UMD AOSC 621 - LESSON 25 (25 pages)

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LESSON 25



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LESSON 25

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Pages:
25
School:
University of Maryland, College Park
Course:
Aosc 621 - Physics And Chemistry Of The Atmosphere II

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METO 621 LESSON 25 Air Pollution Air Pollution Air Pollution London Killer Smog SMOG Word coined by Dr Harold Des Veaux a London physician in 1903 SMOKE FOG SMOG He meant London smog sulfurous fumes from coal burning large water droplets formed around smoke particles soot 1952 Killer smog 4000 deaths Another episode in 1956 led to 1000 deaths In 1940 vegetable crop damage began to be seen in the Los Angeles basin Haagen Smit and colleagues showed that the effect was due to ozone VOC and NOx Schematic of ozone production from VOC SMOG NEEDS Hydrocarbons and nitrogen oxides Strong sunlight to start reactions Warm temperatures to maintain reactions the higher the temperature the faster the rate Peak ozone will be close to peak temperature afternoon Standards Ozone 1 hour 125 ppbv 8 hour 85 ppbv The 8 hour standard is much more stringent and encompasses many areas where transport is the only issue e g Shenandoah National Park PM2 5 daily 65 g m3 yearly 15 g m3 Most areas will have trouble only with the annual standard Visibility a 60 year glide path back to natural conditions parts per billion by volume Ozone isopleths NMHC vs NOx Ozone vs NOx for NHMC 0 6 ppmc Overall scheme for air pollution Dispersion of acid rain The acid scale Natural levels of Acidity in Rain Carbon dioxide dissolves in the rain drop CO2 g H2O aq H2CO3 aq Henry s Law states that H2CO3 KHP CO2 KH 3 4E 2 M ATM 1 In the liquid some of the H2CO3 ionizes H2CO3 aq H aq HCO3 aq This reaction has an equilibrium constant of 4 2E 7 M 3 For the overall reaction CO2 g H2O aq H aq HCO3 aq The equilibrium constant Kc is 1 43E 8 M2 ATM 1 Natural levels of Acidity in Rain H HCO3 where K c P CO2 in a liquid H HCO3 hence H 2 KcP CO2 given that CO2 has a mixing ratio of 320 ppm we get H 2 14E 6 and a pH of 5 67 pH of precipitation over the US Acid rain Acid rain over the Eastern States is the highest most of the sulfur containing coal occurs in this region Shaded areas in the figure show where granite is found If



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