Oceanic air-water exchange of Persistent Organic Pollutants (POPs) and aerosol carbon at a global scale

Transcription

1 Oceanic air-water exchange of Persistent Organic Pollutants (POPs) and aerosol carbon at a global scale Elena Jurado 1, Rafel Simó 2, Jordi Dachs 1 1 Environmental Chemistry Department, CSIC Barcelona - SPAIN 2 Marine Sciences Institute, CSIC Barcelona -SPAIN

2 AEROSOLS ATMOSPHERIC DEPOSITIONAL PROCESSES of POPs (semivolatile organic contaminants) aerosol-bound contaminants gaseous contaminants RAIN VOLATILIZATION DRY DEPOSITION ABSORPTION WET DEPOSITION POPs: tracers of organic aerosol

3 >> objectives Methodology to estimate atmospheric depositional fluxes of PCDD/Fs and PCBs over the Atlantic Ocean using atmospheric concentration sampling data using satellite data coupled with novel parameterizations of the transfer coefficients Relative importance of each transport process Deposition of aerosol organic and black carbon to global oceans

4 >> cruise data Cl 5 DD atmospheric concentration GAS: C g 90ºN 60ºN 30ºN 0º 30ºS 60ºS 90ºS ºN 60ºN 30ºN 0º 30ºS 60ºS AEROSOL: C p [fg m -3 ] RRS Bransfield Oct-Dec 1998, Rainer Lohmann PCDD/Fs 90ºS RV PELAGIA Jan-Feb 2001 [fg m -3 ] Foday Jaward PCBs (Lohmann et al. EST 2001)

5 >> satellite data u 10 : wind speed 20 SSM/I (NOAA) November [m s -1 ] Other satellite parameters: p 0, f, SST, aerosol size (r eff, σ eff, tita), AOD, chl a TSP (algorithm Gassó and Hegg JGR 2003)

6 ATMOSPHERIC DEPOSITIONAL PROCESSES DRY DEPOSITION AIR-WATER EXCHANGE WET DEPOSITION F DD =v D C P v D : f(u 10, aerosol size) Williams 1982, Slinn & Slinn 1980

7 >> dry deposition > aerosol size from MODIS 90ºN Effective Radius + Standard deviation effective radius 60ºN 30ºN 0º parameters lognormal distribution number concentration of aerosols 30ºS 60ºS 90ºS 180ºW 135ºW 90ºW 45ºW 0º 45ºE 90ºE 135ºE 180ºE 1 Volumetric fraction of particles (w i ) MODIS (TERRA, NASA) November [µm] D p : 1-2 µm D p : 2-3 µm w i D p : 3-5 µm D p : Particle Diameter [µm]

8 >> dry deposition > v D vd ( v w ) = Di i i Overall v D November [cm s -1 ]

9 ATMOSPHERIC DEPOSITIONAL PROCESSES DRY DEPOSITION F DD =v D C P AIR-WATER EXCHANGE F AW =k AW (C G /H -C w ) C W : phytoplankton-uptake & sinking model (Dachs 2002) k w (600): Nightingale Ho 1997 WET DEPOSITION F WD =W P C P p 0 +W G C G p 0 W P = W G = 2000 K ia Λ+RT/H

10 >> latitudinal profiles to the Atlantic 90ºN Cl 5 DD 60ºN 30ºN 0º 30ºS 60ºS Wet deposition flux Net air-water exchange flux Dry deposition flux 90ºS [pg m -2 d -1 ] (Jurado et al. EsT, 38, ) (Jurado et al. EsT, 39, )

11 >> mean depositional fluxes to the Atlantic Net Air-water exchange pg m -2 d Wet Deposition Dry Deposition Cl4DF Cl5DF Cl6DF Cl7DF OCDF Cl4DD Cl5DD Cl6DD Cl7DD OCDD PCBs: F AW >> F DD, F WD!! 500 pg m -2 d PCB28 PCB52 PCB101 PCB118 PCB138 PCB153 PCB180 + volatile - volatile

12 >> dominant mass transfer coefficient Cl 5 DD PCB 101 Nov.98 Jan.98 DRY DEPOSITION dominates ABSORPTION dominates WET DEPOSITION dominates

13 >> validation Source Location Name (Latitude, Longitude) measured F WD ΣPCBs [ng m -2 yr -1 ] estimated F WD ΣPCBs [ng m -2 yr -1 ] Mandalakis et al Crete island, eastern Mediterranean (35N, 25E) (820) 107 Van Ry 2002 Tuckerton, US (39N, 74W) 268 (310) 130 Van Drooge 2001 Izaña, Tenerife, NE Atlantic (28N, 16E) 735 (1300) 706 Park et al Galveston Bay, Texas (29N, 95W) (1530) 3600 Without brakets when referred to PCB 28, 52, 101, 118, 138, 153, 180 In brakets when referred to all the PCB congeners Factor 1-2 (Jurado et al. EsT, 39, )

14 >> equations fluxes aerosol carbon Aerosol carbon: Organic Carbon (OC) + Black Carbon (BC) for OC... DRY DEPOSITION FLUX: WET particle DEPOSITION FLUX: F DD_OC = v D C p_oc F WD_p_OC = W P C p_oc p 0 where: C p_oc = TSP f OC strongly dependent on aerosol source and type

15 >> look-up table look-up table: allows to obtain the spatial distribution of dominant aerosol type over the oceans Dominant aerosol type AOD σ AOD Tita [0-1] u 10 (m s -1 ) Other conditions Biomass Burning (BB) Proximity to Fire-Points (ATSR World Fire Atlas) Industrial emissions (IN) Proximity urban centers No BB Dust (DU) 0.3 < 0.6 No BB, No IN Sea-salt (SS) < Distance from coast No BB, No IN, No DU Continentally influenced (BK1) No BB, No IN, No DU, No SS Background aerosol (BK2) No BB, No IN, No DU, No SS, No BK1

16 >> dominant aerosol type Baseline background aerosol Continentally influenced Sea-salt Urban and suburban, industrial emissions Biomass burning Dust plumes Nov sources: MODIS(AOD, tita) + look-up table SSM/I NOAA (u 10 ) ATSR WFA (Fire-counts)

17 >> organic and black carbon aerosol fractions Aerosol type f OC (%) f BC (%) ref. Biomass Burning submicron aerosol supermicron aerosol Brasseur et al Industrial emissions submicron aerosol supermicron aerosol Brasseur et al Dust Kinne et al Sea-salt Cavalli et al Continentally influenced submicron aerosol supermicron aerosol Brasseur et al Background aerosol submicron aerosol supermicron aerosol Brasseur et al. 2003

18 >> comparison estimated/measured measured C OC C BC ORGANIC CARBON log C OC [µg C m -3 ] 1.E+01 1.E+00 Measured Estimated 1.E-01 1.E latitude BLACK CARBON log C BC [µg C m -3 ] 1.0E E E-01 Measured Estimated 1.0E E latitude

19 >> dryd deposition of OC aerosol TOTAL: 20 Tg C yr -1 F DD_OC OC inputs related to DOC/POC enrichment? Nov [mg C m -2 d -1 ]

20 >> wet deposition of OC aerosol TOTAL: 77 Tg C yr -1 F WD_p_OC Tg C yr -1 Duce Nov [mg C m -2 d -1 ]

21 >> deposition OC and BC to global oceans Dry deposition [Tg C yr -1 ] Wet particle deposition [Tg C yr -1 ] Wet dissolved deposition [Tg C yr -1 ] (rainwater DOC) Diffusive absorption gaseous carbon (GOC) [Tg C yr -1 ] OC 20 77??? BC 2 8 Willey 2000 : 80% of the rainwater organic carbon is DOC largely unexplored EXPECTED IMPORTANT ROLE, NOT YET ASSESSED!! IPCC aerosol burden from emissions inventory: OC 1.7 Tg C yr -1, BC 0.3 Tg C yr -1

22 >> CONCLUSIONS Remote sensing is useful to estimate and compare the atmospheric sinks of POPs and organic aerosol to global oceans. Estimated depositional fluxes are associated to an important spatial variability. DRY DEPOSITION WET DEPOSITION Can be significant in high latitudes and areas with raised aerosol amounts (marine aerosol!) but in general its magnitude is be minor than the rest of fluxes. Rain has a dramatic effect. AIR-WATER EXCHANGE Dominant atmospheric depositional process for the more volatile POPs. Diffusive fluxes of gaseous organic carbon: important predicted role. They can be significantly higher than our reported fluxes for dry and wet aerosol organic deposition, which are already sizeable to the oceanic CO 2 uptake.

23 THE END (+ Colloquium end ) ejuqam@iiqab.csic.es