esm222_06_7_structure

esm222_06_7_structure - ESM 222 Structure of Environmental...

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ESM 222 © ARTURO KELLER 1 ESM 222 Structure of Environmental Media ESM 222 © ARTURO KELLER 2 Structure of Environmental Media ± Atmosphere ± Structure ± Aerosols ± Soils ± Structure ± Composition ± Microbial activity ± Water Bodies ± Rivers and Streams ± Lakes ± Oceans ± Particulate Matter ± Sediments
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ESM 222 © ARTURO KELLER 3 Atmospheric Composition Source: Pollution Science, Pepper et al 1996. ESM 222 © ARTURO KELLER 4 Atmosphere ± Pollutants of concern in the atmosphere are: ± Urban air pollutants: ± O 3 via NO x and VOCs, CO, NO x , SO 2 , particulates, HAPs, . .. ± Acid rain gases: ± NO x , SO 2 , … ± Greenhouse gases: ± CO 2 , CH 4 , N 2 O, CFCs, . .. ± Ozone destroyers in stratosphere: ± CFCs, …
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Source: Pollution Science, Pepper et al, 1996. ESM 222 © ARTURO KELLER 6 Atmosphere ± For urban air pollution, troposphere is where all action occurs ± Surface layer ± at bottom of boundary layer ± ~1/10th of boundary layer, typically tens of meters ± surface roughness and surface heat exchange affect properties (temperature, wind speed, humidity)
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ESM 222 © ARTURO KELLER 7 Atmosphere ± Atmospheric boundary layer ± turbulence in this region may cause significant short-term mixing ± interface between troposphere and ground ± only a few hundreds of meters thick ± large-scale airflow patterns affected by surface features, with large vertical gradients of temperature, wind speed and humidity ESM 222 © ARTURO KELLER 8 Atmosphere ± Atmospheric boundary layer ± Height of boundary layer varies throughout day, with maximum thickness by mid- afternoon ± Boundary layer shrinks to about 100 to 200 m at night ± Thermal “inversion” may cause trapping of pollutants in boundary layer, reducing the mixing depth
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ESM 222 © ARTURO KELLER 9 Wind Direction ESM 222 © ARTURO KELLER 10 Wind Direction Source: Environmental Engineering Handbook, 2nd ed., Liu & Liptak, 1996
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ESM 222 © ARTURO KELLER 11 Turbulence ± Dispersion of pollutants due to: ± wind speed ± atmospheric turbulence ± Turbulence considers variations of more than 2 cycles/hr ± Most important are variations in the order of 1 to 0.01 cycles/sec ESM 222 © ARTURO KELLER 12 Turbulence Source: Environmental Engineering Handbook, 2nd ed., Liu & Liptak, 1996
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ESM 222 © ARTURO KELLER 13 Inversions ± When temperature increases with altitude, lapse rate is negative or “inverted” from normal state ± Occurs when warm air “blankets” colder air: atmosphere is extremely stable ± Inversions limit vertical mixing, trapping pollutants in the lower region ESM 222 © ARTURO KELLER 14 Inversions
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Source: Environmental Engineering Handbook, 2nd ed., Liu & Liptak, 1996
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ESM 222 © ARTURO KELLER 17 Topography ± Features that affect small-scale circulation ± natural: hills, tree foliage, lakes, rivers ± anthropogenic: bridges,
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This note was uploaded on 08/06/2008 for the course ESM 222 taught by Professor Keller during the Spring '08 term at UCSB.

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esm222_06_7_structure - ESM 222 Structure of Environmental...

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