Aerosols Why are we interested in them? Health problems Decrease visibility Reduce (normally) the amount of solar radiation that reach the ground Affects surface energy balance Plant growth Provide cloud condensation nuclei Provide surface area for heterogeneous chemical reactions
OZONE AND PARTICULATE MATTER (PM): THE TOP TWO AIR POLLUTANTS IN THE U.S. # millions of people living in areas exceeding national ambient air quality standards (NAAQS) in 2007 75 ppb (8-h average) 15 mg m -3 (day), 65 (annual) 65 mg m -3 (24-h), 15 (annual)
https://www.eea.europa.eu//p ublications/air-quality-ineurope-2017
Figure 7.20 Indirekte skyeffekter pga. aerosoler
The famous T-shirt figure
Potential impact of BC reductions (UNEP, 2011)
A general view of the CCTV towers, headquarters of China Central Television, in Beijing on January 12, 2013 Illustrasjon av redusert siktbarhet. Elektronisk manipulert. http://www.marketplace.o rg/topics/sustainability/w hat-would-your-city-lookbeijings-air-smogsimulator
Shenyang, November 2015
VISIBILITY IN U.S. WILDERNESS AREAS 2001 observations Natural Background; includes transboundary pollution Deciviews 300 150 80 40 20 Visual range (km) Park et al. [2006]
Høy relativ fuktighet i luften i grenselaget gjør at partiklene sveller mer spredning av lys.
The aerosol lifecycle Dråpevekst Köhler teori
Sedimentering (tørravsetning) av aerosoler For mineralstøv
850 hpa wind speed / Mean sea level pressure Monday 6 Nov, 00 UTC T+0 Valid: Monday 6 Nov, 00 UTC Hvorfor er det så klar luft i Oslo i dag?
Composition of aerosols Fine Mode (d < 1.0 μm) Sulphate (SO 2, DMS, H 2 S, OCS) Nitrate (NO x ) Ammonium (NH 3 ) Organics (Primary and secondary) Black carbon Coarse mode (d > 1.0 μm) Sea salt Mineral dust Biological material Fly ash
Størrelsesfordeling partikler Hvordan leser dere verdiene på y-aksen?
WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION
Forurenset byluft Kontinental bakgrunn Marin bakgrunn Aerosol surface area distribution Principle sources for aerosols
1 um 1 nm
Kulmala et al, 2013.
Små og store partikler blir lettere tatt opp av dråper Partikler med diameter rundt 0.1 um (accumulation mode) blir tatt opp minst effektivt
Effekter på kortbølget stråling - Sikt - Strålingspådriv (klima)
Strålingspådriv (radiative forcing)
Strålingspådriv (radiative forcing)
Strålingspådriv pga. direkte effekten av spredende aerosoler (sulfat, nitrat, organisk karbon, mineralstøv). Finner da ΔF=-0.9 Wm -2
+/- Direkte, semi-direkte og indirekte effekter av aerosoler http://www.metoffice.gov.uk/research/areas/chemistry-ecosystems/aerosols
+/- Direkte, semi-direkte og indirekte effekter av aerosoler http://www.metoffice.gov.uk/research/areas/chemistry-ecosystems/aerosols
Direkte, semi-direkte og indirekte effekter av aerosoler http://www.metoffice.gov.uk/research/areas/chemistry-ecosystems/aerosols
Direkte, semi-direkte og indirekte effekter av aerosoler http://www.metoffice.gov.uk/research/areas/chemistry-ecosystems/aerosols
Direkte, semi-direkte og indirekte effekter av aerosoler +/- - - +/- +/- http://www.metoffice.gov.uk/research/areas/chemistry-ecosystems/aerosols
ERF: Effective Radiative Forcing (tar med raske skyeffekter) IPCC, 2013
Indirekte effekter av aerosoler på skyer
IPCC,2013
Remaining fraction (%) Hvordan sammenlikne klimaeffekten av et utslipp av 2 ulike komponenter? Forskjellene i tidsskalaene er hovedutfordringen når vi skal sammenlikne effektene 100 % 80 % 60 % 40 % 20 % CO2 CH4 SF6 N2O HFC-134a CF4 0 % 0 100 200 300 400 500 Years
IPCC (1990, 1992, 1996) ++ Global Warming Potential (GWP) IPCC, 2007
GTP en alternativ metric som bruker ΔT ved tiden H, jfr. 2º mål
AOD (Aerosol Optical Depth) Fra Myhre et al., ACP, 2009. AOD (δ): F t =F s e -δ Ulike observasjonsbaserte estimater spriker Modellene avviker omtrent like mye som forskjellen mellom observasjonene
Total aerosol forcing er lavere, pga. skyer og absorberende partikler Myhre, Science, 2009
ANNUAL MEAN PM 2.5 CONCENTRATIONS (2002) derived from MODIS satellite instrument data
GLOBAL SULFUR BUDGET [Chin et al., 1996] (flux terms in Tg S yr -1 ) cloud 42 SO4 2-4 18 SO 2 t = 1.3d OH 8 H 2 SO 4 (g) t = 3.9d NO 3 OH (CH 3 ) 2 S (DMS) t = 1.0d 10 64 dep 27 dry 20 wet dep 6 dry 44 wet 22 Phytoplankton Volcanoes Combustion Smelters
Anthropogenic Sulfur Dioxide Emissions:1850-2005 by S. J. Smith
U.S. SO 2 EMISSIONS Main source is coal combustion GLOBAL Industrial UNITED STATES Sulfur emissions, Tg a -1 Volcanoes Biomass burning Oceans 78 8.3
FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H 2 4 4 HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) 3 3 4 3 Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution
FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H 2 4 4 HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) 3 3 4 3 Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution
FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H 2 4 4 HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) 3 3 4 3 Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution
AMMONIA EMISSIONS Ammonia, Tg N a -1 GLOBAL Livestock Fertilizer Humans Industry Biofuels Soils/vegetation UNITED STATES Oceans 55 Biomass burning 2.8
What is black carbon aerosols? Product of incomplete combution Fossil fuels or biomass
Bond et al., JGR, 2012
ng/g Annual BC concentration in snow Ice-core location D4 Greenland McConnell et al. (Science, 2007) 6 5 BC concentration in snow 1 st Aug ICEC-D4 FFC BIO 4 3 2 1 0 1850 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 65
Geoengineering. En mulighet er å øke albedoen ved å øke aerosolmengden. SRM: Solar radiation management kan nøytralisere globalt midlet temperaturøkning, men ser ut til å redusere nedbør. Katharine L. Ricke, M. Granger Morgan & Myles R. Allen Nature Geoscience 3, 537-541 (2010)
WILDFIRES: A GROWING AEROSOL SOURCE S. California fire plumes, Oct. 25 2004 Total carbonaceous (TC) aerosol averaged over U.S. IMPROVE sites Interannual variability is driven by wildfires