You could possibly but, PSD usually is for mineral soil materials. The process could yield some clever insights. You could also look at loss of mass following specific oxidation protocals say 5ml 10ml 25 ml of H2O2 at time zero and after some interval. In theory as Organics decay, the should be more easily oxidizable. This will lead to more loss from the wet oxidation.

Just some thoughts.

Prakash. It largely depends on the type of material to be analyzed. The size reduction of materials in different sizes, it is common practice in treating

ores but it is also suitable for usually accelerate or facilitate complete reaction procedure. This sense for the organic compound, it may be in the network of smaller particles and these involved by other binding substance. So the grind liberates (They expose) the best Organic degradation. In this sense the procedure may have some correlation with the quantitative and qualitative measurement of bio degradation.

Our experience in the area of geoelectric methods (geophysical) indicate that biofilms generated around of the soil particular result in decrease of porosity and increase of the soil conductivity (surface conductivity). These biofilms behave electrically similar to an increase in clay content. Then, measuring the clay content we can have an abnormal (not real) increase of clay, indicating presence biodegradation process. More efficiently, we could calculate the surface conductivity (not bulk) of soil, being an efficient parameter to monitoring the biodegradation process. When these processes decline with time, the surface conductivity decreases.

I attached work presented in congress SAGEEP 2006 for better explanation.