diff --git a/source/model/oxygen_mod.f90 b/source/model/oxygen_mod.f90
index 87d69b5e04a1d19fb0f80d8278124eae9744c1b8..999fc4db35011f6fe945df500c87154deb9fcd48 100644
--- a/source/model/oxygen_mod.f90
+++ b/source/model/oxygen_mod.f90
@@ -31,6 +31,7 @@ SUBROUTINE OXYGEN &
 use PHYS_FUNC, only : &
 & HENRY_CONST, &
 & GAS_WATATM_FLUX
+use PHYS_CONSTANTS, only : kappa, z0_bot
 
 use PHYS_CONSTANTS, only : &
 & Kelvin0
@@ -101,9 +102,10 @@ allocate (a(1:vector_length),b(1:vector_length),c(1:vector_length), &
 a(:) = 0.; b(:) = 0.; c(:) = 0.; f(:) = 0.; y(:) = 0.
 
 Foxyg1 = sodbot
+!Foxyg1 = kappa*oxyg(gs%M+1,1)/log(0.25*gsp%ddz(gs%M)*ls%h1/z0_bot) !note: explicit scheme for flux
 
 if (ls%h1 > 0) then
-! 1-st step of splitting-up scheme - diffusion
+! 1-st step of splitting-up scheme - diffusion, explicit scheme for flux
   if (ls%l1 == 0) then
     x = HENRY_CONST(Henry_const0_o2, Henry_temp_dep_o2, Henry_temp_ref, &
     & Twater(1) + Kelvin0)