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Soil Science Society of America Journal Abstract -

Differential Sr-Ca Bonding on Soil as Influenced by Bonding Site1


This article in SSSAJ

  1. Vol. 35 No. 4, p. 566-571
    Received: Jan 4, 1971
    Accepted: Apr 13, 1971

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  1. S. M. Elgawhary and
  2. S. A. Barber2



The Sr-Ca selectivity coefficient, kSr/Ca, was used to interpret the differential Sr-Ca bonding of cation exchange sites in two soils. A dominant complementary cation, K, was used to place the Sr and Ca on sites which favored Sr and Ca over K. As the equivalent fraction of Sr plus Ca in the equilibrium solution was reduced, kSr/Ca decreased, indicating that organic exchange sites were the first to be filled. When the complementary ion was Mg or Ba, kSr/Ca was much larger, indicating that these complementary ions competed more nearly equally with Sr and Ca for all exchange sites. There was a relationship between the log of the equivalent fraction of Sr plus Ca and kSr/Ca that was linear over segments of the range of equivalent fraction used.

Chromatographic separation of Sr and Ca on a Sidell soil reflected the kSr/Ca of this soil at low Sr plus Ca saturations. Little Sr and Ca separation occurred with the Edwards muck apparently because of the over-shadowing of the readily exchangeable cations by Sr and Ca adsorbed in very slowly exchangeable positions resulting in little movement of these ions.

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