Free Radicals Within the Antarctic Vortex: The Role of CFCs in Antarctic Ozone Loss

Abstract

How strong is the case linking global release of chlorofluorocarbons to episodic disappearance of ozone from the Antarctic stratosphere each austral spring? Three lines of evidence defining a link are (i) observed containment in the vortex of ClO concentrations two orders of magnitude greater than normal levels; (ii) in situ observations obtained during ten high-altitude aircraft flights into the vortex as the ozone hole was forming that show a decrease in ozone concentrations as ClO concentrations increased; and (iii) a comparison between observed ozone loss rates and those predicted with the use of absolute concentrations of ClO and BrO, the rate-limiting radicals in an array of proposed catalytic cycles. Recent advances in our understanding of the kinetics, photochemistry, and structural details of key intermediates in these catalytic cycles as well as an improved absolute calibration for ClO and BrO concentrations at the temperatures and pressures encountered in the lower antarctic stratosphere have been essential for defining the link.

Ultraviolet Photolysis of the ClO Dimer

“…ref 29). Indeed, we find up to ∼5% lower ozone mixing ratios until March 1, 2000 employing case a compared to case b (cf.…”

“…Photodissociation of the ClO dimer is a key step in one of the dominant catalytic ozone loss cycles, which are responsible for stratospheric ozone depletion in polar spring. 29 Therefore, the results of the present laboratory experiments have direct implications for the understanding of polar ozone loss. , where quasi-simultaneously measured ozone mixing ratios are available, as well.…”

Persistence of engineered nanoparticles in a municipal solid-waste incineration plant

“…However, these characteristics can pose problems when the nanoparticles enter the natural environment 6 . For example, the use of persistent chemicals such as fluoro-chloro-hydrocarbons in fridges has depleted the stratospheric ozone layer 7 , and the use of fibrous solids such as asbestos in building materials has resulted in high incidences of mesothelioma 8 . Furthermore, the widespread use of insecticides has seen various fluorinated compounds, dioxins and halogenated biphenyl compounds accumulate in the food web 9 .…”

Vacuum synthesis and determination of the ionization energies of different molecular orbitals for BrOBr and HOBr

“…Second, 100 g of HgO ͑yellow͒ powder ͑Ald-rich͒ were previously put in a 500 ml glass flask, which was loosely filled with the glass wool and equipped with inlet and outlet valves. The flask was evacuated to 10 Ϫ3 Torr, and then heated to 100°C for 1 1 2 h to activate HgO. Third, the evacuated flask was filled with dried bromine to about 150 Torr at 0°C in the dark.…”

“…In comparison with the chlorine-containing species, much less is known about bromine-containing species, mainly because of their low thermal stability and the difficulty of obtaining them in a pure state. [1][2][3][4] Bromine-containing species, of either biogenic or anthropogenic origin, released at the earth's surface have been linked to ozone destruction in various altitude regions of the earth's atmosphere. [5][6][7] Recent findings show 8, 9 that the effectively catalytic removal of ozone by bromine on a per atom basis in the polar stratosphere is higher one hundred times than that of chlorine.…”