INTERACTION OF IRON WITH RAINFALL LEACHATES*.

Leachates from decomposing leaves of four species of deciduous trees were collected after each rainfall during the months of May to September. Determinations were made of the capacity of these leachates to take up iron from iron-saturated Dowex-50 and to withhold this iron from exchange and/or adsorption by exchange resins saturated with H, Al, Ca, and Mn. For both characteristics the leachates ranked maple > poplar > birch > beech. The capacity of ion-saturated resins to remove iron from iron-enriched leachates was as follows: H > Al > Ca = Mn. This behaviour may be related to the variable thicknesses of the horizons of eluviation and deposition of iron in various podzolic soils. These horizons are, in general, thinner in the strongly acidic Podzol soils than in Grey-Brown Podzolic soils more highly saturated with calcium. Potentiometric titrations of metal-free and iron-enriched leachates indicated that titratable acid groups were blocked by the added iron. Apparent pK values of metal-free leachates ranged from 3·6 to 3·9, those of iron-enriched leachates, except poplar, from 4·7 to 5·0. [ABSTRACT FROM AUTHOR]