NO2 + OH HNO3 Different ventilation rates Some ideas from experiments in London Results Indoor (2004)
Butler, Karen, Group Editor has reference to this Academic Journal, PHwiki organized this Journal Prof. Dudley Shallcross Atmospheric Chemistry Research Group 2012 Air chemistry (outdoor in addition to indoor) The Atmosphere: Pressure in addition to Temperature O O O UV
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The Chapman Mechanism In the 1930s Sidney Chapman devised a mechanism that accounted as long as the ozone layer in addition to the temperature structure. O2 + h O + O O + O2 + M O3 + M O3 + h O2 + O O3 + O 2O2 Until 1964 the Chapman reactions were thought to be the principal processes governing the ozone balance in the stratosphere. However, measurements indicated that the actual concentration of ozone is smaller than that predicted by about a factor of two to four. Predictions of ozone concentrations by the Chapman mechanism compared with observations at Panama, 1970. Catalytic Ozone Destruction. For a chemical to significantly affect the overall concentration of ozone it either must be present in great abundance or must be involved in a catalytic cycle. Breakthroughs in the 1970s identified a number of NATURAL catalytic processes that all have the as long as m: X + O3 XO + O2 XO + O X + O2 net : O3 + O 2O2 Where X = H, OH, NO, Cl or Br.
CFCs: Molina in addition to Rowl in addition to Nature 249, 810-812 (1974) Importance of reservoirs If the catalysts carried on unabated they would themselves destroy the ozone layer, but happily there are termination reactions that lead to the as long as mation of reservoir species e.g. Cl + CH4 HCl + CH3 ClO + NO2 ClONO2 Active (radicals) Inactive (reservoirs) The ozone hole 27th Anniversary Farman et al. Nature 1985
What might have happened if we did nothing about CFCs Newman et al. Atm. Chem. Phys., 9, 2113 (2009) What might have happened if we did nothing about CFCs Newman et al. Atm. Chem. Phys., 9, 2113 (2009) Take home message 17% of globally averaged ozone gone by 2020 67% by 2065 Collapse of lower strat. tropical ozone by 2060 UV levels double by 2060
Air Pollution in addition to the Troposphere 10 km NO, NO2, VOC VOCs halocarbons 0 km Compounds of both biogenic in addition to anthropogenic origin 1 km The Tropopause The Boundary Layer O3 + sunlight O + O2 < ~ 330 nm O + H2O OH + OH OH + R-H R + H2O VOCs broken down by the OH radical, generated by sunlight Ozone Chemistry- low NOx environment Examples: Marine boundary layer, remote free troposphere Ozone Chemistry- low NOx environment O3 + h O (1D) + O2 ~ 330 nm O (1D) + M O (3P) + M O (1D) + H2O 2 OH CO + OH CO2 + H H + O2 + M HO2 + M HO2 + O3 OH + 2O2 Net: CO + O3 CO2 + O2 Ozone Chemistry- higher NOx environment Examples: Outflow from pollution centres in addition to biomass burning regions Ozone Chemistry- higher NOx environment CO + OH CO2 + H H + O2 + M HO2 + M HO2 + O3 OH + 2O2 NO + HO2 NO2 + OH NO2 + h NO + O(3P) O(3P) + O2 + M O3 + M Net: CO + 2O2 CO2 + O3 Ozone Chemistry- higher NOx environment CO + OH CO2 + H H + O2 + M HO2 + M HO2 + O3 OH + 2O2 NO + HO2 NO2 + OH NO2 + h NO + O(3P) O(3P) + O2 + M O3 + M Net: CO + 2O2 CO2 + O3 Ozone Chemistry- higher NOx environment CO + OH CO2 + H H + O2 + M HO2 + M HO2 + O3 OH + 2O2 NO + HO2 NO2 + OH NO2 + h NO + O(3P) O(3P) + O2 + M O3 + M Net: CO + 2O2 CO2 + O3 NOx Limiting Environment NO2 + OH HNO3 What about the indoor environment Three differences No meteorology slower movement of air (in general) ventilation rates important More surfaces (surface:volume ratio) deposition in addition to emission of chemicals much more important Light levels very different (less UV indoors but may have higher total light levels than outdoors) Different ventilation rates Some ideas from experiments in London
Site features DAPPLE 02 Summer 2004 Marylebone Rd. Gloucester Place Roof conc. approx 10 times greater than Indoor Longer transport time to Indoor position Longer decay time Results Indoor (2004)
Ventilation rates Mechanically ventilated sealed building, air sucked in in addition to pumped out, regulated by levels of CO2. Outdoor air pumped in but filtered to remove particles. Naturally ventilated leaky buildings (most dwellings in addition to many offices), too hot, open a window, too cold, close off room. Inevitable ingress of outdoor air. 2. Emissions in addition to deposition Many chemicals released indoors are also released outdoors but depending on confinement in addition to ventilation, exposure levels indoors may be much much higher in addition to last as long as much longer. Typical sources indoors include; fabrics, varnishes, paint, cooking, heating systems, air fresheners! Cleaning products (with added scents) Some examples of chemicals indoors Paradichlorobenzene Moth crystals, room deodorants Methylene chloride Paint removers, solvent usage Formaldehyde Pressed wood products, foam Styrene Insulation, textiles, disinfectants, plastics, paints Acetaldehyde Glues, deodorants, fuels, preventives, mold growth on leathers Acrolein Component of oak-wood, by-product of the combustions of wood, kerosene in addition to cotton
3. Light levels Glass will cut off high energy UV light from the Sun in addition to will reduce visible light levels. General shading by buildings will also reduce light levels in general. All this means that Chemistry is much slower indoors than outdoors but the build up can be greater because of the slow air movement.
Butler, Karen Group Editor
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