Trends and inferred emissions of atmospheric high molecular weight perfluorocarbons

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 115-119).Atmospheric observations and atmospheric observation-based global emission estimates are presented for the five high molecular weight perfluorocarbons (PFCs): decafluorobutane (C 4 F 1 0 ), dodecafluoropentane (C5 F1 2 ), tetradecafluorohexane (C 6 F14 ), hexadecafluoroheptane (C 7F 16 ) and octadecafluorooctane (C8 F 18 ). Their atmospheric histories are based on measurements of 36 Northern Hemisphere and 46 Southern Hemisphere archived air samples, collected between 1973 and 2011, using two of the "Medusa" cryogenic preconcentration gas chromatography-mass spectrometry instruments, which are part of the Advanced Global Atmospheric Gases Experiment (AGAGE). A new calibration scale was prepared for each PFC, with estimated accuracies of 6.8% for C4Fi0 , 7.8% for C5F12 , 4.0% for CF 14 , 6.6% for C7FE16 and 7.9% for CF8i . Based on our observations, the 2011 globally averaged dry air mole fractions of these high molecular weight PFCs are: 0.17 parts-per-trillion (ppt, i.e., parts per 1012) for C4 F 10 , 0.12 ppt for C5 F 1 2 , 0.27 ppt for CF 1 4 , 0.12 ppt for CFE16 and 0.09 ppt for CF 18 . Newly measured infrared absorption spectra are presented for C7F 16 and CF 1 8 , and using these, their radiative efficiencies and global warming potentials (GWPs) are estimated. We find that the radiative efficiency of C8 F 18 at 0.57Wm- 2 ppb-' is similar to that of trifluoromethyl sulfur pentafluoride's (SF 5 CF 3 ), which has the highest radiative efficiency of any known atmospheric species (Forster et al., 2007). Using their radiative efficiencies, the 2011 observed globally averaged atmospheric mole fractions of the above five high molecular weight PFCs combine to contribute a global average radiative forcing of 0.35 mW m-2, which is 6% of the total anthropogenic PFC radiative forcing (Montzka et al., 2011; Oram et al., 2012). Global emissions for C4 Fio, C5F 12 , C6 F 14 , C7 F 16 and CF 18 were estimated from the observations using a 3-dimensional chemical transport model and a Bayseian inverse method that included a constraint on the annual growth rate of their emissions, consistent with the knowledge of the relevant industries emitting them (Rigby et al., 2011). The derived so-called "top-down" emission estimates show that global emission rates were largest in the 1980s and 1990s for C4 F 10 and C5 F 12 and in the 1990s for C6F 14 , C7F16 and C8F1 . After a subsequent decline, emission rates have remained relatively stable, within ±20 % year-to-year variation, for the last 5 years. Using their calculated 100-year time horizon GWPs, the high molecular weight perfluorocarbons studied here contributed up to 15.4 % of the total PFC emissions expressed in carbon dioxide (C0 2)-equivalents in 1997 and 6 % of the total PFC emissions in 2009. Furthermore, we compare our atmospheric observation-based global emissions to the available so-called "bottom-up" inventories, which are based on production information and end usage. Bottom-up emission estimates are available from the Emission Database for Global Atmospheric Research version 4.2 (EDGARv4.2) for C4F1o, C5 F1 2, C6 F 1 4 and C7F16 , and emission inventories of C4Fio, C5 F1 2 and C6 F14 are also reported to the United Nations' Framework Convention on Climate Change (UNFCCC) by Annex 1 countries that have ratified the Kyoto Protocol (European Commission, Joint Research Centre (JRC)/Netherlands Environmental Assessment Agency (PBL), 2009; United National Framework Convention on Climate Change Secretariat, 2011). The atmospheric observation-based emission estimates are 20 times larger than EDGARv4.2 for C4F10 and over three orders of magnitude larger for C5F1 2 . In contrast, the top-down emission estimates for C6F14 largely agree with the bottom-up estimates from EDGARv4.2. Moreover, the top-down C7 F16 emission estimates are comparable to those of EDGARv4.2 at their peak in the 1990s, albeit with significant underestimation by EDGARv4.2 for the other time periods. There are no bottom-up emission estimates for C8Fi8 , thus the emission rates reported here are the first for this gas. In general, the emission inventories for C4Fio, C5F1 2 and C6F 14 reported to the UNFCCC are five to ten times lower than those estimated in this study from observations. This underreporting to the UNFCCC may be due to only Annex 1 countries reporting inventories and also that some of these countries report a total PFC mixture in C0 2-equivalents, instead of individual PFC emissions rates.by Diane Jean Ivy.Ph.D

Radiative and Dynamical Influences on Polar Stratospheric Temperature Trends

Radiative and dynamical heating rates control stratospheric temperatures. In this study, radiative temperature trends due to ozone depletion and increasing well-mixed greenhouse gases from 1980 to 2000 in the polar stratosphere are directly evaluated, and the dynamical contributions to temperature trends are estimated as the residual between the observed and radiative trends. The radiative trends are obtained from a seasonally evolving fixed dynamical heating calculation with the Parallel Offline Radiative Transfer model using four different ozone datasets, which provide estimates of observed ozone changes. In the spring and summer seasons, ozone depletion leads to radiative cooling in the lower stratosphere in the Arctic and Antarctic. In Arctic summer there is weak wave driving, and the radiative cooling due to ozone depletion is the dominant driver of observed trends. In late winter and early spring, dynamics dominate the changes in Arctic temperatures. In austral spring and summer in the Antarctic, strong dynamical warming throughout the mid- to lower stratosphere acts to weaken the strong radiative cooling associated with the Antarctic ozone hole and is indicative of a strengthening of the Brewer–Dobson circulation. This dynamical warming is a significant term in the thermal budget over much of the Antarctic summer stratosphere, including in regions where strong radiative cooling due to ozone depletion can still lead to net cooling despite dynamical terms. Quantifying the contributions of changes in radiation and dynamics to stratospheric temperature trends is important for understanding how anthropogenic forcings have affected the historical trends and necessary for projecting the future.National Science Foundation (U.S.) (NSF Grant 1419667

Fundamental differences between Arctic and Antarctic ozone depletion

Antarctic ozone depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. The deep Antarctic “hole” contrasts with the generally weaker depletions observed in the warmer Arctic. An unusually cold Arctic stratospheric season occurred in 2011, raising the question of how the Arctic ozone chemistry in that year compares with others. We show that the averaged depletions near 20 km across the cold part of each pole are deeper in Antarctica than in the Arctic for all years, although 2011 Arctic values do rival those seen in less-depleted years in Antarctica. We focus not only on averages but also on extremes, to address whether or not Arctic ozone depletion can be as extreme as that observed in the Antarctic. This information provides unique insights into the contrasts between Arctic and Antarctic ozone chemistry. We show that extreme Antarctic ozone minima fall to or below 0.1 parts per million by volume (ppmv) at 18 and 20 km (about 70 and 50 mbar) whereas the lowest Arctic ozone values are about 0.5 ppmv at these altitudes. At a higher altitude of 24 km (30-mbar level), no Arctic data below about 2 ppmv have been observed, including in 2011, in contrast to values more than an order of magnitude lower in Antarctica. The data show that the lowest ozone values are associated with temperatures below −80 °C to −85 °C depending upon altitude, and are closely associated with reduced gaseous nitric acid concentrations due to uptake and/or sedimentation in polar stratospheric cloud particles

Observed connections of Arctic stratospheric ozone extremes to Northern Hemisphere surface climate

We present observational evidence for linkages between extreme Arctic stratospheric ozone anomalies in March and Northern Hemisphere tropospheric climate in spring (March–April). Springs characterized by low Arctic ozone anomalies in March are associated with a stronger, colder polar vortex and circulation anomalies consistent with the positive polarity of the Northern Annular Mode/North Atlantic Oscillation in March and April. The associated spring tropospheric circulation anomalies indicate a poleward shift of zonal winds at 500 hPa over the North Atlantic. Furthermore, correlations between March Arctic ozone and March–April surface temperatures reveal certain regions where a surprisingly large fraction of the interannual variability in spring surface temperatures is associated with interannual variability in ozone. We also find that years with low March Arctic ozone in the stratosphere display surface maximum daily temperatures in March–April that are colder than normal over southeastern Europe and southern Asia, but warmer than normal over northern Asia, adding to the warming from increasing well-mixed greenhouse gases in those locations. The results shown here do not establish causality, but nevertheless suggest that March stratospheric ozone is a useful indicator of spring averaged (March–April) tropospheric climate in certain Northern Hemispheric regions.National Science Foundation (U.S.) (AGS-1539972

Efficacy of treatment in an opioid –dependent population group using the Maudsley Addiction Profile (MAP) tool

A pilot study was performed to assess the effectiveness of treatment in an opioid dependent population using the Maudsley Addiction Profile (MAP) tool1

Emergence of healing in the Antarctic ozone layer

Industrial chlorofluorocarbons that cause ozone depletion have been phased out under the Montreal Protocol. A chemically driven increase in polar ozone (or “healing”) is expected in response to this historic agreement. Observations and model calculations together indicate that healing of the Antarctic ozone layer has now begun to occur during the month of September. Fingerprints of September healing since 2000 include (i) increases in ozone column amounts, (ii) changes in the vertical profile of ozone concentration, and (iii) decreases in the areal extent of the ozone hole. Along with chemistry, dynamical and temperature changes have contributed to the healing but could represent feedbacks to chemistry. Volcanic eruptions have episodically interfered with healing, particularly during 2015, when a record October ozone hole occurred after the Calbuco eruption.National Science Foundation (U.S.) (FESD Grant OCE-1338814)National Science Foundation (U.S.). Atmospheric Chemistry Program (Grant 1539972

Regulation of epithelial plasticity by miR-424 and miR-200 in a new prostate cancer metastasis model

Using an in vivo cycling strategy, we selected metastatic cancer cells from the lymph nodes (LN) of mice bearing orthotopic DU145 human prostate tumors. Repeated rounds of metastatic selection (LN1–LN4) progressively increased the epithelial phenotype, resulting in a new model of tumor cell mesenchymal-epithelial transition (MET). DU145-LN4 showed increased cell-cell adhesions, higher expression of multiple epithelial markers, such as E-cadherin, EpCAM and cytokeratin 18, and reduced expression of mesenchymal markers such as vimentin. The MET in DU145-LN4 cells was accompanied by increased expression of the miR-200 family, and antimiRs to miR-200c and miR-141 induced an EMT. MET also correlated with the loss of miR-424. Ectopic transient and stable miR-424 expression induced EMT, with reduced epithelial marker expression and increased cell scattering. Our model provides evidence for spontaneous MET in vivo. We show that this cellular plasticity can be mediated through the combined action of miR-424 and the miR-200 family