainability,   Environment,   Water,   Population   and  Communities    Stohl,   A.,   Seibert,   P.,   Arduini,   J.,   Eckhardt,   S.,   Fraser,   P.,   Greally,   B.R.,   Lunder,   C.,   Maione,   M.,  Mühle,   J.,   O'Doherty,   S.,   Prinn,   R.G.,   Reimann,   S.,   Saito,   T.,   Schmidbauer,   N.,   Simmonds,   P.G.,  Vollmer,  M.K.,  Weiss,   R.F.,   Yokouchi,   Y.,   (2009).   An   analytical   inversion  method   for   determining  regional   and   global   emissions   of   greenhouse   gases:   sensitivity   studies   and   application   to  halocarbons.  Atmos.  Chem.  Phys.  9,  1597e1620.    Xiao,   X.,   et   al.   (2010).   Atmospheric   three-­‐dimensional   inverse   modeling   of   regional   industrial  emissions  and  global  oceanic  uptake  of  carbon  tetrachloride,  Atmos.  Chem.  Phys.,  10(21),  10,421–10,434,  doi:10.5194/acp-­‐10-­‐10421-­‐2010.        *Presenting  author:  michela.maione@uniurb.it  

Potential  Industrial  Sources  of  Environmental  Carbon  Tetrachloride:  An  Overview  Archie McCulloch Atmospheric Chemistry Research Group, University of Bristol, UK

Abstract  Based on atmospheric measurements, emissions of carbon tetrachloride (CTC, CCl4) fell sharply from about 100,000 tonnes/year in the 1980s to between 40 and 50,000 tonnes/year around the turn of the century. They are now 30 to 40,000 tonnes/year. Sources of emission from consumption in dispersive uses and from use as process agents (both of which should be reported to the Montreal Protocol) together with fugitive losses from use as a chemical feedstock have been examined. During the period 1993 to 2005, these sources gave total emissions consistent with the atmospheric observations to within 9%; remarkable in view of the variability of the consumption data then. However, since 2005 the reported consumption in emissive uses has fallen significantly and since 2000 feedstock use has remained virtually constant at about 180,000 tonnes/year, an 80% reduction from the peak value in 1989. Currently, the reported consumption for dispersive uses and estimated losses from feedstock uses could account for maximum emissions of 5000 tonnes/year. Consequently, additional, unreported, emissions of approximately 30,000 tonnes/year are required to effect a balance with atmospheric observations. Having accounted for potential feedstock losses, possible industrial sources of the additional emissions are undeclared consumption or use as a process agent.

Archie McCulloch

Visiting Research Fellow in the Atmospheric Chemistry Research Group, School of Chemistry, University of Bristol UK.

Mail Address: Barrymore, Marbury Road, Comberbach, Northwich, Cheshire, UK CW9 6AU

Phone +44-1606891604 e-mail: archie.mcculloch@btinternet.com

Probing broad-scale atmospheric observations for clues to unraveling the carbon tetrachloride conundrum. S. Montzka1*, G. Dutton2, B. Hall1, E. Ray2, F. Moore2, B. Miller2, L. Hu2, J. Elkins1, J. Butler1 1 National Oceanic and Atmospheric Administration, Boulder, USA 2 Cooperative Institute in Environmental Sciences, Univ. of Colorado, Boulder, USA Atmospheric measurements provide an important means by which the effectiveness of production controls on long-lived substances can be assessed. They provide a means to address a primary question: Are global atmospheric concentrations changing as expected? For CCl4 the answer is clearly no; substantial discrepancies between global emissions derived from atmospheric observations and ‘potential’ emissions derived from reported production for dispersive uses have been noted since the late 1990s. The global mean and rate of change in lower-troposphere CCl4 mole fractions is well determined by the global sampling networks, but this is not necessarily true for gradients and signals on smaller scales that could provide additional insight into source or sink magnitudes and distributions. For example, how well determined is the gradient of CCl4 mole fractions across latitudes? Does this gradient inform us about the distribution of unknown sources? Can an accurate hemispheric (N – S) difference in CCl4 mixing ratios be estimated and can it be used to infer a global emission rate? To what extent are hemispheric differences and global rates of change influenced by natural emissions or variations in mass exchange between the stratosphere and troposphere? Here we will investigate observational data from multiple sources to understand which signals and conclusions are robust and reliable. Consideration of previously unpublished data from firn-air measurements, additional instruments, and unique sampling platforms allow for an improved understanding of the lower limit to preindustrial mole fractions and the current atmospheric gradients of CCl4. Multiple features of the observational data continue to point to appreciable ongoing CCl4 emissions in amounts substantially larger than implied by production data reported to the ozone secretariat. *presenter

Carbon  tetrachloride  content  of  chlorine-­‐bleach-­‐containing  household  products  and  implications  for  their  use    

 Mustafa  Odabasi  a*,  Tolga  Elbir  a,  Yetkin  Dumanoglu  a,  Sait  C.  Sofuoglu  b  

 a  Department  of  Environmental  Engineering,  Faculty  of  Engineering,  Dokuz  Eylul  University,  Tinaztepe  Campus,  

35160  Buca,  Izmir,  Turkey  b  Department  of  Chemical  Engineering,  Izmir  Institute  of  Technology,  35430  Gulbahce-­‐Urla,  Izmir,  Turkey  

 

 *Presenting  author:  e-­‐mail:  mustafa.odabasi@deu.edu.tr,  phone:  90-­‐232-­‐301  7122,  fax:  90-­‐232-­‐453  0922  

   

ABSTRACT  

It  was  recently  shown  that  a  substantial  amounts  of  carbon  tetrachloride  (CCl4)  is  formed  in  chlorine-­‐bleach-­‐containing  household  products   as   a   result  of   reactions  of   sodium  hypochlorite  with  organic  product   components.   Use   of   these   household   products   results   in   elevated   indoor   air   CCl4  concentrations.   CCl4   in   several   chlorine-­‐bleach-­‐containing   household   products   (plain,   n=9;  fragranced,  n=4;  and  surfactant-­‐added,  n=29)  from  Europe  and  North  America  were  measured  in  the  present  study.  CCl4  concentrations  ranged  between  0.01  and  169  mg/L  (23.2±44.3  mg/L,  average±SD)  and   concentrations  were   the   lowest   in  plain  bleach,   slightly  higher   in   fragranced  products  and   the  highest   in   the   surfactant-­‐added   products.   Indoor   air   concentrations   from   the   household   use   of  bleach  products   (i.e.,  bathroom,  kitchen,  and  hallway   cleaning)  were  estimated  using  a   simple  box  model.   Estimated   indoor   air   concentrations   ranged   between   0.30   and   1124   (82±194,   average±SD)  µg/m3,  indicating  substantial  increases  compared  to  background  (0.27  µg/m3).      Eventually,   the  majority  of  CCl4   in   chlorine-­‐bleach-­‐containing  household  products   is  emitted   to   the  atmosphere.   Global   annual   CCl4   emissions   from   the   use   of   chlorine-­‐bleach-­‐containing   household  products  were  estimated  using  the  concentrations  measured  in  this  study  and  an  average  per  capita  consumption  of  1  kg/year.  Since  the  shares  of  product  types  (i.e.,  plain  or  surfactant  added)  were  not  known,  emissions  were  estimated  for  two  extreme  cases:   (i)  plain  bleach  having  the  minimum  CCl4  concentration,  (ii)  surfactant-­‐added  bleach  having  the  maximum  CCl4  concentration.  For  these  cases  global  annual  CCl4  emissions  ranged  between  0.06  and  1230  tons.  CCl4  emissions  from  14  European  countries  with  a  population  of  ~600  million  and  known  country  specific  per  capita  household  bleach  consumptions  were  also  estimated.  Annual  European  CCl4  emissions   ranged  between  0.02  and  493  tons.   Per   capita   household   bleach   consumptions   are   highly   variable,   ranging   between   0.22-­‐11.8  kg/year,  and  generally   it   is  >  3  kg/year.  This   suggests   that   the  global  average  per  capita  household  bleach   consumption   may   be   higher   than   1   kg/year   and   as   a   result   global   CCl4   emissions   may   be  underestimated.  Although  the  estimated  global  emissions  are  highly  uncertain  due  to  lack  of  detailed  information   on   product   type   and   usage   amounts,   the   results   of   the   present   study   indicated   that  household   chlorine   bleach   use   is   an   ongoing   source   of   CCl4   emitting   appreciable   amounts   to   the  atmosphere.      Keywords:  Chlorine  bleach;  carbon  tetrachloride;  global  emissions.  

China’sCarbontetrachloride(CCl4)emissiontrendestimatedfromatmosphericobservationsin2008‐2013

ShanlanLi1,SunyoungPark1,2,JensMühle3,Mi‐KyungPark1,ChunOkJo1

1KyungpookInstituteofOceanography,CollegeofNaturalSciences,KyungpookNationalUniversity,Daegu,SouthKorea2DepartmentofOceanography,CollegeofNaturalSciences,KyungpookNationalUniversity,Daegu,SouthKorea3ScrippsInstitutionofOceanography,UniversityofCaliforniaSanDiego,LaJolla,California,USA

AtmosphericconcentrationsofCCl4havebeendecreasingsincereachingapeakin1990,due to the phase‐out of CCl4 use in theMontreal Protocol’s non‐Article‐5 countries. TheArticle‐5countries,includingChinahadalsobeenrequiredtoeliminateCCl4by2010,butasanexemptionallowedundertheMontrealProtocoltothephase‐out,thechemicalfeedstockusecontinueswiththeincreasingmanufactureofHFC. In this study, we estimated the emission rates of CCl4 for China using an interspeciescorrelation method [Li et al., 2011] based on “top‐down” interpretation of atmosphericobservationsobtainedfromtheGosanstation(33oN,126oE)onJejuIsland,Korea.Thehigh‐precision and high‐frequency measurements of CCl4 were made continuously every twohours from 2008 to 2013 using a GC‐MSD coupled with an online cryogenic pre‐concentration system (“Medusa”) under the AGAGE program. To separate periods ofChineseemissioninfluencesfromthe6‐yeartimeseries,weidentifiedair‐masssegmentsoriginated from China using a back‐trajectory analysis. For the interspecies correlationmethod,themostsuitablereferencetracerforChineseemissionswasHCFC‐22,ofwhichtheannualemissionrates inChinawerederived independently froman inversioncalculationbasedonFLEXPARTtransportmodelanalysis.ThentheCCl4emissionrateswereestimatedbyusingtheempiricalcorrelationsbetweenobservedCCl4andHCFC‐22. OurresultsshowtheCCl4emissionsinChinabetween2008and2010wereintherange

between18.7±2.9and23.3±2.7ktyr‐1,andthentherewasastatisticallysignificantdeclinebyca.30%intheemissionfrom2010to2011,inconcurrencewiththescheduledphase‐outofCCl4.However,itisinterestingthattheemissionrateoftheyear2011hadleveledoffuntil2013,stillshowingasignificantemissionrateof16.2±4.4ktyr‐1,whilepost‐2010bottom‐upemissionsofCCl4inChinahavebeenreportedtobenearzero(Wangetal.,2009).ThisdiscrepancymaysuggestCCl4emissionsfromeithernon‐regulatedfeedstockuseorcleaningsolvent source. To identifykey industrial sources forCCl4 emissionsand theirpotentiallocations,wefurtheranalyzetheobservationdatabyusingaPositiveMatrixFactorizationmodelincombinationwithtrajectorystatistics[Lietal.,2014].Moredetailsarediscussedinthepresentation.Overall,CCl4emissionsfromChinaaccountforapproximately23%ofglobaltop‐down emissions derived from AGAGEmeasurements from 2008‐2012 (Fraser et al.,2014).

Terrestrial  sinks  and  natural  sources  of  carbon  tetrachloride  Robert  Rhew    In  the  atmospheric  budget  of  carbon  tetrachloride,  the  magnitude  of  the  soil  sink  remains  highly  uncertain.    In  the  last  two  Assessments,  the  range  of  CCl4  partial  lifetimes  with  respect  to  soil  was  estimated  at  195  years  with  a  range  of  ~100  to  907  years.    The  source  of  the  uncertainty  was  largely  associated  with  tropical  forest  soils.    Recently,  Happell  et  al.  (2014)  provided  a  revised  partial  lifetime  estimate  of  245  years,  based  on  a  much  larger  set  of  field  measurements.    This  revision  would  increase  the  total  atmospheric  lifetime  of  CCl4  from  26  to  27  years,  assuming  the  partial  lifetimes  of  stratospheric  and  oceanic  loss  remained  the  same  (at  44  and  94  years,  respectively).  The  uncertainty  of  the  soil  sink  partial  lifetime  may  be  reduced  through  a  meta-­‐analysis  of  published  studies  to  date.        Although  CCl4  emission  sources  are  almost  entirely  anthropogenic,  this  compound  can  be  synthesized  naturally  as  well.    The  biosynthesis  of  CCl4  was  first  identified  in  the  red  alga  Asparagopsis  (McConnell  and  Fenical,  1977).    Later  field  measurements  showed  CCl4  emissions  from  a  salt  marsh  site  covered  in  macroalgae  (Rhew  et  al.,  2008).    However,  emission  rates  do  not  appear  to  be  globally  significant.    Reports  of  natural  biological  sources  will  be  reviewed  and  assessed  for  their  potential  contribution  to  the  atmospheric  CCl4  budget.                  References:  Happell,  J.,  Y.  Mendoza  and  K.  Goodwin,  2014.    A  reassessment  of  the  soil  sink  for  atmospheric  carbon  tetrachloride  based  upon  static  flux  chamber  measurements.    J.  Atmos.  Chem,  71(2):  113-­‐123,  doi:  10.1007/s10874-­‐014-­‐9285-­‐x.          McConnell,  O.  and  W.  Fenical,  1977.    Halogen  chemistry  of  the  red  alga  Asparagopsis.    Phytochemistry  16:  367-­‐374.    Rhew,  R.,  B.  Miller  and  R.  Weiss,  2008.    Chloroform,  carbon  tetrachloride  and  methyl  chloroform  fluxes  in  southern  California  ecosystems.    Atmospheric  Environment,  42:  7135-­‐7140,  doi:  10.1016/j.atmosenv.2008.05.038.  

Global  and  regional  estimates  of  carbon  tetrachloride  emissions  using  AGAGE  observations    Matt  Rigby,  Mark  Lunt,  Sunyoung  Park,  Shanlan  Li,  Alistair  Manning,  Ron  Prinn,  Simon  O’Doherty,  Qing  Liang    Observations  from  the  Advanced  Global  Atmospheric  Gases  Experiment  (AGAGE)  provide  information  on  carbon  tetrachloride  (CCl4)  emissions  at  both  global  and  regional  scales.  By  examining  trends  in  the  global  background  concentration,  we  can  derive  the  global  fluxes  using  relatively  simple  models  and  inverse  methods.  However,  these  estimates  are  sensitive  to  the  assumed  global  lifetime.  In  contrast,  regional  estimates  can  be  derived  that  are  insensitive  to  the  lifetime,  using  the  observed  high-­‐frequency  signals  measured  at  AGAGE  sites  close  to  major  emissions  sources.  However,  such  approaches  can  only  be  used  to  determine  emissions  within  a  few  hundred  kilometres  of  each  station.      Using  a  two-­‐dimensional  model  of  atmospheric  transport  and  chemistry,  we  derive  a  global  flux  of  57  (40–74)  Gg/yr,  when  assuming  a  lifetime  of  26  years,  as  recommended  in  the  latest  WMO  Scientific  Assessment  of  Ozone  Depletion,  or  36  (22–49)  Gg/yr  when  a  lifetime  of  35  years  (Liang  et  al.,  2014)  are  assumed.    To  derive  regional  fluxes,  we  use  the  three-­‐dimensional  Numerical  Atmospheric  Modelling  Environment  (NAME),  developed  by  the  UK  Met  Office.  Such  models  can  be  used  to  estimate  fluxes  at  relatively  high  resolution,  using  high-­‐frequency  data  from  AGAGE  observations.  However,  care  must  be  taken  to:  a)  minimise  the  influence  of  subjective  choices  made  by  the  investigator  on  the  outcome  of  the  inversion;  b)  appropriately  account  for  the  uncertainty  due  to  the  chemical  transport  model;  c)  ensure  that  fluxes  are  derived  at  spatial  and  temporal  scales  that  can  be  appropriately  resolved  by  the  data.  We  demonstrate  new  approaches  using  hierarchical  Bayesian  methods  and  reversible-­‐jump  Markov-­‐chain  Monte  Carlo  to  address  each  of  these  issues.  Based  on  these  methods,  we  derive  significant  emissions  from  East  Asia,  focused  particularly  on  China,  which  are  of  the  order  of  20  Gg/yr.  Emissions  from  other  regions  close  to  AGAGE  stations  returned  relatively  small  emissions  in  recent  years.    Our  estimates  for  East  Asia  account  for  around  one-­‐third  of  the  global  budget,  if  the  lifetime  is  26  years  and  around  one-­‐half,  if  it  is  35  years.  It  is  likely  that  there  are  other  areas  of  the  world,  such  as  India,  Africa,  South  America  or  the  east  coast  of  the  USA  where  significant  emissions  may  exist,  but  to  which  the  AGAGE  network  is  not  directly  sensitive.  

Summary of CTC presentation Zuerich October 2015: Industry perspective

CTC demand has not only confounded many critics, where there was an expectation that output would shrink to almost zero, but at present shows signs of stabilising at some 180-200 ktpa and has clear indications of growth... this of course being to non-controlled (chemical intermediate) applications. The number refers to production or use, and not to emissions.

In this paper we will review

• fatal production from chloromethanes: how to assess it in general and then how major individual plants individually treat it. We will review the major producing areas. We will note that chloromethanes plants, whilst minimising CTC now, were frequently set up to make CTC deliberately to source the growing CFC industry.

• fatal production from perchloroethylene plants and the global and localised scale • deliberate production of CTC using CS2 technology: all such plants have in fact closed • Incidence of CTC in waste streams and how they are handled (Examples). • Other potential anthropogenic sources of CTC

We will then review consumption patterns of CTC:

• Use to chemical intermediates such as in perchlorination, reduction to other chloromethanes (chloroform, methyl chloride)

• Use in Kharasch reactions notably to make pesticides and new generation hydrofluorocarbons and hydrofluoro-olefins

• "Use" to incineration whereby the resultant HCl may be used in downstream and vital chemical reactions

We will then attempt to display a mass balance.

We will speculate for audience participation on the CTC that is generated in waste streams that may be uncontrolled, that may arise from swimming pools, or from the use of bleaching tablets in conjunction with washing fluids in laundry applications.

David Sherry

Director, NSA Ltd

Overview of University of California, Irvine CCl4 observations: Trends and outliers Isobel J. Simpson, Nicola J. Blake, Simone Meinardi, and D. R. Blake Department of Chemistry, University of California, Irvine, CA 92697 The University of California, Irvine (UCI) has measured carbon tetrachloride (CCl4) concentrations in whole air samples as part of our global monitoring network since 1978 and in support of aircraft field campaigns since 1990. In addition we have made numerous CCl4 measurements during urban studies throughout this period, collecting samples in more than 75 cities worldwide. Our remote global monitoring data show that post-Montreal Protocol CCl4 mixing ratios have decreased along with other regulated halocarbons. However, unlike CFC-11 and CFC-12, the CCl4 samples still routinely have outliers, suggesting ongoing release. For example, in 2014 UCI measured a global average CCl4 mixing ratio of 82.3 ± 0.1 pptv, with outliers of up to 90 pptv at remote receptor sites such as Hawaii and western North America. Our aircraft and urban data can help shed light on these observations by identifying potential emission regions and their changes with time. As an example, in 2012 we collected air samples in Saudi Arabia, a highly polluted yet understudied region of the world. Whereas CCl4 levels in background Saudi Arabian air (86.7 ± 0.1 pptv) were similar to background levels recorded by our global monitoring network at a similar time and latitude (86.4 ± 0.9 pptv), the average CCl4 mixing ratio in Mecca was 92.5 ± 0.8 pptv, with maximum levels of 108 pptv, indicating ongoing CCl4 emissions in this region. By contrast, ground samples including various “source” samples (urban/industrial/oil & gas), were collected along the Colorado Front Range as part of the 2014 FRAPPÉ campaign. While background CCl4 levels during the campaign (82.7 ± 0.2 pptv) were again close to background levels from our global monitoring network for a similar latitude and season (82.2 ± 0.6 pptv), the average CCl4 mixing ratio during FRAPPÉ was only slightly elevated (at 85.3 ± 2.0 pptv) compared to background, and the maximum value was 92.8 pptv. These findings agree with the 2013 US airborne campaign SEAC4RS, which also exhibited only a relatively small number of CCl4 outliers. These and other results will be presented and discussed.

A historical perspective on primary and possible secondary sources of atmospheric Carbon Tetrachloride

Hanwant B. Singh, NASA Ames Research Center, USA

Atmospheric sources of Carbon Tetrachloride (CTC) have been controversial since its detection in the early 1970. Initial proposals were that it is globally uniformly distributed and its lack of current emissions and inferred lifetime indicated that it was likely of natural origin. Historical analysis of CTC use and emissions showed that atmospheric CTC was long-lived and mainly of man-made origin although small natural sources and sinks (e. g. oceans) could not be ruled out. This deduction was hard because a majority of emissions had occurred in early part of the 20th century when CTC was commonly used as a fumigant, a solvent, and a raw material for the manufacture of many chemicals. In the 1940’s adverse health effects of exposure to CTC became evident and its emissions were greatly curtailed and substituted with C2Cl4 which was thought to be much safer. There were smog chamber studies that showed that C2Cl4, a widely used solvent during the late 20th century, could produce CTC with up to a 7% yield. Subsequently it was discovered that this chemistry probably required Cl atoms and since Cl atoms were not abundant in the atmosphere actual yields based on OH oxidation were probably closer to 0.1%. CTC was subsequently banned by the Montreal Protocol to prevent stratospheric ozone depletion and its preferred substitute C2Cl4 was also banned by EPA for reasons of potential carcinogenicity and toxicity. CTC since has been measured in many airborne NASA campaigns in which plumes have been sampled from a variety of regions which may still be emitting CTC. I will briefly discuss this historical perspective of CTC and show some recent data that may shed light on its current sources or lack there off.

Contribution  to  "Solving  the  Mystery  of  Carbon  Tetrachloride"  Workshop  

INVESTIGATING  OCEANIC  UPTAKE  OF  CCl4  USING  GLOBAL  DATA  AND  AN  OCEAN  BIOGEOCHEMISTRY  MODEL  

P.  Suntharalingam,  L.  J.  Carpenter,  S.A.  Andrews,  S.  C.  Hackenberg,  J.H.  Butler,  S.A.  Yvon-­‐Lewis,  O.  Andrews,  E.  Buitenhuis  

 

Recent  analyses  of  oceanic  CCl4   saturation  anomalies   [Butler  et  al.  2011]  have  highlighted  the  need  for  a  revised  quantification  of  the  oceanic  sink  of  CCl4  and  improved  understanding  of   the   processes   governing   this   uptake   and   the   controls   on   CCl4  distribution  in   the   ocean  interior.    The  oceanic  CCl4  distribution  is  governed  by  a  combination  of  processes  including  surface   air-­‐sea   gas   exchange,   ocean   circulation   and   water   mass   mixing,   and   hydrolysis  [Wallace  et  al.  1994;  Huhn  et  al.  2001].  In  addition,  recent  analyses  of  covariance  between  oceanic  CCl4  and  Apparent  Oxygen  Utilisation  (AOU)  and  other  biological  data  (Data    from  J.  Butler,   NOAA-­‐ESRL   and   L.   Carpenter,   University   of   York)   suggest   a   significant   role   for   a  biologically  mediated  loss-­‐process  (as  also  suggested  by  previous  studies,  e.g.,  Wallace  et  al.  1994,  Huhn  et  al.  2001,  Yvon-­‐Lewis  et  al.  2002).  

Here  we  show  data  from  the  Atlantic,  Pacific  and  Arctic  Oceans  [L.  Carpenter,  unpublished  data]  that,  consistent  with  those  of  Butler  et  al.  [2011],  show  persistent  undersaturation  of  CCl4  in  the  oceans.  In  the  Arctic  Ocean,  correlation  of  undersaturation  with  salinity  indicate  that   physical   processes,   likely   associated  with   sea-­‐ice,  moderate   the   CCl4   uptake.     In   the  Atlantic,  CCl4  was  most  strongly  undersaturated  in  waters  high  in  Chl-­‐a  content.        

A  specific  focus  of  this   investigation  is  to  quantify  the  relative  influences  on  ocean  CCl4  of:  (1)   gas-­‐exchange   and   physical   circulation;   (2)   chemical   hydrolysis;   and   (3)   potential  biologically-­‐mediated   loss   processes.     We   show   initial   results   from   global   ocean  biogeochemistry  model  simulations  (NEMO-­‐PlankTOM)  quantifying  these  contributions,  and  also  use   available   surface   and  depth  measurements   to   evaluate   the   relative   influences  of  these  processes  on  the  observed  oceanic  CCl4  distribution.  

References  

Butler,  J.  H.;  Yvon-­‐Lewis,  S.  A.;  Lobert,  J.  M.;  King,  D.  B.;  Montzka,  S.  A.;  Koropalov,  V.,  2011,  A  Revised  Look  at  

the  Oceanic  Sink  for  Atmospheric  CCl4,  American  Geophysical  Union,  Fall  Meeting  2011,  abstract  #A51A-­‐0273.  

Huhn,  O.,  Roether,  W.,  Beining,  P.,  Rose,  H.,  2001.  Validity  limits  of  carbon  tetrachloride  as  an  ocean  tracer.  

Deep-­‐Sea  Res.  48,  2025–2049.  

Wallace,  D.W.R.,  Beining,  P.,  Putzka,  A.,  1994.  Carbon  tetrachloride  and  chlorofluorocarbons  in  the  South  

Atlantic  Ocean,  19  S.  J.  Geophys.  Res.  99,  7803–7819.  

Yvon-­‐Lewis,  S.  A.  and  J.  H.  Butler,  2002,    Effect  of  oceanic  uptake  on  atmospheric  lifetimes  of  selected  trace  

gases,  J.  Geophys.  Res.,  107(D20),  4414.  

High time-resolution mixing ratios of atmospheric carbon tetrachloride. A case study in Northern Spain

Maite de Blasa*, Iratxe Uria‡, Maria Carmen Gómez, Marino Navazo, Lucio Alonso,

José Antonio García, Nieves Durana, Jon Iza, Jarol Derley Ramón School of Engineering, University of the Basque Country UPV/EHU, Bilbao, Spain. a University College of Technical Mining and Civil Engineering. University of the Basque Country, UPV/EHU, Bilbao, Spain. * Corresponding author. Contact information: e-mail address: maite.deblas@ehu.eus Address: Rafael Moreno 'Pitxitxi' 2, 48013 Bilbao, Spain. Tel.: +34 94 601 7812 ‡ Presenter Abstract Since the restriction of CTC under the Montreal Protocol, its average mixing ratio has been thoroughly studied. Most high resolution measurements correspond to background areas in order to study its long-term trend after the banning. The novelty of this work is supported by the fact that high resolution measurements of CTC were performed in two non-background sites in Northern Spain: 1- An urban area (Bilbao), using an auto-GC-MS during one year (March 2007 − February 2008), and 2- A rural area (Valderejo), using an auto-GC-FID covering almost five years (January 2003 − December 2005, July 2010 − June 2011, and January − June 2015). Auto-GC systems were set up to measure up to 67 volatile organic compounds (VOCs) in Bilbao and 65 VOCs in Valderejo, resulting that CTC coeluted with a traffic related hydrocarbon, 3,3-dimethylpentane (33dmpna). In the GC-MS CTC and 33dmpna were resolved by using the Selected Ion Monitoring (SIM) mode, an option not available for the GC-FID. A procedure to determine 33dmpna on FID chromatograms was developed by de Blas et al. [1], using the mixing ratio of a well resolved isomer, the 2,3-dimethylpentane (23dmpna). Although 33dmpna mixing ratio was most of the time negligible in Valderejo, the procedure was applied to amend the CTC mixing ratios when necessary (1,3% of the cases). Hourly CTC yearly mean mixing ratios were 0.16 ppbv in Bilbao (N=3,290) and between 0.11 and 0.13 ppbv in Valderejo (N=16,051), slightly higher than the overall background values in the Northern Hemisphere such as Mace Head (average 0.089 ppbv for 2003-2013 years [2]). CTC mixing ratios did not decrease during the observed period. Indoor measurements confirmed the use of chlorine-bleach products for cleaning purposes as an indoor source of CTC in Bilbao, but other potential sources of CTC will also be detailed on the paper. References [1] de Blas M, Gómez MC, Navazo M, Alonso L, Durana N, Iza I (2014). Estimation of

unidentified non-methane hydrocarbons in urban air based on highly correlated compound pairs. Atmospheric Environment 98, 629-639

[2] World Meteorological Organization (WMO). 2014. Global Atmosphere Watch. World Data Centre for Greenhouse Gases. WDCGG Data Summary. [cited 2015 Jul 17]. Available from: http://ds.data.jma.go.jp/gmd/wdcgg/

Carbon Tetrachloride from space by MIPAS Envisat

E. Eckert1, N. Glatthor1, T. von Clarmann1, U. Grabowski1, A. Linden1, and S. Kellmann1

presenter: Thomas von Clarmann

1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe,Germany

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat was a highspectral resolution infrared limb emission sounder for measurement of atmospheric trace species.It provided global altitude-resolved fields of constituent abundances from 2002-2012. Carbontetrachloride (CCl4) is analyzed using its ν3 band which has an interference from the signal of theCO2 Q branch at 792 cm−1. This implies that line mixing in the CO2 signature has to beconsidered in the radiative transfer calculations. Useful measurements can be made in the uppertroposphere and lower stratosphere. In the stratosphere, CCl4 mixing ratios decrease rapidly withaltitude. In this talk, global CCl4 maps at selected altitudes will be presented and differences inmixing ratios between the Envisat period and balloon-borne measurements in 1992 will bediscussed.

1

Abstract for Solving the Mystery of Carbon Tetrachloride

Long Term Observation of Carbon Tetrachloride at CMA Network in China Bo Yao1*, Martin K. Vollmer2, Lingxi Zhou1, Xiaoling Zhang3, Zhiqiang Ma3, Fan Dong3, Hongyang Wang1,

Zhenbo Zhang1, Stefan Reimann2

1．Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing, China;

2．Empa, Swiss Federal Laboratories for Material Science and Technology, Laboratory for Air Pollution and

Environmental Technology, Dübendorf, Switzerland;

3. Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Chinese Meteorological

Administration, Beijing, China. * give presentation

Abstract

Long term CCl4 in-situ measurement was conducted by an in-situ GC-ECDs system at the Shangdianzi

Global Atmosphere Watch regional station in China since 2006 using the technique from System for

Observation of Greenhouse Gases in Europe and Aisa (SOGE-A). The background concentrations were

decreasing from 90.3 ppt in 2007 to 86.3 ppt in 2010, consistent with those obtained at NH stations of

Advanced Global Atmospheric Gases Experiment (AGAGE), with the decreasing rate at 1.4 ppt/yr. However,

the enhanced polluted concentrations were increased from 5.1 ppt in 2007 to 7.4 ppt in 2011.

Furthermore, weekly samples were collected at 5 background stations at network of China Meteorological

Administration (CMA) and analyzed by the Medusa-GC/MS system using the technique from AGAGE since

2010. The stations were Waliguan in Qinghai (WLG), Shangdianzi in Beijing (SDZ), Lin’an in Zhejiang

(LAN), Longfengshan in Heilongjiang (LFS) and Xiangri-la in Yunnan (XGL). There are limited pollution

events in WLG and XGL with more than 95% of all the valid data being selected as background data for

January 2011 to December 2012. However, the ratios of polluted events of LAN, SDZ and LFS were 76.1%,

64.9%, 30.4% in 2011 and 83.3%, 76.1%, 18.6% in 2012. The enhanced median concentrations were 6.9,

12.5, 5.4 ppt in 2011 and 9.0, 11.1, 4.2 ppt in 2012. The polluted concentrations of CCl4 show significant

correlation with polluted CO data. The ratios between enhanced CCl4 and enhanced CO concentrations

(ΔCCCl4/ΔCCO) during pollution events were 0.0170×10-3, 0.0126×10-3, 0.0047×10-3 at LAN, SDZ and LFS,

respectively, indicating that different ratios should be used in different Chinese regions for emission estimate

by trace ratio method using CO as a tracer.

During one-year campaign from September 2012 to September 2013, enhanced concentrations of 7.8 ppt

(9.1%) and 4.2 ppt (4.9%) were found at two stations in Beijing urban and suburban area. Daily cycles with

night maximum were observed at both stations by high frequency sampling from April 1 to April 4, 2014.

The elevated night-day differences reached 25 ppt and 27 ppt for urban and suburban stations, respectively,

revealing there was relatively high consumption and emission of CCl4 in Beijing.