Dear Ebrahim, I wonder if you mean leaching of anion in soils (it is rather more intensive process, than cation leaching, because majority of soils, or more specifically - clay minerals - have, as average negative charge) or rather the method for determination of Anion Exchange Capacity? From the reason mentioned above it is rarely determined, however in some, especially tropical soils it may have certain importance.

You may find this procedure there

http://link.springer.com/chapter/10.1007/978-3-540-31211-6_27

may be your university has access to this?

And regarding the question- as the anions are mainly in soil solution (nor absorbed by soil colloids) they are leached with any water movement downward. Certainly, in any soil solution the cations are also present. Although they are absorbed by soil colloids, they may be exchanged, for example, if soil is limed. Great amount of Ca cations appear in soil solution, so they replace part of cations (H, Mg, K, Al) from soil sorption complex. Consequently these ions appear in soil solution and are leached after heavy rainfall. However I think you know this very well.

Best regards, Michał

Dear Ebrahim,

I wonder you can use Tessier's scheme for your purposes

http://www.hindawi.com/journals/ijac/2010/387803/