Line data    Source code

       1             : !------------------------------------------------------------------------------
       2             : !                   Harmonized Emissions Component (HEMCO)                    !
       3             : !------------------------------------------------------------------------------
       4             : !BOP
       5             : !
       6             : ! !MODULE: henry_mod.F90
       7             : !
       8             : ! !DESCRIPTION: Module HCO\_HENRY\_MOD contains routines to calculate
       9             : ! The dimensionless liquid-over-gas Henry constant KH as well as the
      10             : ! effective Henry constant HEFF, which accounts for hydrolysis.
      11             : !\\
      12             : !\\
      13             : ! KH   = K0 * exp ( CR * (1/T - 1/Tref)  ) * R * T / 101.325
      14             : !\\
      15             : !\\
      16             : ! HEFF = KH * ( 1 + 10\^(pH-pKa) )
      17             : !\\
      18             : !\\
      19             : ! where K0 is the value of KH at standard conditions [M/atm], CR is the
      20             : ! temperature dependency of KH [K], T is the temperature in Kelvin, Tref
      21             : ! is the reference temperature (298.15 K), and R is the universal gas
      22             : ! constant R = 8.314 JK-1mol-1.
      23             : !\\
      24             : !\\
      25             : ! References:
      26             : ! \begin{itemize}
      27             : ! \item Sander, R: Compilation of Henry's law constant for inorganic and
      28             : ! organic species of potential importance in environmental chemistry, 1999.
      29             : ! \item  http://www.mpch-mainz.mpg.de/~sander/res/henry.html.
      30             : ! \end{itemize}
      31             : !
      32             : ! !INTERFACE:
      33             : !
      34             : MODULE HCO_HENRY_MOD
      35             : 
      36             :   IMPLICIT NONE
      37             :   PRIVATE
      38             : !
      39             : ! !PUBLIC MEMBER FUNCTIONS:
      40             : !
      41             :   PUBLIC :: CALC_KH
      42             :   PUBLIC :: CALC_HEFF
      43             : !
      44             : ! !REVISION HISTORY:
      45             : !  16 Apr 2013 - C. Keller   - Initial version
      46             : !  See https://github.com/geoschem/hemco for complete history
      47             : !EOP
      48             : !------------------------------------------------------------------------------
      49             : !BOC
      50             : !
      51             : ! !DEFINED PARAMETERS:
      52             : !
      53             :   REAL*8, PARAMETER :: TREF = 298.15d0      ! [K          ]
      54             :   REAL*8, PARAMETER :: R    = 8.3144598d0   ! [J K-1 mol-1]
      55             :   REAL*8, PARAMETER :: ATM  = 101.325d0     ! [mPa (!)    ]
      56             : 
      57             : CONTAINS
      58             : !EOC
      59             : !------------------------------------------------------------------------------
      60             : !                   Harmonized Emissions Component (HEMCO)                    !
      61             : !------------------------------------------------------------------------------
      62             : !BOP
      63             : !
      64             : ! !IROUTINE: calc_kh
      65             : !
      66             : ! !DESCRIPTION: Function CALC\_KH calculates the liquid over gas
      67             : ! dimensionless Henry constant for the given tracer and temperature.
      68             : !
      69             : ! Reference: http://www.mpch-mainz.mpg.de/~sander/res/henry.html
      70             : !\\
      71             : !\\
      72             : ! !INTERFACE:
      73             : !
      74           0 :   SUBROUTINE CALC_KH ( thisK0, thisCR, TK, KH, RC )
      75             : !
      76             : ! !INPUT PARAMETERS:
      77             : !
      78             :     REAL*8,  INTENT(IN)    :: thisK0  ! [M/atm]
      79             :     REAL*8,  INTENT(IN)    :: thisCR  ! [-d ln kH / d(1/T) ]
      80             :     REAL*8,  INTENT(IN)    :: TK      ! Temperature [K]
      81             : !
      82             : ! !OUTPUT PARAMETERS:
      83             : !
      84             :     REAL*8,  INTENT(OUT)   :: KH      ! Henry liquid over gas constant [-]
      85             : !
      86             : ! !INPUT/OUTPUT PARAMETERS:
      87             : !
      88             :     INTEGER, INTENT(INOUT) :: RC      ! Error handling
      89             : !
      90             : ! !REVISION HISTORY:
      91             : !  16 Apr 2013 - C. Keller - Initial version
      92             : !  See https://github.com/geoschem/hemco for complete history
      93             : !EOP
      94             : !------------------------------------------------------------------------------
      95             : !BOC
      96             :     !=================================================================
      97             :     ! CALC_KH begins here!
      98             :     !=================================================================
      99             : 
     100             :     ! Assume success
     101           0 :     RC = 0
     102             : 
     103             :     ! Error if not defined
     104           0 :     IF ( thisK0 == 0d0 ) THEN
     105           0 :        RC = -999
     106           0 :        KH = -999
     107           0 :        RETURN
     108             :     ENDIF
     109             : 
     110             :     ! Calculate Henry coefficient for given temperature
     111           0 :     KH = thisK0 * exp( thisCR * (1/TK - 1/TREF) ) * R * TK / ATM
     112             : 
     113             :   END SUBROUTINE CALC_KH
     114             : !EOC
     115             : !------------------------------------------------------------------------------
     116             : !                   Harmonized Emissions Component (HEMCO)                    !
     117             : !------------------------------------------------------------------------------
     118             : !BOP
     119             : !
     120             : ! !IROUTINE: calc_heff
     121             : !
     122             : ! !DESCRIPTION: Function CALC\_HEFF calculates the effective Henry
     123             : ! constant taking into account hydrolysis effects. For instance, aqueous
     124             : ! HBr will dissociate to Br- (and H+), and often we are interested in the
     125             : ! total Br concentration in water, i.e. Brx = HBr + Br-, with the equilibrium
     126             : ! concentration of Brx and gaseous HBr being the effective Henry
     127             : ! constant. This function provides the correction factor to calculate
     128             : ! the effective Henry constant from the 'regular' Henry constant
     129             : ! (above):
     130             : !\\
     131             : !\\
     132             : ! Heff = KH * CORR
     133             : !\\
     134             : !\\
     135             : ! The correction term is derived as following:
     136             : !\\
     137             : !\\
     138             : ! The regular Henry constant is:   H    = HA(liq) / HA(g)
     139             : ! The effective Henry constant is: Heff = ( HA(liq) + A(liq)) / HA(g)
     140             : ! Equilibrium between HA and A is: pH = pK + log ( A/HA )
     141             : ! A(liq) hence becomes: HA(liq) * 10**(pH-pK)
     142             : !\\
     143             : !\\
     144             : ! ==> Heff = ( HA(liq) * ( 1 + 10**(pH-pK) ) / HA(g)
     145             : !          = HA(liq) / HA(g) * ( 1 + 10**(pH-pK) )
     146             : !          = H * ( 1 + 10**(pH-pK) )
     147             : !\\
     148             : !\\
     149             : ! ==> CORR = 1 + 10**(pH-pK)
     150             : !\\
     151             : !\\
     152             : ! !INTERFACE:
     153             : !
     154           0 :   SUBROUTINE CALC_HEFF ( thispKa, PH, KH, HEFF, RC )
     155             : !
     156             : ! !INPUT PARAMETERS:
     157             : !
     158             :     REAL*8,  INTENT(IN)    :: thispKa  ! pKa value [-]
     159             :     REAL*8,  INTENT(IN)    :: PH       ! PH value [-]
     160             :     REAL*8,  INTENT(IN)    :: KH       ! gas/aq Henry constant [-]
     161             : !
     162             : ! !OUTPUT PARAMETERS:
     163             : !
     164             :     REAL*8,  INTENT(OUT)   :: HEFF     ! effective gas/aq constant [-]
     165             : !
     166             : ! !INPUT/OUTPUT PARAMETERS:
     167             : !
     168             :     INTEGER, INTENT(INOUT) :: RC       ! for error handling
     169             : !
     170             : ! !REMARKS:
     171             : ! It should be noted that the correction term calculated here is from a
     172             : ! 'acid perspective', i.e. for compounds with the acid being in the
     173             : ! gaseous phase. The correction term reads 1 + 10**(-pH+pK) for
     174             : ! compounds with the base in the gas phase (e.g. ammonia).
     175             : !
     176             : ! The correction term becomes more complicated for compounds with more
     177             : ! than two equilibrium compounds that are relevant under the current
     178             : ! conditions (e.g. CO2).
     179             : !
     180             : ! We ignore any temperature dependencies of pKa for now.
     181             : !
     182             : ! !REVISION HISTORY:
     183             : !  16 Apr 2013 - C. Keller - Initial version
     184             : !  See https://github.com/geoschem/hemco for complete history
     185             : !EOP
     186             : !------------------------------------------------------------------------------
     187             : !BOC
     188             :     !=================================================================
     189             :     ! CALC_HEFF begins here!
     190             :     !=================================================================
     191             : 
     192             :     ! Assume success
     193           0 :     RC = 0
     194             : 
     195             :     ! Calculate correction term.
     196           0 :     IF ( thispKa > 0d0 ) THEN
     197           0 :        HEFF = KH * ( 1d0 + 10d0**( pH - thispKa ) )
     198             :     ELSE
     199           0 :        HEFF = KH
     200             :     ENDIF
     201             : 
     202           0 :   END SUBROUTINE CALC_HEFF
     203             : !EOC
     204             : END MODULE HCO_HENRY_MOD