Lecture 7 Lecture 7 emissions emissions anthropogenic - - - PDF document

Lecture 7 Lecture 7 emissions emissions anthropogenic - - natural natural anthropogenic IPCC [2007] 1

At mospheric lif et ime Lifetime � = time necessary that the concentration decrease to 1/e concerning the start value: �� � � � � � t � � � � � X ( t ) X ( t 0 ) exp � � � Chemical Lifetimes of atmospheric compounds Chemical Lifetimes of atmospheric compounds (average for total atmosphere) � Compound Chemical lifetime 3-18 days ** Tropospheric O 3 Carbon monoxide (CO) � 57 days* Methane (CH 4 ) � 8.4 years ** SF 6 3200 years ** Toluene (traffic, anthropog.) � 2 days* monoterpenes ( � -pinene) � 1.6 hours* CFCs (sprays, cooling, anthropog.) � 45-1700 years ** * [OH] = 1.0x10 6 molecules cm -3 at room temperature assumed ** IPCC, 2001 2

Time scales for horizontal transport (troposphere) Time scales for horizontal transport (troposphere) Helsinki 1-2 months 2 weeks Frankfurt 1-2 months 1 year D.J. Jacob Typical time scales for vertical mixing Typical time scales for vertical mixing • Estimate time � t to travel � z by turbulent diffusion: � � � 2 z � � � � 5 2 1 t with K 10 cm s turb 2 K turb stratopause (~50 km) � 1-2 years tropopause (~10 km) � 10 years 5 km 1 month 1 week 2 km “planetary boundary layer” 1 day 0 km D.J. Jacob 3

Reservoir of the Earth system and examples of Reservoir of the Earth system and examples of processes exchanging elements between resrevoirs processes exchanging elements between resrevoirs Outer Space Outer Space meteorites escape Atmosphere Atmosphere gas-water exchange photosynthesis decay assimilation assimilation Biosphere Biosphere (Vegetation, animals (Vegetation, animals Hydrosphere decay Hydrosphere decay burial Soils Soils runoff (oceans, lakes, (oceans, lakes, rivers, groundwater) Lithosphere rivers, groundwater) Lithosphere (Earth crust) (Earth crust) subduction volcanoes Deep Earth Deep Earth (Mantle, core) (Mantle, core) Global budget of methane (CH 4 ) Global budget of methane (CH 4 ) Lifetime: 9 years D.J. Jacob 4

Estimated present- -day sources of day sources of tropospheric tropospheric NO NO x Estimated present x Mapping of tropospheric Mapping of tropospheric NO NO 2 2 from the from the GOME GOME satellite instrument satellite instrument Can you observe an effect of mankind? Lights at Lights at night from night from space space AFO2000, 2004 5

Lightning observed from space (2000) Lightning observed from space (2000) DJF JJA D.J. Jacob Present day global budget of atmospheric N 2 O (1994) Present day global budget of atmospheric N 2 O (1994) Source:IPCC [2001] Sources (Tg N yr -1 ) � 17.7 (6.7 – 36.6) � Oceans 3 (1 - 5) � Natural: 0.6 (0.3 - 1.2) � Atmosphere (NH 3 oxidation) � 9.6 (4.6 – 15.9) � 4 (2.7 – 5.7) � Tropical soils (forest, savannah) � 2 (0.6 – 4) � Temperate soils (forest, grassland) � Agricultural soils 4.2 (0.6 – 14.8) � Anthropogenic: Livestock (cattle, feedlots) � 2.1 (0.6 – 3.1) � 8.1 (2.1 – 20.6) � Biomass burning 0.5 (0.2 – 1.0) � Industrial 1.3 (0.7 – 1.8) � Sink (Tg N yr -1 ) (stratosphere) � 12.3 (9 – 16) � Photolysis and oxidation Accumulation/ trend (Tg N yr -1 ) � 3.9 (3.1 – 4.7) � Although a closed budget can be constructed, uncertainties in sources are large! 6

Global budget of CO Global budget of CO D.J. Jacob Sink and source terms for ozone Tg O 3 yr -1 SOURCES 3400-5700 Chemical production 3000-4600 HO 2 + NO (70 %) CH 3 O 2 + NO (20 %) RO 2 + NO (10 %) Transport from Stratosphere 400-1100 SINKS 3400-5700 Chemical loss 3000-4200 O( 1 D) + H 2 O (40 %) HO 2 + O 3 (40 %) OH + O 3 (10 %) others (10 %) Dry deposition 500-1500 7

Microscopic picture Dust storm Why we have to know something about aerosols in the atmosphere ??? • health (respiration) • visibility • radiative balance • cloud formation • heterogeneous reactions • delivery of nutrients • disease carier • ….. 8

Antarctica: > 100 km New Delhi: < 1.5 km Pictures by: Ismo K. Koponen ja Petteri Mönkkönen Atmospheric aerosols – basic characteristics Definition: solid or liquid particles suspended in air (‘aero’ (greek) = air + ‘sol’ (greek) = solid), but no single molecules or water droplets! Sizes: between 1 nm (molecule clusters) and about 100 � m, therefore covering about 5 orders of magnitude in size. Atmospheric lifetimes: a few minutes up to 10 days depending on size, altitude and water solubility 9

Types of atmospheric aerosols Primary aerosols: released preformed from the Earths surface e.g. mineral dust, sea salt, pollen, black soot from fire exhaust Secondary aerosols: formed from low-volatile chemical or reactive compounds in the atmosphere (gas-phase) e.g. sulphuric acid, organics, nitric acid Cloud-phase induced aerosols: formation of low-volatile chemical compounds in the water droplet, which is evaporating, releasing the new particle e.g. sulphuric acid, organics, nitric acids (similar to sec. particles) � But the longer their residence time in the atmosphere, the more these types interact and get mixed! Size characteristics for aerosols Particle diameter [ � m] 0.001 0.01 0.1 1 10 100 Nucleation Aitken Accumulation mode mode mode Fine Particles Coarse Particles 10

Origin of the Cloud-phase atmospheric aerosol secondary Soil dust Sea salt Smoke primary D.J. Jacob Atmospheric chemistry and atmospheric aerosols primary particles secondary aerosol cloud-particle precursors production (H 2 SO 4 , HNO 3 , cloud-phase induced nitrates, organics) � aerosol NO x , SO 2 , Ions, H 2 O VOCs and primary org. compounds (pollen etc.) � VOCs, primary org. compounds soil (soot etc), NO x , SO 2 Sea salt, DMS, halogenates SO 2 , (Cl - , Br - , IO - ) � soot Mineral dust 11

Ambient aerosol size distributions � m 3 /cm 3 Volume highest at largest sizes � m 2 /cm 3 Surface area highest at medium sizes Number highest at smaller sizes � m SEAS experiment, 2000 Typical aerosol volume size distributions Fresh urban Aged urban rural remote Warneck [1999] Note: Concentrations especially of larger particles decrease rapidly with height. D.J. Jacob 12

Vertical distribution and lifetime Jaenicke, 1993 Jaenicke, 1978 Aerosols with sizes around between 100 nm and 1 µm have the longest lifetime Primary aerosols: sources Aerosoltyp Yearly production Tg/year Sea salt Mineral dust 2980 Gaspar, 2004 Mineral dust Vlasenko, PSI, CH Sea salt 10100 Vulcano dust 30 Primary biological 50 particles Soot 200 Pollen Primary particles are www.wikipedia.org larger and observed normally above 1 µm Soot 13

Secondary aerosol sources: Oxidation products by gas phase chemistry Precursors Yearly production in Tg/year Dimethylsulfid (DMS) from algae 12.4 SO 2 from volcanos 20 Biogenic VOCs 11-270 (could be higher up to 1000) SO 2 (antropogenic) from fossil ca. 50 fuels NO x (antropogenic) from fossil 22 fuels Antropogenic VOCs ca. 2 Black carbon emissions DIESEL DOMESTIC COAL BURNING BIOMASS BURNING Chin et al. [2000] D.J. Jacob 14

Primary emissions New European emission inventories for 2005 (EC and OC emission inventory of PM1, PM2.5 and PM10) Emission invent ory Emission invent ory • Measurements of emissions normally only on selected places – Important: • It most be representative for a certain area • Measurements under different atmospheric relevant conditions (temperature, humidity, stress, ...) • If possible measurements with different techniques (‚cross check‘) Biogenic VOC measurements at the earth surface (Isopren) Guenther et al., ACP, 2006 15

Emission invent ory Emission invent ory • Emission measurements (campaign or monitoring) – A) direct: Measurement down-wind of an emission source (e.g. at the exhaust pipe of a car or at the chimney of a factory) – B) indirect: Relaxed Eddy Accumulation (REA)-Systeme Hyytiälä, Universität Helsinki a) Dir ect measur ement s • Measurements direct in the • Emission measurements in the exhaust gas flow of a chimney canopy or exhaust pipe – Enclousure of a certain part from the tree in a cuvette or teflon bag – Sensor will be mounted direct at the exhaust pipe or the exhaust – Sampling over a certain time gas will be measured in a period on tenax tubes chamber – Or online measurment with – Adsorption on sampling material insturments of high temporal and or online measurement high sensitive sensitivity – Variation in the way you run the engine (motor speed) http://www.atm.helsinki.fi/SMEAR/index.php?option= Yu et al., 2008 com_content&task=view&id=22&Itemid=56 16

Direct analyses: PTR- MS (-TOF) • Proton-Transfer-Reaction Mass Spectroscopie (PTR-MS) • Important: the concentration has to be hgher than the detection limit (about 20-50 ppt depending on compound) and the proton affinity has to be stronger than the one for water � � � � � H O X H O XH 3 2 Ionicon, 2007 b) I ndiret measurement s • Possible for large-scale areas of homogeneous vegetation or street canyons • Measurements of the individual compounds inside and above the forest • Calcualtion of the exchange coefficients � Relaxed Eddy Accumulation Systeme: – Vegetation considered as a box – Up and down-ward transport will be calculated based on the vertical wind gradients 17