scholarly journals A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

2017 ◽  
Vol 17 (19) ◽  
pp. 11929-11941 ◽  
Author(s):  
David E. Oram ◽  
Matthew J. Ashfold ◽  
Johannes C. Laube ◽  
Lauren J. Gooch ◽  
Stephen Humphrey ◽  
...  
Keyword(s):  
East Asia ◽  
Marine Boundary Layer ◽  
Atmospheric Transport ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Tropical Regions ◽  
Upper Troposphere ◽  
Order Of Magnitude ◽  
The Western Pacific

Abstract. Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS) are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODSs. An important remaining uncertainty concerns the role of very short-lived substances (VSLSs) which, owing to their relatively short atmospheric lifetimes (less than 6 months), are not regulated under the Montreal Protocol. Recent studies have found an unexplained increase in the global tropospheric abundance of one VSLS, dichloromethane (CH2Cl2), which has increased by around 60 % over the past decade. Here we report dramatic enhancements of several chlorine-containing VSLSs (Cl-VSLSs), including CH2Cl2 and CH2ClCH2Cl (1,2-dichloroethane), observed in surface and upper-tropospheric air in East and South East Asia. Surface observations were, on occasion, an order of magnitude higher than previously reported in the marine boundary layer, whilst upper-tropospheric data were up to 3 times higher than expected. In addition, we provide further evidence of an atmospheric transport mechanism whereby substantial amounts of industrial pollution from East Asia, including these chlorinated VSLSs, can rapidly, and regularly, be transported to tropical regions of the western Pacific and subsequently uplifted to the tropical upper troposphere. This latter region is a major provider of air entering the stratosphere, and so this mechanism, in conjunction with increasing emissions of Cl-VSLSs from East Asia, could potentially slow the expected recovery of stratospheric ozone.

scholarly journals A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

2017 ◽  
Author(s):  
David E. Oram ◽  
Matthew J. Ashfold ◽  
Johannes C. Laube ◽  
Lauren J. Gooch ◽  
Stephen Humphrey ◽  
...  
Keyword(s):  
East Asia ◽  
Marine Boundary Layer ◽  
Atmospheric Transport ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Tropical Regions ◽  
Upper Troposphere ◽  
Order Of Magnitude ◽  
The Western Pacific

Abstract. Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS) are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODS. An important remaining uncertainty concerns the role of very short lived substances (VSLS) which, owing to their relatively short atmospheric lifetimes (less than 6 months), are not regulated under the Montreal Protocol. Recent studies have found an unexplained increase in the global tropospheric abundance of one VSLS, dichloromethane (CH2Cl2), which has increased by around 60 % over the past decade. Here we report dramatic enhancements of several chlorine-containing VSLS, including CH2Cl2 and CH2ClCH2Cl (1,2-dichloroethane), observed in surface and upper tropospheric air in East and South East Asia. Surface observations were an order of magnitude higher than previously reported in the marine boundary layer, whilst upper tropospheric data were up to 3 times higher than expected. In addition we provide further evidence of an atmospheric transport mechanism whereby substantial amounts of industrial pollution from East Asia, including these chlorinated VSLS, can rapidly, and regularly, be transported to tropical regions of the western Pacific and subsequently uplifted to the tropical upper troposphere. This latter region is a major provider for air entering the stratosphere and so this mechanism, in conjunction with increasing emissions of Cl-VSLS from East Asia, could potentially slow the expected recovery of stratospheric ozone.

scholarly journals Deriving an atmospheric budget of total organic bromine using airborne in situ measurements from the western Pacific area during SHIVA

2014 ◽  
Vol 14 (13) ◽  
pp. 6903-6923 ◽  
Author(s):  
S. Sala ◽  
H. Bönisch ◽  
T. Keber ◽  
D. E. Oram ◽  
G. Mills ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Radiative Heating ◽  
Western Pacific ◽  
Data Set ◽  
Tropical Regions ◽  
Upper Troposphere ◽  
Tropical Tropopause ◽  
Vertical Range ◽  
The Western Pacific

Abstract. During the recent SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive data set of all halogen species relevant for the atmospheric budget of total organic bromine was collected in the western Pacific region using the Falcon aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully automated in situ instrument GHOST-MS (Gas chromatograph for the Observation of Tracers – coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground-based state-of-the-art GC / MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CH2BrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2σ measurement uncertainties. In contrast to the suggestion that the western Pacific could be a region of strongly increased atmospheric VSLS abundance (Pyle et al., 2011), we found only in the upper troposphere a slightly enhanced amount of total organic bromine from VSLS relative to the levels reported in Montzka and Reimann et al. (2011) for other tropical regions. From the SHIVA observations in the upper troposphere, a budget for total organic bromine, including four halons (H-1301, H-1211, H-1202, H-2402), CH3Br and the VSLS, is derived for the level of zero radiative heating (LZRH), the input region for the tropical tropopause layer (TTL) and thus also for the stratosphere. With the exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka and Reimann et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.

Detection of Fourth Generation Synthetic Halocarbons in the Upper Troposphere

2021 ◽  
Author(s):  
Tanja Schuck ◽  
Katharina Meixner ◽  
Peter van Velthoven ◽  
Simon O’Doherty ◽  
Martin Vollmer ◽  
...  
Keyword(s):  
Degradation Products ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Gas Chromatography Mass Spectrometry ◽  
Fourth Generation ◽  
Oh Radicals ◽  
Sample Collection ◽  
Upper Troposphere ◽  
Wide Range ◽  
Air Sample

<p>Synthetic halocarbons are used for a wide range of applications, for example air conditioning or foam blowing. Many of them are long-lived greenhouse gases contributing to climate change and, in addition, may contribute to stratospheric ozone depletion if containing chlorine or bromine. Therefore, their production and use are regulated by the Montreal Protocol and its amendments. These long-lived halocarbons are increasingly replaced by a fourth generation of unsaturated short-lived halocarbons, the hydrochlorofluoroolefines (HCFOs) and hydrofluoroolefines (HFOs). The main removal process of these compounds in the atmosphere is reaction with OH radicals, and their average lifetimes are of the order of up to a few tens of days.</p><p>As part of the IAGOS-CARIBIC instrument package we operate an automated air sample collection system during regular flights in the upper troposphere and lowermost stratosphere. At altitudes around 10-12 km, samples are collected in stainless steel and glass flasks at predefined times. Post-flight laboratory analyses include gas chromatography - mass spectrometry measurements of a wide range of halocarbons. The short-lived compounds HFO-1234ze(E) and HCFO-1233zd(E) were detected in a small number of samples, indicating that these compounds are sufficiently long lived for transport into the upper troposphere. There were not found in stratospheric samples.</p><p>At this altitude, low abundance of OH and low temperatures may slow down chemical decay, and tracer lifetimes may increase significantly. Based on average temperatures and OH abundance, we estimate local lifetimes of HFO-1234ze(E) and HCFO-1233zd(E)  in the mid-latitudes of up to 75 days and 200 days, respectively. Short-lived H(C)FOs reaching the upper troposphere could thus be transported over large distances and their degradation products may be deposited  far from their emission sources.</p>

Atmospheric impacts of short-lived chlorinated species over the recent past: a chemistry-climate perspective

2021 ◽  
Author(s):  
Ewa Bednarz ◽  
Ryan Hossaini ◽  
Luke Abraham ◽  
Peter Braesicke ◽  
Martyn Chipperfield
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Lower Boundary ◽  
Montreal Protocol ◽  
Recent Past ◽  
Substantial Impact ◽  
Ozone Depleting Substances ◽  
The Impact

<p>The emissions of most long-lived halogenated ozone-depleting substances (ODSs) are now decreasing, owing to controls on their production introduced by Montreal Protocol and its amendments. However, short-lived halogenated compounds can also have substantial impact on atmospheric chemistry, including stratospheric ozone, particularly if emitted near climatological uplift regions. It has recently become evident that emissions of some chlorinated very short-lived species (VSLSs), such as chloroform (CHCl<sub>3</sub>) and dichloromethane (CH<sub>2</sub>Cl<sub>2</sub>), could be larger than previously believed and increasing, particularly in Asia. While these may exert a significant influence on atmospheric chemistry and climate, their impacts remain poorly characterised. </p><p> </p><p>We address this issue using the UM-UKCA chemistry-climate model (CCM). While not only the first, to our knowledge, model study addressing this problem using a CCM, it is also the first such study employing a whole atmosphere model, thereby simulating the tropospheric Cl-VSLSs emissions and the resulting stratospheric impacts in a fully consistent manner. We use a newly developed Double-Extended Stratospheric-Tropospheric (DEST) chemistry scheme, which includes emissions of all major chlorinated and brominated VSLSs alongside an extended treatment of long-lived ODSs.</p><p> </p><p>We examine the impacts of rising Cl-VSLSs emissions on atmospheric chlorine tracers and ozone, including their long-term trends. We pay particular attention to the role of ‘nudging’, as opposed to the free-running model set up, for the simulated Cl-VSLSs impacts, thereby demostrating the role of atmospheric dynamics in modulating the atmospheric responses to Cl-VSLSs. In addition, we employ novel estimates of Cl-VSLS emissions over the recent past and compare the results with the simulations that prescribe Cl-VSLSs using simple lower boundary conditions. This allows us to demonstrate the impact such choice has on the dominant location and seasonality of the Cl-VSLSs transport into the stratosphere.</p>

scholarly journals First Evidences of Methyl Chloride (CH3Cl) Transport from the Northern Italy Boundary Layer during Summer 2017

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 238 ◽  
Author(s):  
Paolo Cristofanelli ◽  
Jgor Arduini ◽  
Francescopiero Calzolari ◽  
Umberto Giostra ◽  
Paolo Bonasoni ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
Stratospheric Ozone ◽  
Methyl Chloride ◽  
Temporal Correlation ◽  
Northern Italy ◽  
Montreal Protocol ◽  
Anthropogenic Activity ◽  
Bivariate Analysis

Methyl Chloride (CH3Cl) is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. While the atmospheric CH3Cl emissions are predominantly caused by natural sources on the global budget, significant uncertainties still remain for the anthropogenic CH3Cl emission strengths. In summer 2007 an intensive field campaign within the ACTRIS-2 Project was hosted at the Mt. Cimone World Meteorological Organization/Global Atmosphere Watch global station (CMN, 44.17° N, 10.68° E, 2165 m a.s.l.). High-frequency and high precision in situ measurements of atmospheric CH3Cl revealed significant high-frequency variability superimposed on the seasonally varying regional background levels. The high-frequency CH3Cl variability was characterized by an evident cycle over 24 h with maxima during the afternoon which points towards a systematic role of thermal vertical transport of air-masses from the regional boundary layer. The temporal correlation analysis with specific tracers of anthropogenic activity (traffic, industry, petrochemical industry) together with bivariate analysis as a function of local wind regime suggested that, even if the role of natural marine emissions appears as predominant, the northern Italy boundary layer could potentially represent a non-negligible source of CH3Cl during summer. Since industrial production and use of CH3Cl have not been regulated under the Montreal Protocol (MP) or its successor amendments, continuous monitoring of CH3Cl outflow from the Po Basin is important to properly assess its anthropogenic emissions.

scholarly journals Brominated VSLS and their influence on ozone under a changing climate

2017 ◽  
Vol 17 (18) ◽  
pp. 11313-11329 ◽  
Author(s):  
Stefanie Falk ◽  
Björn-Martin Sinnhuber ◽  
Gisèle Krysztofiak ◽  
Patrick Jöckel ◽  
Phoebe Graf ◽  
...  
Keyword(s):  
21St Century ◽  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Atmospheric Transport ◽  
Stratospheric Ozone ◽  
Chemical Transformations ◽  
Mixing Ratios ◽  
Ocean Atmosphere ◽  
The Impact

Abstract. Very short-lived substances (VSLS) contribute as source gases significantly to the tropospheric and stratospheric bromine loading. At present, an estimated 25 % of stratospheric bromine is of oceanic origin. In this study, we investigate how climate change may impact the ocean–atmosphere flux of brominated VSLS, their atmospheric transport, and chemical transformations and evaluate how these changes will affect stratospheric ozone over the 21st century. Under the assumption of fixed ocean water concentrations and RCP6.0 scenario, we find an increase of the ocean–atmosphere flux of brominated VSLS of about 8–10 % by the end of the 21st century compared to present day. A decrease in the tropospheric mixing ratios of VSLS and an increase in the lower stratosphere are attributed to changes in atmospheric chemistry and transport. Our model simulations reveal that this increase is counteracted by a corresponding reduction of inorganic bromine. Therefore the total amount of bromine from VSLS in the stratosphere will not be changed by an increase in upwelling. Part of the increase of VSLS in the tropical lower stratosphere results from an increase in the corresponding tropopause height. As the depletion of stratospheric ozone due to bromine depends also on the availability of chlorine, we find the impact of bromine on stratospheric ozone at the end of the 21st century reduced compared to present day. Thus, these studies highlight the different factors influencing the role of brominated VSLS in a future climate.

scholarly journals Deriving an atmospheric budget of total organic bromine using airborne in-situ measurements from the Western Pacific during SHIVA

2014 ◽  
Vol 14 (4) ◽  
pp. 4957-5012 ◽  
Author(s):  
S. Sala ◽  
H. Bönisch ◽  
T. Keber ◽  
D. E. Oram ◽  
G. Mills ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Source Region ◽  
Western Pacific ◽  
Tropical Regions ◽  
Mixing Ratios ◽  
Air Sampler ◽  
Vertical Range ◽  
German Aerospace ◽  
The Western Pacific

Abstract. During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset of all halogen species relevant for the atmospheric budget of total organic bromine has been collected in the West Pacific region using the FALCON aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas cHromatograph for the Observation of Tracers – coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CHBrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2 σ measurement uncertainties. In contrast to the suggestion that the Western Pacific could be a major source region for VSLS (Pyle et al., 2011), we found only slightly enhanced mixing ratios of brominated halogen source gases relative to the levels reported in Montzka et al. (2011) for other tropical regions. A budget for total organic bromine, including all four halons,CH3Br and the VSLS, is derived for the upper troposphere, the input region for the TTL and thus also for the stratosphere, compiled from the SHIVA dataset. With exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.

scholarly journals Brominated VSLS and their influence on ozone under a changing climate

2017 ◽  
Author(s):  
Stefanie Falk ◽  
Björn-Martin Sinnhuber ◽  
Gisèle Krysztofiak ◽  
Patrick Jöckel ◽  
Phoebe Graf ◽  
...  
Keyword(s):  
21St Century ◽  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Atmospheric Transport ◽  
Stratospheric Ozone ◽  
Chemical Transformations ◽  
Mixing Ratios ◽  
Ocean Atmosphere ◽  
The Impact

Abstract. Very short-lived source gases (VSLS) contribute significantly to the tropospheric and stratospheric bromine loading. At present, an estimated 25 % of stratospheric bromine is of oceanic origin. In this study, we investigate how climate change may impact the ocean-atmosphere flux of brominated VSLS, their atmospheric transport, chemical transformations, and evaluate how these changes will affect stratospheric ozone over the 21st century. Under the assumption of fixed ocean water concentrations and RCP6.0 scenario, we find an increase of the ocean-atmosphere flux of brominated VSLS of about 8–10 % by the end of the 21st century compared to present day. A decrease in the tropospheric mixing ratios of VSLS and an increase in the lower stratosphere are attributed to changes in atmospheric chemistry and transport. Our model simulations reveal that, in line with the reduction in the troposphere, the total amount of bromine from VSLS in the stratosphere will decrease during the 21st century. Part of the apparent increase of VSLS in the tropical lower stratosphere results from an increase in the corresponding tropopause height. As the depletion of stratospheric ozone due to bromine depends also on the availability of chlorine, we find the impact of bromine on stratospheric ozone at the end of the 21st century reduced compared to present day. Thus, these studies highlight the different factors influencing the role of brominated VSLS in a future climate.

scholarly journals Airborne measurements of HCl from the marine boundary layer to the lower stratosphere over the North Pacific Ocean during INTEX-B

2008 ◽  
Vol 8 (1) ◽  
pp. 3563-3595 ◽  
Author(s):  
S. Kim ◽  
L. G. Huey ◽  
R. E. Stickel ◽  
R. B. Pierce ◽  
G. Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Stratosphere ◽  
Marine Boundary Layer ◽  
North Pacific Ocean ◽  
Stratospheric Ozone ◽  
Background Level ◽  
Upper Troposphere ◽  
Airborne Measurements ◽  
The North ◽  
The Impact

Abstract. Gas phase HCl was measured from the marine boundary layer (MBL) to the lower stratosphere from the NASA DC-8 during five science flights (41 h) of the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) field campaign. In the upper troposphere/lower stratosphere (UT/LS, 8–12 km) HCl was observed to range from a few tens to 100 pptv due to stratospheric influence with a background tropospheric level of less than 2 pptv. In the 8–12 km altitude range, a simple analysis of the O3/HCl correlation shows that pure stratospheric and mixed tropospheric/stratospheric air masses were encountered 30% and 15% of the time, respectively. In the mid troposphere (4–8 km) HCl levels were usually below 2 pptv except for a few cases of stratospheric influence and were much lower than reported in previous work. These data indicate that background levels of HCl in the mid and upper troposphere are very low and confirm its use in these regions as a tracer of stratospheric ozone. However, a case study suggests that HCl may be produced in the mid troposphere by the dechlorination of dust aerosols. In the remote marine boundary layer HCl levels were consistently above 20 pptv (up to 140 pptv) and strongly correlated with HNO3. Cl atom levels were estimated from the background level of HCl in the MBL. This analysis suggests a Cl concentration of ~3×103 atoms cm−3, which corresponds to the lower range of previous studies. Finally, the observed HCl levels are compared to predictions by the Real-time Air Quality Modeling System (RAQMS) to assess its ability to characterize the impact of stratospheric transport on the upper troposphere.

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