thank you so much for the reply, i do understand the concept of it as tracker, but tell me please if the following is correct or not: T indicates how much of the flux is in an area but it is not concentration that can be calculated from the flux that we have define as input
can we assume that the value of T is the area share amount of uniform concentration
so if we calculated a uniform distribution of the passive scalar in the boundary box , t will equal how much of the amount of the uniform concentration is at any point in the map
for example, if the uniform distribution = 2 g/m3 then concentration in point 1 (T in this point equal 4) equal 4x 2= 8g/m3
and if T in point 2 equal to 0.1 then concentration is equal to 0.2; make sense?!?! 
