Gaseous Pollutants

Gaseous Pollutants - Chap 2.3 Gaseous Pollutants Carbon...

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08/12/09 1 Gaseous Pollutants Carbon oxides Sulfur compounds Nitrogen compounds Hydrocarbon compounds Photochemical oxidants Chap 2.3
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08/12/09 2 Carbon Oxides Two major carbon oxides – Carbon dioxide (CO 2 ) Carbon monoxide (CO) CO 2 Natural atmospheric constituent Sources: Natural Aerobic biological processes, combustion and weathering of carbonates in rock and soil Anthropogenic: Combustion of fossil fuels • Land use conversion
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08/12/09 3 CO 2 Essential atmospheric gas Present in variable concentrations Not considered to be toxic Environmental concerns are relatively new Changes in atmospheric concentrations Geological time The modern period 1.5-1.7 ppmv/yr Long atmospheric lifetime (~100 years) Figure 2.2 What’s the impact if there is no CO 2 in the atmosphere? Is CO 2 emission regulated? Should it be?
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08/12/09 4 Figure 2.3 CO 2 Major sink processes Oceans Forests More discussion in Atmospheric Effects • Pre-industrial revolution: 98% of exchangeable CO 2 were in the oceans and 2% in the atmosphere; for anthropogenic CO 2 , only 42% dissolves in oceans
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08/12/09 5 CO Colorless, odorless, tasteless gas Produced as a result of incomplete combustion ) O t (sufficien CO 2 O 2CO ) O ent (insuffici 2 2 2 2 2 2 2 + + CO O C
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08/12/09 6 CO Sink processes Photochemistry with OH · (hydroxyl radical) Soil uptake Atmospheric lifetime (1 month in the tropics and 4 months in mid-latitudes) + + + + + 2 2 2 2 HO CO O H CO H CO OH CO Adverse effects on the consumption of OH·? Formation of O 3 M O M O P O P O NO h NO OH NO NO HO M HO M O H + + + + ν + + + + + + 3 2 3 3 2 2 2 2 2 ) ( ) ( Overall 3 2 2 O CO h O CO + ν + + Increase CH 4 concentration thus enhancing global warming M: an energy absorbing molecule, e.g. N 2 or O 2 OH · : hydroperoxyl radical O( 3 P): ground-state atomic oxygen h ν : a photon of light energy
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08/12/09 7 CO Background level concentration Vary with latitude, lower in the tropics and higher in the northern middle latitudes Average 110 ppbv Increasing 1%/yr, mostly in the northern middle latitudes Urban/suburban levels Vary from few ppmv to 60 ppmv: mainly associated with transportation emissions Average highs (10-20 ppmv) Higher concentrations in higher altitude cities Why higher in higher latitudes and altitudes?
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08/12/09 8 Sulfur Compounds Sulfur Oxides: Sulfur trioxide (SO 3 ), Sulfur dioxide (SO 2 ) Reduced sulfur compounds (COS, CS 2 , H 2 S) Natural sources Volcanoes Oxidation of reduced S compounds Sulfur Oxides Anthropogenic sources Combustion of S-containing fuels Smelting of metal ores SO 2 Colorless, sulfurous odor gas Major sulfur oxide in the atmosphere Produced on S oxidation May be converted to SO 3 Produced from SO 2 oxidation Rapidly reacts with water Very short atmospheric lifetime SO 3
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08/12/09 9 Data from http://www.uea.ac.uk/~e490/su/sulfur.htm What is the overall picture?
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This note was uploaded on 09/11/2011 for the course ENV 4101 taught by Professor Wu during the Spring '08 term at University of Florida.

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Gaseous Pollutants - Chap 2.3 Gaseous Pollutants Carbon...

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