Fate of Chloromethanes in the Atmospheric Environment: Implications for Human Health, Ozone Formation and Depletion, and Global Warming Impacts

Tsai, Wen‐Tien

doi:10.3390/toxics5040023

Cited by 59 publications

(35 citation statements)

References 30 publications

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“…Then again, CHCl 3 has other uses, e.g. as solvent (Tsai, 2017), without any potential c-C 4 F 8 emissions.…”

Section: Emissions From Eastern Asiamentioning

confidence: 99%

Perfluorocyclobutane (PFC-318, c-C4F8) in the global atmosphere

Mühle¹,

Trudinger²,

Rigby³

et al. 2019

Preprint

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Abstract. We reconstruct atmospheric abundances of the potent greenhouse gas c-C4F8 (perfluorocyclobutane, perfluorocarbon PFC-318) from measurements of in situ, archived, firn, and aircraft air samples with precisions of ~&#8201;1&#8211;2&#8201;% reported on the SIO-14 gravimetric calibration scale. Combined with inverse methods, we found near zero atmospheric abundances from the early 1900s to the early 1960s, after which they rose sharply, reaching 1.66&#8201;ppt (parts per trillion dry-air mole fraction) in 2017. Global c-C4F8 emissions rose from near zero in the 1960s to ~&#8201;1.2&#8201;Gg&#8201;yr&#8722;1 in the late 1970s to late 1980s, then declined to ~&#8201;0.8&#8201;Gg&#8201;yr&#8722;1 in the mid-1990s to early 2000s, followed by a rise since the early 2000s to ~&#8201;2.2&#8201;Gg&#8201;yr&#8722;1 in 2017. These emissions are significantly larger than inventory based emission estimates. Estimated emissions from eastern Asia rose from 0.36&#8201;Gg&#8201;yr&#8722;1 in 2010 to 0.73&#8201;Gg&#8201;yr&#8722;1 in 2016 and 2017, 31&#8201;% of global emissions, mostly from eastern China. We estimate emissions of 0.14&#8201;Gg&#8201;yr&#8722;1 from Northern and Central India in 2016 and find evidence for significant emissions from Russia. In contrast, recent emissions from North Western Europe and Australia are estimated to be small (&#8804;&#8201;1&#8201;% each). We conclude that emissions from China, India and Russia are likely related to production of polytetrafluoroethylene (PTFE, &#8220;Teflon&#8221;) and other fluoropolymers that are based on the pyrolysis of hydrochlorofluorocarbon HCFC-22 (CHClF2) in which c-C4F8 is a known by-product. The semiconductor sector, where c-C4F8 is used, is estimated to be a small source. Without an obvious correlation with population density, incineration of waste containing fluoropolymers is probably a minor source, and we find no evidence of emissions from electrolytic production of aluminum in Australia. While many possible emissive uses of c-C4F8 are known, the start of significant emissions may well be related to the advent of commercial PTFE production in 1947. Process controls or abatement to reduce c-C4F8 by-product were probably not in place in the early decades, explaining the increase in emissions. With the advent of by-product reporting requirements to the United Nations Framework Convention on Climate Change (UNFCCC) in the 1990s, concern about climate change and product stewardship, abatement, and perhaps the collection of c-C4F8 by-product for use in the semiconductor industry where it can be easily abated, it is conceivable that emissions in developed countries were stabilized and then reduced, explaining the observed emission reduction in the 1980s and 1990s. Concurrently, production of PTFE in China began to increase rapidly. Without emission reduction requirements, it is plausible that global emissions today are dominated by China and other developing countries, in agreement with our analysis. We predict that c-C4F8 emissions will continue to rise and that c-C4F8 will become the second most important emitted PFC in terms of CO2-equivalent emissions within a year or two. The 2017 radiative forcing of c-C4F8 (0.52&#8201;mW&#8201;m&#8722;2) is small but emissions of c-C4F8 and other PFCs, due to their very long atmospheric lifetimes, essentially permanently alter Earth's radiative budget and should be reduced. Significant emissions outside of the investigated regions clearly show that observational capabilities and reporting requirements need to be improved to understand global and country scale emissions of PFCs and other synthetic greenhouse gases and ozone depleting substances.

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“…Then again, CHCl 3 has other uses, e.g. as solvent (Tsai, 2017), without any potential c-C 4 F 8 emissions.…”

Section: Emissions From Eastern Asiamentioning

confidence: 99%

Perfluorocyclobutane (PFC-318, c-C4F8) in the global atmosphere

Mühle¹,

Trudinger²,

Rigby³

et al. 2019

Preprint

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“…Chloromethane (CH 3 Cl) is the most abundant halogenated volatile organic compound (VOC) in the atmosphere and contributes substantially to destruction of stratospheric ozone [ 1 , 2 ]. Global emissions reach about 2.0 ± 0.6 Tg CH 3 Cl per year [ 3 , 4 ].…”

Section: Introductionmentioning

confidence: 99%

Methanol consumption drives the bacterial chloromethane sink in a forest soil

et al. 2018

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Halogenated volatile organic compounds (VOCs) emitted by terrestrial ecosystems, such as chloromethane (CH3Cl), have pronounced effects on troposphere and stratosphere chemistry and climate. The magnitude of the global CH3Cl sink is uncertain since it involves a largely uncharacterized microbial sink. CH3Cl represents a growth substrate for some specialized methylotrophs, while methanol (CH3OH), formed in much larger amounts in terrestrial environments, may be more widely used by such microorganisms. Direct measurements of CH3Cl degradation rates in two field campaigns and in microcosms allowed the identification of top soil horizons (i.e., organic plus mineral A horizon) as the major biotic sink in a deciduous forest. Metabolically active members of Alphaproteobacteria and Actinobacteria were identified by taxonomic and functional gene biomarkers following stable isotope labeling (SIP) of microcosms with CH3Cl and CH3OH, added alone or together as the [13C]-isotopologue. Well-studied reference CH3Cl degraders, such as Methylobacterium extorquens CM4, were not involved in the sink activity of the studied soil. Nonetheless, only sequences of the cmuA chloromethane dehalogenase gene highly similar to those of known strains were detected, suggesting the relevance of horizontal gene transfer for CH3Cl degradation in forest soil. Further, CH3Cl consumption rate increased in the presence of CH3OH. Members of Alphaproteobacteria and Actinobacteria were also 13C-labeled upon [13C]-CH3OH amendment. These findings suggest that key bacterial CH3Cl degraders in forest soil benefit from CH3OH as an alternative substrate. For soil CH3Cl-utilizing methylotrophs, utilization of several one-carbon compounds may represent a competitive advantage over heterotrophs that cannot utilize one-carbon compounds.

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“…5 In subcolumn FE, the metal fraction exposed [CO ads /(Pd + Au)] and d (metal particle size) are calculated as 1.2/FE [45]. 6 In subcolumn H/Pd is shown the ratio of moles of H 2 released during TPHD trace to moles of Pd, T max shows the position of maximum in the trace.…”

Section: Temperature-programmed Hydrogenation Of Catalysts After Hdclmentioning

confidence: 99%

“…However, removal of just one chlorine atom from the CCl 4 molecule yields chloroform (CHCl 3 ), which already has a lower environmental impact as compared to CCl 4 . Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) for the both compounds are: ODP CCl4 = 1.1, GWP CCl4 = 1730, ODP CHCl3 = 0.01, GWP CHCl3 = 16 (for ODP and GWP values, the reference compound is from CFC-11, for which the values are 1.0 and 4600, respectively) [6].…”

Section: Introductionmentioning

confidence: 99%

Towards High Efficacy of Pd-Au/C Catalyst for Tetrachloromethane Hydrodechlorination

et al. 2021

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We present an efficient strategy for synthesising the PdAu catalysts with a homogeneous PdAu alloy phase for environmentally important hydrodechlorination of tetrachloromethane in the gas phase. The synthesis of carbon-supported catalysts involved two major steps: (i) incorporation of palladium and gold nanoparticles into carbon support and (ii) activation of the catalysts. The critical part of this work was to find the optimal conditions for both steps. Thus, the incorporation of the nanoparticles was carried out in two ways, by impregnation and direct redox reaction method using acetone solutions of metal precursor salts. The activation was performed either by a conventional thermal reduction in hydrogen or flash irradiation in a microwave oven. The homogeneity and structure of the PdAu alloy were found to depend on the catalyst activation method critically. In all cases, we observed better homogeneity for catalysts that were subject to microwave irradiation. Moreover, the flash microwave irradiation of prepared catalysts provided catalysts of better stability and selectivity towards the desired products (hydrocarbons) in the hydrodechlorination of tetrachloromethane as compared to the catalyst obtained by conventional thermal activation in hydrogen.

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Fate of Chloromethanes in the Atmospheric Environment: Implications for Human Health, Ozone Formation and Depletion, and Global Warming Impacts

Cited by 59 publications

References 30 publications

Perfluorocyclobutane (PFC-318, <i>c</i>-C<sub>4</sub>F<sub>8</sub>) in the global atmosphere

Perfluorocyclobutane (PFC-318, <i>c</i>-C<sub>4</sub>F<sub>8</sub>) in the global atmosphere

Methanol consumption drives the bacterial chloromethane sink in a forest soil

Towards High Efficacy of Pd-Au/C Catalyst for Tetrachloromethane Hydrodechlorination

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Fate of Chloromethanes in the Atmospheric Environment: Implications for Human Health, Ozone Formation and Depletion, and Global Warming Impacts

Cited by 59 publications

References 30 publications

Perfluorocyclobutane (PFC-318, &lt;i&gt;c&lt;/i&gt;-C&lt;sub&gt;4&lt;/sub&gt;F&lt;sub&gt;8&lt;/sub&gt;) in the global atmosphere

Perfluorocyclobutane (PFC-318, &lt;i&gt;c&lt;/i&gt;-C&lt;sub&gt;4&lt;/sub&gt;F&lt;sub&gt;8&lt;/sub&gt;) in the global atmosphere

Methanol consumption drives the bacterial chloromethane sink in a forest soil

Towards High Efficacy of Pd-Au/C Catalyst for Tetrachloromethane Hydrodechlorination

Contact Info

Product

Resources

About

Perfluorocyclobutane (PFC-318, <i>c</i>-C<sub>4</sub>F<sub>8</sub>) in the global atmosphere

Perfluorocyclobutane (PFC-318, <i>c</i>-C<sub>4</sub>F<sub>8</sub>) in the global atmosphere