deletions | additions       diff --git a/From_lab_to_field_Although__.md b/From_lab_to_field_Although__.md  index d94f866..a02612a 100644  --- a/From_lab_to_field_Although__.md  +++ b/From_lab_to_field_Although__.md 
...
##Isotope tracers  Stable isotopes of especially Ca and Sr have been used extensively to source the origin of Ca in drainage water .   Applied to plant tissues, it could potentially traceback trace  plant nutrients back to their primary source. It has been primarily used to study the apatite weathering.  Apatite is a calcium-phosphate mineral, and as P has no stable isotopes, the uptake dynamics can only be studied via the Ca ion (or potentially the ¹⁸O/¹⁶O in the phosphate group) .  As apatite is generally only a minor mineral in the soil mineral matrix, its contribution to the soil solution Ca pool is minor compared to other minerals. 
...
How these small scale mechanisms are upscaled can have major consequences on the model behavior at soil level.  The most well-known weathering model, PROFILE \cite{Sverdrup_1993} is based on a series of chemical dissolution reactions simulated at the scale of soil layer 'bulk' soil solution.   The parameterization is based on  batch experiments with organic and inorganic weathering agents. Based on this model, and its application in many boreal forest soils, Sverdrup \cite{Sverdrup_2009} concludes that protons are the major weathering agent in these soils, organic chelators like oxalate only play a minor role.  The main critique on the PROFILE model from a fungal point of view is that simulating weathering on a soil layer scale overlooks the potential importance of local, fungal-scale, high concentrations of fungal weathering agents\cite{Finlay_2009}.  But, as illustrated in \cite{Smits_2009}, due to the specific dissolution kinetics of the main dissolution reactions, local concentration of weathering agents do not automatically lead to higher dissolution rates.