GAW Report No. 205 - IGAC Project

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CHAPTER 8 – KEY ISSUES AND OUTLOOKin Figure 4 were collected through deployments of aerosol mass spectrometers, which measureonly non-refractive particles with a diameter less than 1 µm. Consequently, they are insensitive toblack carbon, dust, and sea salt and thus overestimate the contributions for the chemicalcomponents they do measure. Figure 5 (also shown below) presents a more complete speciationof PM in Mexico City, which can be compared to the Mexico City result in Figure 4 (note thedifferent colour coding in the two figures.)Figure 4 - Comparison of composition of non-refractive PM1 at many sites in the <strong>No</strong>rthern Hemisphere [Zhang et al., 2007].Pie charts show the average mass concentration and chemical composition: organics (green), sulphate (red), nitrate (blue),ammonium (orange), and chloride (purple). Colours for the study labels indicate the type of sampling location: urban areas(blue), 100 miles downwind (pink).(Also shown in Chapter 1 as Figure 6)Figure 5 - Submicron PM composition (mass and percent) measured during (a) March 2006; (b) April 2003 field campaignsat surface sites in the Mexico City basin. [From Aiken et al., 2009](Also show in Chapter 5 as Figure 18)288
CHAPTER 8 – KEY ISSUES AND OUTLOOKThe sources of organic aerosol (OA) are currently the subject of vigorous debate in thescientific community. The consensus is that most OA in rural areas is not directly emitted, butrather formed in the atmosphere from condensation of oxidized VOCs (secondary organic aerosolor SOA) [Zhang et al., 2007]. Radiocarbon dating of OA typically shows a very high fraction ofmodern carbon, suggesting that most SOA is formed from biogenic VOCs [Bench et al., 2007]. Onthe other hand, SOA typically correlates very well with the oxidation products of anthropogenicVOCs, suggesting that urban emissions play an important role in its formation [de Gouw et al.,2005]. Several studies indicated that there is much more SOA in urban air than models canaccount for [de Gouw et al., 2005; Volkamer et al., 2006]. Figure 6 summarizes some of the recentresearch aimed at explaining the observed levels of SOA using detailed chemical models. Thegraph shows that models underestimate SOA by 1-2 orders of magnitude over a wide range of thedegree of photochemical processing of an air mass. Given the relatively poor understanding of thesources of OA, it is very difficult to predict how a reduction in the emissions of precursors will affectthe levels of OA in the atmosphere. Since OA accounts for such an important contribution to totalPM levels, understanding OA sources is a high priority for establishing effective PM controlstrategies.Figure 6 - The ratio between measured and modelled secondary organic aerosol (SOA) as a function of photochemical age,i.e. the degree of photochemical processing, of a polluted air mass [Volkamer et al., 2006]It is important to note that currently developing megacities can benefit from the experiencesof megacities that developed earlier. An excellent example is provided by comparison of theevolution of maximum ozone and PM concentrations in three similarly sized megacities (Figure 7).Ozone concentrations peaked in Los Angeles about 1970 and have decreased over the followingfour decades. PM concentration measurements started later, but seem to have followed a similartrajectory. In Mexico City, a later developing megacity, the ozone concentrations apparently neverreached the peak concentrations observed in Los Angeles and dropped more rapidly, approachingLos Angeles concentrations. PM concentrations in Mexico City have approximately paralleled theozone concentrations. Evidently Mexico City avoided some to the most severe air pollutionproblems experienced in Los Angeles through implementation of emission controls beforeproblems became so severe. In contrast, pollutant concentrations in Beijing may be following adifferent trajectory; PM concentrations are decreasing, but ozone concentrations, which have beenlow, are evidently rising. Increased attention is being paid to air quality concerns in Beijing, and itwill be very enlightening to see how ozone concentrations evolve there in the future.Correlations between ambient concentrations of air pollutants can yield importantinformation regarding source emissions. For example, Parrish et al. [2009a] report ambientmeasurements of hydrocarbons, carbon monoxide, and nitrogen oxides from three megacities(Beijing, Mexico City, and Tokyo) and compare them with similar measurements from US cities inthe mid-1980s and the early 2000s (Figure 8). The common hydrocarbon pattern seen in all datasets indicates that emissions associated with gasoline-fuelled vehicles dominate in all of thesecities. This commonality suggests that vehicular emission controls are important to begin as soon289
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The second lead authors meeting was
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CHAPTER 1 - INTRODUCTIONatmospheric
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CHAPTER 1 - INTRODUCTIONThe impact
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CHAPTER 1 - INTRODUCTIONEquations 1
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CHAPTER 1 - INTRODUCTIONThere is a
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CHAPTER 1 - INTRODUCTIONFigure 8 -
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CHAPTER 1 - INTRODUCTIONLow-income
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CHAPTER 1 - INTRODUCTION1.5 SCIENTI
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CHAPTER 1 - INTRODUCTIONthese aeros
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CHAPTER 1 - INTRODUCTIONFigure 16:
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CHAPTER 1 - INTRODUCTIONReferencesA
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CHAPTER 1 - INTRODUCTIONLeibensperg
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CHAPTER 2 - AFRICACoordinating auth
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CHAPTER 2 - AFRICAFigure 3 displays
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CHAPTER 2 - AFRICAabout 2,000 mm pe
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CHAPTER 2 - AFRICAFigure 5 - NO2 me
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CHAPTER 2 - AFRICAIn West-African c
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CHAPTER 2 - AFRICAratios in Bamako
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CHAPTER 2 - AFRICAAs shown in Figur
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CHAPTER 2 - AFRICAof the city of Jo
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CHAPTER 2 - AFRICAlow smoke coal wa
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CHAPTER 2 - AFRICAcompleted, their
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CHAPTER 2 - AFRICAepidemiological d
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CHAPTER 2 - AFRICAPopulationGrowthR
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CHAPTER 2 - AFRICAcycle with levels
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CHAPTER 2 - AFRICAcomparable to tho
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CHAPTER 2 - AFRICAFavez, O., Sciare
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CHAPTER 2 - AFRICASeagrave, J., McD
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CHAPTER 3 - ASIAThe bottom-up and t
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CHAPTER 3 - ASIAFigure 2 - (a) CO e
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CHAPTER 3 - ASIAand Kim Oanh, 2002]
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CHAPTER 3 - ASIAFigure 4 - Annual a
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CHAPTER 3 - ASIAmaintenance program
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CHAPTER 3 - ASIAnearly half of the
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CHAPTER 3 - ASIARelationships of th
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CHAPTER 3 - ASIAFigure 12 - Graphic
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CHAPTER 3 - ASIAAnother significant
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CHAPTER 3 - ASIAand international),
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CHAPTER 3 - ASIAFigure 17 - (a) Var
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CHAPTER 3 - ASIAEmissions inventory
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CHAPTER 3 - ASIAAir Quality Index r
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CHAPTER 3 - ASIA• Strict restrict
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CHAPTER 3 - ASIAis due the ban of l
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CHAPTER 3 - ASIAAvailability of air
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CHAPTER 3 - ASIAFigure 26 - Box plo
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CHAPTER 3 - ASIAResearch projects o
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CHAPTER 3 - ASIAmonitoring stations
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CHAPTER 3 - ASIApreliminary stage.
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CHAPTER 3 - ASIATable 8 - National
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CHAPTER 3 - ASIAControl strategiesA
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CHAPTER 3 - ASIAMetro Manila Air Qu
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CHAPTER 3 - ASIAmoves inland and O
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CHAPTER 3 - ASIAHong Kong and Macau
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CHAPTER 3 - ASIAFigure 39 - A 52-ye
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CHAPTER 3 - ASIAClimatic change iss
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CHAPTER 3 - ASIAEmission sources of
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CHAPTER 3 - ASIAIn the case of PM 1
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CHAPTER 3 - ASIAdue to yellow sand
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CHAPTER 3 - ASIAEmission inventorie
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CHAPTER 3 - ASIAatmosphere, which i
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CHAPTER 3 - ASIAEmissions of NO X f
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CHAPTER 3 - ASIAFigure 58 - Annuall
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CHAPTER 3 - ASIAThe predominance of
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CHAPTER 3 - ASIAthe negative health
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CHAPTER 3 - ASIAAsrari, E., Ghole,
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CHAPTER 3 - ASIAGuo H, Fine AJ, So
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CHAPTER 3 - ASIALi L., Chen C.H., H
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CHAPTER 3 - ASIAPollution Control D
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CHAPTER 3 - ASIAYu JZ, Tung JWT, Wu
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CHAPTER 4 - SOUTH AMERICAand human
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CHAPTER 4 - SOUTH AMERICA4.1.2 Emis
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CHAPTER 4 - SOUTH AMERICATable 4 -
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CHAPTER 4 - SOUTH AMERICAemissions
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CHAPTER 4 - SOUTH AMERICAthird moun
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4.3 BUENOS AIRES, ARGENTINACHAPTER
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CHAPTER 4 - SOUTH AMERICAless than
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CHAPTER 4 - SOUTH AMERICApart of Sa
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CHAPTER 4 - SOUTH AMERICAThe Nation
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CHAPTER 4 - SOUTH AMERICA4.7 SÃO P
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CHAPTER 4 - SOUTH AMERICAhydrocarbo
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CHAPTER 4 - SOUTH AMERICAthat such
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CHAPTER 4 - SOUTH AMERICACorvalán,
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CHAPTER 4 - SOUTH AMERICALongo, K.
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CHAPTER 4 - SOUTH AMERICARomero Lan
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CHAPTER 5 - NORTH AMERICACoordinati
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CHAPTER 5 - NORTH AMERICAstories fo
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CHAPTER 5 - NORTH AMERICAthat impro
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CHAPTER 5 - NORTH AMERICA5.2 THE US
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CHAPTER 5 - NORTH AMERICAcontributi
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CHAPTER 5 - NORTH AMERICAseason fro
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CHAPTER 5 - NORTH AMERICAtoluene, a
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CHAPTER 5 - NORTH AMERICAand small
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CHAPTER 5 - NORTH AMERICABlumenthal
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CHAPTER 5 - NORTH AMERICALei, W., Z
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CHAPTER 5 - NORTH AMERICAVelasco, E
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CHAPTER 6 - EUROPEFigure 1 shows a
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CHAPTER 6 - EUROPE6.1.3 Pollution l
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CHAPTER 6 - EUROPEFigure 4 - [Carsl
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CHAPTER 6 - EUROPEFigure 7 - Greate
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CHAPTER 6 - EUROPEFigure 9 - Partit
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CHAPTER 6 - EUROPEFrom a regulatory
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CHAPTER 6 - EUROPEB) Particulate ma
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CHAPTER 6 - EUROPE• During the wi
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CHAPTER 6 - EUROPEFigure 17 - Total
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CHAPTER 6 - EUROPEair quality in th
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CHAPTER 6 - EUROPEfaculty of MSU, I
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CHAPTER 6 - EUROPE2007; Andersson e
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CHAPTER 6 - EUROPETable 3b - Past a
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CHAPTER 6 - EUROPEexpectancy in NRW
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CHAPTER 6 - EUROPEtime range of sev
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CHAPTER 6 - EUROPEFigure 25 - Inhab
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CHAPTER 6 - EUROPEPiemonte (Turin):
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CHAPTER 6 - EUROPEFigure 31 - Numbe
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CHAPTER 6 - EUROPEAs for the develo
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CHAPTER 6 - EUROPEsub-tropical fron
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CHAPTER 6 - EUROPEpollutants around
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CHAPTER 6 - EUROPEaddition to local
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GAW Report No. 205 - IGAC Project

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