Trends and emissions of six perfluorocarbons in the Northern Hemisphere and Southern Hemisphere

Perfluorocarbons (PFCs) are potent greenhouse gases with global warming potentials up to several thousand times greater than CO2 on a 100-year time horizon. The lack of any significant sinks for PFCs means that they have long atmospheric lifetimes of the order of thousands of years. Anthropogenic production is thought to be the only source for most PFCs. Here we report an update on the global atmospheric abundances of the following PFCs, most of which have for the first time been analytically separated according to their isomers: c-octafluorobutane (c-C4F8), n-decafluorobutane (n-C4F10), n-dodecafluoropentane (n-C5F12), n-tetradecafluorohexane (n-C6F14), and n-hexadecafluoroheptane (n-C7F16). Additionally, we report the first data set on the atmospheric mixing ratios of perfluoro-2-methylpentane (i-C6F14). The existence and significance of PFC isomers have not been reported before, due to the analytical challenges of separating them. The time series spans a period from 1978 to the present. Several data sets are used to investigate temporal and spatial trends of these PFCs: time series of air samples collected at Cape Grim, Australia, from 1978 to the start of 2018; a time series of air samples collected between July 2015 and April 2017 at Tacolneston, UK; and intensive campaign-based sampling collections from Taiwan. Although the remote “background” Southern Hemispheric Cape Grim time series indicates that recent growth rates of most of these PFCs are lower than in the 1990s, we continue to see significantly increasing mixing ratios that are between 6 % and 27 % higher by the end of 2017 compared to abundances measured in 2010. Air samples from Tacolneston show a positive offset in PFC mixing ratios compared to the Southern Hemisphere baseline. The highest mixing ratios and variability are seen in air samples from Taiwan, which is therefore likely situated much closer to PFC sources, confirming predominantly Northern Hemispheric emissions for most PFCs. Even though these PFCs occur in the atmosphere at levels of parts per trillion molar or less, their total cumulative global emissions translate into 833 million metric tonnes of CO2 equivalent by the end of 2017, 23 % of which has been emitted since 2010. Almost two-thirds of the CO2 equivalent emissions within the last decade are attributable to c-C4F8, which currently also has the highest emission rates that continue to grow. Sources of all PFCs covered in this work remain poorly constrained and reported emissions in global databases do not account for the abundances found in the atmosphere

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

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

Time, the Written Record, and Professional Practice: The Case of Contemporary Social Work

Drawing on a three year ethnographically-oriented study exploring contemporary professional social work writing, this paper focuses on a key concern: the amount of time taken up with writing, or ‘paperwork’. We explore the relationship between time and professional social work writing in three key ways. Firstly, as a discrete, measurable phenomenon - how much time is spent on writing? Secondly, as a textual dimension to social work writing – how do institutional documents drive particular entextualisations of time and how do social worker texts entextualise time? Thirdly, as a particular timespace configuration of lived experience - how is time experienced by professional social workers? Findings indicate that a dominant institutional chronotope is governing social work textual practice underpinned by an ideology of writing which is at odds with social workers’ desired practice and professional goals. Methodologically, the paper illustrates the value of combining a range of data and analytic tools, using textual and contextual data, as well as qualitative and quantitative frames of analysis

Evaluation of stratospheric age of air from CF4_{4}, C2_{2}F6_{6}, C3_{3}F8_{8}, CHF3_{3}, HFC-125, HFC-227ea and SF6_{6}; Implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials

In a changing climate, potential stratospheric circulation changes require long-term monitoring. Stratospheric trace gas measurements are often used as a proxy for stratospheric circulation changes via the “mean age of air” values derived from them. In this study, we investigated five potential age of air tracers – the perfluorocarbons CF4, C2F6 and C3F8 and the hydrofluorocarbons CHF3 (HFC-23) and HFC-125 – and compare them to the traditional tracer SF6 and a (relatively) shorter-lived species, HFC-227ea. A detailed uncertainty analysis was performed on mean ages derived from these “new” tracers to allow us to confidently compare their efficacy as age tracers to the existing tracer, SF6. Our results showed that uncertainties associated with the mean age derived from these new age tracers are similar to those derived from SF6, suggesting that these alternative compounds are suitable in this respect for use as age tracers. Independent verification of the suitability of these age tracers is provided by a comparison between samples analysed at the University of East Anglia and the Scripps Institution of Oceanography. All five tracers give younger mean ages than SF6, a discrepancy that increases with increasing mean age. Our findings qualitatively support recent work that suggests that the stratospheric lifetime of SF6 is significantly less than the previous estimate of 3200 years. The impact of these younger mean ages on three policy-relevant parameters – stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials – is investigated in combination with a recently improved methodology to calculate FRFs. Updates to previous estimations for these parameters are provided

Abrupt reversal in emissions and atmospheric abundance of HCFC-133a (CF3CH2Cl)

Hydrochlorofluorocarbon HCFC-133a (CF3CH2Cl) is an anthropogenic compound whose consumption for emissive use is restricted under the Montreal Protocol. A recent study showed rapidly increasing atmospheric abundances and emissions. We report that, following this rise, the at- mospheric abundance and emissions have declined sharply in the past three years. We find a Northern Hemisphere HCFC-133a increase from 0.13 ppt (dry air mole fraction in parts-per-trillion) in 2000 to 0.50 ppt in 2012–mid-2013 followed by an abrupt reversal to 0.44 ppt by early 2015. Global emissions derived from these observations peaked at 3.1 kt in 2011, followed by a rapid decline of 0.5 kt yr−2 to 1.5 kt yr−1 in 2014. Sporadic HCFC-133a pollution events are detected in Europe from our high-resolution HCFC-133a records at three European stations, and in Asia from sam- ples collected in Taiwan. European emissions are estimated to be <0.1 kt yr−1 although emission hotspots were identi- fied in France

Bromocarbons in the tropical coastal and open ocean atmosphere during the Prime Expedition Scientific Cruise 2009 (PESC 09)

Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, and CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu–Sulawesi seas during a two-month research cruise in June–July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 for CHCl2Br, and 0.1–0.4 pmol mol−1 for CHClBr2. There was no significant correlation between bromocarbons and in situ chlorophyll a, but positive correlations with both MODIS and SeaWiFS satellite chlorophyll a. Together, the shortlived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine loading, which is similar to that found in previous studies from global sampling networks (Montzka et al., 2011). Statistical tests showed strong Spearman correlations between brominated compounds, suggesting a common source. Log–log plots of CHBr3/CH2Br2 versus CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and to derive a value of 32 Gg yr−1 for the Southeast (SE) Asian region (10◦ N–20◦ S, 90–150◦ E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity

Evaluation of stratospheric age of air from CF4, C2F6, C3F8, CHF3, HFC-125, HFC-227ea and SF6; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials

In a changing climate, potential stratospheric circulation changes require long-term monitoring. Stratospheric trace gas measurements are often used as a proxy for stratospheric circulation changes via the <q>mean age of air</q> values derived from them. In this study, we investigated five potential age of air tracers – the perfluorocarbons CF₄, C₂F₆ and C₃F₈ and the hydrofluorocarbons CHF₃ (HFC-23) and HFC-125 – and compare them to the traditional tracer SF₆ and a (relatively) shorter-lived species, HFC-227ea. A detailed uncertainty analysis was performed on mean ages derived from these <q>new</q> tracers to allow us to confidently compare their efficacy as age tracers to the existing tracer, SF₆. Our results showed that uncertainties associated with the mean age derived from these new age tracers are similar to those derived from SF₆, suggesting that these alternative compounds are suitable in this respect for use as age tracers. Independent verification of the suitability of these age tracers is provided by a comparison between samples analysed at the University of East Anglia and the Scripps Institution of Oceanography. All five tracers give younger mean ages than SF₆, a discrepancy that increases with increasing mean age. Our findings qualitatively support recent work that suggests that the stratospheric lifetime of SF₆ is significantly less than the previous estimate of 3200 years. The impact of these younger mean ages on three policy-relevant parameters – stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials – is investigated in combination with a recently improved methodology to calculate FRFs. Updates to previous estimations for these parameters are provided

Evidence for strong, widespread chlorine radical chemistry associated with pollution outflow from continental Asia

The chlorine radical is a potent atmospheric oxidant, capable of perturbing tropospheric oxidative cycles normally controlled by the hydroxyl radical. Significantly faster reaction rates allow chlorine radicals to expedite oxidation of hydrocarbons, including methane, and in polluted environments, to enhance ozone production. Here we present evidence, from the CARIBIC airborne dataset, for extensive chlorine radical chemistry associated with Asian pollution outflow, from airborne observations made over the Malaysian Peninsula in winter. This region is known for persistent convection that regularly delivers surface air to higher altitudes and serves as a major transport pathway into the stratosphere. Oxidant ratios inferred from hydrocarbon relationships show that chlorine radicals were regionally more important than hydroxyl radicals for alkane oxidation and were also important for methane and alkene oxidation (>10%). Our observations reveal pollution-related chlorine chemistry that is both widespread and recurrent, and has implications for tropospheric oxidizing capacity, stratospheric composition and ozone chemistry

Screening for Microsatellite Instability Identifies Frequent 3′-Untranslated Region Mutation of the RB1-Inducible Coiled-Coil 1 Gene in Colon Tumors

BACKGROUND: Coding region microsatellite instability (MSI) results in loss of gene products and promotion of microsatellite-unstable (MSI-H) carcinogenesis. Recent studies have indicated that MSI within 3'-untranslated regions (3'UTRs) may post-transcriptionally dysregulate gene products. Within this context, we conducted a broad mutational survey of 42 short 3'UTR microsatellites (MSs) in 45 MSI-H colorectal tumors and their corresponding normal colonic mucosae. METHODOLOGY/PRINCIPAL FINDINGS: In order to estimate the overall susceptibility of MSs to MSI in MSI-H tumors, the observed MSI frequency of each MS was correlated with its length, interspecies sequence conservation level, and distance from some genetic elements (i.e., stop codon, polyA signal, and microRNA binding sites). All MSs were stable in normal colonic mucosae. The MSI frequency at each MS in MSI-H tumors was independent of sequence conservation level and distance from other genetic elements. In contrast, MS length correlated significantly with MSI frequency in MSI-H tumors (r=0.86, p=7.2x10(-13)). 3'UTR MSs demonstrated MSI frequencies in MSI-H tumors higher than the 99% upper limit predicted by MS length for RB1-inducible coiled-coil 1(RB1CC1, mutation frequency 68.4%), NUAK family SNF1-like kinase 1(NUAK1, 31.0%), and Rtf1, Paf1/RNA polymerase II complex component, homolog (RTF1, 25.0%). An in silico prediction of RNA structure alterations was conducted for these MSI events to gauge their likelihood of affecting post-transcriptional regulation. RB1CC1 mutant was predicted to lose a microRNA-accessible loop structure at a putative binding site for the tumor-suppressive microRNA, miR-138. In contrast, the predicted 3'UTR structural change was minimal for NUAK1- and RTF1 mutants. Notably, real-time quantitative RT-PCR analysis revealed significant RB1CC1 mRNA overexpression vs. normal colonic mucosae in MSI-H cancers manifesting RB1CC1 3'UTR MSI (9.0-fold; p = 3.6x10(-4)). CONCLUSIONS: This mutational survey of well-characterized short 3'UTR MSs confirms that MSI incidence in MSI-H colorectal tumors correlates with MS length, but not with sequence conservation level or distance from other genetic elements. This study also identifies RB1CC1 as a novel target of frequent mutation and aberrant upregulation in MSI-H colorectal tumors. The predicted loss of a microRNA-accessible structure in mutant RB1CC1 RNA fits the hypothesis that 3'UTR MSI involves in aberrant RB1CC1 posttranscriptional upregulation. Further direct assessments are indicated to investigate this possibility.Bogdan C. Paun, Yulan Cheng, Barbara A. Leggett, Joanne Young, Stephen J. Meltzer, Yuriko Mor

Mutation of von Hippel–Lindau Tumour Suppressor and Human Cardiopulmonary Physiology

BACKGROUND: The von Hippel–Lindau tumour suppressor protein–hypoxia-inducible factor (VHL–HIF) pathway has attracted widespread medical interest as a transcriptional system controlling cellular responses to hypoxia, yet insights into its role in systemic human physiology remain limited. Chuvash polycythaemia has recently been defined as a new form of VHL-associated disease, distinct from the classical VHL-associated inherited cancer syndrome, in which germline homozygosity for a hypomorphic VHL allele causes a generalised abnormality in VHL–HIF signalling. Affected individuals thus provide a unique opportunity to explore the integrative physiology of this signalling pathway. This study investigated patients with Chuvash polycythaemia in order to analyse the role of the VHL–HIF pathway in systemic human cardiopulmonary physiology. METHODS AND FINDINGS: Twelve participants, three with Chuvash polycythaemia and nine controls, were studied at baseline and during hypoxia. Participants breathed through a mouthpiece, and pulmonary ventilation was measured while pulmonary vascular tone was assessed echocardiographically. Individuals with Chuvash polycythaemia were found to have striking abnormalities in respiratory and pulmonary vascular regulation. Basal ventilation and pulmonary vascular tone were elevated, and ventilatory, pulmonary vasoconstrictive, and heart rate responses to acute hypoxia were greatly increased. CONCLUSIONS: The features observed in this small group of patients with Chuvash polycythaemia are highly characteristic of those associated with acclimatisation to the hypoxia of high altitude. More generally, the phenotype associated with Chuvash polycythaemia demonstrates that VHL plays a major role in the underlying calibration and homeostasis of the respiratory and cardiovascular systems, most likely through its central role in the regulation of HIF