Global transport of POPs: the role of aerosol particles

Global transport of POPs: the role of aerosol particles Sunling Gong Air Quality Research Division

Persistent Organic Pollutants Organic chemical compounds and mixtures that include industrial chemicals like PCBs, pesticides like DDT HCH and wastes like dioxins. Volatile and semi-volatile Long life time in the atmosphere

Grasshopper Effect

Global Emissions of α-hch and Arctic Concentrations Emissions (kt/year) 200 180 160 140 120 100 80 60 40 20 China (Li and Bidleman, 2003) India and Soviet Union 1000 900 800 700 600 500 400 300 200 100 Concentration (pg/m^3) 0 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 0 Year

Cycles of POPs in the Atmosphere Atmospheric Particle Surface and Particle Removal Atmospheric Processes Partitioning Dry and Wet Removals Chemical Degradation F S F W F A Atmospheric Transports C S C w soil water anthropogenic Exchanges/Emissions

Transport Model

Modeling System CANadian Model for POPs CAN/POPs Framework Transport Models Emissions Exchange Modules Aerosol Module PCB Simulation Results

Transport Model - GEM Global Environment Model Canadian Weather Forecast Model Global Uniform 400x200 ~ 90 km Variable Global Focused ~ 25 km Limited Area ~ 200 m

Properties by Transport Model Advection Vertical Mixing Metrological Parameters Wind speed, clouds, precipitation, T, P, RH.

Exchanges/ Emissions

Air/Water Exchange AIR F w CG Deposition CG,I CW,I Total Resistance R O = r A + r w 1/DA or r A Flux (mol/m 2 /s) k W F W = K TA (C W. K AW -C G ) Mass transfer coefficient K TA (s/m) Boundary layers WATER 1/Dw or rw CW k w 30 > H (for PCB s) > 0.1 0.01 > K AW > 10-5 1 / K TA = 1 / k A + K AW / k w a) in water (Wanninkhof, 1992) k w = [ 2.5 ( 0.5246 + 1.6256x10-2.T + 4.9946x10-4 T 2 )+ 0.3u 2 10 ].(Sc/660)-1/2 b) in air (Mackay et al., 1983) k A (m/s) = 10-3 + 4.62x10-04 x (6.1+0.63u 10 ) 0.5 u 10 [Sc pcb,air ] -0.67

Air/Soil Exchange F S AIR d=5cm SOIL CG CG,I Soil-Air Surface Exchange C S,I Transfer of chemical between soil layers 10cm Deposition C S(1) C S(2) C S(3) Total boundary layer resistance R A =r G +r B r B, vegetation r G, air 0-1 cm 1-3 cm r S, soil Flux (mol/m 2 /s) F S (0, t) Total resistance (s/m) T = 1 R T ( C [ K R r ] R = + SA G, soil A (0, t) -C 2 L 1 exp 4. DES t s G,air (0, t).k SA ) 3-10 cm K SA the soil-air equilibrium coefficient and D ES (m 2 /s) the effective diffusivity of the chemical in the soil matrix

Anthropogenic PCB Estimated cumulative global usage of PCBs (T) Breivik (2001) < 0.1 0.1-1 1-10 10-50 50-100 100-500 > 500

PCB Atmospheric Processes

Removals Dry deposition Water, Snow and Vegetation Scavenging by Snow and Rain OH Reaction

Partitioning PCB-28 PCB-180 aerosol Junge-Pankow Partition (Junge, 1997; Pankow, 1987) Φ = c. Θ = P0 + c. Θ C L P C P + C Θ - the aerosol surface area available for adsorption (m 2 aerosol/m 3 air), P 0 L - the liquid-phase saturation vapour pressure of pure compound (Pa) c - a parameter that depends on the thermodynamics of the adsorption process and surface properties of the aerosol (Pa.cm). G

Atmospheric Aerosol Distributions PCBs partitioned to aerosol particles will be removed from the atmosphere by the same mechanism as the aerosol particles by dry deposition, in-cloud and below-cloud removals.

Global Aerosol Distributions (courtesy of S. Kinne MPI, Hamburg, Germany)

Types of Aerosol Emissions Anthropogenic SOx, NOx,, VOC, BC/OC Bio-mass burning emission Governmental (or private) statistics Meteorology redistributed Natural Sea-salt, DMS, biomass burning, soil dust Nature Meteorology driven, surface features

Clear Sky Dynamics Aerosol Dynamics Clear Sky Dry Deposition Sulphur Chemistry Nucleation Condensation Coagulation OH, NO3, O3, HNO3 Gas Chemistry Module Gas H 2 SO 4 Condensation Nucleation [5,7] k Coagulation Aerosols Ambient size r c Clouds

Wet Processes Wet Processes Wet Processes Below-Cloud Scavenging of Aerosols Rain or Snow (Washout) Aerosol Activation CCN Evaporation of Clouds to Aerosols Bi-modal Formation Precipitation Removals Rain or Snow (Rainout) Cloud Chemistry CTM

Global Aerosol Surface Areas

Simulation Results

Model Configurations Meteorology - Year 2000 2º x 2º 2 resolution 20 minute integration time GEIA Emissions for aerosols PCB emissions (Breivik( et al. 2001) Initial atmospheric, soil and water PCB concentrations from MSC-E E modeling results.

PCB 28 ngm -2

PCB 153 ngm -2

PCB 180 ngm -2

EMEP POP Stations

Monthly PCB 153 vs PCB 180 Roervik Concentration [pg/m 3 ] 10 1 Observations Model PCB153 10 Concentration [pg/m 3 ] 1 Observations Model PCB180 0.1 0 2 4 6 8 10 12 Month 0.1 0 2 4 6 8 10 12 Science and Technology Month Branch

Daily PCB 153 vs PCB 180 100 Observations Model PCB153 Kosetice Concentration [pg/m 3 ] 10 1 100 Observations Model PCB180 0.1 0 100 200 300 Concentration [pg/m 3 ] 10 1 Julian Day 0.1 0 100 200 300 Julian Day

PCB 153 vs PCB 180 Spitsbergen Concentration [pg/m 3 ] 10 0 10-1 10-2 PCB153 PCB180 10-3 Observations Model 10-1 10-4 0 100 200 300 Concentration [pg/m 3 ] 10-2 10-3 Observations Model Julian Day 10-4 0 100 200 300 Science and Technology Julian Branch Day

PCB 153 vs PCB 180 100 Arctic Alert Concentration [pg/m 3 ] 10 1 0.1 0.01 PCB153 0.001 Observation Yr 2000 Model Observation Yr 1992 10 1 10 0 PCB180 0.0001 0 100 200 300 Julian Day Concentration [pg/m 3 ] 10-1 10-2 10-3 10-4 Observation Yr 2000 Model 10-5 0 100 200 300 Julian Day

Vertical Profiles ng m -3

Vertical Profiles ng m -3

Intercontinental Transports PCB28 Particle/Gas kg/year PCB180

Intercontinental Transports PCB28 Particle/Gas kg/year PCB180

Intercontinental Transports PCB28 Particle/Gas kg/year PCB180

Intercontinental Transports PCB28 Particle/Gas kg/year PCB180

Intercontinental Transports PCB28 Particle/Gas kg/year PCB180

Summary Global transport patterns of POPs varies greatly by their chemical and physical properties. Aerosol particles play an important role in the global transport of POPs for semi volatile POPs. Heavy PCBs are transported through particle phases while lighter PCBs through gas phases. Lighter PCBs transport longer distances than heavy PCBs Inter-continental transports of PCBs are dominated by light PCBs.

Future Works More accurate emissions of POPs are needed. Comparison of model results with observations of network monitoring needs to be done to validate model results. For some persistent POPs,, a global survey of the soil concentrations is needed due to its function as a dominant source of POPs. Seasonal and inter-annual variability of inter- continental transports need further stidy