how does leaching occur?

Answer 1

Leaching is the process by which inorganic or organic contaminants are released from the solid phase into the waterphase under the influence of mineral dissolution, desorption, complexation processes as affected by pH, redox, dissolved organic matter and (micro)biological activity.

Answer 2

Does that answer your question... it is unclear what kind of leaching you are asking about.

Bacterial leaching patterns on pyrite crystal surfaces.
J C Bennett and H Tributsch
ABSTRACT

Selected pyrite crystals were placed as a bacterial energy source into stationary cultures of Thiobacillus ferroxidans. Scanning electron microscope studies performed after a period of 2 years on these crystals revealed bacterial etching pits in characteristic patterns; they include pit arrangements in loose statistical disorder, in pairs, in clusters, and most remarkably in pearl-string-like chains. It has previously been confirmed that the chemical processes of bacterial leaching occur mainly in the region of contact between bacteria and the sulfide surface. The evidence presented in this experiment strongly suggests that the observed bacterial distributions are critically dependent on crystal structure and on deviations in the crystal order (fracture lines, dislocations) of the leachable substrate.

Answer 3

When liquid creeps through a solid material. Example, water through thick soil.