Modeling the Dynamics and the Dynamics and Modeling Kinetics of - PowerPoint PPT Presentation

Modeling the Dynamics and the Dynamics and Modeling Kinetics of Gaseous Pollutants and Kinetics of Gaseous Pollutants and Aerosols in the Atmosphere: : Aerosols in the Atmosphere Estimation of the Environmental Estimation of the Environmental Impact of Forest Fires Impact of Forest Fires A.E. Aloyan , , V.O. Arutyunyan V.O. Arutyunyan, A. N. Yermakov , A. N. Yermakov INM RAS, , Moscow Moscow INM RAS

Computational Grid Size: (60 x 60 x 30 x 100 x 30) = 3.24 x 10 8

Model Structure • Atmospheric Thermohydrodynamics (nonhydrostatic, mesoscale, terrain-following, cloud microphysics, turbulence, heat- and mass-exchange in soil and water) • Pollutant Diffusion and Transport (gas- and aqueous phase chemistry, anthropogenic and biogenic emissions, aerosol processing, ion composition of clouds and aerosols, mass-exchange between gas and liquid) • Homogeneous Nucleation (New-Particle Formation) (Binary [H 2 O-H 2 SO 4 ] and ternary [H 2 O-H 2 SO 4 -NH 3 ]) • Condensation/Evaporation • Coagulation • Optimization and Risk Assessment

Aerosol Formation (Gas-to-Particle Conversion)

General Equation for Gas-Aerosol Dynamics The system of equations for the pollution transport and transformation ( Aloyan, 2000; Aloyan et al., 2002 ) ∂ ∂ ∂ ∂ C C C + = − − + + + = gas nucl cond phot aqu i i i u F P P P P K , ( j 1 , 3 ) ∂ ∂ ∂ ∂ j i i i i i jj t x x x j j j ∂ ϕ ∂ ϕ ∂ ϕ ∂ + − δ = + + + + = aer nucl cond coag k k i ( u w ) F P P P K , ( j 1 , 3 ) ∂ ∂ ∂ ∂ j j 3 g k k k k jj t x x x j j j C i ( i = 1, …, N ) and ϕ k ( k = 1, …, M ) are the concentrations of gaseous species and aerosols, respectively; N and M are the numbers of gaseous components and aerosol fractions, respectively.

Regional Model Equations of Atmospheric Hydrodynamics

Pollution Transport Governing equation ∂ ϕ ∂ ∂ ϕ ∂ ∂ ϕ ∂ ∂ ϕ = − ϕ + + + + ϕ F div u K K K B ( ) σ ∂ ∂ ∂ ∂ ∂ ∂ σ ∂ σ i x y t x x y y Solution domain [ ] [ ] [ ] [ ] { ( ) } = × = σ ∈ − ∈ − σ ∈ D t D 0 , T , D x , y , : x X , X , y Y , Y , 0 , H ∂ϕ ( ) 1 = ϕ − ϕ K Pollution flux in the surface layer ∂ + + z surf z r r r a b c ϕ = ϕ < b if u 0 , Boundary conditions Γ i i n ∂ ϕ ϕ = ϕ = 0 for 0 , t = ϕ ≥ b i if u 0 . i i ∂ i n ϕ = ϕ = n b for z H . Γ i i

Photochemistry The chemical mechanism used in this work is an improved version of that described in Aloyan et al. (1987) and Aloyan et al. (1995). Additional species and chemical reactions were included into the mechanism from the Carbon- Bond Mechanism (CBM-IV) (Gery et al., 1989). The reaction rate constants were taken also from (Anderson 1976; Atkinson and Lloyd, 1984). This approach allows us to describe the intermediate species in more detail, while the computational burden increases only slightly. In total, the resulting hybrid model includes a total of 44 chemical species and 204 chemical reactions. The total list of chemical species is as follows:

Condensation and Coagulation The kinetic equation for the change of aerosol particle-mass distribution ( Aloyan et al., 1993; Aloyan et al., 1997 ) ∞ ∂ ϕ ∂ g 1 ~ ~ ∫ ∫ + ϕ = + ϕ ϕ − ϕ ϕ v J ( g , t ) K ( g , g ) dg K ( g , g ) dg − ∂ ∂ g 1 g g g 1 g 1 g 1 t g 2 1 1 1 0 0 where g is the particle mass, J is the nucleation rate, K is the coagulation kernel, v g is the rate of condensation.     απ λθ   2 2 / 3 1 / 3 d nv g g   = − −   T *   v 1 exp 1   + g   1 / 3 1 / 3   4 ( 1 3 dg / 8 l  kT g  1

Coagulation Model The coagulation equation has the form [ Golubev and Piskunov, 1999; Aloyan and Piskunov, 2005 ] α g ∂ α 1 ∫∫ C ( g , , t ) − α − β β − α − β β β − = K ( g s , ; s , ) C ( g s , ) C ( s , ) dsd ∂ 2 t 0 0 ∞ ∞ ∫∫ − α α β β β C ( g , , t ) K ( g , ; s , ) C ( s , ) dsd 0 0 where g is the total mass of particles, α is the mass of pollutant, K is the coagulation coefficient, C ( g , α , t ) is the total concentration of particles . α β ≅ α β ≡ K ( g , , s , ) K [ g , ( g , t ) ; s , ( s , t ) ] k ( g , s , t )

Main integral characteristics of the particle-size distribution g ∫ = α α n ( g , t ) C ( g , , t ) d 0 g ∫ = α α α ( , ) ( , , ) m g t C g t d 0 C(g, α , t) = c(g, t) δ ( g – α ) + c c (g, α , t) ∞ g ∂ 1 ∫ ∫ n ( g , t ) − − − = K ( g s , s ) n ( g s ) n ( s ) ds n ( g ) K ( g , s ) n ( s ) ds ∂ 2 t 0 0 ∞ ∂ g ∫ 1 m ( g , t ) ∫ − − − = m ( g ) K ( g , s ) n ( s ) ds K ( g s , s ) n ( g s ) m ( s ) ds ∂ 2 t 0 0 ∞ g ∂ 1 ∫ ∫ c ( g , t ) − − − = K ( g s , s ) n ( g s ) m ( s ) ds c ( g ) K ( g , s ) n ( s ) ds ∂ 2 t 0 0

Condensation Model = − α m ( g , t ) α = g g ( g , t ) c p 0 n ( g , t ) c = − α = δ − − α m ( g , t ) ( g g ) n ( g , t ) c ( g , , t ) n ( g , t ) ( g g ) c po c c c po ∂ ∂ ( ) [ ] c + = δ − v c J ( g , t ) g g * t ( ) ∂ ∂ g t g ∂ ∂ ( ) n + = c v n 0 ∂ ∂ g c t g

Binary Nucleation (H 2 SO 4 -H 2 O) Скорость нуклеации J зависит от трех основных переменных : массовой концентрации кислоты в паровой фазе ( С ), относительной влажности воздуха ( Rh ) и температуры ( T ). Пусть в атмосфере в пересыщенном паре при температуре T и давлении Pv имеется бинарный кластер , состоящий из n w молекулы вещества w и n a молекул для a с мольными фракциями x iv ( i = w,a ). Свободная энергия для образования жидкого зародыша в бинарной смеси имеет вид = ∆ = ∆ µ + ∆ µ + σ W G n n A w w a a где ∆ G – изменения свободной энергии Гиббса , A – площадь поверхности , σ – поверхностное натяжение , ∆ µ i = µ il ( T,Pv,x il ) – µ iv ( T,Pi,x iv ), где µ il и µ iv – химические потенциалы в жидкой и паровой фазах , соответственно .

радиус критического кластера определяется из уравнения Кельвина σ ν * * 2 ( x ) ( x ) = * i r   ρ free   kT ln   i ρ free *  ( x )  i , s работа для формирования критической нуклеации будет 4 2 = π σ * * * ( ) w r x 3 общее выражение для скорости нуклеации имеет вид   − * w w ( 1 , 2 ) = ρ − J z ( 1 , 2 ) exp     kT где ρ (1,2), w (1,2) – численная концентрация и энергия образования дигидрата серной кислоты , соответственно , а z – кинетический коэффициент Зельдовича

Ternary Nucleation ( H 2 SO 4 – H 2 O – NH 3 )

Gas- and Aqueous-Phase Chemistry Model [ ]   i [ ] [ ] d C k = − −  −  g i i i i i w w  C k C  L gen , g loss , g g i aq i   dt k k T H b [ ]   i [ ] [ ] d C k 1 = − −  −  aq i i i i i w w  C k C  gen , aq loss , aq g i aq i   dt k k T N H b A − 1   2 4 r r = +   k is the coefficient of mass-exchange processes α i   3 D 3 c   g i i k b is the Bolzmann constant, D g is the diffusion coefficient, α i is the accomodation coefficient, c i is the mean thermal velocity.   ∆   o H 1 1 =  − −  i i r 298 exp K K     is Henry’s constant, H ( T ) H ( 298 )     R T 298 ∆ Is the thermal effect of gas component dissolution at Т = 298 К o H r 298

Aqueous-phase chemistry : • One-way aqueous-phase chemical reactions: 35 • Aqueous-phase photochemical processes: 6 • Reversible chemical reactions (equilibrium): 21 Sulfite oxidation mechanism : (aq) → SO 4 2- + H 2 O + 2H + , - (aq) + H 2 O 2 + H + •HSO 3 (1) •SO 2 + O 3(aq) → HSO 3 - (aq) + O 2(aq) + H + (aq) , (2) 2- + O 3(aq) → SO 4 2- + O 2(aq) , •SO 3 (3) (aq) + O 3(aq) → HSO 4 - - - •HSO 3 (aq) + SO 3 (aq) . (4) These pathways differ essentially in that the final products of the sulfite oxidation – sulfate ions – are generated directly in reaction (1).