Organic tin compounds stick to soil, sediment, and particles in water. Organic tin compounds

can be degraded (by exposure to sunlight and by bacteria) into inorganic tin compounds. In water, organic tin compounds are mostly attached to particles in water. Organic tin compounds may also settle out of the water into sediments and may remain unchanged for years. Thus any sort of storage that can ensure the prevention to sunlight and bacteria activities, would be OK. 

i think you can dry freeze the sediment and store it but for the water it should analyze directly 

I've never done, but try putting some anti-caking (to prevent caking and clumping of very fine silts and clays with phi-particles larger than 5) and would keep it in a refrigerator to delay the putrefaction of organic matter. Samples would not keep more than a week.

For periods longer, would think weather or something add some disinfectant to kill organic matter without altering the chemical composition of the sediments (may be hydrogen peroxide H2O2).

With hydrogen peroxide, organic matter oxidase are not alter the aqueous medium (density) and not alter the minerals.

the gain sufficient assurance steps are: first hydrogen peroxide (until it stops reacting, or blowing bubbles) and then caking.

When using the samples you must re-measure the density of the liquid (for granulometric studies), because the density changes anticaking medium

sorry, I misunderstood the question. None of hydrogen peroxide !.

The anticaking prevents caking organic material with fine clays and silts.

Again I apologize for my mistake in the interpretation of the question. Thank you

I had saved my sediment samples in 20 cc penicillin bottles in cold chain (-20 deepfreeze)  for 1 year before I made my Gas Cromatography analysis. The penicillin bottles must be sealed using crimper with suitable gasket and cover after sediments are put into the bottles. This way is really useful and I strongly recommend...